Blown Head Gasket! w/large pics

[NecroWolf]

Re: Blown Head Gasket! w/large pics

don't suppose the seaant threw your torque specs off? 65ftlbs sounds awfully low for a head bolt. i'd suggest using the high side torque spec. and in all the 4.3 heads i have ever swapped i never used sealant on the bolt holes. and i did several on my xwifes blazer and there was never any leaking. l35 heads like to crack between the valve seats if they get hot and you don't get told about the truck over heating for a couple weeks

 

[supersports10]

Re: Blown Head Gasket! w/large pics

I used a straightedge on the block and it seems to be flat as can be, at least with my limited equipment. I could snap a photo with a bright light behind the straightedge if someone really wants to see.

Yesterday I took the head, gasket etc. to the machine shop for them to look over. They were surprised to find the head is still flat and reusable. They said it is likely because I only drove it for 5 miles after it blew. The 3 machinists agreed it was a very unusual way for the gasket to blow into the bores like that, all at once. While I waited, they milled my exhaust manifold for a nice seal when it goes back together.

Today I am going to start pulling the other head off (they strongly encouraged it).

To answer some questions:

Exhaust Porting: I meant to show the mismatch in the upper corners of the exhaust ports. I didn't think anybody would really try to port the entire manifold to match the head (you'd probably destroy the manifold)

Head Bolts: I did everything by the book 100%. Correct torque sequence, 3 sequences with loosens to burnish the threads followed by a final sequence, etc. Here's a look at the head bolts I pulled out, you can see all my sealer/moly lube:

sy445 Vortec bolt crack: Thanks for the tip, I checked but found nothing (These heads were brand new, even now they only have 700 miles on them and never even seen 195*F).

Detonation theories: The pistons look good, the plugs look good, the datalog looks good, I can't find any evidence it went lean ANYWHERE. Its still possible that something happened in the past on a run I didn't datalog I guess?? Look at Robert's melted JE piston, you would think if I was detonating, my Factory Stock pistons would have had that type of damage or worse..

Cometic Head Gaskets: Once again I am sitting on 1 pair of Victors and 1 pair of Cometics trying to decide which to use (just like last Fall). I did a Google search on cometic leaks and found dozens of threads. Even guys who had the block & head fully machined!! I paid $150 for these premium Cometic gaskets but man, thats a damn lot of work to put it together and "gamble" that it won't leak out the side of the block when I start filling it with coolant! I'm leaning towards using the Victors again and just crossing my fingers that this was a fluke. I mean, what else can I do?

i say go with the stacked head gasket plan :rotf:

i have 2 stock naturally asperated 4.3 gaskets stacked on the pass side i hit 27 psi, and stayed in it yesterday, and it is still holding!!!:tup:

fyi......my stock sy/ty gasket was 0.070

and a stock 4.3 gasket was 0.035

so 0.035 x 2 = 0.070

when my vortec longblock goes in i am going to be using double gaskets on those too!!:rotf:

also when i put mine together, i went a little further than the factory spec, and added 10 ft lb to the specs.:tup:

 

[Tooky]

Re: Blown Head Gasket! w/large pics

OK a few days ago I got the other head off and it took about 5 hours to do. Pull the head off and lo and behold........................... Nothing wrong!! Pistons look perfect and the head gasket does too. I contacted ARP Tech and while I'm not sure how deep they looked into it, the tech claimed the gasket failure appeared to be from detonation "even though it didnt show on your datalogs". The ARP tech also said it would be acceptable to increase torque by 10 FT-LB but that it won't solve my "detonation issue".

The heads are getting washed at the machine shop and the manifolds are getting blasted free of rust, in preparation of some high temp VHT FlameProof 1500* Cast Iron paint. I should get them back this afternoon and I'm sure I'll be spending at least another 12 hours putting it all back together.

Gonna just use the stock Victor gaskets and hope it doesn't happen again.

BTW Clint - my Cometic gaskets and stock Victor gaskets are both .040" - and the original gaskets I pulled off this GM shortblock were identical too. I would be suspicious whether your .070" gaskets were really stock?? If I remember I will measure my new Victors just to be sure.

 

[Don W.]

Re: Blown Head Gasket! w/large pics

Josh,

Have you thought of having the heads surfaced ever to slightly just to be sure they absolutely true?

 

[Tooky]

Re: Blown Head Gasket! w/large pics

Josh,

Have you thought of having the heads surfaced ever to slightly just to be sure they absolutely true?

The machine shop checked them over with intentions of surfacing but the machinist found that they are still flat and no surfacing is necessary. (Check post #19 )

 

[Don W.]

Re: Blown Head Gasket! w/large pics

Ya, saw the post. Was just thinking out loud. Kinda "better safe than sorry" thought, that's all.

