Hi guys. I finally got my 2 1/2 inch manifolds. Wow! Very poor quality. None the less, I have decided to try and make them work rather than wait several more months for replacements. I wish to port match these to the heads as the ports on the manifolds are obviously smaller than those on the heads. So here's my question. The bolt holes on these things are oversized. the outer 4 very oversized. The 2 center bolt holes only slightly oversized. I can't install the manifolds before installing the heads. Soo, with these large bolt holes and the weight of these manifolds. How do I know I have the ports lined up properly when installing these later with the engine in the car.
My thought is to scribe the head on both ends of the manifold so I can see when they are lined up correctly as I tighten up the bolts. However, the gaskets would cover said scribe marks and the gaskets can also shift around.
My thought is to not run a gasket at all and use this high temp silicone instead.

Some photos of what I'm up against.


As you can see those outer holes are gigantic. I have some really nice thick hardened washers I will be putting on these bolts. But after port matching. I need to get these on the heads, engine in the car. and keep them properly lined up.
High temp silicone good enough?
Any other thoughts or idea's?
Thanks Guy's.

 

Sleeve the holes with brass sleeves from McMaster Carr.....

Jebby

 

O.K. so how long will that take to get to Australia I wonder.
None the less, perhaps I can find something locally.
So your saying the high temp silicone won't work on it's own?

 

I snuged up the two center bolts. Sleeving does not look do-able.





As you can see looking into each of the 4 outboard holes. they are not at all centered. perhaps why they made them so large.

 

Wow, that is pretty terrible…..
Anyway….no, I would not use high temp silicone.
Use a 1404 Fel Pro Header gasket…..

Jebby

 

I looked at those header gaskets. they look fairly thin edge wise. and not certain they will line up properly. Not to mention another 50 bucks and another week or so.
Isn't it true that the factory used nothing?
No gaskets of any kind?

 

The factory used no gaskets true but all heads were cast iron….
I have used the 1404 on manifolds for over 20 years.

Jebby

 

YOu can source aluminum gaskets, they seal really well. As for port matching use thick tape as a template on the heads. Cut out the center hole then Install the manifolds and trace the oustide onto the tape, then remove and transfer the pattern over to the manifolds lining up the outside mark and see where the hole is. If you have your gaskets you can do the same with them but you may need to trim them if they block the hole

 

Well... if you wanted to you could make alignment pins in at least three locations to align the manifold. There looks to be lots of meat beside the holes for the bolts. Drill into that on the back side, or through and into the head, and install a small pin that will engage a small hole you'd make in the heads. Pins can be small and holes in the head shallow. It's just got to be enough to get it aligned.
No sure how you feel about drilling into your heads and manifolds though.
Even two locations would be sufficient I believe. The bolt holes and their cumulative alignment are only going to allow so much slop in any case.

Do the ports line up now with all bolts in? or is some porting going to be needed?

 

I relation to the head itself; how FLAT & SQUARE are the manifold flanges ? That's what's Most important. Lay a straightedge across them.

If ya don't already know ... Brzezinski did sell / port iron manifolds; and perhaps still does. https://www.castheads.com/

 

I used "Play Dough" for getting my ports cleaned up. I used a flat piece between the two surfaces, in place of a gasket and bolted the manifold on. It takes time but is worth it in the end. I also matched the gaskets to fit without blocking any of the flow.

This was the same play dough I used to test for Piston to Valve clearance. It was a real PIA to have to bolt the heads on with play dough on top of the pistons but it proved beyond a doubt that I had the room.

I have always loved the soft aluminum Header gaskets as they help get a good seal.

 

That alignment pin idea sounds perfect..or some studs, threaded rod to locate. to see if it will even go on first without massaging, then you are located?

