lstvr

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.

cam

iTrader: (9)

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.

STAR

iTrader: (1)

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.

lstvr

The 3.08 really suits the car, as soon as you are above 2k, it runs lovely. I am thinking multiple Throttle Bodies, but it is loads of money.

STAR

iTrader: (1)

A lower gear(numerically higher) will get you in your powerband faster. Big cams don't like spending time in the lower rpms...more gearing and higher compression will help. As for more throttle bodies I have read that they are difficult to set up and very expensive.
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.

someday

whats the compression on the motor? 65cc chambers makes it sound a bit low... i'd take about 10 degrees out of the cam and move to a 3.50 gear...

Jimbo1367

lstvr

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.

davidws6

iTrader: (36)

+1 for overlap causing the low rpm troubles. ITB's would be a way out but $$ or Pounds !

I'd like to try em myself but ITB's under a 4th gen f body hood ? = Prolly NOT.....

Jimbo'sZO6

iTrader: (1)

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

lstvr

Well.. i bit the bullet and found some 55mm Kinslers that are pre used, of a Mosler race car, and bought them, i'll let you guys know how i get on!

ringram

Alpha-n tune!?

bene

iTrader: (16)

Off topic:

It's nice to see some muscle heads in England.

davidws6

iTrader: (36)

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....

Patrick G

iTrader: (14)

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.

lstvr

Too late as i have sold it, and the TB's were too good to miss, and the 70rwhp this cam gave me cant be missed!!

Bring the Noise

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