L92/L76 427 results and questions (*edit, big gains later)
05-25-2008, 12:19 PM
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L92/L76 427 results and questions (*edit, big gains later) I have a TSP selected combo using an LS7 block, 10.9 to 1, TSP ported L92 heads and 240/248/.608/615/112+3 cam. Attached is my dyno sheet after a full tune. Before you go off about how terrible the numbers are, please consider that the engine is showing less than it's potential because the motor is currently in my '03 S10 pickup, and could be held back by any of any of the following factors:
Intake tract: 100mm maf to 85mm plastic intake elbow piece to 90mm TB ?
11" Yank truck torque converter
Very heavy wheels
Very heavy 2 pc driveshaft
1 3/4 LT headers w/ 3 tubes moderately dented to clear stuff, they have 3" collectors going into 2.5 dual mid pipes, no cats, into Magnaflow dual in / dual out 2.5 muffler w/X-pipe into crush bent dual 2.5 tail pipes.
Now, here are my real questions. This motor is going into our '02 Trans Am M6 next weekend, and I am debating about how much the poor power curve is related to the above factors vs. the compression and cam. I will be using TSP 1 7/8 headers in the car, with a better overall intake and exhaust setup.
Should I just leave it alone and see how much it improves in the car, or do some of you know for a fact that if I changed the cam I could gain a ton of low and mid back without giving up much if any high end ?
Thanks in advance for any intelligent feedback.
Erik
Intake tract: 100mm maf to 85mm plastic intake elbow piece to 90mm TB ?
11" Yank truck torque converter
Very heavy wheels
Very heavy 2 pc driveshaft
1 3/4 LT headers w/ 3 tubes moderately dented to clear stuff, they have 3" collectors going into 2.5 dual mid pipes, no cats, into Magnaflow dual in / dual out 2.5 muffler w/X-pipe into crush bent dual 2.5 tail pipes.
Now, here are my real questions. This motor is going into our '02 Trans Am M6 next weekend, and I am debating about how much the poor power curve is related to the above factors vs. the compression and cam. I will be using TSP 1 7/8 headers in the car, with a better overall intake and exhaust setup.
Should I just leave it alone and see how much it improves in the car, or do some of you know for a fact that if I changed the cam I could gain a ton of low and mid back without giving up much if any high end ?
Thanks in advance for any intelligent feedback.
Erik
Last edited by esams; 12-16-2009 at 10:33 AM.
05-25-2008, 01:13 PM
#2
That is ugly. I feel the cam is too big for the L92 intake. I would go with something smaller. I have the same package in my m6 f-body with a small cam and have 475 ft lbs at 3300rpm. With the monster cam I had 257/266 I had a pk hp of 570 but this small cam package will walk all over that big cam with these heads and intake. I think I gained something stupid like 150 ft lbs down low over the peak hp cam.
05-25-2008, 05:22 PM
#3
That is ugly. I feel the cam is too big for the L92 intake. I would go with something smaller. I have the same package in my m6 f-body with a small cam and have 475 ft lbs at 3300rpm. With the monster cam I had 257/266 I had a pk hp of 570 but this small cam package will walk all over that big cam with these heads and intake. I think I gained something stupid like 150 ft lbs down low over the peak hp cam.
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05-25-2008, 10:55 PM
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Yes the converter was run unlocked. 3000 Yank which is probably really a 3600 behind this motor. My previous motor dynoed equally low proportionately, that is why I listed the above factors so everyone doesn't just think my motor combo sucks. I had a 10.1 compression LS1 346 with Dart 225 heads, 228/228/.588/.588/112 cam in there and it only dynoed 320hp/300tq in the truck.
So...... I guess it's cam time, so do I hear any recommendations besides what BUSA is running ? Sounds like I can't go wrong with that one anyway.
So...... I guess it's cam time, so do I hear any recommendations besides what BUSA is running ? Sounds like I can't go wrong with that one anyway.
05-25-2008, 11:15 PM
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I also meant to say that I am open to having this motor being a science project for all of us to learn, so really tell me some cams that you would like to see run in this motor and I will test them out for us. I don't have a problem springing for 3 to 5 of them in a year and having the vehicle re-tuned for them. As soon as a better intake comes out, I will put that on too.
Remember this is going in an M6 TA now, the auto/stalled truck is going bye bye.
Remember this is going in an M6 TA now, the auto/stalled truck is going bye bye.
