Compression ratio limit with Felpro 8519 head gaskets? POSSIBLE UPDATE

[69SuperBee451]

Discovered a lot of bubbles in my cooling system, running hot on the expressway, and steam cleaned plugs in cylinders 2, 4, and 5 on my 451. I did have some bad detonation in the past due to distributor issues which I have corrected. I’m currently running the felpro 8519s with an actual 10.6 to 1 with 452 heads. What is the limit of these gaskets? I have never retorqued them. I was looking at the 1009s, but also read issues with the fire ring overhanging the cylinder and/or chamber. Any suggestions?

 

[lewtot184]

limits may be a foggy thing to put your finger on. any gasket may fail from multiple causes. usually the 8519 is pretty forgiving on not so perfect surfaces. i would think 10.6 would be well within the 8519's limits. something i do believe is the big blocks bolt circle and 7/16" fasteners are not really ideal for anything above 12:1. of course this gets into the "results may vary" scenario. best thing is just start diagnosing parts; especially cooling. are the head bolts bottoming out? surfaces not flat? look around the head bolt holes in the block to make sure none have a protruding ridge above the deck surface. detonation kills everything it touches.

 

[lewtot184]

Is this a .060" over 440, or a 4.375" bore 400 block?

 

[69SuperBee451]

Is this a .060" over 440, or a 4.375" bore 400 block?

4.375” 400 block

 

[dvw]

Detonation can destroy a head gasket. If the plugs are steam cleaned pop the heads and find out.
Doug

 

[lewtot184]

A 1009 definetely won' t work on that block. The reason i asked about a .060" 440 is they will split a cylinder. A 400 at .030" over might but not as likely. Hate to say it but it may be tear down time if nothing obvious shows up.

 

[69SuperBee451]

A 1009 definetely won' t work on that block. The reason i asked about a .060" 440 is they will split a cylinder. A 400 at .030" over might but not as likely. Hate to say it but it may be tear down time if nothing obvious shows up.

Yeah, I already started pulling it apart. I put 125psi of compressed air into cylinders 2, 4, and 5 and have bubbles in the radiator. I just don’t want to run another set of these head gaskets if they won’t hold up to such a mild compression ratio. I know what detonation can do. I checked a couple of the head bolts on the P/S, and they didn’t have that “snap” when loosening them. I do have a set of ARP head bolts coming that were half price. Just need to sort out the head gasket issue.

 

[Bee1971]

I run the FEL PRO 8519 on my 383/432 Edelbrock E Street 75cc with ARP bolts
10.5 to 1 Compression 195 PSI on all eight

Eight years now , zero issues

Peace

 

[lewtot184]

I run the FEL PRO 8519 on my 383/432 Edelbrock E Street 75cc with ARP bolts
10.5 to 1 Compression 195 PSI on all eight

Eight years now , zero

I have 12yrs on one engine and 9yrs on another with 8519's. But, i don't push detonation limits, heat limits or other factors that can damage a street engine.

 

[69SuperBee451]

Pulled the passenger side head and I am not seeing anything on the head gasket indicating it is blown. Plugs 2 and 4 were steam cleaned, #2 being the worst. The head looks perfectly fine and there is no porcupining around the bolt holes on the deck, and the stock head bolts are not bottoming out. I have another pair of 8519s coming as well as a set of ARP bolts. None of the head bolts had a “snap” when loosening them. The condition of the head gasket is puzzling though. I don’t see anything on the fire rings, and nothing indicating cylinder pressure escaping into the cooling system

 

[Cranky]

limits may be a foggy thing to put your finger on. any gasket may fail from multiple causes. usually the 8519 is pretty forgiving on not so perfect surfaces. i would think 10.6 would be well within the 8519's limits. something i do believe is the big blocks bolt circle and 7/16" fasteners are not really ideal for anything above 12:1. of course this gets into the "results may vary" scenario. best thing is just start diagnosing parts; especially cooling. are the head bolts bottoming out? surfaces not flat? look around the head bolt holes in the block to make sure none have a protruding ridge above the deck surface. detonation kills everything it touches.

When it comes to smaller fasteners....rather have 5 smaller ones in that circle than 4 bigger ones....and I agree about detonation killing stuff but generally, it'll wreck a piston before taking out a gasket.

 

[68-500]

Top gasket between middle cylinders looks suspicious to me. Once it goes between 2 cylinders compression and combustion could easily push air to the nearest coolant passageway.

 

[lewtot184]

What heads are you using? Usually the center cylinders will show some heat on the gaskets but i wonder about 4 & 6.

 

[69SuperBee451]

What heads are you using? Usually the center cylinders will show some heat on the gaskets but i wonder about 4 & 6.

452s

 

[69SuperBee451]

Top gasket between middle cylinders looks suspicious to me. Once it goes between 2 cylinders compression and combustion could easily push air to the nearest coolant passageway.

Yeah it does look a little iffy between 4 and 6. The puzzling part is cylinder #2 almost looked like a brand new plug. #6 looked normal, and #4 was clean on one side.

 

[lewtot184]

452s

Quench dome pistons? KB215?

 

[69SuperBee451]

Quench dome pistons? KB215?

Yes, 215s, .030” over.

 

[lewtot184]

Yes, 215s, .030” over.

I think you'll have a difficult time making that combo pump gas friendly. I don't have a problem with KB hypereutictics and quench domes, in fact i use them. The issue is cylinder pressure. No piston configuration by itself can cure a cylinder pressure issue, especially with less than ideal combustion chamber design.

 

[69SuperBee451]

I think you'll have a difficult time making that combo pump gas friendly. I don't have a problem with KB hypereutictics and quench domes, in fact i use them. The issue is cylinder pressure. No piston configuration by itself can cure a cylinder pressure issue, especially with less than ideal combustion chamber design.

It does have a fairly large cam in it. Idle vacuum is 10in/hg at 1000rpm, that I’m sure bleeds off quite a bit of compression.

 

[lewtot184]

I don't think big cams by themselves are an ideal option to cover for cylinder pressure issues. It's never done right because people don't understand how to bleed pressure.