TheSamba.com :: View topic - Post-Mortem of a 1904: Need some input

Fri Jan 08, 2021 2:37 pm

Thanks for the input, guys. And hi, Brian. We PM’d a few times over the summer about heads for this motor.

I don’t mind using a shim but that would make my deck height .066 or so all around which is way higher than I’d like.

I have another set of p/c’s I can try in order to see if piston height or the cylinders are the issue before tearing it down further. I can also bring these cylinders and rods to a shop for measuring. Otherwise, I’m happy to keep tearing down and measuring as I’m learning quite a bit and have a number of measuring tools and etc.

What would be the best course of action here?

Fri Jan 08, 2021 3:03 pm

Put the cylinders in each side with a straight edge across the top. There should be no rocking. If the machining was .010 off side to side, it might be off cylinder to cylinder also.

What are you running now for spacers?

Were the cylinders trimmed already?

Sorry, I didn't reread the whole thread.

Brian

Fri Jan 08, 2021 3:18 pm

I think the builder has used "B" pistons in this build. Otherwise it does not make sense that the case is decked (which is good imho) and then the cylinders needed to be trimmed. My guess is that the engine is very narrow. The B pistons are not bad as such, it just gives you un nessessary costs on a low reving mild stroke.
As for the difference in deck. First, check that all cylinders are the same height from surface to surface. If yes, the issue is most likely in the machining of the case. It - can - of course also be a lucky strike that the pistons and rods have been mixred so it ends up like that, but I doubt it. I am leaning more towards that the case have been Hungerhoned in its previus life. That does put the crank about 0,08 to 0,010" offset.

It is ALWAYS a b**** to come as nr 2 or even 3 and have to fix other people´s goof ups. No matter what you do you will end up buying a good deal of parts to make that engine good. I had one just before Christmas. Decent engine on paper, thrown together with a shovel. Ends up costing him 3000 bucks to get back to where he originally wanted to be.

Fri Jan 08, 2021 4:23 pm

Brian_e wrote: What are you running now for spacers?

No spacers at all right now.

Brian_e wrote: Were the cylinders trimmed already?

Yes, but I don’t know by how much.

Alstrup wrote: I think the builder has used "B" pistons in this build. Otherwise it does not make sense that the case is decked (which is good imho) and then the cylinders needed to be trimmed. My guess is that the engine is very narrow. The B pistons are not bad as such, it just gives you un nessessary costs on a low reving mild stroke.

He did use B pistons. When I sent all my parts to the builder way back when, I sent A pistons but he didn’t like how much positive deck it gave and how many shims he’d have to use. I still have those A pistons in a closet somewhere and can also try the p/c set to see if there’s any difference.

Alstrup wrote: As for the difference in deck. First, check that all cylinders are the same height from surface to surface. If yes, the issue is most likely in the machining of the case. It - can - of course also be a lucky strike that the pistons and rods have been mixred so it ends up like that, but I doubt it.

I can do this check tomorrow as you and Brian have suggested.

Alstrup wrote: I am leaning more towards that the case have been Hungerhoned in its previus life. That does put the crank about 0,08 to 0,010" offset.

I bought this as a new case and the motor has less than 4K miles on it. I sold the car it was in and now am trying to make the motor more appropriate for my 1970 Riviera. I don’t know if this starting life as a new case and having so few miles on it suggests another reason why the deck is off or not.

Fri Jan 08, 2021 4:40 pm

OK.
Well, opinions vary, but dependant on how much the case was decked and the actual brand of pistons and cylinders you would have to have barrel shims about 2,2 mm thick plus what the case is trimmed, say 1,25 mm, = approx 3,3 - 3,4 mm. So what. Shims can be bought large and then precission grind them down to the desired height. If there is a height difference side to side you can compensate in the shims. No problem.
That said, there are advantages with pistons that have low pin height apart from the engine width, but on a relatively low reving engine the functional advantages are really minor.

Fri Jan 08, 2021 4:58 pm

Alstrup wrote: OK.
Well, opinions vary, but dependant on how much the case was decked and the actual brand of pistons and cylinders you would have to have barrel shims about 2,2 mm thick plus what the case is trimmed, say 1,25 mm, = approx 3,3 - 3,4 mm. So what. Shims can be bought large and then precission grind them down to the desired height. If there is a height difference side to side you can compensate in the shims. No problem.
That said, there are advantages with pistons that have low pin height apart from the engine width, but on a relatively low reving engine the functional advantages are really minor.

The pistons and cylinders I just took off the motor were Mahle B’s.