05-26-2008, 08:50 AM
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Ow man I think you got the bigger is better bug from them guys at TSP they are a great group there but they usually use too big a cam for these engines. Heck guys with the LS7 top end like me are even using smaller cams, and our heads and intake outflow the L92/L76 stuff stock unported. I can tell you from experience that I have tried more cams then most on my combo and the one I settled on was acually one of the smallest. Now just to give you an example I have a QM600 cam high 240 intake, high 250 exhaust, 657/648 113+2, A GT21 238/254 640/631, a torquer by katech 220/244 615/648 110, my patrick G custom 244/256 657/630 110+4, and my Lethal Z custom 231/249 640/640 113+2. Now I tested all of these on my fully built 427 and I have about 11.8 to 1 and my patrick G made the most peak out of them all. It is a great cam but for a car driven daily it was not the most pleasent to drive. My fault cause I told him when he speced it that I didnt care bout driveability, but drive it for a few monthes and it gets old LOL. So I talked with Mr Z bout his cam even though it was small (the Lethal) he said it had great driveability, killer torque, and great top end pull. I was a little skeptical but decided hey why not give er a try. I cant believe the way my car behaves, great driveability, fantastic lope not excessive, alot better MPG, instant insane torque throughout the powerband, and it makes the most average rwhp out of all my cams. The other cams are very peaky some peak great down low the torquer and GT21 both behave pretty good great torque and midrange but only ok top end. I have learned that timing events are so important to how the car runs and makes power. I have over 400 rwtq from just over 2700 and it dont go below that even up too redline at 7100, im over 500 from 3900 too 6300. Cant beat that onslaught of power!!!! So what you need to do is get a cam thats set up for the heads and you will be so happy you did
05-26-2008, 12:39 PM
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Thanks for the great feedback. Regarding the compression, we do only have 91 octane here in AZ, so should I leave it at 10.9 or would it be worth having the heads milled .02 to get 11.2 or so ? On the exhaust, I don't want it to be too loud so I just went with the Magnaflow catback. I was told it would only lose about 15rwh compared to the true duals, so if that's true it is worth the trade off to me. If you guys think it will lose more, let me know.
bandit1, thanks for sharing your experience. I definitely want the best average curve possible.
bandit1, thanks for sharing your experience. I definitely want the best average curve possible.
05-26-2008, 02:12 PM
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No problems thats what we are here to do share our experiences and help guide ya the right way. Someday you will do the same for someone else Im sure. As to a few other thing I live in Utah and we only have 91 as well and I run 11.8 without a single problem, something to think about.
As to the exhaust lets just put it this way I went from a magnaflow catback with a dual 3in ORY pipe and with no other changes except a custom 3in true dual setup with dr gas X-pipe gained over 28 rwhp on my car. Some can be attributed to the dynos were a couple weeks away from each other but they were done on the same dyno around the same time a day and it was in the fall average temps were in the mid 70s for both days. I noticed a huge difference. I had to retune it after running my HP tuners scanner cause it wanted more fuel. It did make a bunch more torque especially down low and the gains were across the board, again something to think about. If cost is a factor shop around to find a good shop willing to do it. Cause with 2 magnaflow mufflers and the x-pipe the whole thing only cost a little over 600.
As to the exhaust lets just put it this way I went from a magnaflow catback with a dual 3in ORY pipe and with no other changes except a custom 3in true dual setup with dr gas X-pipe gained over 28 rwhp on my car. Some can be attributed to the dynos were a couple weeks away from each other but they were done on the same dyno around the same time a day and it was in the fall average temps were in the mid 70s for both days. I noticed a huge difference. I had to retune it after running my HP tuners scanner cause it wanted more fuel. It did make a bunch more torque especially down low and the gains were across the board, again something to think about. If cost is a factor shop around to find a good shop willing to do it. Cause with 2 magnaflow mufflers and the x-pipe the whole thing only cost a little over 600.
05-26-2008, 03:32 PM
#16
Compression is all on your tuner's abilities. If you are 100% confident in his work go for higher compression. You just don't want higher compression but have to run 18* timing cause your tuner has knock issues that can't be fixed. I am not a tuning guy by any means but this is what I have heard throughout the process. But no I do not feel the small 10.9 to 11.2 would be worth the time or money imo.
05-26-2008, 07:38 PM
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Busa is right compression is in the tuners abilites. Luckily for me I am my tuner so it helps that i am confident in my abilites but if you are gunna do it at least go up too 11.5 that little .3 bump you wont even notice
05-26-2008, 09:04 PM
#20
Be careful with the compression if you're gonna run a smaller cam. The last thing you want to do is end up with too high a DCR and end up having to pull timing. A bump of .3 may be worth it, with the smaller cam.
The magnaflow cat back will knock some of the life outta that motor. I can attest to a 25 hp gain/loss versus the true duals. Especially with the bigger motors.
The magnaflow cat back will knock some of the life outta that motor. I can attest to a 25 hp gain/loss versus the true duals. Especially with the bigger motors.