hey guys and gals Im kinda new to this whole posting threads but i just had one question and if some could clear up the whole log manifold and efi manifold theory for me please. Are they worth it and do you really feel the difference?? The reason i ask is becuz i was at the junkyard today and finally found a inline 6 with efi mani's on a truck still just wanted to know if there worth getting?

oh by the way im a haha just wanted to post that!

 

The efi manifolds are pretty much the same as shorty headers compared to the log style, close to double the cubic inch I believe....

have the walker Y pipe and 2.5 inch out the back and pretty happy with it(think stock was 1 7/8 out)

 

GET THEM !!!!

I just helped a friend put a set of EFI exhaust manifolds on his '72 F100 with a 300, added 2" dual exhaust with Flowmaster 40s, exit just behind the axle. Let's just say the performance increase was felt from idle on up. The engine now breathes freely, and accelerates much freer. Now if he could just keep his foot out of it, and not rev it until windows shatter, he might get a few more MPG out of it. But that dual exhaust sound on an I6 alone is more than worth the hassle to change the manifolds, IMHO.

 

I put a pair on mine when I still had my 1bbl carb, out through a 2.5" single exhaust (high flow cat and muffler), and the difference between them and the log manifold was NIGHT and DAY. You lose nothing, and gain everything, as far as performance is concerned.
No joke, the log exhaust manifold is such a restrictive exhaust, it's probably a 10 - 20hp gain. Very impressive. Plus, maybe a 1mpg increase on the highway.

There are other things to consider though, when doing the swap. You MUST redo the exhaust, since the EFI manifolds won't bolt up to the stock exhaust pipes.

Also, all of your carb heat provisions will be gone, since the stock intake bolts to the stock exhaust for warmth. There are ways to create your own, but it's something you'll need to be aware of.

Lastly, what year engine/truck is it going on? All of the emissions equipment bolts to the stock exhaust manifold, so if you need it to pass emissions tests, you have some work ahead of you to hook the EGR and smog pump back up.

 

Thanks guys for all the feedback this will be a must for me tomorrow!!

Abandoned Bronco- my truck is a 1986 f150 as far as for the emission stuff I have no cat they stop doing emission tests here where i live