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Jeremiah's 73 412 restoration project
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Jeremiah Berger
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PostPosted: Wed Apr 03, 2024 5:00 pm    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

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PostPosted: Mon Apr 08, 2024 6:03 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Here are some pics of the rear air ride setup

I took this idea from other air ride setups that used an air strut basically a coilover with an airbag instead of a spring.what I didn't like about that is it put all the weight on that eye on the bottom of strut in the middle of the bolt.I used this contraption to achieve a similar objective of getting the pivot of the whole thing inline with the travel of the shock.The spring had the ability to flex with a curve to it where the bag has to stay straight so cannot mount above like spring...

The bottom has bronze fittings pressed in. And the top of the airbag bolts up to the spring seat from the inside.I also added extra support to the bottom where all the weight now sits .

This is all very custom and made by fit and at this point still considering it a mockup of what I will continue to make better.Just thought it may help others with ideas they may have.
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have.
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hulken
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PostPosted: Tue Apr 09, 2024 1:29 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
Here are some pics of the rear air ride setup

I took this idea from other air ride setups that used an air strut basically a coilover with an airbag instead of a spring.what I didn't like about that is it put all the weight on that eye on the bottom of strut in the middle of the bolt.I used this contraption to achieve a similar objective of getting the pivot of the whole thing inline with the travel of the shock.The spring had the ability to flex with a curve to it where the bag has to stay straight so cannot mount above like spring...

The bottom has bronze fittings pressed in. And the top of the airbag bolts up to the spring seat from the inside.I also added extra support to the bottom where all the weight now sits .

This is all very custom and made by fit and at this point still considering it a mockup of what I will continue to make better.Just thought it may help others with ideas they may have.
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have.


Nice solution! What about the upper mount? The picture of the lower mount is a bit blury, did you have to modify the mount in any way - looks like an extra bracket or something?
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PostPosted: Tue Apr 09, 2024 6:28 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

It appears that Jeremiah welded a square flat pad across the opening where the original shock normally went up through the trailing arm from below.

That's a pretty good method of strengthening that area which will also allow you to use any shock whose eye is maybe not exactly the same as the stock shock. It also allows using higher torque on the cross bolt without bending the structural tube. It's also easily reversible with five minutes from an angle grinder.

Thank you for posting the detailed pictures of the Bilstein strut inserts. Those are very ....odd.

So, for those who do not know, the reason those Bilstein struts have what looks like a strut rod that is like 3X normal diameter, it's because that is not the strut rod you are looking at.

These are an example of Bilstein "upside down" strut technology. I had heard of it but never really looked into what it was because I was not buying any of them for what I drive and up until recently....these....Bilstein offers nothing to fit the 411/412.

What these are are literally what it says. Instead of the outer body of the strut insert tube being just the lower reservoir with a piston attached to the end of the rod moving up and down inside.....you instead have the piston still at the end of the rod, but with a large machined cover tube, welded to the actual strut rod with its open end facing downward and inside of the strut outer tube.

So, on a normal strut cartridge, the piston is the lower guide for the strut rod and the outer rod seal at the top is the secondary rod guide. The problem long term with the original design is that as the strut takes up side loads either because of its rake from how it's mounted in the car or because of any issues with the upper bump stop design....the piston rod side loads its outer seal and the inner piston head and eventually wears out the outer seal first. This starts leakage from the outer seal and eventually causes the gas in the lower piston section to start leaking upward into the oil reservoir section and out the upper rod seal.
On one hand if the normal strut has lasted long enough...Bilstein and other strut mfs would not care because you just buy new ones!

So, this upside down design....and I finally found a detailed explanation or what it IS....basically has an upper shield surrounding the rod just like a normal two eye shock absorber like you would use on the front of an A-arm car that keeps the rod and rod seal totally shielded from view and from water and dirt.

BUT....what they have done is to polished the outer surface of that upper rod shield and add its own set of bushing/bearings inside of the strut body and put the shield inside of the strut tube instead of outside of the body like you would on a normal two eye shock. They then gave it an outer surrounding oil seal that you can see.

