dmruschell

I just put my engine back together with AFR 180 heads and have been trying to find the massive exhaust leaks I have on both sides. All of the bolts are tight and gaskets are new.

Then, I noticed that the AFR heads have a protrusion in between the two center head bolts below the manifold, a protrusion that contacts the exhaust manifold before the gasket seals. My old heads did not have that protrusion there. I'm using Speedway Smoothie manifolds with a 2.5 inch outlet.

I guess ill I'll be getting some different exhaust manifolds and possibly different downpipes, which is a shame because I really like the smoothie manifolds.

jb78L-82

I have AFR 180's on my 78 L-82. I originally had Mcjacks shorty headers after the rebuild and some issues with the spark plug boots being too close to the McJacks which I did not have with the OEM 882 heads with the McJacks. This past year, Jan 2017, I went with XSPower long tube headers and have zero clearance issues. Both headers sealed perfectly against the AFR 180's though. These are the XS power LTH's:

http://shop.huronspeedproducts.com/X...rs-c2c3hug.htm

dmruschell

At $1600 for the heads, that wouldn't be my first choice lol. I'd rather spend $250 on a new front exhaust setup (manifolds, downpipes, etc) than mess up a brand new set of heads lol.

I used to have headers on this car, but I removed them. It's a DD and I got tired of dealing with the headers.

Street Rat

I would get on the phone with AFR and find a solution.

dmruschell

I called AFR and they said clearancing that "boss" (as they called it) was okay.

I got a set of 2 inch outlet manifolds locally cheap, and they're worse than the smoothies, so the smoothies are going back on.

I dont know why they would design a head that needs to needs to be modified to use stock exhaust manifolds.

rcread

I had to grind that down on my AFR heads. It only took a few minutes per head. The aluminum machines down quickly. Once installed you forget you ever had to do it (I forgot until just now).

Jartanyon

Same here.

dmruschell

I don't think I'll forget that I had to do it. I spent all day trying to figure out the issue, and then having to take the exhaust apart and manifolds off to get to the part that needed grinding. I still don't have it all back together yet.

If if I had checked the fitment while the heads were off the car, it would have been a lot easier to fix. I didn't think that a stock style manifold would have any issues. As it is, it cost me a whole day of frustration. Hopefully, this post will warn others so they can grind that piece down before everything is assembled.

rcread

I was building a new engine out of the car, on a stand. I discovered it in the process of test fitting everything before I dropped the engine in the car. It sounds like I lucked out by deciding to test fit the exhaust manifolds as well. One of the lessons I've learned is that aftermarket parts rarely do not often go on without modifying something.

cv67

most companies assume youll use headers
grind it down its worth it they are nice performing pieces

Kid Vette

Of course its kinda pointless to run AFR heads with stock manifolds. Exhaust ports on the AFR heads are 1.450" H x 1.550" W. Ports on stock exhaust manifolds are about 1.300″ x 1.300. If you want to stay with cast iron manifolds, I would at least go with these.

jb78L-82

Exactly...I ran 1 5/8 inch McJacks for 2.5 years on my rebuilt/upgraded 355 L-82 with AFR's and finally figured I had to bite the bullet with LTH's to maximize the benefit of the AFR's:

http://shop.huronspeedproducts.com/X...rs-c2c3hug.htm

I was shocked at the difference in mid to high RPM power...it was VERY noticeable!

cv67

big primaries but shoot cant beat those for the price

To quote Joe Sherman "more you have the more you get"

"gtfo out of my shop"

jb78L-82

they overstate the primary size a bit...I measured the inside of the primaries and they look to be between 1 3/4 and 1 7/8 at most maybe in certain places, not 2 inches, which appears to be from measuring the outside diameter of the primaries. Same on the collector...3.5 inch collector, not 4 inches...either way they are a great deal.....

1 3/4 inch primary LTH for my 355 with the AFR's seems to be perfect....

dmruschell

The manifolds I'm using are 2.5 inch outlet aftermarket manifolds with larger than stock ports. I noticed virtually no difference in SOTP power after removing my long tube headers and putting those on.

Even so, there's no reason to have that "boss" there if many people just grind it down anyways.

7T9Shark

Greetngs - I just installed a BP 383 and am using the smoothies also. My question is, where do I find 2.5" exhaust pipes? My old pipes are 2.5" but they are reduced down to 2" at the manifolds. I've exhausted (pardon the pun) all the common sources like Summit, Speedway, etc.

dmruschell

If your car is a manual, you can use downpipes from a 65 Corvette. If your car is an automatic, you might need to have them custom made, either locally or by calling up a vendor to see if they have downpipes that will work. If you look for threads I've posted in on the exhaust subject, there was mention of a vendor that will make the automatic transmission pipes with a 2.5 inlet, but I don't remember the name of the vendor.

7T9Shark

Yep its an automatic. I was hoping some one would identify an older C3 that came from the factory with 2.5 downpipes and just order those. Ill do a search on your posts and see what pops up. Thanks