440 headgasket to lower compression

[kaj750]

Hey, all.

Bakground:
I have an old RV 440 that was built to what appears to be 10.1-10.2 C/R, based on the part number I found for the pistons built with the OEM block and heads. I had been fighting detonation for two years before finding the info on the pistons. Being in California, I am assuming my issue is the C/R + CA gas. Any time my intake temps are over 100*F, I get pinging like you wouldn't believe, any time I put any load on the engine. Even leaving a stoplight gets it going, a bit. Cruising is fine. Using Sniper EFI, I've reduced timing a ridiculous amount and added fuel as much as I could, with no result other than a huge loss of power.

My point:
For unrelated reasons, I've acquired a set of 440Source Stealth heads. Before putting them on, I'm considering finding a set of head gaskets that are thick enough to drop the C/R.

Does this make sense? Also, 440Source says that a teflon head gasket is best, as it bridges the difference in expansion between the aluminum and iron. How would I know how thick to go? Compressed thickness of the 440Source standard gasket is 0.051".

Thanks, in advance.

 

[pnora]

What heads are on it now?

 

[493 Mike]

Hey, all.

Bakground:
I have an old RV 440 that was built to what appears to be 10.1-10.2 C/R, based on the part number I found for the pistons built with the OEM block and heads. I had been fighting detonation for two years before finding the info on the pistons. Being in California, I am assuming my issue is the C/R + CA gas. Any time my intake temps are over 100*F, I get pinging like you wouldn't believe, any time I put any load on the engine. Even leaving a stoplight gets it going, a bit. Cruising is fine. Using Sniper EFI, I've reduced timing a ridiculous amount and added fuel as much as I could, with no result other than a huge loss of power.

My point:
For unrelated reasons, I've acquired a set of 440Source Stealth heads. Before putting them on, I'm considering finding a set of head gaskets that are thick enough to drop the C/R.

Does this make sense? Also, 440Source says that a teflon head gasket is best, as it bridges the difference in expansion between the aluminum and iron. How would I know how thick to go? Compressed thickness of the 440Source standard gasket is 0.051".

Thanks, in advance.

If you eliminate all the quench space it will not perform. Aluminum heads alone will provide about 1 point reduction in CR in operation. That said when you pull a head the piston top to deck height should be measured at TDC. Then you should be better informed as to gasket thickness. Cam specs?
Mike

 

[kaj750]

What heads are on it now?

Whatever comes on the RV 440, I'd guess. The only modification I've found is adjustable rockers. 906, I believe it is. No idea if the block or heads have been resurfaced.

If you eliminate all the quench space it will not perform. Aluminum heads alone will provide about 1 point reduction in CR in operation. That said when you pull a head the piston top to deck height should be measured at TDC. Then you should be better informed as to gasket thickness. Cam specs?
Mike

 

[33 IMP]

If you were keeping iron open chamber heads, a thicker head gasket would be an easy solution, since it hasn't got any quench now.
But, with the closed chamber aluminum heads, a thick hg will throw away the quench you just bought.
The aluminum heads can tolerate a higher comp ratio (at least that's the theory), but the heads your adding will probably bump your cr about anither point.. Time to calculate what you will end up with for cr.
Have you pulled the heads off to measure the deck height? Without some actual measurements, we have nothing but educated guesses.
(What you probably really need is a piston change along with the 440 source heads.)

 

[kaj750]

If you were keeping iron open chamber heads, a thicker head gasket would be an easy solution, since it hasn't got any quench now.
But, with the closed chamber aluminum heads, a thick hg will throw away the quench you just bought.
The aluminum heads can tolerate a higher comp ratio (at least that's the theory), but the heads your adding will probably bump your cr about anither point.. Time to calculate what you will end up with for cr.
Have you pulled the heads off to measure the deck height? Without some actual measurements, we have nothing but educated guesses.
(What you probably really need is a piston change along with the 440 source heads.)

Engine is still together, so no way to take measurements. I only got the heads because 440Source says they were a direct bolt on and I was told an aluminum head could help with the detonation issue. I'm not rebuilding the block to swap heads. I'd rather find a way to ship in better gas (run e85 if the Sniper will allow it) and leave things as they are and sell the aluminum heads.

 

[33 IMP]

Engine is still together, so no way to take measurements. I only got the heads because 440Source says they were a direct bolt on and I was told an aluminum head could help with the detonation issue. I'm not rebuilding the block to swap heads. I'd rather find a way to ship in better gas (run e85 if the Sniper will allow it) and leave things as they are and sell the aluminum heads.

