I have a 68 stang with a late model GT-40 engine. I currently have full length headers, but am thinking about replacing the headers with the early model (1967) Hi-Po exhaust manifold that was used on the k-code 289s, and then using a standard dual exhaust. Has anyone had experience using this manifold in a true performance application?

 

I will let you know in about 2 weeks. I'm finishing the rebuild of my 66 289. I slipped a "LeMans" cam into it, and swapped out the stock exhaust for the HiPo exhaust manifolds. SHould be running in about 7-10 days.

Tom
Bryson City, NC

 

how did the manifold work out for you?

 

how did the manifold work out for you?

 

Do you have the factory tube headers from the GT40 engine? If so, I'd guess they are either better or just as good as the HiPo's. The HiPo's are an upgrade over the log-style header, but are no where near the levels of flow that can be gained by modern tube headers.

 

The HiPo exhaust manifolds were a bear to install with the engine already bolted in, but they do fit with about 1mm to spare on the drivers side, easier on the passenger side.

They look like they belong there, and look much nicer than the stock exhaust. I'm not sure I would invest in them for a performance modification as you could get a decent set of headers for not much more which would net more horsepower, but a side-by-side comparison before I bolted them on makes it clear that they flow much more smoothly and should boost power above the stock manifolds. As for any seat of the pants comparision, I made too many other modifications to say they boosted my power, but I will say that engine is a screamer now that is happiest when above 3000rpm, and a bog-monster at idle.

Going for the "stock look" I screwed up with them though. I painted them with a high-temp cast iron spray from Eastwood, then sprayed the engine flange area with Old Ford Blue to match the factory overspray which should be present. They look terrific and stock NOW, but I suspect in time the cast-iron spray will begin to peel or flake off and then my mistake will be evident. I should have lightly sprayed them with WD-40 or an equivalent and bolted them on without painting them as that is how the STOCK manifolds were installed.

Tom
Bryson City, NC

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I think Shelby had the right idea to get rid of the factory hipo manifolds and go to tri-ys. He did a lot of winning with the Shelby add ons to the factory 289 hipo.
Walt

 

keep the headers....... they flow much better then manifolds. When you say Gt-40 engine, do you mean an engine out of a GT-40, or a engine with gt-40 heads?