What this does is it gives the strut rod....two extra guide points. The inner set of what they fall "linear bearings"....bushings.....and that outer perimeter seal around the fat shield welded to the strut rod.

What this does is it gives the strut rod four guide points instead of the original two guide points explained above....and makes it very rigid against side loading, wear and leakage.

Why did they do this? Because it's one of the only ways to make strut cartridges with HIGH PRESSURE gas that perform and last a long time and have less directional change in sporty driving.

Which brings me to my point......how did these perform on your type 4 car? These are B6 spec for sports car level driving.
I would think....speculate.... that they would be rough on a 411/412....basically out running the stock springs and hammering the ball joints as well.

Great technology though! And I have found several listing that list them for the 411/412.

I will post the cross section diagram of these I found later.

EDIT:

Here is a link to the PDF explaining the Bilstein inverted shock technology.

Here is a screen shot of what they are talking about if the link does not work for you.

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So looking at that diagram....I had part of it right and part of it wrong. The piston rod is actually bolted or welded to the outer tube....at the bottom of the tube. That fat upper shield...moves up and down so there are actually several points of lateral support. Great technology.

And, the bump stop is actually inside at the bottom. So it really is just a shock absorber suffed into a strut tube upside down.


Ray
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PostPosted: Wed Apr 10, 2024 8:24 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

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Y
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Yes as Ray has mentioned I welded a plate across the bottom section to strengthen it and allow for a good torque without collapsing (note I put it to tight and had to adjust the bag mount and shock bottom to work, don't do that)if I did it again I'd have made it a bit taller and allowed more room from the bottom of plate to the bolt hole.The top just mounts to the spring seat and bolts to frame just a couple holes drilled so nothing major that can't be undone.the hardest part of that was a custom angled washer to compensate for angle at one side of spring mount area and working through the tiny hole.I considered adding bigger access doors.You can also see where the air line goes in through here...

That's very interesting Ray I never really thought about the design much truthfully, I just said oh wow when I got it and made sure they worked and didn't consider much about why they where so different. Truthfully it wasn't the best ride up front but it wasn't horrible either and I was running them with e30 springs which did not give enough precoil? ( is that what it's called?)in my opinion and I thought it was more because of that. I have certainly cringed at the sound of my ball joints slamming in potholes but it wasn't too bad and it all bolted right up and got the nose down where I wanted it, and never really had many complaints the few years I drove it like that.
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PostPosted: Tue Apr 16, 2024 12:56 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

[quote="Jeremiah Berger"]
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Since I have no access to my car at the moment, do you have the diameter and wall thickness of the tube and the thickness of the plate?
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PostPosted: Sun Apr 28, 2024 7:26 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Thoughts on the deluxe cam kit vs. deluxe PLUS kit? Do you think I need the chromoly pushrods, vale retainers and rocker studs and hd springs? Or should I just go with the deluxe? I definitely want to maximize any quality parts possible but keeping it less complicated and as stock as possible.I was always under the impression that chromoly pushrods where louder and where overkill if you don't need them... seams like I should just go all the way though?
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PostPosted: Mon Apr 29, 2024 11:29 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
Thoughts on the deluxe cam kit vs. deluxe PLUS kit? Do you think I need the chromoly pushrods, vale retainers and rocker studs and hd springs? Or should I just go with the deluxe? I definitely want to maximize any quality parts possible but keeping it less complicated and as stock as possible.I was always under the impression that chromoly pushrods where louder and where overkill if you don't need them... seams like I should just go all the way though?


Sorry, meant to answer you the other day but after the storms, internet has been up and down.


Given.....you want to put these heads into the best condition as possible. the heads are both the strong and weak point of the type 4 engine. In a type 4 cCAR (not a bus) that was driven moderately....they can live a very long and strong life and during a high quality refurbishment they will need less than the same heads run in a bus.

