SBC exhaust manifolds don't fit

[MikeB]

Do the double hump heads have the threaded bolt holes for the engine accessories? Early 327 heads do not have the threaded holes.

I've read where these service replacement double hump heads did have the bolt holes.
041
370
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[deucecoupe]

Okay. The second question in my original post was poorly worded.

Here's the corrrected question. I have the two supposedly matched exhaust manifolds and y-pipe from a '76 to '80. When I look at the mount of the y-pipe to the RH manifold, everything lines up and the little "donut" fits between the two perfectly.

But on the left hand site, the exhaust manifold is domed outward. The dome fits in the receiving end of the y-pipe, but there is no place for the donut.

Is this correct? Would this cause exhaust leaks or excess noise?

I'm actually going to run duals, and SQUAREROOT has me thinking again about headers. Nonetheless, I ask the above question since I want to know how these work.

Thanks everyone for your great responses and for indulging me on this last question.

Pics attached.

 

[bucket]

Addendum - pic of the Alan Grove bracket for alternator mounting when there is no bolt hole in the head. Stock bracket on the right, Alan Grove bracket on the left.

That's a nifty little bracket!

Exhaust manifold spreader? Is that also known as exhaust manifold cracker?

Man, that's a first for me after 50+ years of working on Chevy small blocks. I still learn something new almost every day.

To be fair, most of those manifolds crack themselves. Well, maybe not most... but a lot of them, lol.

Okay. The second question in my original post was poorly worded.

Here's the corrrected question. I have the two supposedly matched exhaust manifolds and y-pipe from a '76 to '80. When I look at the mount of the y-pipe to the RH manifold, everything lines up and the little "donut" fits between the two perfectly.

But on the left hand site, the exhaust manifold is domed outward. The dome fits in the receiving end of the y-pipe, but there is no place for the donut.

Is this correct? Would this cause exhaust leaks or excess noise?

I'm actually going to run duals, and SQUAREROOT has me thinking again about headers. Nonetheless, I ask the above question since I want to know how these work.

Thanks everyone for your great responses and for indulging me on this last question.

Pics attached.

The dome-to-flange should be correct. It's actually the other side that may be incorrect. Often the right side manifold will have a flat flange and long studs, so a heat riser will get sandwiched between the manifold and downpipe. The heat riser will have a flat surface to mount to the manifold and a dome surface to mate with the downpipe.

But a lot depends on the year and application. There were different connection types for similar manifolds.

 

[AuroraGirl]

@AuroraGirl

Check this picture of the 327, (L-79?) No bolt holes.

You must be registered for see images attach

283 didnt either , the one i have only has an alternator. or rather, a 12 volt alt(10DN I Think?) on it and the long bracket. The ram horns I assume the driver side has the provision for the bottom, but i could be wrong. Cant remember off top of my head

You must be registered for see images attach

 

[Turbo4whl]

Okay. The second question in my original post was poorly worded.

Here's the corrrected question. I have the two supposedly matched exhaust manifolds and y-pipe from a '76 to '80. When I look at the mount of the y-pipe to the RH manifold, everything lines up and the little "donut" fits between the two perfectly.

But on the left hand site, the exhaust manifold is domed outward. The dome fits in the receiving end of the y-pipe, but there is no place for the donut.

Is this correct? Would this cause exhaust leaks or excess noise?

I'm actually going to run duals, and SQUAREROOT has me thinking again about headers. Nonetheless, I ask the above question since I want to know how these work.

Thanks everyone for your great responses and for indulging me on this last question.

Pics attached.

The exhaust manifolds you pictured, the heat riser valve would be on the driver's side. The top of the heat riser would mount to the manifold with out a gasket (cast iron to cast iron). Then the bottom of the heat riser would have the donut gasket to the pipe.

283 didnt either , the one i have only has an alternator. or rather, a 12 volt alt(10DN I Think?) on it and the long bracket. The ram horns I assume the driver side has the provision for the bottom, but i could be wrong. Cant remember off top of my head

You must be registered for see images attach

Yes, all the early small block heads had just one or no threaded bolt holes.

 

[AuroraGirl]

Yes
Im guessing the one hole was for AC compressor or power steering provisions?(probably one or the other, but I guess I dont know)

 

[AuroraGirl]

The exhaust manifolds you pictured, the heat riser valve would be on the driver's side. The top of the heat riser would mount to the manifold with out a gasket (cast iron to cast iron). Then the bottom of the heat riser would have the donut gasket to the pipe.



Yes, all the early small block heads had just one or no threaded bolt holes.

You must be registered for see images attach

Also did you mean the OPs manifolds? I appear to have the same ones(With AIR ports) but it has a passenger flapper for it. but the engine came out of a car, so thats in play

 

[fast 99]

Exhaust manifold spreader? Is that also known as exhaust manifold cracker?

Man, that's a first for me after 50+ years of working on Chevy small blocks. I still learn something new almost every day.

If the manifold breaks it was previously cracked. Never had that happen.

 

[Powerhouse Ranch]

What I did with mine, was bolt them on with the center 2 bolts, and ran the engine for a little while get them hot. 2 went in afterwards, 2 just took a little prying with a lug wrench to get the other 2.

i'm like beside myself hearing this. I'd have to see such a thing to believe it

 

[AyWoSch Motors]

i'm like beside myself hearing this. I'd have to see such a thing to believe it

Hahaha. Its true, i did do just that. But sorry, no video or pics.

Bolt the middle, get em hot, they pry with one hand, and try to slip the bolt in without crosstreading with the other.

 

[fast 99]

Exhaust manifold spreader? Is that also known as exhaust manifold cracker?

Man, that's a first for me after 50+ years of working on Chevy small blocks. I still learn something new almost every day.

If the manifold breaks when spread, it was already cracked. Saves time doing the job twice.

Don't expect anyone to go out and buy a one but I used a 9/16th frame reamer to enlarge the holes. Cast iron is a b**ch to drill.

 

[Grit dog]

i'm like beside myself hearing this. I'd have to see such a thing to believe it

Can confirm. Although I haven’t touched a sbc exhaust manifold since I was in high school I think, used a torch and a rosebud tip and some prying.
That’s most of the reason they crack in the first place I believe, trying to tear themselves apart while being pinned in place by the bolts.

 

[Rusty Nail]

Exhaust Manifold Spreader is a valuable tool.
Install the two inside bolts and run the engine to temp, like he suggested @AyWoSch Motors. I have done that before. Good luck!