"Enlarged" TPI Runners
 

Found a set of polished TPI runners for a reasonable cost.


Only thing is, they've been "enlarged" 9%--most likely they ran one of those tools through the passages in order to remove dents before polishing.


Original diameter of TPI runners is 39mm, if I recall correctly, 9% would mean they're at 42.5mm....would this actually make any notable difference in the torque curve? Unlike many people working on a Camaro, I want to keep torque in the low/midrange as they were new, not interested in making it into a 7,000 RPM screamer.


I'm thinking since the length of the runners is unchanged, I'm not likely to notice much, of any of a difference, which is fine by me...am I thinking right, that there shouldn't be any issue?

Re: "Enlarged" TPI Runners
 

That change in size isn't going make any noticeable difference

Re: "Enlarged" TPI Runners
 

Exactly what I was thinking...thanks!

Re: "Enlarged" TPI Runners
 

I agree.

....and beyond that, those "enlarged" runner auctions have been around on Ebay forever. -assuming you're talking about the ones where they run the steel balls through them, and not actual "larger" aftermarket runners. I've always been skeptical of whether or not that's actual possible to stretch the runner. And even if it is, the flange at the plenum and manifold are cast, so how would THEY be larger? -although you could port that part.