First, in a perfect world if the engine was driven hard and poorly maintained and/or exhibits any signs of over heating.....you should replace the valve seatrs. Or if these are from a bus...change the valve seats.

The quick test for a 411/412/914 owner...strip all of the valves and springs out and place the heads in an oven on a cookie sheet at 400* F for about 45 minutes. Take the sheet pan out and lay it on something sturdy. The tile floor will do. Lift the head up about 6" with the chambers facing down and drop it on the pan. If any of the seats fall out or can be felt to be loose....you need new seats.

Check the valve guides carefully. If any are cracked on one end or they are worn....you need new guides. .do the rock test. A better way is to find a head shop that has the correct 3 point micrometers for measuring guide bores and have them checked.

Lets take these in order:

Chromoly pushrods: The key here first is getting correct geometry. I highly reccomend using Porshe swivel feet adjusters. And, when you do that and you are getting new valves....its highly possible that your stock aluminum pushrods will not ge able to give you great geometry without excessive shimminh of the rocker stands...which is to be avoided on a type 4...because this will affect the position of the spring clips that keep the floating pushrod tubes in place. And, with swivel feed adjusters there is limited room under the valve cover already.

In that case, when you find you need new pushrods...cut to nw proper length to maintain proper valve geometry without shimming rockers....the chromoly PR set will allow you to properly set up the geometry. They are also very good. Are the stock PR's less than teh chromoloy in quality? No. But if they are the wrong size after you get the heads done....you will have to order something.

My suggestion is to finish the heads first. Then contact someone like Type 4 store or Auto Atlanta and buy ONE adjuster first, buy or scavenge a stock aluminum pushrod (I probably have a spare if you need one)...and make an adjustable PR tool (or just buy one).
Set up your original cam in the case...just put cylinders and heads on it. N need for crank and pistons. You can use light springs from the ardware store.

Check your geometry with a stock Pushrod and the swivel foot with the stock aluminum pushrod. If its not good, use the adjustable one and find out the length you need. If you can do it with stock PR's maybe a single shim each of no greater than 0.015 to 0.020"...thats close enough. Just use the stock PR's. If its more than that...get the chromoly pushrods.

Valve retainers: Yes...the ones in the kit are made by Crower and they are excellent quality for the price. If you look at the stock ones with a lot of miles you will see quite a bit of wear. With high miles they can occasionally swage or pull through. If you are putting new springs and valves in, these are a cheap enough piece of insurance.

Springs: Yep...you should get new springs. Age and miles take a bit out of the stock springs over time. The ones in the kit are Crower and are very good springs.

Rocker studs: 50/50 on this one. I have more often than not found the need for new studs. Over a lot of miles...and probably more than one time or two taking the rocker shafts loose, the outer threads get a little rolled from the tension of cranking these back on. The issue manifests itself over high miles with one nut that occasionally gets loose mysteriously.
These are good quality studs in the kit.

Ray
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PostPosted: Mon Apr 29, 2024 12:52 pm    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Thanks for the reply. That all makes sense I will definitely do the valve seat test....The heads themselves are very great condition 70 k miles in a 412 wagon the engine is definitely been babied and the pistons did not have any skirt collapse or signs of overheating, but the exhaust valve guides do need replaced and the seat is a little tiny bit beat.I planned on new exhaust guides and Valve job and all new valves...bit o will definitely check the seats first...I will focus on the heads first, all very helpful.Thanks
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PostPosted: Tue Apr 30, 2024 11:35 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

I did the drop test on the valve seats today and everything went fine othere then the smell.of an overheating VW im my kitchen...its a good.thing i do allmost all the Cooking. They seem to be holding well for now

Kind of a rookie move for me like usual. I am always learning two steps behind and even though after diving deep into type 4 valve seats last night at this point I would have probably just said hell and bought new heads but unless I wanna send back the Neway cutters and the valves and guides and reamer I already bought ..and all the work I've already put into the heads...I think I'm just gonna hope for the best and honestly they are quite nice heads.

