383ci making 340whp - advices needed
07-19-2008, 01:11 PM
#81
well, you could do a cranking compress. test to make sure you dont have a valvetrain problem, or worse a ring problem. find out what the cranking compresion is with all the sp. plugs removed, and the throttle held wide open. search for dynamic compression/cranking compression to see how yours compares, and that all cyl.s are pretty close to equal. I believe the acceptable range is 10%. so if one cyl has 150, they should all be near that. with no more then a 10% swing from lowest cyl. to highest cyl. press.
that would show that the pushrod length is correct, and that the valves are doin there job, and that the cyl. rings are sealing to the walls reasonably. last I remember, typical LS1's are around 220psi with the typical 11:1 ish cr most people shoot for with heads/cam. do you have the cam card? you could also get a degree wheel kit and double check that the cam you actually have, is the one he told you. its a little trickier to test in the car with the heads on, but intirely poss. for not too much money. but that wouldnt matter too much if your goin to replace the cam anyways.
chris
that would show that the pushrod length is correct, and that the valves are doin there job, and that the cyl. rings are sealing to the walls reasonably. last I remember, typical LS1's are around 220psi with the typical 11:1 ish cr most people shoot for with heads/cam. do you have the cam card? you could also get a degree wheel kit and double check that the cam you actually have, is the one he told you. its a little trickier to test in the car with the heads on, but intirely poss. for not too much money. but that wouldnt matter too much if your goin to replace the cam anyways.
chris
08-17-2008, 06:29 PM
#84
I've just realised that my torque curve falls way too fast. It reaches maximum at 4500-4600, and power starts to drop after 5300-5400. From 4500 to 5700 it drops 20%. Does it look right?
Here's graph from GTech, numbers are some 50whp lower than they should be, but it's shape of curves that is important
Here's graph from GTech, numbers are some 50whp lower than they should be, but it's shape of curves that is important
08-18-2008, 03:04 PM
#85
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well hell u beat me you may have to pull a couple of the studs out,that makes it alittle easier.a 59 cc chamber would really help but if you don't want to pull the heads you will have to make a compromise.
what does your complete exhaust setup consist of,long tubes and a good ory ?
maybe go with a cam like a 232/236 on comp xer lobes or xfi of similar duration on a 110 +2 or so to try to keep the dcr as high as possible to keep from killing your torque. hit up predator-z or patrickg on here and they should steer you in the right direction.
what does your complete exhaust setup consist of,long tubes and a good ory ?
maybe go with a cam like a 232/236 on comp xer lobes or xfi of similar duration on a 110 +2 or so to try to keep the dcr as high as possible to keep from killing your torque. hit up predator-z or patrickg on here and they should steer you in the right direction.
if it was me and you are planning on forced induction just pick up a good used nitrous kit jet the hell out of it and have some fun.....good luck
08-18-2008, 03:06 PM
#86
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what I've just realised that my torque curve falls way too fast. It reaches maximum at 4500-4600, and power starts to drop after 5300-5400. From 4500 to 5700 it drops 20%. Does it look right?
Here's graph from GTech, numbers are some 50whp lower than they should be, but it's shape of curves that is important
Here's graph from GTech, numbers are some 50whp lower than they should be, but it's shape of curves that is important
08-18-2008, 10:15 PM
#88
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It's been said already, but I would swap cams and if I still wasn't happy, spray it! Good luck! G-Tech's can provide a decent performance measure, and certainly can measure any improvements from parts changes.
08-19-2008, 02:23 AM
#89
I'm already spraying it, but can get at most 45whp from 125 shot.
As I understand, for some new cams I will need another rockers and smth. else? How do I make sure I buy cam that will work with my 7.400" rockers (that's what I have according to previous owner)?
As I understand, for some new cams I will need another rockers and smth. else? How do I make sure I buy cam that will work with my 7.400" rockers (that's what I have according to previous owner)?
08-19-2008, 06:38 PM
#91
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Do you think cam won't give me some 25whp for this engine?
You see something is still wrong even when we account for low compression. When CR was discussed here on forum I remember seeing 3-4% increase of power/torque for one point of CR.
