4.2 HG bore ok?

enkeivette

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Joined
Mar 30, 2008
Messages
990
Well I'm going to place my order with Jegs right now. My SBC is bored to 4.03, I was recommended a Fel Pro HG with a 4.166" bore. I'm ordering a thicker HG to lower the compression and this one will be a 4.2" bore, is that going to be ok?

I'm fairly certain that it is, but I just wanted to double check before I placed the order.
 
The only problem is if your block was plate honed with a 1003 and changing to a 4.200 will distort the cylinder differently but if it was not plate hined it wont matter at this point as you must be using the 1044 gasket correct.

Good luck Carl
 
.061, and I ordered it already :D It should bring me down from 9.4:1 to 9:1.
 
The consensus seems to be that with forced induction quench is either not a great concern or of no concern at all.

I've ordered the HG already. If the 4.2 bore is not ok, someone speak up while I can still return it.
 
using a thicker head gasket to compensate for wrong parts choice (heads/pistons) is not best choice but a necessity in this case... can't really change parts without a signifficant impact to budget.... if money wasn't an object I'd say get the pistons machined or get different heads to lower CR... messing with HG and quench to compensate for CR is not a good choice.... it might work and I wish you success with this but the first gasket blew for a reason and the next (thicker) gasket will also blow ..just my 2c...
 
The first gasket was a cheapo Fel Pro, not meant for boost. The new gasket will be an MLS. Not to mention, some of the head bolts felt loose. This time I will retorque after warm up. And maybe even periodically.

I've been discouraged from running 19lbs of boost in the future. So I'll probably stick with 15-16 when I get an intercooler, and I will be well within the safety net.
 
The consensus seems to be that with forced induction quench is either not a great concern or of no concern at all.

I've ordered the HG already. If the 4.2 bore is not ok, someone speak up while I can still return it.


I have built 3 Roots type set-ups. I always set up the quench at .045 or close as possible. Maybe the thinking here is that, because of the added turbulence caused by the pressure of the boost, quench is not the concern it is with a naturally aspirated engine.
 
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