I went ahead and got the rocker studs out today... decided that it was worth the bundle considering the parts I definitely want so I'll probably just order the deluxe PLUS kit now and if I have some extra PRs in the end it's not the end of the world.

Here's the heads. I've got them all stripped and exhaust guides pulled...intake valves seats just had a tiny bit of pitting, went ahead and lapped them with one of the better old valves once to clean them up.cleaned up the ports and the chambers and pulled the exhaust studs to replace.
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PostPosted: Sat May 18, 2024 5:56 pm    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Well I could tell you a story you probably heard many times about a newb who thought he was gonna show the world and do his own vw head rebuild and know needs new heads..

But long story short is I cracked two of the guide bosses and snapped a guide off in the head and know I'm done trying to do stuff that a machine shop should be doing and am just gonna buy new heads.

That is easier said then done though. ... everything I'm reading is that the AMC are better then AA but the hardware is crap.But I see AA sells AMC heads with upgraded hardware.Does that mean they have the same low quality valve seats though? Would AMC heads with new springs retainers and valves but not seats be efficient for a stock build for a 412?Do I buy the AMC and strip the hardware and replace with quality?

Kinda back to the drawing board now so open to any suggestions. Thanks
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PostPosted: Sat May 18, 2024 7:45 pm    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
Well I could tell you a story you probably heard many times about a newb who thought he was gonna show the world and do his own vw head rebuild and know needs new heads..

But long story short is I cracked two of the guide bosses and snapped a guide off in the head and know I'm done trying to do stuff that a machine shop should be doing and am just gonna buy new heads.

That is easier said then done though. ... everything I'm reading is that the AMC are better then AA but the hardware is crap.But I see AA sells AMC heads with upgraded hardware.Does that mean they have the same low quality valve seats though? Would AMC heads with new springs retainers and valves but not seats be efficient for a stock build for a 412?Do I buy the AMC and strip the hardware and replace with quality?

Kinda back to the drawing board now so open to any suggestions. Thanks


Wait...post pics of your heads and the guides.

Guides on type 4 are critical. They should not have more than...and just going off memory here...so do not quote me. I have it written down.....but its no more than about 0.002" interference fit (actually probably less). The heads should only be about 225*-ish and the bores must be pre-measured and the guide OD must be set up to match the interference fit of the bore.

The problem with type 4 heads and guides is that zillions of heat cycles and expansion and contraction will compress the aluminum against the bronze many times causing it to work harden. So...you find that when you pull most high mileage guides out they seem to be loose with very little interference fit.

Thats because they are loose from the heat cycling. So when you buy standard first oversized guides from someone like AutoAtlanta (good source)....when you measure the actual bores....you usually find that the first oversize is not quitelarge enough. Not quite enough interference fit.

So if you can find them you go to 2nd oversize and they are too much.

Or...you find that the bores are not clean enough or havea burr and must be lapped or broached. Then you are now onto a completely different oversize.

I learned all of this from some very good head builders and a short conversation with Len at HAM Inc.
He was kind enough to tell me where he gets his valve guides and at what temp and interference fit to install them.

The guys at SI valves can get you exact sizes..anything you want...for about the same prices as stock. They make all of them on demand and stock many stock sizes as well.

If you are building a stock high compression 1.7L...you REALLY want 1.7L heads. That dimple on the edge of the quench area...is designed to match the domed pistons and makes a difference.

There are heads out there from good 1.7L 411, 412 and 914's that are worth rebuilding. As long as they are not from a bus.

Ray
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PostPosted: Sun May 19, 2024 3:34 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Well one of them went in perfect, but then the next seized up about 90%of the way and cracked the boss.just a tiny crack could have been repaired or run maybe.Decided to do the other head and it went horribly.I cracked the boss bad and literally shattered the guide into prices.After that I put them in the bin.I think my problem could have just been my setup and the time it took to pump my hand pump press the guide probably got hot and expanded. I did not have a mic small enough for measuring the tolerances either.So yeah they are gone I took them all the way to the dump in disgust and decided to stop trying to do things above my level.