In the builder’s words, the AA 90.5 A piston and cylinder set I originally sent him was going to require “approximately a .200 barrel spacer” and he sent the pic below as one of the reasons not to go ahead with the A pistons. It was 8 years ago and I didn’t think to question it....

Fri Jan 08, 2021 5:03 pm

Brian_e wrote: sled wrote: how much can/do rod lengths and piston pin heights vary? (I don't mean that argumentatively, genuinely curious)

CB rods +/-.0010
AA rods +/-.0025
stock rebuilt +/-.015" I have had some really bad rebuilt rods.

Pin heights are usually all within .0020".

My guess is your case was machined .010 different side to side. Easy to do if they used one of those drill press boring "tools".

Brian

Mine are rebuilt stock rods from DPR circa 2012.

Fri Jan 08, 2021 5:30 pm

That looks more like the need for about 0,150" but that´s splitting hairs. I suspect it because he set it up with a "healthy" deck height.

But keep taking it apart so you know EXACTLY what you have. Then it is much easier to get it right the next time.

Fri Jan 08, 2021 5:56 pm

If the pin bushings are bored to size, then the length can be made all the same. That is how vw did it.
The pin bushing bore itself might be +/- .003 off the nominal length.
So if you replace the bushing and HONE it to size, the length will vary. If the big ends are re-sized the length varies even more. It could be up to .015 difference depending on luck.

I do not think DPR bores the bushings.
He's a crank specialist, maybe not a rod miracle worker.
Not criticizing, just saying how it is, and it's probably what people want.
If they want blueprinted rods they buy new ones because it's a better deal.

Sat Jan 09, 2021 4:36 pm

Well, I put the cylinders in on both sides and laid a straight edge over them and got no rocking so they’re even on each side.

I also measured from the case to the end of each cylinder and got the same length end-to-end on all 4 of them.Admittedly, it was just a basic ruler and not a precision instrument and the cylinders aren’t torqued down but don’t both of my results suggests that the deck surface and cylinder height are not the issue here?

What’s the next measuring move I can make? Total piston height? Pull the rods and bring them to a shop for measuring the total length of the rod? Any rod measurements I can do at home?

Sat Jan 09, 2021 4:47 pm

yeah you can measure rod length with calipers. Measure from hole to hole then add half the size of each hole. (measurement+ approx 1.571)
What is the issue? It's been a long time I can't recall.

Sat Jan 09, 2021 4:56 pm

modok wrote: yeah you can measure rod length with calipers. Measure from hole to hole then add half the size of each hole. (measurement+ approx 1.571)
What is the issue? It's been a long time I can't recall.

Yeah, I didn’t touch the motor except to move it around since the end of June so it has been a while.

The issue is that when I checked deck height in preparation for ordering new heads, I found that the height is .066 on the 1/2 side and .055 on the 3/4 side. I’m trying to figure out the reason and then try to fix it if I can or if it requires machining, I’ll send it to a person or shop who can do it.

Sat Jan 09, 2021 5:11 pm

Next step I would do is measure the chamber volumes. See if they were machined different to compensate for the mismatched deck machining.

If they are the same, I would take the cylinders with more deck, and have the bases machined again. Have them cut .010" off only those two. This will make all decks pretty close, and the compression from side to side really close.

Are you planing new heads anyways?

If so, have ALL the cylinders trimmed so they will be close to .045" deck and then have the new heads built to match the compression you are wanting.

Only bummer is next time you need cylinders, they will need to be machined. The other option is to tear the whole thing apart and have the case decked again, hopefully to the correct height, and both sides matching.

Brian

Sat Jan 09, 2021 6:16 pm

Brian_e wrote: Next step I would do is measure the chamber volumes. See if they were machined different to compensate for the mismatched deck machining.

If they are the same, I would take the cylinders with more deck, and have the bases machined again. Have them cut .010" off only those two. This will make all decks pretty close, and the compression from side to side really close.

Are you planing new heads anyways?

If so, have ALL the cylinders trimmed so they will be close to .045" deck and then have the new heads built to match the compression you are wanting.

Only bummer is next time you need cylinders, they will need to be machined. The other option is to tear the whole thing apart and have the case decked again, hopefully to the correct height, and both sides matching.

Brian

Yeah, this whole thing started with wanting new heads and I’m still headed in that direction. Maybe a cam (which is why I’m not that worried about splitting the case or anything) and that’s about it.

I’ll check chamber volumes tomorrow. In looking back through build pics and invoices I see I was charged for cc’ing one chamber so I’m not optimistic that each one was matched to its corresponding cylinder.

Overall, given the level of detail, documentation, and attention to this build, I’m kinda baffled as to why this deck height issue went unaddressed.

