Air-cooled newbie looking for advice on Type 4 rebuild

[sunny74]

Hey there everyone, My name is Tyler. Last fall I picked up a 74 Bus from ND and brought it to my home in WI.

I'll try and be brief.

I recently got the engine running after getting some fuel delivery issues sorted out. I replaced the mech. fuel pump, all fuel lines and rebuilt the PDSIT 32-34 carbs and refreshed the supporting components. After all that the bus ran for the first time in what I understand is over 15 years. After getting it running I wanted to drive it the following day and when I went to do so the engine would not start. I isolated this to crud in the fuel tank blocking the supply line. To get this ironed out the tank needs to come out and be cleaned out.

With all that I decided I would drop the engine and and trans, pull the tank and clean it, clean up the engine bay and most importantly decide what I want to do with the engine....Which is why I am here.

The engine has 112k on it and I am fairly certain it is original and unmolested.

I am looking for guidance and advice on where I should go with the engine rebuild and how deep I should get into it. My overall goal for the bus is a reliable, fun weekend cruiser. I would prefer reliability to speed but would not turn down the idea of some improved performance over stock.

Does my engine require a full rebuild or top end refresh? I'm not on a budget but I would like to spare some expense when possible. I have no time constraints.

Should I attempt this rebuild myself?

Are there any highly recommended must do items when rebuilding a Type 4 engine?

I have been closely reviewing Clatter's "cheap junk" build thread as well as the Tom Wilson "How to rebuild your VW Air-Cooled engine" book.

As for my experience level....about 10 years ago I rebuilt a 67 Triumph Tiger cycle engine, more recently I did a mild performance rebuild on a 5.7L Small Block Chevy engine both of them ran well when I sold the projects off. Also, I spent 15 years in the VW service industry where I worked on and around service and repair every day. I was a parts dept manager for most of that time. Currently I am a MFG. Engineer where I build automated machinery for production using a manual mill and lathe. That said, I am new to air-cooled VW engine building, I do have some experience but I would consider myself very much a novice with the capacity, aptitude and ability to figure shit out when I get down to it...resourcefullness maybe...if that's a word?

Here are some pics to get the conversation going:

[sawed off]

You have it out and it has over 100000 miles on it. I would pull it completely down and rebuild the engine. Check or change the clutch, service trans, replace fuel lines, brake lines, check brakes and front end. Maybe new tires.

[bugguy1967]

Yes, do it yourself. As long as you take your time and ask us plenty of questions, you'll be fine.

At the very least, you should check your crankshaft endfloat, check your oil, and maybe even send a sample for analysis (very cheap), good valve job, and replace your piston/cylinder assembly. I wouldn't do the top end until I found out the condition of the bearings, which the oil analysis will tell you. Once you crack open the crankcase, Ray Greenwood can help with the particulars. He's more versed on what needs to be done on the insides of Type 4s.

Here's a good thread on a very stout, low revving engine that makes a ton of low-end torque: https://www.thesamba.com/vw/forum/viewtopic.php?t=...db5f2b91a7

[timvw7476]

some say: 'it's out, rebuild it"
it's actually a pretty fast bus compared to later 2.0Ls.
Best thing to do is plug the old welch plugs with threaded plugs,
they are a known failure point. Check the clutch disc wear/replace
if needed. These are easy to do now that it's out.
Do those two things, bolt it back in & enjoy.

[theKbStockpiler]

If the oil pressure and compression is good leave it alone.
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[Danwvw]

A Type 4 engine is a bit of a challenge if you have never rebuilt VW or Porsche Air Cooled engines before. Shops don't always know all the details it takes to get one right so it will go another 100K and the Type 4 will easily.
Maybe first just clean it up and get it back in the bus and drive it to find how well off it is. It's got to be needing a Rebuild by now though. I think though some do run well over 150K miles. Probably needs a clutch and main seal. Probably the 1974 1.8 Liter engine! Be prepared to buy two of these Heads if you rebuild it.
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[nsracing]

I would advice against a complete rebuild. I will only do that if I suspect something is pretty chewed inside.

Type IV engines are pretty tough. If the camshaft checks out and lifters look good, I will not teardown the block. If the flywheel seal is not leaking, leave it alone.

But, I will recommend a topend rebuild....or refresh if I were you. Pull the heads off and have them cleaned, inspect the guides and valves and seats. More than likely, the guides will be worn ...esp the exhaust guides. You need to find someone who can refresh these heads without cracking the guide bosses.