 

[Tooky]

Re: Blown Head Gasket! w/large pics

Well they are the same shop that surfaced them in the first place last fall. Another concern brought to my attention from an engine-builders forum was that the Vortec heads apparently have an unusually thin deck surface, which some engine builders were concerned was flexing and the cause of my problem. (Judging by all the other Vortec SyTys not blowing head gaskets, I'm not sure I agree). But either way it seems like a reason to shy away from cutting the heads again (they already got cut .004" to begin with).

 

[Don W.]

Re: Blown Head Gasket! w/large pics

Yup, sounds good to me. Good luck with the re-install.

 

[Ty 1885]

Re: Blown Head Gasket! w/large pics

I always put silicone on the treads, and torque heads 75-80 psi. NEVER had any issues in 25 years!

 

[It's just a six]

Re: Blown Head Gasket! w/large pics

. I contacted ARP Tech and while I'm not sure how deep they looked into it, the tech claimed the gasket failure appeared to be from detonation "even though it didnt show on your datalogs". .

That is what I already stated.

http://www.syty.net/forums/showthread.php?t=58327&page=2&pp=15
Re: Truck started misfiring all of a sudden, need ideas

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You did the compression check when it was warm?
To me,it looks like slight detonation on your spark plugs IMO. Probably cracked rings?
We have borescopes @ work than can take videos or still pics,sorry can't lend it out. Very pricey.
Squirt some oil down the bad compression cylider after its warmed up & do another compression check.

 

[It's just a six]

Re: Blown Head Gasket! w/large pics

So what was the final outcome?

 

[Tooky]

Re: Blown Head Gasket! w/large pics

Well I never found out what caused it. Seems everyone I talked to or showed the gasket was either mystified or had a theory that didn't really match the evidence enough to convince me.

I put it back together and it took a total of 2.5 months downtime. I kept a log of how many hours I put into it but its 3 pages long. If anyone really wants to know I will add them up and post it here.

I used another pair of stock Victor 5855 head gaskets and the same ARP bolts at 65# torque. I compression tested the engine ice cold (I know that's not optimal) and the cylinders ranged from ~140 to 180! The good news is that obviously my compression is back up, but the bad news is that they never ranged so widely between cylinders.

I made a new thread about my wideband/O2 wiring problems that caused me a lot of trouble trying to get it running again. After I solved that I found the tune needed a lot of redoing for the warm summer weather, either that or I have spent so much time studying EFI tuning latley that I am now able to see more problems in my tune than I could see previously (probably a little of both.)

Now I'm just sorting out smaller bugs but it's back on the road and even in 90*F "Hottest day of the year so far" I had 1 or 2 runs with flatline 0.0 knock at 15-20 PSI and was spinning the tires a little bit from a 30 MPH roll in 2nd gear, DM Dyno is saying like 565 HP and 690 TQ so I know its getting back to normal.

I also put an especially small restrictive 2.5" dirty K&N air filter on the turbo with a 2.5" pipe, to test and see if it really causes a reduction in performance. It seems like the vacuum/sucking noise is louder under boost now, but if there's a drop in performance it's pretty slight. My theory was that if a small air filter significantly impacts performance, it would strongly suggest that a larger air filter would improve it. (I had been running a short 6" long, 3" diameter K&N cone filter 99% of the time.) So pretty soon I'll swap back to my normal filter and see if I really "gain" anything at all. If I don't, it proves to me that air filters are not worth wasting a lot of time on.

The 2 biggest issues I have now are the random stalling at idle apparently caused by a strange sudden drop in voltage, and the false knock all the time at part throttle. I still have knock disabled below 2800 RPM but man the thing picks up knock counts all the time, even under hard decel conditions where the fuel BPW is 0.0 and 20:0 AFR and the engine is just decelerating on its own! So I really think the knock is false but I'm hoping it's not caused by my hot camshaft. I really don't know how I'm going to solve this problem.

Once it cools off here I'm gonna get some high quality videos for you guys of the idle and some boost launch videos while the thing is running!!

 

[Tooky]

Reassembly Photos

Reassembly Photos

Here are some photos from during reassembly:

Getting close.....!

Getting closer!!

I spent some time "Polishing My Pipe!" :lol: I hand polished the upper portion of my PTE downpipe as it was getting rather dull. You can also get a great look at how KILLER my VHT "Cast Iron" high temp exhaust manifold paint turned out!

(So far the manifolds' hottest areas have turned a more chalky, lighter gray but no flaking or defects I can see, yet. I'll get some current pics and post them on my Exhaust Manifold Paint thread)


Here's a look at that restrictive air filter I put on for testing purposes...

I know a lot of you are thinking "What Kind of Guy Deliberately Chokes His Engine??" :rotf: :lol: :tup: :silly: But I can tell you so far, even this air filter would still run 11s in 90*F heat NO PROBLEM...

 

[It's just a six]

Re: Blown Head Gasket! w/large pics

Just curious, if the spool up time is any different/slower than w/no air filter or a large air filter?