"Squish" problems

[tubman]

Any of you that have been following my threads about my "adventures" with my used Edmunds heads knows that I massaged them until I had 62 cc chambers and (I thought) .045 "squish". I measured this by putting 5-6 foil balls on each piston top and turning the engine over and then measuring them. To do this, I installed the heads with the used Mercury script gaskets that had been on the engine and looked to be in remarkable good shape. I didn't torque the heads, just cranked the bolts down good and tight with a 1/2" drive ratchet.

After everything, the engine starts and runs great, but still has an external head gasket leak on one side. To correct this, I got some "Iron-Tite" ceramic sealer. To make a long story short, their procedure requires running the engine for at least 60 minutes at operating temperature. While doing this I noticed a "tapping" sounds coming from the engine after it was fully warmed up. It sounded like a loose lifter, but I listened with a tube down into valve chamber, and I don't think that's the problem. The only things I changed were the heads, so it must be them. My neighbor is an avid snowmobiler and he showed me a trick they use to check for rod stretch. We stuck some .060 diameter solder through the plug hole and over the piston top and turned the engine over. The results were that all of my cylinders have a squish dimension of between .022 and .031". this is about .020 less than I have seen recommended here. The heads were installed with new "Fel-Pro" gasket coated with spray-on "Copper-Coat" and torqued several times.

It is my belief that the tapping is one or more of the pistons "kissing" the head. My next move is to go back to the shop and go through my stash of gaskets and see if I can find some thicker ones (I need .020 more; I have some copper gaskets somewhere that I seem to remember being thicker). The only other solution I see is to grind .020 out of the chambers. That seems to be a lot of work on a set of marginal heads. I welcome your thoughts on this. As a point of reference, all cylinders have about 170 lbs of compression.

Oh yeah, the Iron-Tite" didn't stop the leak; more on that later.

[saltracer]

what did you factor in as the compressed thickness of the gaskets? I believe Fel Pros are something like .047 thick when installed.So if the pistons just cleared the heads without a gasket you would think this would end up right where you wanted to be. Phil

[tubman]

Looking back, it was a mistake on my part to assume that a compressed "Mercury" gasket would be the same as a compressed "Fel-Pro". My problem is coming back from this situation.

[GOSFAST]

Originally Posted by tubman

Looking back, it was a mistake on my part to assume that a compressed "Mercury" gasket would be the same as a compressed "Fel-Pro". My problem is coming back from this situation.

Hi Den, you don't say which Fel-Pro part numbers you are working with but most of our builds get the 1055'/1056's (for the later Flatheads). If these are the same numbers they measure .062", fairly "thick"!!

We also use the 7525B-1/7526B-1 numbers when the others aren't readily available, same gaskets mentioned above, different packaging/pricing?

I would give all here a "tip" when checking P/H clearances, install the heads (both sides) without any head gaskets and make certain the crank/pistons rotate with no clearance issues. If it turns without gaskets (most times) you will be good to go. On some rare occasions it may require looking closer at everything but generally speaking it will be good.

Thanks, Gary in N.Y.

P.S. On a side note here, that compression number seems a bit high even for hi-comp heads?? Also that earlier offer still stands on the heads!

[Bored&Stroked]

Whose pistons are in the engine? The reason I ask is that there are different crown/dome profiles - and the profiles on the heads need to match (if you're going for a tight squish).

On many OEM Ford type pistons (cast), the dome is not a consistent radius - it is a combination of three tangent arcs. A good example is an early 4-ring cast Jahns piston - completely different dome than the 3-ring racing Jahns.

The forged Ross pistons have a consistent radius profile - typically .1875 deep. Most modern head manufacturers use a dome pocket profile that is very close to the Ross profile (though not compatible with some of the cast pistons). I recently had to have the domes on a new set of Edelbrock heads CNC profiled to match the early 4-ring Jahns pistons on a given engine.