So yeah I need new heads.
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PostPosted: Sun May 19, 2024 3:37 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

I was also currently planning on using flat top pistons as I could find no domed piston replacements anywhere...
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PostPosted: Sun May 19, 2024 6:37 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
I was also currently planning on using flat top pistons as I could find no domed piston replacements anywhere...


Eight sets available.

https://www.thesamba.com/vw/classifieds/detail.php?id=2029263

But....be careful and only buy a set with good pictures of the parts. Westcoast core has a spotty reputation.

Did you drill out the centers of the guides before pushing them out?
Also you have to ACCURATELY measure the guide bores before measuring the new guides to know if they will fit.
Sometimes, the old guide will leave a bore surface that is less than perfect so the bore needs to be lapped to be smooth or straight enough for a new guide.

Other times there is the mistake of trying to install a guide that is slightly too large. Just a little too much interference fit. It can take excessive pressure. Guide needs to be chilled and the heads heated just enough.

Anyway, if you are not going to use the stock 1.7L heads.....if you can even get new 1.7L heads....you will either need to get some domed pistons or possibly have your cylinders turned down (or both) to get useful compression....or maybe even have the head seating surface flycut.
I would bet that the combustion chambers are larger than you want.

If you are using D-jet, you do not want compression lower than factory. Very hard to tune and hot running.

I looked at AA's site.....they have 1.7L heads and they show the dimples are cast in like stock....but....they note that the heads have the two "smog pump" holes drilled in them. Junk.

Ask them two questions before you buy them:
1. What is the combustion chamber size
2. Can they make a set without smog holes.

https://aapistons.com/products/new-amc-1-7l-type-4-aircooled-cylinder-head

Ray
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PostPosted: Sun May 19, 2024 8:43 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

So why are the ones with smog ports junk? Just hard to properly seal the unneeded ports or does it affect the head in some other way? I don't see anyone selling anything but those same heads that aa has.

I realize I might run into cc size and compression issues but I'm not really sure where to start now. I thought I was gonna be close with the flat top pistons and the lack of the shim with the factory heads but now I'm not sure of anything.I guess getting heads and cc'ing them first then setting up deck height..I was trying to not have to get things machined because that is not easy to find here and the one qualified shop is so expensive.


Unfortunately I've already been down the route of buying non legit mahle.pistons and returning them and now have a set of AA flat tops.I can return them maybe, with 20%fee though ..

I'm getting pretty frustrated truthfully.Gonna give it some time to think about it all....
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PostPosted: Sun May 19, 2024 1:30 pm    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
So why are the ones with smog ports junk? Just hard to properly seal the unneeded ports or does it affect the head in some other way? I don't see anyone selling anything but those same heads that aa has.

I realize I might run into cc size and compression issues but I'm not really sure where to start now. I thought I was gonna be close with the flat top pistons and the lack of the shim with the factory heads but now I'm not sure of anything.I guess getting heads and cc'ing them first then setting up deck height..I was trying to not have to get things machined because that is not easy to find here and the one qualified shop is so expensive.


Unfortunately I've already been down the route of buying non legit mahle.pistons and returning them and now have a set of AA flat tops.I can return them maybe, with 20%fee though ..

I'm getting pretty frustrated truthfully.Gonna give it some time to think about it all....


The problem with flat tops....not a real problem but it is a minor issue.....is that if they are the original 411 pistons they "should" give about 7.8:1 compression. The dished pistons are known to provide 7.3:1.....flat tops are ~3.5ccs less deck than dished . Domes are ~3.5cc less deck than flat tops. It should be pretty linear.

Domes 8.2:1 . Dish 7.3:1.....so 0.9 compression increase across 7 cc....so 0.12857 compression increase per 1cc....so 0.450 compression increase from 7.3:1 to 7.75:1 going from dished to flat tops.

Typically deleting the head gasket and shim at the cylinder base gives about 0.2 up to ~0.3 compression increase. So you can get 8.05:1 easily with no machine work with flat tops.