So if I'd have 11.2:1 instead of 9.2:1, I'd have only 6-8% more, that would make 360-370whp. Is that really what 383ci should produce?
I'm totally new to LSx scene, but from reading around I thought at least 450whp should be no problem on manual 383ci car?
You see something is still wrong even when we account for low compression. When CR was discussed here on forum I remember seeing 3-4% increase of power/torque for one point of CR.
So if I'd have 11.2:1 instead of 9.2:1, I'd have only 6-8% more, that would make 360-370whp. Is that really what 383ci should produce?
I'm totally new to LSx scene, but from reading around I thought at least 450whp should be no problem on manual 383ci car? As an example...my 383 made 484 RWHP/440RWTQ..N/A with the following.
59cc LS6 heads (bigger valves)
11.2-1 Compression
Cam was 229/242 .631/.631 114 CL
Fast 90 intake/90mm TB
LT's/ORY/Catback
Is it necessary to change them if I put a bit wilder cam? Wouldn't want to do that, to be honest
09-17-2008, 05:28 AM
#93
Finally measured compression on mine (it's hell on this V8!!), it was about 11bar/160psi, with difference between cylinders about 4 psi.
However while I was taking plugs out, engine has cooled down a lot, plus my battery is not new, that might account for few psi. Also I think a bit of oil is going in the cylinders.
But in general, is this compression OK for 9.2:1 engine?
However while I was taking plugs out, engine has cooled down a lot, plus my battery is not new, that might account for few psi. Also I think a bit of oil is going in the cylinders.
But in general, is this compression OK for 9.2:1 engine?
09-25-2008, 07:30 PM
#95
compression sounds about what Id expect to see. the fact that there all near the same means the cyl. walls are good. as for the 110mph question, no. my car made 320rwhp on mustang dyno, and that was unlocked so maybe locked it would be closer to 345. and I trap 113-114 running 11.7's. with a 3800 stall obviously through an auto and 3:42 stock rear. being a stick, Id expect your mph with the same exact power to be 3-5 mph higher then mine.
09-25-2008, 11:29 PM
#98
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Hear this out -
You bought a LOW COMPRESSION motor, which is obviously not going to run well NA. It is built for turbo or SC.. which you already know, so my question for you is - Why would you buy a low compression motor and want to run it before you can afford an FI setup? If you can't afford it, WAIT UNTILL YOU CAN!!
There is nothing "wrong" with your engine.. but everything is wrong with your planning/setup!
Cam choice is BAD for an NA motor.. and the low compression is killing you the most.
That being said, DECIDE WHAT YOU WANT TO DO AND WHAT YOU CAN REALISTICALLY AFFORD! I've noticed you're worried about $$ when changing parts.. how were you planning on affording the turbo setup? I'd honestly swap out the pistons and throw a cam in it. Cheap (compared to a turbo) and it will run like it should, to it's fullest potential.
And NO I didn't read the whole thread, just the first page or two, so if you've answered these.. disregard this post.
You bought a LOW COMPRESSION motor, which is obviously not going to run well NA. It is built for turbo or SC.. which you already know, so my question for you is - Why would you buy a low compression motor and want to run it before you can afford an FI setup? If you can't afford it, WAIT UNTILL YOU CAN!!
There is nothing "wrong" with your engine.. but everything is wrong with your planning/setup!
Cam choice is BAD for an NA motor.. and the low compression is killing you the most.
That being said, DECIDE WHAT YOU WANT TO DO AND WHAT YOU CAN REALISTICALLY AFFORD! I've noticed you're worried about $$ when changing parts.. how were you planning on affording the turbo setup? I'd honestly swap out the pistons and throw a cam in it. Cheap (compared to a turbo) and it will run like it should, to it's fullest potential.
And NO I didn't read the whole thread, just the first page or two, so if you've answered these.. disregard this post.
09-26-2008, 01:08 PM
#100
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Low compression + baby cam = low hp. It's setup for FI, and to make it run good NA you will need to change it around. If you don't want to spend the money doing that, wait untill you can afford the boost. Even changing the cam isn't going to give you the numbers you should have.. it may help some but compression would help the most.