Due to the above, I have two different 3D CAD models for the domes - such that I can get the CNC work done to "tune" the squish to match the specific pistons, gaskets and compression height of a specific engine.

[Bluebell]

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I have C7RA ali heads. I had them faced, one needed more than the other.
I have Ross pistons. Without gaskets they lifted the heads when I turned the motor over.
I mentioned it on this forum. Another kiwi on here told me to measure the lift with a dial gauge on each cylinder, which I did. I wrote each measurement in each chamber and sent my heads to Brian. Brian had previously built a jig and made a tool to cut the heads to suit the Ross domes. I am lucky and grateful for his help. One head needed on average about 0.040" thou out, and the other about 0.022" out. The heads are on, but as yet the engine is not yet finished.
I have used Best composite gaskets which I am told settle out at about 0.055".

[tubman]

I just got back from my shop where I looked things over some more and did a little measuring. I measured both the Compressed Mercury gaskets I initially removed from the engine and the Fel-Pro I just took out. Both measured .050". I then went through the new gaskets I have on the shelf. Here's what I got :

1 set of Fel-Pro 7521 and 7522 - .060 thick
3 sets of Fel-pro 7525 and 7526 - .072 thick
1 set Victor 1084K and 1085K - .075 thick
1 set Best Gasket 521-1 and 521-2 - .060 thick
I set Speedway "Big Bore" copper gaskets - .075 thick

It looks like the gaskets compress about .015 when torqued, so it looks like none of those I have will help much. Unless some knows of substantially thicker gaskets, it looks like I'm looking at a bunch of hand work.

Gary, I had the Fel-Pro 7525/7526 gaskets in the engine this last time. I did set the heads on the engine without gaskets and turned it over and couldn't see or feel any movement. As to the high compression numbers, I was surprised as well, so I tried a second gauge and got about the same thing. I have 12 volts on my test stand, and it really turns over fast. I will keep your offer on the heads in mind; you're my "Ace in the hole".

Dale, the engine has stock Mercury pistons. You're way ahead of me on this stuff; you have CAD models and CNC capability, while I have a die grinder and a Dremel. Oh well, this was just an exercise to try to get the most out of an old set of heads. One thing; I think this experience has cured me of buying used heads.

And I still have the leak problem.

[Ross F-1]

I don't envy you having to scrape all the shredded gasket and CopperKote off. I used that once with comp gaskets, never again!! I doubt there is any benefit with Felpro's anyway.

I also use the Felpro 7525/7526's and I've measured them at .050 - .055" at the fire rings.

[saltracer]

I'm missing something here. If the heads did not lift without gaskets, why should you not have at least the thickness of the gaskets as clearance?

[tubman]

"Saltracer", now that you say that, it makes perfect sense. The only thing I can think of is I was planning on doing it, but never got around to it. I've had the heads on and off this engine so many times this summer my head is spinning. It also doesn't make sense that the squish should be less when both gaskets measured the same .050" when compressed. I think I'm getting too old for all of this.

Ross, luckily, the engine had only been together about a week, so everything came apart easily. Is that .050-.055 you measured on a new or used gasket?

[saltracer]

don't feel back, I did something similar. Except I switched out heads without checking clearances and the pistons hit the heads so hard they caved in a little!

[Bassman/NZ]

When I first did mine, I used the tinfoil trick. When I fired the engine up I had a noise, so shut it down and pulled the heads. I discovered the milling had altered the relationship of the piston dome to squish area, and I could see the marks where the pistons had kissed the heads. I laid the gaskets on the heads and marked the outline on the heads with a fine sharpie, then very carefully smoothed the squish area out to the sharpie marks, taking care not to take any material from the centre of the squish area. I used flap wheels to do this as they don't remove too much at a time. After a couple of refits and tweaks, I got them to where I had fairly consistant 0.045". Works fine now. I have 160-165lbs across all 8 cylinders. Can't help with the leak, sorry. I like the Best copper gaskets with a smear of grease both sides. The graphtite ones are a pain in the bum to remove.

