Set-up issues.
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From: Clarksville, TN
Set-up issues. So I did a heads/cam swap and noticed that I was running identical times (1/8mi) to my old cam-only set-up (MTI C1) so I jumped in on a dyno-day and ran my car on the rollers in between tuning some other cars...
I only put down 415/383 corrected... Needless to say I was a little disappointed. There are a few factors that might be contributing and I was hoping to get a general consensus as to how much they would be hurting me; enough to cause my current #'s or if there's something else wrong that I haven't thought of yet
Anyways, here's the combo
PRC stg 2.5 5.3l heads - 2.04/1.585 valves, PRC dual springs
228/232 112+0 XE-R grind cam
3" steel driveshaft
9" - micropolished 4.22 gears
275/60/R15 MTDR's
SLP headers, highflow cats, open Y-pipe
And here's what I'm thinking - I had 26" slicks the last time I ran at the track cam-only. Would the 28" DR's really slow me down that much on an 1/8mi track? Can't get to a 1/4mi any time soon since they're so few and far between down here. Old time was 7.80 @ 89 w/ 1.7 60', new time is 7.9 @ 91 w/ 1.8 60'
Also, would my rear and the tires really suck that much out of the graph? Unfortunately I don't have a graph of cam-only with the rear.
I tuned a VERY similar set-up to mine that weekend with a stock drivetrain that put down 446/386. Am I losing 30hp to my rear-end?
I won't be able to make the track again with 26" slicks until I buy some more drag wheels so that comparo is kinda out.
Patrick G. has already spec'd me out a new cam, I just want to make sure everything else is good before I try it.
Anyways, here's the graph:
I only put down 415/383 corrected... Needless to say I was a little disappointed. There are a few factors that might be contributing and I was hoping to get a general consensus as to how much they would be hurting me; enough to cause my current #'s or if there's something else wrong that I haven't thought of yet
Anyways, here's the combo
PRC stg 2.5 5.3l heads - 2.04/1.585 valves, PRC dual springs
228/232 112+0 XE-R grind cam
3" steel driveshaft
9" - micropolished 4.22 gears
275/60/R15 MTDR's
SLP headers, highflow cats, open Y-pipe
And here's what I'm thinking - I had 26" slicks the last time I ran at the track cam-only. Would the 28" DR's really slow me down that much on an 1/8mi track? Can't get to a 1/4mi any time soon since they're so few and far between down here. Old time was 7.80 @ 89 w/ 1.7 60', new time is 7.9 @ 91 w/ 1.8 60'
Also, would my rear and the tires really suck that much out of the graph? Unfortunately I don't have a graph of cam-only with the rear.
I tuned a VERY similar set-up to mine that weekend with a stock drivetrain that put down 446/386. Am I losing 30hp to my rear-end?
I won't be able to make the track again with 26" slicks until I buy some more drag wheels so that comparo is kinda out.
Patrick G. has already spec'd me out a new cam, I just want to make sure everything else is good before I try it.
Anyways, here's the graph:
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Well, suspension has a lot to do with how quick can you deliver that power to the ground. Is yours dialed in?
Do you have relo-brakets, Is your pinion angle correct with a -2 variance. are you transferring weight correctly, tire pressure etc....
Also with larger diameter tires, that 4.22 gears get smaller numericaly, are you launching at proper rpm? Shifting at right rpm to keep you in the band?
Lastly, did you degree your cam? a straight up cam can find itself retarded if not degreed, that would pull some ponies out of the equation, not to mention trq.
Do you have relo-brakets, Is your pinion angle correct with a -2 variance. are you transferring weight correctly, tire pressure etc....
Also with larger diameter tires, that 4.22 gears get smaller numericaly, are you launching at proper rpm? Shifting at right rpm to keep you in the band?
Lastly, did you degree your cam? a straight up cam can find itself retarded if not degreed, that would pull some ponies out of the equation, not to mention trq.
Thread Starter
12 Second Club
iTrader: (1)
Joined: Apr 2004
Posts: 1,369
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From: Clarksville, TN
Suspension = BMR adj. chassis-mount TA, set at -1
UMI relo brackets, UMI adj. LCA's
I believe the 28"s and the 4.22's put me at an equivalent 3.90 with 26"ers
Launching as high as I can without wheelspin, usually 4500-4800 (I've got some HAL's on the way that'll help me launch higher)
Was shifting at ~6500, I think I might bump it up to 6700, but still on the stock shortblock with no budget for a rebuild as of now.
Cam was installed dot-to-dot. I don't have adjustable timing gear, used a rollmaster single cam-sprocket and chain. Left the stock crank sprocket on.
UMI relo brackets, UMI adj. LCA's
I believe the 28"s and the 4.22's put me at an equivalent 3.90 with 26"ers
Launching as high as I can without wheelspin, usually 4500-4800 (I've got some HAL's on the way that'll help me launch higher)
Was shifting at ~6500, I think I might bump it up to 6700, but still on the stock shortblock with no budget for a rebuild as of now.
Cam was installed dot-to-dot. I don't have adjustable timing gear, used a rollmaster single cam-sprocket and chain. Left the stock crank sprocket on.