The exhaust studs sometimes get really chewed from service. You may need to find better heads if yours do not check out.

Also, pull the cylinders and install new rings, if the cylinders are not too worn. Refresh the surfaces on the cylinders -just bottle brush finish. I do not recommend using de-glazing tool. The bottl brush carbide tool is best for refreshing the cylinders.

Install new O-rings on the pushrod tubes. It is not as simple as it sounds but you can do it. I have done many top-end only on Type IVs when I worked at a shop and they lasted years before we saw the van again.

And the cost is minimal but with a lot of return - provided the camshaft is good in the case. Pull the lifters out and see. Post pics here of the lifters. We can go from there.

Install a new clutch if you like. New throw-out bearing. new pilot bearing.

Hope this helps.

[sunny74]

My initial thought for the engine was a top end rebuild and possibly a pair of upgraded heads or to have the stock heads checked, ported and rebuilt. With the cost involved in rebuilding it seems I'd be 75% of the way to upgraded heads. I may just spare the stock heads. I guess we'll let my inspection make that determination.

Based on the feedback received and my feeling that the engine is pretty sound minus some common leaks around the cylinder jugs I will open it up to check the lifters and camshaft. Provided all is good there I will stick to the top end rebuild as "nsracing" advised.

With the help of you all, I have full confidence in my ability to refresh the cylinders, re-ring the pistons, re-seal the push rod tubes, replace the clutch, replace the heads etc.

Over the next few days I'll get into some light tear down and inspection of the camshaft and lifters.

What are the preferred replacement heads for this engine? I know there are quite a few options out there. Are the AMC heads any good?https://aapistons.com/collections/cylinder-heads-c...inder-head

The trans will be coming out and I will service it. I also have a back up 3-rib that was given to me in a pile of parts from a friend. I may as well service that one right away too.

[raygreenwood]

NEVER reuse ANY of the stock type 4 cams.

They are all suspect....at anything over about 70k miles. The lifespan even witj perfect care....because of its unique wear pattern....is never safe over 100k. Leaving it in ....if its still acceptable.....would simply net you another 25k of life along with all of the brand new parts.

Its likely a 1.8L as mentioned....if its the stock engine. The 1.8L with twin carbs was a great running reliable engine.

Also.....do not just do a top end rebuild. As mentioned....you MUST replace cam and lifters as a set. If you have the case open......its ideal to check and inspect the main bearings.

With the type 4 main bearing fit and sizing issues these days....if your main bearings are origibal with just minor and normal wear.....simply have the crank polished and reuse them. In well cared for stock vehciles with good oil change habits.....the stock main bearings can run 200+ K miles.

If the main bearings are worn out....but the case is round and still standard....leave it that way...DO NOT arbitrarily align bore a type 4 engine. If the main journals of the crank are in good shape....and standard....just have them polished andcput in a standard/standard main bearing set.

Same for rod journals. In fact you are likely to find most of your wear in the rod journals and not the mains on a type 4.

Since you need to have your rods completely rebuilt...always......thats check, straighten, re-size, new bushings and balanced.....if need be you can have only your rod journals regriund to .010" undersize.
Its far easier to find good rod bearings right now than perfect main bearings.

Get a webcam and web lifters. There are several grinds almost identical to stock. Mic out and lap your stock oil pump and reuse it.

Probably from what I hear.....right now a new set of AA pistons and cylinders are your best bet for quality and price....but you will have to spend the time to go through them and measure....and ask Modok or others what rings are working best with those these days

For heads....do not screw around. There are only about three shops in the US that consistently do type 4 heads right and have heavy type 4 experience.

Can you reuse your head castings?....sure....but its almost as expensive to do them right than to get new ones that are done right.

You need to have them crack tested...especially in the exhaust ports. You need need valve seats with .006" interference fit. New guides and a slight flycut to clean up the seats. The better shops use quality valves. If that is in question....just buy the valves and supply them for your build.
Manley makes a perfect set for the 914 Porsche . Your 1.8L valves should be 41mm x 34mm. Manley makes a set that have the correct stem length and diameter but are 42mm x 36mm.....which is close enough and makes only a small tuning change on the 1.8L w8th carbs. Runs great. They are a standard catalog part in Manleys catalog and are superb material.

