(Ken)-96GMC K1500 SC

I have a built 383 stroker shortblock in my garage and it has -31cc dish pistons which is 8.5 to 1 with my 64cc Vortec heads and if I want 9.0 to 1 I will need to mill the heads so my chambers are 57cc as the thinnest headgasket I can run is .039 as my deck height is .005

I am running a Vortech V1-S-trim blower at 10psi max...down the road I plan on running a V1-T-trim at 15psi...this is through a 7.3L turbo diesel "huge" intercooler up front I was running 14.1@95.5mph with the old 350 engine with 130K miles on it at 8psi of boost (had stock internals at 9.4 to 1 compression)

This is in my GMC K1500 4x4 truck 5300 lbs with me in it.

How much difference in power will .5 compression make on the low end? Can anyone plug these numbers in a computer dyno software and let me know?

Cam is a Crower 214/220 476/496 114
Thorley Headers 1 5/8 w/high flow exhaust system.
80mm bbk tbi
Mildly ported vortec heads with 1.5 crane roller rockers.

BTW it has a built 4L60E trans with a 2500 stall TC boost is about 4psi at 2500rpms, shifts at 5300 rpms with 3.73 gears rimmomg 31" tall C rated tires on light weight 15" weld rims (60 lbs total)

Thanks for any help or suggestions guys!

Ken

1999stepside

Aren't the new Lightnings and Cobra's running 8:5 compression? They also have a roots style blower which may make up for the loss as opposed to your centrifigal?

Kent

Slowverado

this isn't an LS1 is it? you are in the wrong place if you want info on a non ls1 engine, these guys went of on some poor guy a few days ago for posting about a NON ls1 engine. good luck though.

Matt

XLR8NSS

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by slowverado:
<strong> this isn't an LS1 is it? you are in the wrong place if you want info on a non ls1 engine, these guys went of on some poor guy a few days ago for posting about a NON ls1 engine. good luck though.

Matt </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">What thread? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Pro Stock John

iTrader: (34)

If you plan to run a T-trim I would keep it at 8.5:1... Since you have a 383ci the torque from extra cubes will help your low end. Plus at 15 lbs of boost you might need that reduced compression to avoid needing race gas.

I have a 99 Tahoe with the 5.7 Vortec (L31) so I hope you keep posting here there are a few of us here. I only have a catback so far but UPD is coming out with an airbox for our trucks.

John
16.3 bonestock

XLR8NSS

iTrader: (4)

Hi Ken (Glad to see you over here <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> )

I typed up something last night but, when I hit Add Reply the board was down. <img border="0" alt="[bang head]" title="" src="graemlins/gr_banghead.gif" /> <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Anyway, to summarize <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

At the boost levels your talking about stick with the 8.5:1 cr. Like PSJ said the added cubes will help as well as the extra boost you'll be seeing down low. That extra .5 point in compression won't be worth but 10-15hp at the most. I just did up a quick 383 on Desktop Dyno 2000 and going from 8.5 to 9.0 cr was only worth 7-10tq and 3-10hp across the rpm range.

Are you planning on pulleying for 15psi by 5300rpm? <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> That will make for a very responsive setup but, may require a little more than 93 octane. I'd think 12-13 would be alot safer on pump gas. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

We may not be the best place for non LS1 based info but, we'll help if we can. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

John

GREGGO

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by slowverado:
<strong> this isn't an LS1 is it? you are in the wrong place if you want info on a non ls1 engine, these guys went of on some poor guy a few days ago for posting about a NON ls1 engine. good luck though.

Matt </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">John, this is the thread Matt is refering to:
https://ls1tech.com/ubb/ultimatebb.p...;f=18;t=003190


Matt,
Some of the guys that come on here from other boards without LS1 based engines are very welcome to ask questions if they want. One thing we have in common is the truck. In this instance, Ken is very welcome here. He is a very smart guy that can help a lot of us out. He experiments with different things and is very thorough in his findings.

Anybody else reading this:
Please don't bash the non-ls1 based guys. We are all here to help each other out. If you can't answer a TBI based question, then don't and go on. But other than part specific, the goals are the same. PERFORMANCE. If enough guys come here that have TBI based trucks, maybe onday we can create a forum for pre 99 trucks and pre 2000 SUV's.

Ken,
Looks like PSJ and XLR8NSS did more help for you that I could, so I'll agree with them. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

hyde

Ken, if you can get the compression get it...It will only make that much more power...Guys don't forget he is talking about intercooling the blower, with that he will lose some boost so 15 might only be 13...Plus it will be cooler so less detonation. People forget, that once over 10 psi boost multiplies, and does not follow the standard hp increases. So to answer your question, yes i would add the compression, so if you have the belt off it still runs good. Tap your lower intake at the head and see what your psi is there not off a vacum off the intake, it will be differnt...Good luck

XLR8NSS

iTrader: (4)

Hyde - you bring up some good points. He already has the intercooler on the truck though afaik so I'm assuming he is talking about the actual manifold pressure when he says 15psi.(not blower outlet pressure)

If you read about his old motor I don't think he'll be taking the belt off very often.(130K miles at 8psi) <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

The compression issue really depends on what type of gas you want to run this on. I'm only assuming Ken is talking about pump gas. In that case take the slight loss of N/A performance for the added safety under boost. If we're talking about running 15psi with race gas and less boost with 93octane then by all means increase the cr a little. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John

hyde

Well John, you can get away with pump gas and 15 psi you just have to under normal take out 2 degrees of timing or so to kill the det. But with the intercoller he should be a OK...Look at all the Procharger adds....There compression and boost numbers on pump gas.....