StatoJase

So the gt4294 is too small for my 408 engine. I am going to head to the track to see what its got but the 770ftlb torque from below 3000rpm is a traction issue for sure. Thinking of changing out my 3:7 gears and have access to a set of 2:75 gears. These are a really tall gear but I think the bulk torque shouldn't make it too lazy should it? Turbo 400, 3500 stall, 9", 26x10x15 mt drag radials, 3700lb weight, Primarily a street car.

Old Geezer

iTrader: (3)

26" tall tires are adding to the problem. Maybe step up to 28/29"???

StatoJase

I have thought about running a taller radial slick but there is only couple of race meets left this season so didn't want to buy just yet. The gears are available now and I can fit them in a few hours with my spare centre. I guess I will just throw them in and see what happens, then judge the results. I have read quite a few turbo cars run these very tall gears and still go hard.

Cam72aro

iTrader: (28)

I run a 3.08 in my gt91 408 with a 4l80.

StatoJase

Cam72aro have you done many 1/4 mile runs? what are your 60' times like and what sort of power you feeding the 3.08 ratio?

Cam72aro

iTrader: (28)

I haven't had a chance to get to the track, but at 14psi it should be in the high 700 to low 800 range. I project it to go high 9's with around a 1.5 60' time on the fb. I love the gear in the car. Boost builds very quickly as the motor is loaded hard because of the gear.

BMF_Racing

iTrader: (6)

new setup is not done yet, but last years stock 6.0L with the 88mm 60ft times were 1.371 to 1.40 pending on track. I run 3.25 gears with 28" tire and turbo 400 trans. I have a 3.00 I may go to this year if needed for new setup. Hope that helps.

StatoJase

Thanks for the replies, I have set up the 2.75 ratio in my spare centre that I have and I think I will give it a go with my 26x10.5x15 mt radials that I have, only be 1 more session at the track this season anyway. Will post up my results in a couple weeks.

StatoJase

Just an update to this thread, finally ran at the track and pulled 10.91 @ 124mph first time out with this set up 1.6xx 60ft. Ran the 2.75 ratio in the rear end with 3800lb race weight, 26x8.5 drag radials. Maybe 1 or 2 psi off the line as I wasn't ready. Rain put a dampener on the rest of the night. Could definitely feel the gt42 choking this 408 up top. Season over so on the market for a turbo upgrade now.

LilJohn

Gt5518 with a matching camshaft.

StatoJase

A friend has A 4708 available for next to nothing which I have measured up and should be able to make fit without too much mod. This has 92mm turbine which is smaller than the 96+ mentioned but should be a decent step up from my gt4294. This turbo has a 76mm inducer on a 108mm compressor wheel. How does that differ from the usual 80mm inducer I always see on 4708 specs? Boost come slower? faster? Less power?

bad6as

iTrader: (17)

28'' drag radial and a th400 and 3.27's. You can still over power the tires.