lowering compression - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 13 (permalink) Old 06-10-2007, 05:50 AM Thread Starter
 
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lowering compression

Would it be a good idea to try and lower my compression... I am running about 550hp and I was wondering what the advantages of running a thicker head gasket would do.?
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post #2 of 13 (permalink) Old 06-10-2007, 01:51 PM
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I don't know, I have heard that running a .010 or .020 marine gasket can lower compression a little. And other times I have heard it doesn't make that big of a difference.

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post #3 of 13 (permalink) Old 06-10-2007, 04:48 PM
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Lowering compression will allow you to run higher peak cylinder pressures, thats about it. Running a 12v marine gasket will lower compression, but only slightly, In that situation, you are really only doing it for a little extra security so you don't pop a head gasket, But it doesn't give you that much extra room.

If you're really serious about lowering compression I would suggest pistons. But I don't really think you have to worry about getting your cylinder pressures that high in a VP44 equipped truck. Just studs and o-rings and a marine head gasket should keep you plenty safe to get near the max potential of that pump.
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post #4 of 13 (permalink) Old 06-10-2007, 05:53 PM
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How much boost are you pushing and are you injecting anything else in the mix?

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post #5 of 13 (permalink) Old 06-10-2007, 08:30 PM
 
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Quote:
Originally Posted by diesel_ram_man
I don't know, I have heard that running a .010 or .020 marine gasket can lower compression a little. And other times I have heard it doesn't make that big of a difference.
It does but it is a very small amount. mustly like sean said it lowers pressures and reduces chance of blow-out.
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post #6 of 13 (permalink) Old 06-11-2007, 05:53 PM
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Good advice above. On a VP truck, a .020" Marine gasket and studs should hold everything you are going to throw at it. If you start ruuning boost over 55-60psi consistently you could also consider o-ringing the head. Although that is a crap shoot on a 24v.
post #7 of 13 (permalink) Old 06-13-2007, 06:50 AM Thread Starter
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Right now on my truck with it turned all the way up.. When it locks in 3rd and 4th gear I am running anywhere from 58-62psi... I have a 60lb boost gauge and I can make it go past 60lb on lockup sometimes at the track with the right weather conditions. I have studs, I thought that lowering the compression actually helpded on the #s a little. What about the ATS plenum do these things actually help when your in the mid 500hp range??
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post #8 of 13 (permalink) Old 06-13-2007, 05:17 PM
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I've heard mixed reviews on the plenums. If you do a gasket to lower compression you probably won't see any performance gain, you're just lowering it enough to hold a little more boost. I think you're safe to run more boost than that with the stock gasket and studs, but thats just my opinion.
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post #9 of 13 (permalink) Old 06-14-2007, 03:23 PM
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Quote:
Originally Posted by sstockton
Lowering compression will allow you to run higher peak cylinder pressures, thats about it. Running a 12v marine gasket will lower compression, but only slightly, In that situation, you are really only doing it for a little extra security so you don't pop a head gasket, But it doesn't give you that much extra room.

If you're really serious about lowering compression I would suggest pistons. But I don't really think you have to worry about getting your cylinder pressures that high in a VP44 equipped truck. Just studs and o-rings and a marine head gasket should keep you plenty safe to get near the max potential of that pump.
Sean
Lowering compression also let's the engine turn more RPM's without destroying itself. I worked on a Super Stock tractor one summer. It was decompressed to ~14:1 (as I recall) by machining the pistons. On a pull, it would turn upwards 7500 RPM's on an engine that redlined at 2400 RPM's from the factory. Decompressing makes diesel engines much harder to start. The puller could only be started on ether and would hardly idle. On startup and low RPM, it would belch out clouds of that whitish grey smoke that is the telltale sign of a low compression diesel engine.
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post #10 of 13 (permalink) Old 06-14-2007, 03:53 PM
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Thanks, thats good info. I haven't really played with a truck that was running lowered compression. Just what I've heard from others. That RPM thing makes a lot of sense, then you'd just need to fuel that high.
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
www.totalperformancediesel.com
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