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10-15-2003, 01:44 AM
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quench question for the blower guys
ok i ended up nearly .030 in the hole. i am using speedpro blower pistons 76 cc heads is suppost to yeild 7.55 to 1 cr. think i need to have it decked? i also checked into getting block o-ringed was quoted 75 usd. i thought it was going to cost much more so i was shying away from it, but now i am thinking might as well. the only drawback is having to run copper head gaskets? so the block is going back to the machine shop anyway.
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10-15-2003, 02:09 AM
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I`d shoot for a Quench distance of around .045, anything up to .060 is okay, but not past, if you run it around .040, make sure you check the piston to wall clearances, enough piston rock and the piston will kiss the head. that`s why i perfer it to be in the mid to high 40`s to give it a little leeway after wear takes place. I`d think to have it O ringed is a good idea.
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10-15-2003, 12:57 PM
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Having the block oringed is not a bad idea, but unless you are going crazy with boost it is probably not needed. Small chevys hold a gasket better than most other engines since they get 5 instead of many others 4 head studs per cylinder. Notice I said studs since you need to plan on them with the boost. They will also help keep things in place. I thought about having mine oringed, but decided against it after someone brought up a good point: If you oring, the pistons could become the fusable link when you detonate it. I say when because it will happen at some point unless you are just pouring fuel to it or you have a super high dallar EMS system. If you stay with the standard race composite head gasket, it will likely let go before anything else craters. I actually have run across guys that have lost pistons before the head gasket on small chevys with no orings.
It is kindof a judgement call, and not an easy one. Chris
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10-15-2003, 03:23 PM
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appreciate the replies. i guess i am the only one here thats has an uncurable need for more speed. my thinking is once i am o ringed i can turn up the pressure more with less worries and having reusable head gaskets appeals to me as well i like to work on and experiment with my stuff but i hate buying parts. plus there is hopefully not going to be a better time to do it. head studs are going on that decision was already made thanks for looking out. as much fun as i am having building this thing once i take it to the track then it needs to stay together as long as possible since i built it myself is a pride thing. i have learned a great deal here and am thinking about having 2 blown cars cause i know a couple of places i could have done better but i had to do it to find this out.
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10-15-2003, 04:54 PM
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these sreedpro blower pistons are same as the trw L2441F has the same number even, the difference is they have started duracoating the skirts of the forged pistons like they have been doing with the hyper-pathetics. my bore is 4.031 as far down as i can measure (at least 4 inchs) which is right where its suppost to be but the things will rock a bit. when measuring deck height it will come up .025 one one side .030 on the other one revolution and switch on the next. i hope this goes away when i put another rod on the journal and the other 23 ft lbs on the rod bolts. i am not real impressed with these slugs so far. i have never had a piston that can go in the hole crooked (even though the bore is correct) before but these can and will until you tighten the rod caps. i don't wanna tourqe the rods to spec until i have good deck height to prevent bolt stretch, plus i am not looking foward to taking these dowel h beams apart again is hard enough outside the block, any thoughts on splitting them on the crank? double vision we have that heart of dixie on our car tags where i live are we neighbors?
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10-15-2003, 07:56 PM
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our tags used to say Alabama
and under it was Heart Of Dixie now it says "stars fell on Alabama" and I hate it, makes it sound like a bunch of sissies live here, I can`t say the reason why it was changed without offending some.
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10-15-2003, 09:11 PM
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dang they did change those things. mine has 47 first 2 numbers. same as before everything else is different though. and i know what you mean.
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10-16-2003, 12:49 AM
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I also agree on the o ring issue.
Its not needed at anything but extreme levels and its much less trouble to replace the head gasket than the pistons  On my 72 camaro Im running 19lbs of boost on 7.5.1 355 with a 6-71 and I dont have my block o ringed. I do run some good gaskets as well as studs though.
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