440 headgasket to lower compression

[ckessel]

Lloyd, @beanhead, hooked me up with Mike Silva in Fresno. Silva's Automotive Machine. 559-706-6148. One man band.

 

[kaj750]

Welp ..

Got started.

Looks like the heat crossover thingamajigs definitely were not blocked.

 

[autoxcuda]

Mentioned before, but need to get measurement of head cc, head gasket thickness and piston to deck deal to find out true calc’d compression.

 

[ckessel]

1215 Fel Pro bathtub has the crossover blocked.

 

[Curiousyellow71]

The fact that the car doesn't detonate when it's cold also points to problems that are common with cams of this size on pump gas. The 292H has a bunch of overlap.
A 292H may be big enough to lower the dynamic compression on paper, but overlap means hot exhaust is getting mixed into the incoming air when the intake valve opens. The hotter things get..the worse it gets. This type of cam can make good power w open headers and race gas. But, when its in a car w full exhaust that is running pretty hot..your not the first one to have experienced detonation.

 

[kaj750]

Also, out with the baby radiator, in with Papa radiator.

 

[kaj750]

Mentioned before, but need to get measurement of head cc, head gasket thickness and piston to deck deal to find out true calc’d compression.

Well, I'm not quite to that point yet, but will get to it.

 

[kaj750]

1/19/26 Update.

Heads pulled and here's what all I found.

Plugs in order of cylinder numbers 1-8:

:

 

[kaj750]

Driver's-side cylinder head. For some reason, they loaded out of order: 5, 7, 1, 3.

 

[kaj750]

Passenger-side cylinder head in order, 2-8:

 

[kaj750]

Pictures of cylinders 2-8 (lighting was bad on 1-7)

 

[ckessel]

Looks like some deposits there contributing to the ping etc issues. Need to figure out where thats coming from.

 

[BLK 68 R/T]

Looks like it’s been burning a bit of oil.

 

[JC Boatguy]

1/19/26 Update.

Heads pulled and here's what all I found.

Plugs in order of cylinder numbers 1-8:


View attachment 1980504View attachment 1980505View attachment 1980506View attachment 1980507View attachment 1980508View attachment 1980509View attachment 1980510

Holy melted pistons BATMAN!!!

 

[kaj750]

Holy melted pistons BATMAN!!!

Um... Okay.

 

[Curiousyellow71]

I don't know how much detonation has been going on since this engine was put together. But, eventually detonation takes the tension out of the rings and if they are moly...it flakes off. As it gets worse it uses oil. Just looking at the deposits in the pictures..I think some damage has been done. It likely needs honed and new rings.
Probably not what you want to hear.

 

[Frank Mopar]

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

Agree. I would start here with colder plug. Simple and cheap.

 

[493 Mike]

I recommend you pull the engine apart and start at zero with a complete reassemble. Check and double check each component as you go. Check the cam lobe positions, keyway indexing, degree the cam, check deck heights, check the damper with TDC.
Clean out water passages in the block and heads-start from scratch!
Mike

 

[BLK 68 R/T]

What head gaskets were in it?

 

[33 IMP]

I recommend you pull the engine apart and start at zero with a complete reassemble. Check and double check each component as you go. Check the cam lobe positions, keyway indexing, degree the cam, check deck heights, check the damper with TDC.
Clean out water passages in the block and heads-start from scratch!
Mike

Clean a piston and measure deck height, and measure the head gasket too, before you take it any more apart. Check balancer timing mark against top dead center first too.
Do an accurate compression ratio check (assuming each number for the head from probably 86 to 90 cc's), now that you'll know deck height and gasket thickness.