[Skip Fix]

I had to use a little sealer on the driver's side and one nut I can't get all the way tight.

[jhein]

Right now I have a set of RARE 2.45" manifolds on order. The ones I have now are 2.313". After everything I've read here, and my own results, It's kinda hard to justify the money for the 2.45" manifolds. As said, I doubt I'll see much difference.

[Gator67]

Originally Posted by jhein

Right now I have a set of RARE 2.45" manifolds on order. The ones I have now are 2.313". After everything I've read here, and my own results, It's kinda hard to justify the money for the 2.45" manifolds. As said, I doubt I'll see much difference.

Were you able to fit ram air manifolds on your IAII? Last time I tried they interfered with freeze plugs. Ground freeze plugs down but still too close for comfort. Can’t remember which version of the manifolds we used.

[jhein]

Originally Posted by Gator67

Were you able to fit ram air manifolds on your IAII? Last time I tried they interfered with freeze plugs. Ground freeze plugs down but still too close for comfort. Can’t remember which version of the manifolds we used.

There was some interference with the casting locating bosses on the sides of the block but not the freeze plugs. He had to grind the bosses down a little.

[Quad]

Not all 9/16" sockets are the same. Couldn't get to one bolt with the 1/2 inch drive socket. Easily get to all 6 bolts with the well worn & visibly slimmer 3/8 drive socket I was given. RARE 2.45" with their hardware & downpipe.

[Formulajones]

I generally use a 12 point socket to get onto mine as those sockets are a thinner wall. For sure the 6 points won't go on a couple of the nuts. For that to work those pipes have to come down absolutely straight off the manifolds. If they are tilted the slightest bit it makes one or 2 of the nuts impossible.

I will sometimes heat the pipe and then tap a 6 point socket up there just to clearance the pipe a smidge, making things a bit easier.

[Murf]

I used socket head bolts & a ball end Allen wrench on my wife’s car. It has those big down pipes from RARE. Don’t know if they still offer them.

I used them cause they seemed to hang down less.

https://www.ramairrestoration.com/po...y-headers.html

Murf

[Skip Fix]

With the curve of the head pipe you can;t get a socket on it, or a box end with the 2.5 head pipe and flange.

[GTOLou]

Did anyone mention Doug's headers in this thread? Work great. Seal great. Pretty much my go to. I'd not install dynaflow or Summit or even Hookers..

[MidnightAuto]

that engine masters was pretty awesome. had to laugh about the back pressure comment.

[421mike]

Does anyone make headers for 61 big cars anymore?

[SD455DJ]

Originally Posted by Formulajones

It's been talked about a bunch, and numerous dyno tests done.

In a nut shell, the ram air manifolds work the best with a nice mandrel bend. If you put a crush bend right at the outlet to make the 90 degree turn, it really hurts HP.

The factory manifolds, although touted as 2.25" opening, I think are closer to 2" if you stick a micrometer in there. Been a while since I've looked at mine but I think that's what I remember.

As far as whether they are the same casting as the 2.5" outlets, I'm not sure. I've had both on my engine and as far as outside appearances or clearance, nothing really changed. Still the same clearance at my factory starter. Only big difference I noticed is that a 2 1/2" exhaust pipe is a really tight fit between the studs on the manifold. Tells me they didn't make the outside of the manifold any bigger. Least not there anyway.

FJ, Here are my factory 455HO RA exhaust manifold outlets I measured before reinstalling on the GT-37 and was surprised (disappointed really) they were no larger than the D-port log manifolds at 2 1/16" and 2 1/8", but they still allowed 430 hp/530 lb-ft torque from the 455HO on the dyno.

Dennis

[Formulajones]

Originally Posted by SD455DJ

FJ, Here are my factory 455HO RA exhaust manifold outlets I measured before reinstalling on the GT-37 and was surprised (disappointed really) they were no larger than the D-port log manifolds at 2 1/16" and 2 1/8", but they still allowed 430 hp/530 lb-ft torque from the 455HO on the dyno.

Dennis

Thanks Dennis, I seemed to remember it was something close to 2 inches. I guess that's not far from 2 1/4 inches either, lol. They do seem to work well enough though.

[b-man]

The mid to late ‘60s D-port log manifold outlets I’ve measured with a caliper were 1.850” on the driver’s side and 2.050” on the passenger side with or without the flapper valve. I’ve opened up the drivers side outlets to match the passenger side, which ends up almost the exact same I.D. as a 2-1/4” head pipe.

The log manifolds aren’t all that bad really: https://forums.maxperformanceinc.com...d.php?t=630943