Depending on what the actual deck is on these flat tops at TDC .....if it's anything like the domed and dished pistons ....it's at best about 0.065" and at worst about 0.079". If it's the lower deck....you could easily be at 8.1:1....probably good enough. I do not like D-jet below 8:1. It's a tuning problem in type 4 D-jet systems.

All of this is with about a 52cc combustion chamber on a stock 1.7. The range stated is from 51 to 53cc in most sources. So ask them the question.

Other options to normalize the compression would be to either flycut the heads to decrease the chamber....which starts beating on the quench pads and dimple pretty fast but without domes you don't need that dimple.

Or.....install a piston, measure the deck and calculate what you have to have lathed off the top opening.

Ok.....so.....I have a set of 1.7L head castings that are my spare set. I bought them 20 years ago. They are from a 411 or 412. They have no damage and no cracks and also no valves and no springs. The guides are intact and so are the seats. But....it's poor economy to NOT replace at least the seats on a type 4 head with unknown miles.

I could part with them for next to nothing....but you should have them properly rebuilt with NEW valves and seats. Ray
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PostPosted: Mon May 20, 2024 6:26 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Thanks Ray I appreciate that, maybe I will take you up on it but the problem is for me is finding a place to do that work.

Im also curious as to why the AMC heads are not a good option with the dual smog ports.That seams to be all that is available and by the look of it is the same casting that LN uses to build their heads, obviously they put new seats and everything in them.Others builders on forum have told me that they use AMC heads with not replacing seat but all hardware with no problems..At this point I would definitely just pay for the new heads.

Although Im worried those heads would get me even lower compression since they are designed to compensate for not running the shim right?

I found this single OEM new head on eBay but it's only one. Maybe a miracle will happen and I can find another one!

https://www.ebay.com/itm/25420111302
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Jeremiah Berger
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Jeremiah Berger is offline 

PostPosted: Mon May 20, 2024 10:37 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Edit*I did confirm the AMC heads are 55cc

Another thing I am considering is I can set up my p&C's and find out my deck height first and wether I'm using domed or flat tops can get the heads cc for another $80 to exactly what I need.And considering most of my options include fly cutting to get the right compression I'll probably just use my flat tops I have.

I did message about the dome tops for more pictures but in the one pic on there I swear it looks like a dish not dome ...
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raygreenwood
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PostPosted: Mon May 20, 2024 11:11 am    Post subject: Re: Jeremiah's 73 412 restoration project Reply with quote

Jeremiah Berger wrote:
Another thing I am considering is I can set up my p&C's and find out my deck height first and wether I'm using domed or flat tops can get the heads cc for another $80 to exactly what I need.And considering most of my options include fly cutting to get the right compression I'll probably just use my flat tops I have.

I did message about the dome tops for more pictures but in the one pic on there I swear it looks like a dish not dome ...


Nope...thety are definately domed pistons. They are the correct part #.

The machioned or cast in "step" in the new 1.7L heads...or any new type 4 heads...I consider to be a screw up. While they pretty much mimic the original head gasket thickness....I think it was about .025" to 0.028" after gasket crush...its mainly a bus thing.

In fact, making all of these 1.7L heads with both the step and the air injection ports is strictly a "California" bus mentality thing.

The air injection ports are not really a big problem. Its a 10mm hole into tehexhaust port. You needto plug it with a 10mm threaded plug, locktight it and then carefully grind the inside so that none of the bolt is protruding into the exhaust port...because if it does it gets red hot and can cause combustion in the ports on rich overrun which eventually causes exhaust gaskets to leak and shortens the life of the muffler...been there and done that.

Then stake the outside thread so that these plugs do not back out.

I also suspect this hole weakens the head and may promote cracks in the ports but I think you will be fine.

From your last post....I agree with the fear issue. Its hard enough finding a really GOOD head shop....but twice as hard to find one that actually has type 4 experience. Type 1 head shops....not interested.
Too many supposed type 1 experts I see in these forums (and they are experts on type 1 and aftermarket)....but the numbers they quote for valve seat and guide intereference fit...for type 4...are flat out wrong and WILL f*ck up a type 4 head in the long run.

