Blown Ls7
Thread Starter
Burning Brakes
Joined: Feb 2004
Posts: 885
Likes: 0
From: Point Pleasant wv
Blown Ls7
I need some help on an issue I'm having with the LS7 I have installed into my 2001 vette. Here is the problem I had a LS7 built by Texas Speed and Performance ( Specs on the car are as follows:
Eagle ls1 stroker crankshaft
Eagle Ls1 h beam connecting rod set with arp bolts
texas speed ls7 flat top pistion set 3.88cc valve relief for ls7 heads
cnc ported ls7 heads
ls1 camshaft 232/240 .609"/.623" 115 lsa
arp head bolts
cometic head gaskets .051"
Procharger f1
A and A 8 rib pulley system
60 lb motron injectors
Here is the issue, my car on the dyno is at 700 lb of torque at 3700rpms and running 10 psi of boost,I'm being told that the Compression is to high (about 11.1) for this application! And if I lower the boost it will not help me! Because it would make the motor use extra power to turn the blower!And also the motor will not last long running like this! Anyone have any Ideas? Or Help? Its stressing me out LOL!!!
Eagle ls1 stroker crankshaft
Eagle Ls1 h beam connecting rod set with arp bolts
texas speed ls7 flat top pistion set 3.88cc valve relief for ls7 heads
cnc ported ls7 heads
ls1 camshaft 232/240 .609"/.623" 115 lsa
arp head bolts
cometic head gaskets .051"
Procharger f1
A and A 8 rib pulley system
60 lb motron injectors
Here is the issue, my car on the dyno is at 700 lb of torque at 3700rpms and running 10 psi of boost,I'm being told that the Compression is to high (about 11.1) for this application! And if I lower the boost it will not help me! Because it would make the motor use extra power to turn the blower!And also the motor will not last long running like this! Anyone have any Ideas? Or Help? Its stressing me out LOL!!!
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
If your engine isn't knocking, I don't see why you can't keep running it. You can turn the boost down a couple of pounds though. It won't be as parasitic as you're acting. If you're nervous about it, sell your pistons and put some lower compression ones in or have cometic custom make you a set of .120 head gaskets. Lowering your compression with head gaskets is not the optimum way to do it because you kill your quench which affects the efficiency of combustion by slowing the flame propagation in your cylinders which will in turn increase the need for timing, yet increase the possibility for detonation. Your 3 best choices are to get new pistons, turn your boost down a little, add meth. The nice thing about centris is that they don't build too much boost down low, so that helps your situation a little bit.
Burning Brakes
Joined: Mar 2005
Posts: 822
Likes: 1
From: Henderson Texas
just run it on good gas when you are going to go and play with it on the street or the track and don't worry about it too much. you probably should have specified a little lower compression though when you had the motor built though.
Racer
Joined: Dec 2006
Posts: 322
Likes: 0
From: Alexandria Louisiana
St. Jude Donor '08
Detonation
I'm with Bret. Add methanol injection and/or use some Torco to raise your octane then U'll be OK. TSP builds solid motors & it looks like yours has all of the important forged stuff so enjoy!! 
Just a stupid question for my own curiousity - why'd U have the motor built w/11.1 CR if U were planning on going FI or didja buy it already built?
Still, the additional compression makes for some GREAT low end power, doesn't it??? 
Gene
Just a stupid question for my own curiousity - why'd U have the motor built w/11.1 CR if U were planning on going FI or didja buy it already built?
Still, the additional compression makes for some GREAT low end power, doesn't it??? Gene
Last edited by Mean Gene55; Sep 4, 2008 at 10:44 AM. Reason: add comment
Racer
Joined: Mar 2006
Posts: 464
Likes: 0
From: silverdale washington
The only real thing that matters is what your DCR is. Find an online calculator or the shop who built it should be able to tell you. Then tune a little fat and shoot meth. As long as it dont knock you should be fine. At least with the centri you wont make alot fo boost when lugging the engine which works to your advantage.
Thread Starter
Burning Brakes
Joined: Feb 2004
Posts: 885
Likes: 0
From: Point Pleasant wv
Just a stupid question for my own curiousity - why'd U have the motor built w/11.1 CR if U were planning on going FI or didja buy it already built? Still, the additional compression makes for some GREAT low end power, doesn't it???