 

Rookie guess....Step-by-Step:

Buy some threaded studs or All-thread/use antiseize to screw the studs into the head exhaust manifold threaded holes.
TEMPORARILY USE 4 drops of SUPERGLUE to hold the exhaust gasket onto the head and install a exhaust manifold gsaket.
put flat washers and nuts snugly against the exhaust manifold gasket to hold it in place onto the heads.
trim the exhaust manifold gasket to match the exhaust holes in the head. If the gasket holes are larger than the holes in the head, bevel/remove head metal to match the holes in the exhaust gasket.
If the exhaust gasket holes are smaller than the exhaust holes in the head, trim the exhaust gasket to match the head holes.
Now the exhaust gaskets match the head openings.


Remove the nuts and flat washers from the exhaust gasket..(the Superglue will hold the exhaust gasket in place)
Smear a layer of water-based cheap red or black caulking/sealer onto the exhaust gasket mating surface.
place the exhaust manifold onto the head ..use your hardened flat washers and nuts to snug the exhaust manifold onto the head so the sealer leaves a good mark/stain onto the mating surface of the exhauSt manifold.
Scribe a line onto the exhaust gasket so you can trim the excess gasket to match the edges of the exhaust manifold.
Remove the exhaust manifold and grind/bevel the protruding excess metal which the sealer/caulking shows is in the way of good exhaust flow.
Remove e exhaust gasket with a sharp paint scraper to break the SUPERGLUE bond.
Remove thevsealer/caulking.
Trim off the excess exhaust gasket along the scribed line.
Remove all sealer/caulking and Superglue from the head, exhaust gasket, and exhaust manifold.
Test fit the head, gasket, and exhaust manifold together.

IF all looks good....use the technique on the other head/gasket/manifold assembly.

I had a 200 rpm idle increase once I did the above porting.

Expert members......feel free to tweak any part of my procedure!!!

Clean

 

With the 2 1/2 inch manifold, make sure you continue all the way out the back of the exhaust with 2 1/2 inch pipe. I see many people put larger diameter manifold/pipes and have a smaller diameter section. This totally cancels the advantage of larger manifold or pipes.

 

Thanks for all the ideas guy's. I like the idea if pinning them.
I'll get some gaskets coming.

 

Is that a cast stainless manifold?

 

Ceramic coated cast iron.
Yes they need a lot of work on the ports. the "In" holes are way smaller than the ports on the heads. The "Out" hole has a large ledge.
They need some work.

 

Put all 4 bolts in but loose. Do they actually move around on the bolts enough that you need to do anything to align them?

 

If it's a cast iron header bolted to a cast iron head, I'd get a sleeve type dowel and drill out the inner portion of one outer hole at each end and drill into the head slighlty if you want to hold it in place. You may still have issues with it squirming from thermal expansion that way, but it should hold together and everything should stay put.

If it's a cast iron header bolted to an aluminum head, I'd probably run what you have there. If you're going to "port match" the manifold inlets to the head ports, then maybe sleeve/dowel exactly one of the holes closest to the center of the header. I'd also definitely use a multi-layer metal gasket with the stainless rings at each exhaust port in that setup. And I'd seriously consider stainless hardware (302 and 304 is the most common alloys for those, although 316 can be found in marine hardware sources for sea water environments). Stainless bolts are comparable to grade 5 hardware for yield strength and should get about the same tightening torque as grade 5 bolts (I usually go about 10% lower). You may want to use high temperature thread locker, or a mechanical retaining device to keep them from turning. Mr. Gasket 2230G for small block or 2231G for big block would be my recommendation for the bolts, unless you plant to take this apart and put it back together many times.

Oh, and I'd ceramic coat the inside of the passages after you get them "port matched" at both ends. With headers and exhaust manifolds, thermal barriers inside the pipes/manifolds do a much better job of keeping things cool than on the outside. Eastman has a spray coating kit that includes a nozzle you can run through the passages to apply the coating if you want to DIY.

 

As I understand one of your issues is how to get the ported manifolds to line up with the heads at install with the oversized holes.
I would get a couple of flat head 3/8 -16tpi bolts long enough to seat on the manifolds and secure them to the head. This will allow you to bolt the manifold to the head in the same relative position every time you remove and reinstall them.
Use the flat heads in the same 2 holes every time and for final install, install the regular bolts in the other holes and then swap the flat heads out.