Why do I keep blowing head gaskets?

-
RockinRobin said:
UPDATE: Gasket failed between 4-6 and 6-8. #2 was fine. View attachment 1716295978
Click to expand...
I agree with @Newbomb Turk that looks like a tune up issue. And it may not be taking months to do the damage. You could have a problem in really good, cool air and not have those conditions all the time. Do you keep track of DA and weather conditions for your runs?
 
We have a blown bbc at w.o.t. with 12lbs of boost the compression is 15.5 to 1
It runs on 100 LL av gas with a quart of toluene per 5 gals.

From the research we've done
100 LL av gas will support up to 15 to 1

The added toluene we put in just bumps up the octane a bit and slows the burn.

The OP should be fine with straight 100 LL av gas. (do your own research to make your decision.)

Also it's typically only about 1 dollar per gal. More then 91 here in AZ.
We recently had this Engine apart for a refresh and it was perfect inside.
No signs of detonation
We even reused the rod bearings because they looked like new after 5 years of running.

Just Our Experience...
 
If the engine overheated from coolant loss, the alum might have lost it's heat treatment & gone 'soft'.
 
TT5.9mag said:
I agree with @Newbomb Turk that looks like a tune up issue. And it may not be taking months to do the damage. You could have a problem in really good, cool air and not have those conditions all the time. Do you keep track of DA and weather conditions for your runs?
Click to expand...
Yes I do. The last time we had good cold air was February. March was cool but high humidity drove the DA's up this year.
 
RockinRobin said:
In my case it takes a year of beating it at the track. An average of 2 races per month and we run 10 months out of the year. If it was detonation I would think it would show up a lot sooner than that.
Click to expand...
Forced induction really speeds up the process. It's cheap to try a higher-grade fuel
 
Well, I'm being told by the modern Hemi folks that for hi compression Gen 3 's the gasket to go with is the Cometic MLX series. I can get them for $108.00 a piece in about 2 weeks, or get them right now for almost $300 a piece. Going to put a Fel Pro in there right now and finish out this season with it, then look at the Cometic MLX over the winter.
 
I think the finish on the head surface has a lot to do with seal. Block as well. The aluminum has almost a mirror like finish. 13.5 static is not that big of deal, depending on cam specs. Sounds like maybe a few little things adding up to the big thing.
 
Had to google it. Apparently 2 ways to "O-ring the head". Generally means a groove cut in the head for a stainless-steel wire, which aligns with the softer "fire ring" of the head gasket to crush into it. The wire sits proud of the head surface ~10 mil. Stronger sealing is a "fire ring", which is a similar mild-steel wire in a groove cut into the head, but it squashes against the block. You cut out the integral fire ring in the head gasket to allow that. The later might only be done on Cummins diesel engines with high boost (1st link).

But, raises a thought. Owners of 273 engines have fretted over the over-size fire rings on the "interchangeable" small block gaskets, since that leaves a large quench zone. Perhaps it fills with carbon so no issue. If not, seems you could install a mild-steel fire ring in a groove, which would be inside the gasket's fire ring so you don't need to cut it out, giving a belt & suspenders sealing. Downside is looks like ~$500 per head, plus high shipping unless a local shop does it. Would be great if the Chinese aluminum head makers would offer this, at least for the 273, for say $100 extra. The ring might have to be soft copper for an aluminum head to squash it. If really lucky, might be a standard-size metal seal ring which fits. We used those in aerospace propulsion (usually C-channel metal ring) to seal pressures above 1000 psig since rubber O-rings tend to extrude at those pressures, even with a teflon back-up ring, plus need metal for higher temperatures.

https://www.ruttsmachine.com/assets/pdf/literature/en/Fire-Ring-vs-O-Ring.pdf
Cylinder Head - O.Ring Service
 
BillGrissom said:
Had to google it. Apparently 2 ways to "O-ring the head". Generally means a groove cut in the head for a stainless-steel wire, which aligns with the softer "fire ring" of the head gasket to crush into it. The wire sits proud of the head surface ~10 mil. Stronger sealing is a "fire ring", which is a similar mild-steel wire in a groove cut into the head, but it squashes against the block. You cut out the integral fire ring in the head gasket to allow that. The later might only be done on Cummins diesel engines with high boost (1st link).

But, raises a thought. Owners of 273 engines have fretted over the over-size fire rings on the "interchangeable" small block gaskets, since that leaves a large quench zone. Perhaps it fills with carbon so no issue. If not, seems you could install a mild-steel fire ring in a groove, which would be inside the gasket's fire ring so you don't need to cut it out, giving a belt & suspenders sealing. Downside is looks like ~$500 per head, plus high shipping unless a local shop does it. Would be great if the Chinese aluminum head makers would offer this, at least for the 273, for say $100 extra. The ring might have to be soft copper for an aluminum head to squash it.

https://www.ruttsmachine.com/assets/pdf/literature/en/Fire-Ring-vs-O-Ring.pdf
Cylinder Head - O.Ring Service
Click to expand...


The O rings need to be stainless steel and you need to use dead soft copper gaskets.
 
B99315C1-539A-4160-886C-C02DB41F719D.jpeg
 
You must log in or register to reply here.
-

Back
Top