If you're willing to keep the iron heads, pull em and throw some big fat thick cometic head gaskets on it. (Or fat solid copper, might seal better. Cometics really want a certain block and head finish) Problem solved.
What pistons do you think you have?

 

[Geoff 2]

Cometic gaskets will make a custom set of h/gaskets. Work on your cooling system to get it to run cooler.

 

[INTMD8]

Based on some of your other threads-

To start, if you haven't, you need to find number 1 tdc. Actual TDC. Could use a dial indicator through the plug hole or even a piece of coat hanger with lines drawn on it to get close.

Then confirm timing mark on dampener aligns with tdc on tab. If it doesn't, make new marks with paint or whatever to establish true tdc timing reference.

If that mark changed from whatever you previously thought to be true you can then set timing based on the new/correct mark and retry.

Could also do a cranking compression test to see if it's what you would expect or exceptionally high.

Agree aluminum heads should increase tolerance but I don't think you should have this problem in the first place unless timing is way off or there's something restricting coolant flow.

 

[kaj750]

If you're willing to keep the iron heads, pull em and throw some big fat thick cometic head gaskets on it. (Or fat solid copper, might seal better. Cometics really want a certain block and head finish) Problem solved.
What pistons do you think you have?

Cometic sounds finicky and not fun to deal with.
Pistons:

Cometic gaskets will make a custom set of h/gaskets. Work on your cooling system to get it to run cooler.

So that the IATs won't matter as much?

Based on some of your other threads-

To start, if you haven't, you need to find number 1 tdc. Actual TDC. Could use a dial indicator through the plug hole or even a piece of coat hanger with lines drawn on it to get close.

Then confirm timing mark on dampener aligns with tdc on tab. If it doesn't, make new marks with paint or whatever to establish true tdc timing reference.

If that mark changed from whatever you previously thought to be true you can then set timing based on the new/correct mark and retry.

Could also do a cranking compression test to see if it's what you would expect or exceptionally high.

Agree aluminum heads should increase tolerance but I don't think you should have this problem in the first place unless timing is way off or there's something restricting coolant flow.

I've used a tool that goes into the spark plug hole, I've confirmed that with the cam/lifter/rocker position on cylinder 1, and anything else I can think of. I've verified 0* and 10* timing via Sniper software. Compression is 150-155 on all cylinders. The engine has had detonation issues since it was built, according to old receipts I've found (previous owner had the car at a shop for the same reason).

 

[Curiousyellow71]

Perhaps .060 over it has a hot spot from a thin spot on a cylinder wall. What temp doees the engine run? You could try running evans coolant rather then antifreeze. It is better for transferring heat away from surfaces which can help prevent detonation.
Other then that I would look at a issue with your sniper because its likely in the mid 9's w those heads/pistons and verified by your compression check and shouldn't ping.

Does it stop pinging w better gas?

 

[33 IMP]

150-155 should NOT detonate. (My opinion).


And looking at the piston box, .001 to .002 p/w?!? Who runs a forged piston that tight? I sure dont!
And they claim they're accurate to 25 HUNDRED thousandths!?! A quarter of a thousandth? Really?

 

[R413]

They had the apprentice secretary make those labels!

 

[BLK 68 R/T]

What do your plugs look like? And what is your base timing and all in advanced timing?

 

[Curiousyellow71]

What spark plugs?
To hot of a plug could also cause detonation.

 

[kaj750]

Looking at all the info I have, I can't see why the car would detonate either, to be honest. I've given up due to not finding a fix. The only reason I'm posting now is because I thought I was going to swap to the aluminum heads and be able to help my situation. If it's pointless and I'm back to square one, then I'll just leave everything as-is. I've been dealing with it this long, it's not going to hurt to keep on truckin'.

Perhaps .060 over it has a hot spot from a thin spot on a cylinder wall. What temp doees the engine run? You could try running evans coolant rather then antifreeze. It is better for transferring heat away from surfaces which can help prevent detonation.
Other then that I would look at a issue with your sniper because its likely in the mid 9's w those heads/pistons and verified by your compression check and shouldn't ping.

Does it stop pinging w better gas?

The car ran the same with the carb or the Sniper. Detonated either way. Car runs right around 190-200*. I've used Evans in my race cars, didn't think about it for this car, seeing how water runs cooler, despite hot spots.
At this point, I'd try anything short of an engine rebuild.

