what the hell.
ok, so I installed a set of siamese runners on my car last friday. no vacume leaks, no issues. took my car to the track later that day and low and behold.......14.9@92mph.

pretty amazing when compared to a 14.6@94mph on the oem runners.

everything was installed perfect, any ideas what the hell happened........I'm really hurtin' here

 

You will never get good numbers choking out that 400sbc with tpi. Even a heavily modded one wont do much for you. I switched to HSR because of it. Cant explain the higher qtr time though. Sometimes things dont always work the way aftermarket products claim they will. You certainly should have shaved a little more time off tho. How was your launch etc. It could be the driving (not a knock on you). The slightest difference can lead to different times. Did the tires hook? etc.etc.....

 

60' was the same. the shortage was defanetly in the top end. however I'm going to take it apart and port the upper manifold and see if that makes a difference.

still reseaching swiching to an LT1 manifold

 

Upper plenum porting will help, but not much. The biggest restriction is in the base, right before the air enters the head. You can widen that area a lot and pick up some power. It will never run out like a short runner manifold would though.

Botch

 

If you're running high 14's with a 400ci engine, something is wrong. My 355 with stock-runner TPI ran 13.2 at 102, stock runners. I can see where the airflow restriction is limiting the 400's power production, but it can't possibly choke it down to make less power than a smaller engine...

 

I would do a search to find out which manifold is best for you. There are several comparisons available. Each manifold is set to handle only so many cfms. If it handles 270 cfms then that is what you get unless you port and polish. From what i understand runners need to be ported in at least 2 inches. In effect what you are doing is shortening the length of the runner by doing that. However, I would think that even with a 400 and tpi you ought to be doing better than 14.9. What are you running for a cam? The cam makes a difference on high end as well.

 

he runs good on the street though kept up with me but i was spinning.

 

If he has a 400 and is having trouble keeping up with your stock l98 it is sick!

Charlie

 

What about different weather conditions?

your 60 foot time might be the same but if the air density was lower your motor wouldn't be making as much power so the rest of the run could suffer?

Thing is to lose that much would need quite a difference in power...
Just wondered if it might be a contributing factor?

 

where are you guys from in maryland? i live in west virginia, about 15 minutes from hagerstown.