Slow Blowthru engine build.

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
June wasn't bad or great on my Buick. It has been running great on the street but as soon as I get it on stage to do work at the local 1/8th mile drags, issues show up.
It was very hot to be out in the sun beating on the car and it had started building excess pressure in the cooling system but continued to run alright. Had boost problems all day that also led to over fueling and falling on its face. This same engine had gone through testing of two failed waste gate diaphragms and has seen several hits with boost nearly 40 psi and no fuel to cover it. Last week I got a new waste gate diaphragm and installed it in a different waste gate and went for a test drive of boost control and both or at least one Fel-Pro 9441pt head gasket has let go from all this. As time allows I'll swap in 2 new much better head gaskets and continue testing.
 
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WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
Last post in this thread from me in 2018.
Update: I'm repairing my engine hoist that I broke in July getting the Nailhead/TH400 out of my '82 Regal. Once it's working I'm pulling the 397 block out of the blowthough car for inspection and tear down, I need the heads/valve train.
I have a 3rd 109 block I'll be building in January, it will get everything from the old engine that is good (top end). It will be another stock crank/rods .030 over bore with speedpro forged slugs.
 

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
Old 397 block is out and I didn't see anything bad on the way out with it. The turbo survived whatever happened to the engine and I'll find that out this week with a tear down/clean up of parts I'm reusing.
20190127_224403.jpg
 

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
First time for this to happen on my stuff. This is after the first hit on the street with the wastegate being repaired, prior to that it had several hits with no boost control. #1 cylinder exhaust pushrod made it through the rocker arm, intake almost did. I found what looks to be two more rocker arms cracked.
20190128_223220.jpg
 

b4black

Well-Known Member
May 24, 2001
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Aurora, IL
www.flash.net
Yikes. I didn't know that was something that happens. Is the spring pressure too great, or is the cam lift too high? (Are the coil springs becoming bound - touching each other?)
 

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
Everything is setup right. That was the result of tremendous cylinder pressure and the pushrod trying to open the exhaust valve. Thick wall quality pushrods riding on top of a roller lifter the rocker arm was the weak point.
 

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
Pulled the odd bank head and no blown head gasket, head is good. I can see all the top rings intact on the odd pistons, so no ring ring break up. Removed even bank valve cover and had three more cracked stock rocker arms but none had the pushrod go though on that bank.
 

WarWagon

Caustic Cacophony
Mar 10, 2007
1,903
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Fairmont WV
I got taken off this job for a bit but back on. I removed the even bank head and it's fine. So not even one blown Fel-Pro 9441PT head gasket on this engine, no piston rings broken up. This is more proof this 397 casting is my hero block! Had the most nitrous sprayed through it, overheated several times and lastly seen the biggest boost number from me. I'll retire it now, onto another 109 block to build.
 
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