It’d definitely be easier to get the cylinders trimmed, but I see what you mean about having to get new ones trimmed next time I have to do something to this motor. Are there still shops that deck cases the right way? That might be a controversial question so if anyone wants to say who to go to via PM I’m okay with that.

In any event, I’ll cc the heads tomorrow and post the results.

Sat Jan 09, 2021 6:24 pm

the simple thing to do is put .010 shims on one side, or just leave it alone. But I assume you are frustrated with halfassery at this point.

It's a shame to be be re-machining the case AND honing and replacing the rings just for the sake of .010" or .015" but by traditional wisdom that's what should be done.
If the rings are broken in, you should not make the piston run higher in the cylinder than it did before.
On the plus side done right, you will know the case is right, and have better ring seal than new cylinders.

Dial calipers are adequate to check the rod length and pin height, AND the cylinder length.
but checking the case is going to require at least some combination of things you probably don't have. I've tried all kinds of ways, does not seem to be an easy way.

Sat Jan 09, 2021 6:57 pm

modok wrote: the simple thing to do is put .010 shims on one side, or just leave it alone. But I assume you are frustrated with halfassery at this point.

It's a shame to be be re-machining the case AND honing and replacing the rings just for the sake of .010" or .015" but by traditional wisdom that's what should be done.
If the rings are broken in, you should not make the piston run higher in the cylinder than it did before.
On the plus side done right, you will know the case is right, and have better ring seal than new cylinders.

Dial calipers are adequate to check the rod length and pin height, but checking the case is going to require at least some combination of things you probably don't have. I've tried all kinds of ways, does not seem to be an easy way.

Yeah, the rings are broken in. Mahle 1st and 3rd rings and Total Seal 2nd rings.

I could do a .010 ring on one side which would bring the deck height all around to about .065 and that’s big, no? Per the CB engine calculator, I’d need combustion chambers of 53cc’s.

Though according to that calculator, if I had .050 deck height, I’d need 55cc chambers to get my desired compression ratio of 8.5 which begs the question (for me anyway) of does a larger deck matter all that much if desired CR can be achieved by taking 2 cc’s out of the chamber?

Sat Jan 09, 2021 7:12 pm

Asking about deck height gets some people pretty heated for some reason.

Anything more than .055 is no go IMO. The .065-.085 is a definite no go. More than .085 and you start to go into semi-hemi, and that can work ok too.

If you are setting deck height, might as well actually set it. .045 is a good target. Anything less than .040 gets a bit sketchy, unless your parts and measurements are very precise.

Sat Jan 09, 2021 8:51 pm

Pruneman99 wrote: Asking about deck height gets some people pretty heated for some reason.

Anything more than .055 is no go IMO. The .065-.085 is a definite no go. More than .085 and you start to go into semi-hemi, and that can work ok too.

If you are setting deck height, might as well actually set it. .045 is a good target. Anything less than .040 gets a bit sketchy, unless your parts and measurements are very precise.

Hmmm.....so at .065 I’m definitely in that no-go range.

Would there be anything to be learned by mocking up this short block up a little further using the A p/c’s that gave positive deck and which the builder didn’t want to go with? It’d require shims but are shims an all out fail or just something that conscientious machinists think of as making up for machining failures?

Sat Jan 09, 2021 8:57 pm

Realizing I should have never even opened my mouth, because this darn engine is like a combination of all the things that DON'T work for me.

I don't use china heads, and I don't make ports bigger than the valves can flow, don't use engle 110 cams, don't use gapless second seal rings, I don't make rods different lengths (unless requested) and I don't deck blocks unevenly, and I don't shorten cylinders.....(maybe sometime I do, but only 92 or 94).
because it didn't work for ME, works for some people I think, but not me.

I don't build engines more than .060 narrower than stock because last time I did that.... the pushrod tubes crinkled and I ended up machining the pushrod seats deeper to correct that.

What "I" would do, is take it apart, and scatter the parts to opposite ends of the country so it cannot ever be (even accidentally) assembled again.

What YOU should do...... is up to you, or ask somebody else because I'm just not the right guy for the job,
Now I remember why I said what I did on page 1, sorry my memory is totally shot.
Not anything personal at all. If you want ME to make some custom rods or something that's cool, but keep telling my about the particulars of this engine I'm going to have to put my fingers in my ears and go "bla bla bla i can't hear you". :shock:

Sat Jan 09, 2021 9:21 pm

Easiest way to fix excessive deck is to use a longer rod. Keep your "B" pistons.

What rod is in there now? Stock?