Deck Height for ‘77 rebuild

[grillage]

I am rebuilding the top end on my 77 2.7L and am about to start putting things back together.

I just got the cylinders back from EBS - Alusil cylinders redone in Nikasil - and the heads are coming back from Craig this week.

Some cylinder porn for you:





when I took apart the cylinders before, I unfortunately did not note the copper shims - but I do know that they cant have been the same and that at least one was as thick as 1.25mm

I read in Wayne’s book about using solder to measure and adjusting based on that. But do I do that for each cylinder? And if they’re different could that cause issues when I got to install the cam box?

Thanks,

[stownsen914]

Usually you have the same cylinder base gaskets thickness on all cylinders. Did your motor have different size ones on the different cylinders?

[PeteKz]

Same question as stownsen914. If you have different thickness copper base gaskets, something is strange.

[grillage]

It seems that they did have different sizes at least one bank to the other. The whole banks might have been the same, but they can’t have all been the same

I have three 1mm, three 0.5mm and six 0.25 mm
They could all be put together to make 1mm for all cylinders — however, at least one cylinder was 1.25mm - that I know because a 0.25 and a 1mm were stuck together so well I though I had a 1.25mm gasket.

I’ll do the tests when the heads arrive here in a couple days

[stownsen914]

Gotcha. Different from right to left sides of the engine is possible. It's common to check piston to head clearances on at least one cylinder on each side. Most people don't check all 6.

A couple things:
1. 1.25 mm is a lot. Not necessarily a problem, especially since you'll be measuring the clearance, but worth noting. Do you know if the history of case and head machining? It sounds like this engine has been rebuilt at least once before.
2. Some advise against stacking base gaskets. Let's see if others chime in on this topic. It is possible to purchase one piece, thicker gaskets. EBS may have them.

[SalParadise]

Great thread. I am doing the exact same thing right now. FINALLY got a reasonable set of Mahle P/Cs new-in-box.

Sending out the heads and will be in the exact same boat. Will be reading this one...

[icarp]

Do not use what was there!!! Shims come in .25mm .50mm .75mm 1mm
Make your own measurements
.033” to .040” is the correct deck height for a street engine
Measure them all 5 times
One shim per cyl with a very very very thin film of curl T 2.
That 3 cyl head bank must be built and tourqued in 60-70 min? Stomski wrist pin tool helps much
So practice alot!!!!! Set wrist pin clips only on the real assy… So the base shim is going to seal against oil leaks

All cyls must be the same height per side

[pocv0]

The cylinders should be the same overall height from bottom sealing surface to the top sealing surface. You need to measure the heights on all of them. When your heads arrive they will all be the same thickness. The stack up is very important, the cam towers need to mount to the heads, and the head top surface across the bank needs to be planar, otherwise the cam tower will distort and the camshafts will bind, not good.

[grillage]

Thanks all, the heads just arrived so I'll do a bunch of measuring and thinking before I try to assemble

[icarp]

My thought is to measure for your own real data, dont expect the old stuff to be correct

You either know or you don’t know

[PeteKz]

Emphasis on what Ian and the others said about verifying everything yourself.

[grillage]

Good Morning all,

I measured from bearing surface to bearing surface on the cylinders and they are all within 0.05 mm of each other. so that's good

Then today, I installed all the cylinders with no spacers and ran a straight edge over the top to see if there was any irregularities. I can fit the very smallest of my feeler gauges in a couple spots but that's a very very small variation





next step is to do the solder trick to see what my clearance is. for that I'll start with way more shims on the cylinders and come down.

Everything making sense so far?

[pocv0]

So your shims will be the same thickness on each bank. Just rotate cylinder #1 to TDC and check the distance from the cylinder top to the outer band of the piston top. That should measure 1mm I believe. Calculate the shim thickness based on that measurement. Both banks will most likely be the same thickness shim required.

[grillage]

OK, so I put 1mm stacked shims on a few cylinders, installed the pistons and did some measuring.
I get about 1.35mm of gap at the top of the pistons to the top of the cylinders. I’ve seen some people suggesting 1mm, and Wayne’s book recommends 1.25 to 1.5mm

Do I need to account for any work on the heads? They’ve had 0.25mm taken off this go around, and maybe more before

[pocv0]

It gets a bit complicated not knowing how much material has been removed from the head sealing surface. The camshaft centerline will be closer to engine center, CR increases . The camshaft centerline needs to be concentric with the chain housing within a certain tolerance . I don't recall what that tolerance is.

[stownsen914]

You'll see many advocate for closer to 1 mm of piston to head clearance, and it's said to improve combustion to keep the "squish" volume lower. 1.35 is in the range though, as you note.

As for accounting for surfacing of the heads, you've done this by taking your measurements.

pocv0 makes a good point about making sure the camshaft is centered in the cam housing bore. As you deviate from factory settings with machining, etc. this measurement will tend to move. I think Wayne's book mentions this, and may recommend keeping the cam within .5 mm of center, or something like that. I believe people do things like stack chain housing gaskets if needed. There may be spacers available too?

[r lane]

Enough has been said, but measure the thickness of the head, cam housing mating surface to cylinder mating surface. That will tell you how much has been cut. needs to be the same at least per side. If excessive then a bunch of bandaids will need to be applied. chain housing and chain length issues. Also where the heads have been cut, that area is now broader and extends further into the chamber. One mod leads to many others. Stay after it. Bob

[grillage]

Thanks all, I have done a bunch of test fitting and so far so good!

[grillage]

I just wanted to thank everyone again for the help here!

I have the car back up and running and it's just fantastic!
late addition of SSI's as I realized just how bad the old heat exchangers really were

Still have a little fuel tuning to do to get it perfect but the car runs better than it ever has

thanks again!
some pics of the rest of the process

[SalParadise]

That is amazing. Really nice job. Must feel really, really good.