Buy new valve springs from type 4 store or AC.net ....and if you have these heads rebuilt at Headflow masters, fat performance, European motorworks or HAM inc. (New heads only).... you will get the same quality springs.

First you need to carefully tear it down and measure a few things....the main bores and crank....and check the flatness of the cylinder seating areas to see if the case needs to be decked.

Tear down carefully as you kay be reusing main bearings....but never cam or rod bearings.

Also do not be sloppy with the old cylinders or pistons. They were superb quality. If they are in shapemm..check 5hem and measure them. They are worth saging for spares for a spare engine build.

Always replace ALL the galley plugs with threaded ones. I am slowly building a 1.8L as we speak. I should have and update this week. The rods are going to the shop for rebuild tomorrow. I should have it mocked up out to the heads this week....then just waiting on heads.

https://www.thesamba.com/vw/forum/viewtopic.php?t=693726
Ray

[nsracing]

0.006" interference on the valve seats is laughable. Have you ever installed them that loose and they stayed, Ray?

I called Roger Crawford many years ago when I was rebuilding many Type IV heads about that amount of interference and he laughed so hard. He recommended a number on the proper interference on the seats what they use in their off-road vehicles and it is NOT that.

Also, to the OP -if you are going to do all that upgrade on the motor might as well get another longblock to experiment on. Pulling all the plugs and tapping them is not for the beginner. Another, most people will screw up the tiny 6mm stud by the center cam if you don't pay attention. Take baby steps. A topend job is well within your ability w/ minimal guidance. Get that done first and then tear into the whole thing when you find more confidence. Preferably on another motor you don't need right away. Then you can take your time w/ it, tap every hole if you like.

But what I forgot to say was to check the rod bearings. You can change them easily while the shortblock is together.

A good future project for you is a 2.0Liter Porsche 914 engine -one w/ pan windage tray and steel flywheel. Porsche will have the steel flywheels. VW bus will have the cast iron flywheel.

Just pull the heads and cylinders/pistons for now and you can see what the
cam lobes look like. Then you will know how to proceed.

enjoy.

[modok]

I sure have. No problems.

.006-.008" interference is good
You can run more press with soft steel valve seats going into rough bores, but nobody does that since "many years ago"

[raygreenwood]

[nextgen]

Hi Sunny, welcome to the T-4 world, your Bus is a the perfect example why T-4 engine in the much lighter bugs last ( almost ) forever. As for your engine at first as with some of the other guys I was thinking run it to do a compression test. But as Ray said the Freaking Cam, is the Achilles Heel of the T-4. Like if your water cooled car need a the timing belt, the mechanic will say spend the extra bucks for a water pump, they are cheap and if it goes, you will be doing the expensive timing belt removal again.

BTY Ray, what you did not mention upgrading cam also makes a major improvement in performance. If it is a 1700 great I like those heads best for a bus, I feel they are the strongest of the T-4 heads. Not the best flowing but in a bus I look for a head that can take a beating.

Which leads to the subject of piston size. Is it a good idea to go to 2.0 with the 1.7 heads??? My opinion if you do not go for the stock 71 mm rods and Crank of a 2.0 for more torque stick with the 1.7. I guess that can be debated.

There are guys on this NG that have amazing Air-cooled knowledge, but very few have much T-4 experience. I say 90 % of a T-1 is like a T-4, it is that extra 10% that will kill you.

Ray is the most experienced on T-4, but take what you can from everyone. Keep an open mind debating is a great learning tool !!!!
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[sunny74]

So much great information coming in on this. I really appreciate it and please keep it coming. As I said, I am not in a hurry. There is plenty for me to do on this project to keep me occupied while I decide what to do with the engine. I am trying to acquire a VW engine stand from the service department I used to work in.

I am not scared of a complete tear down and rebuild. I just wanted to know how necessary it was for what I want to get out of the bus. The advice and perspective about the camshaft and it’s lack of durability worry me enough that a full rebuild might happen regardless of the compression or condition of cam and lifters. Again, I value all the feedback given here I even appreciate the debate.

Mofoco seems to get a mixed review on here but they are local to me and have more experience than any other machine shop near me on VW’s. I will likely commission their help on some of the machine work.

Any thoughts on the AMC heads mentioned earlier?

BTW it is a 1.8 for those that questioned.