What they fail to understand is that type 4 engines are minimum 125,000 mile engines....not crappy type 1's that everyone is happy with if they go 50k and they slam on another cheap set of Chinese heads for a fraction of what ours cost...and motor away.

I know of a world class shop that has done several sets of heads for me. They have everything. Flow benches, huge machine shop, diamond hones for valve guides, annealing ovens for reconditioning heat cycled aluminum...and above all experience with everything under the sun from NASCAR and drag boats down through Porsche and VW.

The most important thing is that when you speak to them you need to bring exact measurements and requests for what you want done. You tell them what to do and they can do it.

If you bring in all of the parts and specs....you re looking at about $800-900 for a total rebuild of the heads ...including annealing to cut for new seats, three angle valve job, flycut and guide install and hone to fit.

There are other shops around the country just like this.

But that only really works well if you can see them in person over the counter and communicate what you need. Its not really a mail order process.

I think you will be fine with the AA heads...but you should proceed like this:

1. Install one of your pistons in your cylinder on the case. Check the deck height at TDC.

2. Make a cheat sheet with calculated compression using that deck height and piston diameter for 50cc, 51cc, 52cc, 53cc and 54cc combustion chamber volumes. You will not have to worry about calculating in the gasket height because a. you are not using one and b. its built into these new heads as a "step".

3. Decide what you can live with for compression. Personally....I would not try to build a D-jet injected type 4 engine that is LESS than the stock 8.2:1 compression. More ...up to a point is good. Less...sucks.

4. Tell the guys at AA what CC's your heads will require to get you what you need.

If you split the difference and tell them a chamber volume that calculates out to 8.3:1....have them flycut your heads.
Most likely they will cut away that stupid step along with about an extra 0.010".

My worry is that about half of the shops I have run into over the years whodo not have experience with the kind of complex shape of 1.7L type 4 heads...just guestimate and chop it....and next thing you know you have 49cc chambers that you cannot work with or worse....they cut so deep you are sitting on the top fin of the cylinder.

Or you can do like I did...and with some cheap plastic and a little double stick tape, you can make a mock up plate that mimics the combustion chamber and quench area shape...throw in a used stock head gasket to mimic the step....and CC your old heads. Each layer of plastic film I put over the comnustion chamber shape and re-cc....is about 0.010".

First CC with the shim. Then CC without the shim which mimics flycutting out the step. Then add a layer of plastic film and re-cc. I just use a decent 50cc syringe. You will within 0.5ml to a burette.

So you can get damn close...and be able to tell AA how many thousandths you want flycut out.

I will post a picture later of the plastic testing disc. Easy to make.


The other problem is that no...you cannot just easily flycut the heads enough to straighten out the compression difference between domes and flat tops.
The loss of 3.5cc going from domes to flat tops has to come from somewhere. Thats a lot.

Many people have had this same problem. There is just not enough chamber material to remove in 1.7L heads to get enough to make up for "dished" pistons. Nowhere near enough. You might get lucky and have enough material to remove to set up flat tops....but I am betting not.

This is why the domed pistons are sought after by those building 1.7's for 412 adn 914 cars...because there is just no good answer in head work to fix the compression issue.

You either have to flycut enough to remove 3.5cc from the combustion chamber...which probably cannot be done without cutting too deep. The 1.7L chambers are really small to start with. Its mostly quench area already.
The 1.8L heads are almost as bad.

Or....you will need to remove a little from the chambers...and as much as possible from the deck...by having the cylinders turned down in a lathe.
I will lay money on it that your deck with these pistons will be right around 0.070".

Thats huge. And...you might be able to get all you need for compression simply by leaving the heads alone and use them as they are...just have them shave the step off of them and nothing more.....because...an 0.070 inch deck on 90mm pistons = 11.3cc's.

Going down to best minimum deck of 0.040" can subtract 6.39cc;s from the deck.

Ray
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