[Charlie ny]

Consider covering the pistons and valve heads with a light coat of dark grease then installing each head with 4 finger tight bolts, turn the motor over by hand a few times and then remove the head/s and see the witness marks left by the grease. What you see of course are the areas of interference. You may be surprised with the mismatch between the crowns of the piston and the location of the chambers. In my experience
every flathead I've done one bank favors 3 o'clock the other bank favors 9 o'clock.
It's not good to assume the location of the cylinders (pistons) and the location of the
chambers are the same. I relieve the contact areas with a die grinder and go at it again.
I strictly use BEST gaskets from VanPelt, they squash down to .040 after torquing which gets me where I want to be after after massaging the chambers to 100% true location to the pistons.
Charlie ny

[tubman]

Charley, Thank you for this useful information. This is not the first time you've helped me out. Now, if you would only get me the jetting specifications you mentioned for a '52 Olds 4 bbl carb on a flathead, I'd be in fat city.

[51 MERC-CT]

Originally Posted by Charlie ny

I strictly use BEST gaskets from VanPelt, they squash down to .040 after torquing which gets me where I want to be after after massaging the chambers to 100% true location to the pistons.
Charlie ny

Question, do the gaskets squash to .040 or after torquing is the head to piston gap .040?

[tubman]

I have found an outfit that sells .020 steel shims for head gaskets. It seems they are use a lot to correct valve geometry on OHV engines after the heads have been trued. They have them in stock for flatheads. A .020 shim will put me at .042-.051 squish, which is where I want to be. I have never used head gasket shims. Does anyone here have any experience with them? Any other feedback?

[Bored&Stroked]

Another option to consider is using a Cometic MLS head gasket -- they are available in a whole range of different thicknesses. I'm using them on my highly modified 42 Merc engine in my 32 Cabriolet (wanted to try them - so far, so good). They are expensive (about $250 a set), but time is money - so maybe a set of .070 ones will help you. They will not compress like other gaskets and many folks reuse them.

Here is a link to Jegs:

http://www.jegs.com/p/Cometic-Gasket...49500/10002/-1

[JSeery]

A flat shim is going to have very limited sealing capability so the surface it mates with is going to have to be nearly perfect to get a seal. I would go with the thicker head gasket if it was me.

[tubman]

Looks like the Cometic gaskets are for '48 and earlier only (at least at Jeg's). And those prices are each, not a set. I'm waiting to see what the shims cost. If they're cheap enough, I may try them first.

EDIT : I just looked at the Cometic website. Looks like they only make them for the earlier flatheads. I can't be sure though, because the first three entries that showed up under "Flathead Ford" were for a late model Dodge 4 cylinder; the have obvious incorrect pictures with some of the listings as well. I guess I'll have to call them. I'm still put off by the price, though.

[Charlie ny]

tubman,
'52 Olds Rochester jets size primaries 51's secondaries 56's
Extensive trials with my A/F meter showed the motor.......274, Max-1, 8to1 comp,
sbc/8ba dist.........was happiest once I plugged the power valve. I tried different combos of jets and bringing the curve in earlier and later but settled on the above.
The motor pulls hard to 5000 rpm any time I ask it to and can easily outrun the
brakes and suspension and most any flathead in my area. Most any, not all.
SQUISH
The BEST head gaskets I use from VanPelt are composition and squash down to .040.
Yikes......save your $$$$$ and further frustration ,shim style gaskets will find
leaks you would otherwise never have. Humor me and do the grease thing, I usually
take 6 to 8 hours to do a head but I start knowing each chamber will require full recontouring and I use only iron heads. By your description I think you'd be looking at maybe 8 hours to do both, maybe even less. Doing this way you know you have .040 over each piston once the BEST gasket are torqued....plus you now have what I believe is maximum street compression.
Be reasonable.......see things my way.
Best of results what ever you do !
Charlie ny