Gene[/QUOTE]
I really don't know how it got that high! I think it was an oversight on mine and TSP.I had told TSp it was going to be a blown motor.
Still, the additional compression makes for some GREAT low end power, doesn't it??? Gene[/QUOTE]
I really don't know how it got that high! I think it was an oversight on mine and TSP.I had told TSp it was going to be a blown motor.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
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Burning Brakes
Joined: Aug 2000
Posts: 894
Likes: 1
From: Bethel Township Ohio
Just a little more info. The car does knock with a 10.0-1 AFR and 6degrees of ignition timming. Thats how we found out the motor was 11.4 to 1 not 9.0 to 1. I do not have the DCR in front of me but I can tell you with a 232/240 .609"/.623" 115 lsa cam on a 4.12 X 4 it is going to be WAY up there. I dont think we can back the boost down on a F1 to maintain 5 PSI unless it only makes boost for a very short RPM range. I also think the cylinder pressure will be to much on pump gas at 5 PSI.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
Like I mentioned earlier, if you have no knock, drive it. If it's knocking, better to pony up for some pistons now rather than whatever else you damage later. I would have meth no matter what you decide.
There are a few cars out there running stock compression and 10psi boost with more timing and no knock. I had a Maggie with 10psi and 10.5:1 and no knock and those put more cylinder pressure on the table at lower rpm's for sure which I would expect to induce knock.
There are a few cars out there running stock compression and 10psi boost with more timing and no knock. I had a Maggie with 10psi and 10.5:1 and no knock and those put more cylinder pressure on the table at lower rpm's for sure which I would expect to induce knock.
Last edited by BLOWNBLUEZ06; Sep 4, 2008 at 02:29 PM.
Le Mans Master
Joined: Sep 2000
Posts: 6,976
Likes: 527
From: Clouds Over California
I need some help on an issue I'm having with the LS7 I have installed into my 2001 vette. Here is the problem I had a LS7 built by Texas Speed and Performance ( Specs on the car are as follows:
Eagle ls1 stroker crankshaft
Eagle Ls1 h beam connecting rod set with arp bolts
texas speed ls7 flat top pistion set 3.88cc valve relief for ls7 heads
cnc ported ls7 heads
ls1 camshaft 232/240 .609"/.623" 115 lsa
arp head bolts
cometic head gaskets .051"
Procharger f1
A and A 8 rib pulley system
60 lb motron injectors
Here is the issue, my car on the dyno is at 700 lb of torque at 3700rpms and running 10 psi of boost,I'm being told that the Compression is to high (about 11.1) for this application! And if I lower the boost it will not help me! Because it would make the motor use extra power to turn the blower!And also the motor will not last long running like this! Anyone have any Ideas? Or Help? Its stressing me out LOL!!!
Eagle ls1 stroker crankshaft
Eagle Ls1 h beam connecting rod set with arp bolts
texas speed ls7 flat top pistion set 3.88cc valve relief for ls7 heads
cnc ported ls7 heads
ls1 camshaft 232/240 .609"/.623" 115 lsa
arp head bolts
cometic head gaskets .051"
Procharger f1
A and A 8 rib pulley system
60 lb motron injectors
Here is the issue, my car on the dyno is at 700 lb of torque at 3700rpms and running 10 psi of boost,I'm being told that the Compression is to high (about 11.1) for this application! And if I lower the boost it will not help me! Because it would make the motor use extra power to turn the blower!And also the motor will not last long running like this! Anyone have any Ideas? Or Help? Its stressing me out LOL!!!
At best you could lower the boost to 5-6 psi and run good gas (93-100 octane) and or meth and it should yield good results and should last.
Or you could simply take the blower off (sell it) and run a 150 shot on your motor if you want a little extra kick.
I am assuming those pistons are forged.
You are not going to lose that much torque on the bottom end with a 427cid that you will notice. You can't stab the throttle to wot in 1st and 2nd with a stock 427cid anyway. For your setup it would be best to be concerned about how it is pulling from 3500-6500 rpms. That's where the fun will be.
Former Vendor
Joined: Mar 2008
Posts: 2,279
Likes: 1
Nothing wrong with the CR but you will need a different cam to bring the DCR down. 11.4 leaves your window of tuning real small however. You need to be real sharp on your tuneup. If you can get some thicker gaskets ad get rid of that cam-get something like a 244/254 on XE lobes on a 112.
