Thinking of going smaller on cam?
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Joined: Nov 2007
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From: Birmingham UK
Thinking of going smaller on cam? My engine is shunting on low rpm, 1200-1800rpm, it is down to the cam i am sure, how much lower can you go without substantially cutting down the power. cam spec in sig. Cheers Paul.
Once you crest 230 on duration the low speed problems start up. Some tuners can work magic and minimize the disturbance but thats a pretty safe bet. 230 or less on duration ( @.500 of course ) and its streetable, any bigger and it becomes more painful but will make more power up top ( typically )
I suppose the question you really need to ask yourself is what do you want the car for? If its for go fast only then suffer with it. If its a street car that you want to go fast in but have civil manners then change it.
I suppose the question you really need to ask yourself is what do you want the car for? If its for go fast only then suffer with it. If its a street car that you want to go fast in but have civil manners then change it.
That's a big cam for for your displacement! What is the LSA on that cam? Overlap is what causes low speed bucking or surging which is big duration and/or tight lobe separation. I'm guessing your cam has over 22° of overlap at .50 and that is your problem. Some tuners are better than others at smoothing out the low rpms, but it takes a lot of time and you can only do so much. Speed density would be the way to go for best results.
I bet you can swap out the cam to something smaller and only loose a few hp right at the top. Speak with a knowlegable cam designer and discuss your concerns and he should be able to pick a cam to suit your needs.
BTW, I noticed you have 3.08 gears. By going to a 3.73 or 4.10 that will move your rpms higher at lower speeds and might get you out of the bucking range.
I bet you can swap out the cam to something smaller and only loose a few hp right at the top. Speak with a knowlegable cam designer and discuss your concerns and he should be able to pick a cam to suit your needs.
BTW, I noticed you have 3.08 gears. By going to a 3.73 or 4.10 that will move your rpms higher at lower speeds and might get you out of the bucking range.
Thread Starter
10 Second Club
Joined: Nov 2007
Posts: 458
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From: Birmingham UK
That's a big cam for for your displacement! What is the LSA on that cam? Overlap is what causes low speed bucking or surging which is big duration and/or tight lobe separation. I'm guessing your cam has over 22° of overlap at .50 and that is your problem. Some tuners are better than others at smoothing out the low rpms, but it takes a lot of time and you can only do so much. Speed density would be the way to go for best results.
I bet you can swap out the cam to something smaller and only loose a few hp right at the top. Speak with a knowlegable cam designer and discuss your concerns and he should be able to pick a cam to suit your needs.
BTW, I noticed you have 3.08 gears. By going to a 3.73 or 4.10 that will move your rpms higher at lower speeds and might get you out of the bucking range.
I bet you can swap out the cam to something smaller and only loose a few hp right at the top. Speak with a knowlegable cam designer and discuss your concerns and he should be able to pick a cam to suit your needs.
BTW, I noticed you have 3.08 gears. By going to a 3.73 or 4.10 that will move your rpms higher at lower speeds and might get you out of the bucking range.
Who tunes your car? Speak with them and see if improvements can be made with the driveability. If not, a smaller cam would solve your concerns.
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Thread Starter
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Joined: Nov 2007
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From: Birmingham UK
Car is at 11.5:1 comp ratio, hardly low. The car cruises nicely at 90mph on that gearing. Besides around town i could select a lower gear to up the revs, but its on coast down and tiny throttle settings is where it shunts. Its called cross over i believe, where the big overlap causes it to breath its own fumes with a plenum chamber. Hence the thinking of going TB's. I reckon thats the direction i am goung to head so i can have it all...i hope.
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Your cam is not to big for a 416. You need more gear, (3.42 or 3.73) and need to find another tuner. The cam in my 416 is similar to yours but has more overlap, (27*), and driveability is not much of an issue for me. The tuner who did my street tuning spent alot of time with me driving around and making lots of minor adjustments to the idle air, throttle cracker and low rpm fuel trims. Don't give up on it yet, the right tuner will get it to behave much better. 
Jimbo
Jimbo
ITB's Used ones... Nice. Let us know how they work out ! When you get them installed, Please post the height of them from the Valley cover to the top.....
Birmingham UK, I was there in March 2004 for 2 weeks while I was working in Italy for my company. For a yankee, it was a different place. The brew was good ! Then I went to Edinbrugh for 2 weeks. That was a different world. When the gals talked that northern accent, it sounded So Sexy....
Birmingham UK, I was there in March 2004 for 2 weeks while I was working in Italy for my company. For a yankee, it was a different place. The brew was good ! Then I went to Edinbrugh for 2 weeks. That was a different world. When the gals talked that northern accent, it sounded So Sexy....
Why don't you put the cam you had in before this one? As I recall, you liked the overall performance and it was smaller.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Thread Starter
10 Second Club
Joined: Nov 2007
Posts: 458
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From: Birmingham UK
TECH Regular
Joined: Nov 2005
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From: Arlington, TN
If the TKO 5spd has stock gears then the 3.08 rear is just fine for that light a car (2600 lbs is a nice race weight).
If you go with the ITB setup then make sure you have a good tuner for your ECU and get the part throttle optimized (kinda goes without saying).
For others that are wondering about the gearing below is a comparison of a stock 99 T56 gears -vs- a TKO 600.
‘99 F-Body T56 Gear listing.
1st - 2.66, 2nd - 1.78, 3rd - 1.30, 4th - 1.00, 5th - 0.74, 6th - 0.50, and reverse 2.90
TKO-600 5spd manual
1st - 2.87, 2nd - 1.89, 3rd - 1.28, 4th - 1.00, 5th - 0.64, and reverse 3.00
If you go with the ITB setup then make sure you have a good tuner for your ECU and get the part throttle optimized (kinda goes without saying).
For others that are wondering about the gearing below is a comparison of a stock 99 T56 gears -vs- a TKO 600.
‘99 F-Body T56 Gear listing.
1st - 2.66, 2nd - 1.78, 3rd - 1.30, 4th - 1.00, 5th - 0.74, 6th - 0.50, and reverse 2.90
TKO-600 5spd manual
1st - 2.87, 2nd - 1.89, 3rd - 1.28, 4th - 1.00, 5th - 0.64, and reverse 3.00
