runner length

[novi306]

if i were to change upper intakes ( i currently have a gt-40 to a custom made upper )( box style)would i lose a lot of bottom end until the boost comes in ? this is a street car but i dont drive it very often . i know runner length plays an important factor in low speed torqe but would it be that much of a factor in a 306??

[speedytang]

The cars I have driven with a box upper just are flat till about 3000+rpm with a blower or without.

[novi306]

so would it not be a wise choice to switch uppers? i was thinking that if it didnt come on until 3000 rpm it might help getting out of the hole without alot of tire spin. do you think that the top end might outweigh the lost torqe?

[speedytang]

I don't see the purpose of a box intake without 4.30 gears or lower and a radical cam that functions above 3500rpm. I build over 500 rwhp with the Cobra intake and only at 14psi. I just don't see the benefit of killing mpg and torque for a daily driver or a Tri-Car(Drag,Autocross,Daily) when the average shift rpm is 4500.

[novi306]

the cam i have now the range it has is 2200 to 6200 so it wouldnt be worth it unless i change gears also?

[speedytang]

The gears are used to get the rpms up and to get the cam and intake into the correct power range. I would forget the upper and just pulley up into the 10psi range.

[novi306]

thanx for the info,Rich

[NMNOTCH]

What heads and cam are you running with this intake. IMO it isn't worth putting the box upper on the GT40. There are far better long runner intakes available that can still give you the power you are looking for down low and pull strong ahead of the Gt40 on the top end. Its all combonation and an efficent one wil make more power with less boost pressure.:happy:

[novi306]

i have a comp xe274hr with older cast iron windsor heads with 68cc 2.02 1.60 valves

[NMNOTCH]

Are they windsor sr's or windsor jr's The comp 274hr makes power to 6200 easily on a NA motor with the right intake and heads. I currently run the 282HR in my 347 and shift points are as high as 7300. There are a few more things involved though to get the HR to rev this high:)

[novi306]

they are windsor sr's seems it runs out of steam by 6000 rpms though

[NMNOTCH]

Ah yes the good ol windsor sr's this is a great proven cylinder head and you should have no issues with spinning this combo a little higher with the blower for sure. The only problems will be your intake and stock ecu's ability. Even at a 6000 rpm limit this combo should make plenty of power acxross the board once you have the proper fuel and timing.

[novi306]

so what do you think would be a better intake then? i have thought about using the tweecer or andersons pms. right now this combo works best when you shift about 5700 rpm though, so is it the intake the limiting factor?

[NMNOTCH]

You could probably find about 30-40 hp in switching to a holley systemax with this combo. Of coarse it will depend on the tune. I would go with the anderson PMS if you have never tuned before, it is much more user friendly than most of the other things out there.

Don't get me wrong however I still love the GT 40 for a street speciific car as I run one on my mostly stock 93 with bolt ons and a small dry shot and for fun factor with the torque the GT40 makes down low is a blast on any street car.