Don Terrill’s Speed-Talk

Cut the pipe off, mark it again, and watch a new line appear...

How accurate is it? because I don't think its a reliable practice. I just heard it from somebody and wanted to see if it is anything really worth trying.

You say cast iron manifolds.

Are you allowed to run the old Chevy "ram horn" manifolds?

They are much better than later model cast iron in my experience

The rule book is "Stock unmodified exhaust manifolds only for subject car," for 1978 - 1986 or 87 model years. I don't think there is or even was a Ram-horn style in that 305 CID era. Pretty boring class rule wise I think, but its fun and we are finally allowed to use a aluminum radiator! lol

There is increased "backpressure" from a lot of things all pertaining to the ability to flow enough for the power level of the motor. Anyting added to a system like mufflers, running tubes to the back bumper etc can hurt the power level as it can not flow enough building pressure on the exhaust side of an engine.
There is also "backpressure" from too large an exhaust system and what happens is atmospheric pressure has an easier time equalizing pressure from the atmosphere in the intake side to the atmosphere pressure on the exhaust side during overlap and less air moves at slower engine speeds.
Both situations are not good for the largest power curve.

Wow you are opening a thread that is 11 years old but I guess you see that.

1972ho wrote: ↑Wed Oct 07, 2020 11:48 am Wow you are opening a thread that is 11 years old but I guess you see that.

Well ok, just saw this. I feel many folk can use a bit more reflection on "back pressure".

exhausted wrote: ↑Thu Oct 08, 2020 9:40 am

1972ho wrote: ↑Wed Oct 07, 2020 11:48 am Wow you are opening a thread that is 11 years old but I guess you see that.

Well ok, just saw this. I feel many folk can use a bit more reflection on "back pressure".

I think most of us here enjoy your posts when you put topics out for reflective work Calvin!

I'm working on a oval track motor with a rpm range of 4800 to 6500 peak around 5500.The tuned length headers make the most peak ,but fall off hard after 6000. Because of chassis, they are a bundle of snakes. The short straight headers make more from 6000 to 6500 and are fastest on the track. Your overlap comment makes sense of why the short headers are down at peak and i'm trying to understand flow, reverse flow of headers. We have made modification to the headers that restrict reverse flow (at the collector) and have found power.Any suggestion or ideals where to go from here.

Fahlin Racing wrote: ↑Fri Jan 02, 2009 11:49 am
As I thought about that, the question came up in my mind for our 305 muffler (since we have to run them). The exhaust can be dual but with a maximum pipe diameter of 2 1/2 OD pipe with factory manifolds. The torque converters have to be stock, heads can not be ported. Although we can use SS or Z28 heads (over the general 305s with 1.72s) with the 1.85 intakes & 1.50 exhausts with a .420 lift cam. Stock converter.

What is the scoop?

STOCK O.E.M. torque convertors are different in different size cars using the same transmission so, what transmission are you using ...?