Also, it almost looks as if the cylinder heads were sandblasted at some point. Is it possible that this engine was rebuild already at an earlier time? Any surefire way that I can tell?

[[email protected]]

Rebuilding a running engine is a LOT cheaper and easier than one which has blown up.
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[nextgen]

Ha, that is why I like John from Air-cooled. He don't talk much but when he does, his one liners says what I try to say in Paragraph.
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[raygreenwood]

First an apology to nsracing....I was not trying to be snarky in that last post.

The issues with interference fit and some other small but significant issues when rebuilding type 4 heads is WHY there are so few head re-builders in the country that are trusted by the type 4 community to do correct work....because of experiences over the years.

You can have an absolute head expert...with 40 years of type 1 head experience that can absolutely ruin a set of type 4 heads due to some very small items that are only found on type 4 heads.

The Example:
I am looking for the correct photograph posted years ago on the STF...I think by Piledriver(?)...so if any know the picture...please post it for me.

But...it was a cross section of several type 4 heads across the intake port...on a vertical band saw. It was primarily concerned with looking at intake port entry angles between 1.7L, 1.8L and Porsche 914 2.0L heads.

Along with that set of pictures was one sawn across the exhaust port....which shows a very important spot to pay attention to. Right below the seat...on one side of the exhaust port in which one of the exhaust manifold studs is threaded into.....is a VERY thin spot....maybe 8mm thick at most.

Many many type 4 heads have been destroyed...by either porting on the wide curve side in the exhaust port....which does one of two things....it either removes enough cross section material that you break into the thread bore for the exhaust stud....head is now junk......or more commonly...you take aw away too much cooling mass behind that edge of the valve seat...and you get a very short lifespan in which the valve seat literally recedes at an angle while it mushes this thin area down.

But...the key point here....is that I have seen MANY type 4 heads ruined...in this exact area by head "experts" not knowledgeable about this thin area.....using EXCESSIVE....interference fit.

Even when using heated heads and chilled seats.... having .007"-.008" of interference fit will require using a LOT of press force and or some hammering....which can easily crack that thin ledge....destroying the head. .....and I have seen waaaay too many heads destroyed this way.

Type 4 heads have their own issues. Some of the middle years original 411 and 914 1.7L heads had a year and a half of defective intake valves...stretchy stems. Its been so many decades virtually none of those are on the road.

Then you have a pretty much "bus only" issue...of readily dropping valve seats...especially on the 1974 and up 1.8L heads.....wherein it is easily found if you have ever had an NOS 1.8L head in your hands....and had teh seats pulled out too set up for larger valves....that the factory was a little limp wristed on the interference fit.

And it can be hard to tell exavct interference fit after the fact...but the skilled head people I had pulling these few NOS 1.7L and 1.8L head seats out years ago...noted that it appeared to be right at .003" to .004"...which is fairly weak.

Having only .003"-.004" of interference fit on valve seats was actually not a problem on a LIGHT vehicle like a 411/412/914/912 with a type 4...because they are lightly loaded, had better gears and rarely overheated.....tossing a valve seat was REALLY rare on those vehicles.

Experience has shown that an absolute bare minimum of .005" and right at .006" is excellent on type 4 heads and keeps teh pounding or press pressure to an absolute minimum.

Ray

[Clatter]

Just take it apart and see what it needs.
You're already most of the way there.

Inspection will show what you have to do.

It's not rocket surgery.
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[Wreck]

This is a link to a thread with the photo Ray is writing about http://www.shoptalkforums.com/viewtopic.php?f=1&t=72300&p=492496#p492496

It is the short side Ray that is the issue , also Fly cutting heads for compression is also very limited . The head specialist I use has vast experience with Type 4 heads from the days when type 4's were widely used in dirt oval racing in Australia ,google Peter Gumley Australian Hill Climb . his heads were done by the same person . He uses .011 crush , he doesn't use force , heads get heated in an oven and the seat get cooled in liquid nitrogen .

As to the question in hand , It all depends on the budget and what you want the bus to do . If you just want stock power and don't use the bus as an every day driver I'd be inclined do a compression test check the end float ,even go so far as to remove a valve spring and check valve guide wear . if all good then just run it .
Type 4's are expensive to rebuild mainly because of the heads . AMC make new complete heads that are over twice the price of type 1 heads . there is a lot of information on SSHulks type4 build thread .

[raygreenwood]