 

[69Bee]

150-155 should NOT detonate. (My opinion).


And looking at the piston box, .001 to .002 p/w?!? Who runs a forged piston that tight? I sure dont!
And they claim they're accurate to 25 HUNDRED thousandths!?! A quarter of a thousandth? Really?

With todays CNC machine technology and laser measuring, it is very easy to maintain a 2.5 ten-thousandth of an inch tolerance. As far as the piston clearance goes, this isn't 1975 and some the old ways are not relevant anymore. With better piston alloys and skirt profiles, it is possible to run them that tight for a street only motor. Now, do I run them that tight, no, I usually set them up at 0.0012"-0.0013" clearance for a regular street motor with no problems. A higher performance motor or one with power adders will get more clearance not to mention wider ring gaps. I ask the customer what his intentions are for the motor and build it accordingly.

Coated pistons can run tighter also, hell I have seen Subaru's that had a piston clearance spec of -0.0005" to +0.0012".

 

[DanielSlocum]

What happens if you add some octane booster? If you dont put a lot of miles on....maybe that could be your simple solution.
If it doesnt help....then the hot spot or too hot spark plugs theories may be correct. A too lean fuel-air mixture will deonate easily also.
Is the heat crossover in your intake blocked? You want it blocked in hot weather situations. Is the engine inhaling 200 degree underhood air?

 

[Doorkicker]

Something is off here. First, and I may have missed it, but what is the exact gas you're running? What octane rating and how much ethanol is advertised?

Anyway, this shouldn't be pinging... I have more CR and piston psi than you and run on pump 93 all day long in the middle of hot North Carolina summers.

Let's do some math....

Let's assume you have a stock block with a deck height of 10.725 (big assumption), a stock stroke (3.750), and stock rod length (6.768). Those pistons have a compression height of 2.061. Granted, it's just math and not real measured numbers from the block, that means the piston is 0.021 in the hole... good.

I'm sure someone will correct me, but the 906 has a 79cc (also listed at 80 and 88. So not sure honestly...). Let's go with 79cc. Let's assume the builder threw on a very common Fel-Pro head gasket that has a compression thickness of 0.039.

Crunch the numbers and you get 10.18:1 CR, which is right at what you said from the beginning... so the numbers check out. But what doesn't check out is the pinging... that is not a high CR.

Let's go back to timing.. you mentioned using a Sniper for timing, so I'm assuming a Hyperspark for IGN box? If so, did you use the phaser tool for the distributor install and set the sniper to lock out the timing to check it? If you did... then I'm going to assume you're not dealing with a timing issue - which is what this problem sounds like if I'm honest. If the distributor isn't phased and the sniper GCF doesn't have the correct ignition reference angle set for the phase, you could be putting way over 50* of timing. I know you said 10* off the mark for setting, but just confirming you used the phase cap tool, that you locked out the timing control when you sync'ed the ignition to the sniper with a light, and the ignition reference angle is set correctly. (As a side note, sync'ing with less than 15* can cause issues, that's why Holley recommends 15*) And, importantly, that you have the right setting in the GCF for the reference angle (which if memory serves it's 57.5, but you definitely want to check that)... I'm not trying to tell you something you already know, but 90% of sniper/hyperspark issues are improper timing being set/configured.

Others already talked about hot spots... perhaps put a bore scope in the spark plug hole and look for one. If you're pining at 10.1:1 and it's a hot spot, you'll definitely see it.

Beyond what others have said... I've seen a couple super odd things cause pinging noises... like a bad wrist pin hammering the cylinder wall. A way to find that without taking the motor apart is unplug #1, drive around... plug back in and unplug #2, drive around... repeat. See if it's stops pining on a given cylinder.

I'm thinking timing... or something mechanical. OR... you're running the worst gas on the planet, which is pretty likely because of where you live.

Sidebar... Since at cruise it doesn't ping... I'm assuming you're AFR is in a good range... generally between 12.4 and 14.3? Or is it higher than 15+ when it pings?

 

[33 IMP]

I'm pretty sure that if he has 906s, or the later variants, the combustion chamber cc's will be 88-90, unless it's been seriously milled.
My closed chamber maxwedge are over 82.
75-79 might be right, IF it has 915s on it.

Edit: the BEST pump gas available in california is 91, with around 10% alcohol in it. 93 would be a dream.