I've done some searching in the forum and ,although I'm fairly sure the information will be lurking somewhere, I can't quite find what I need. Hence, this post.

Relevant background: We bought a half restored 1969 350ci auto car with factory A/C. The engine was out and half disassembled when we bought it. Heads were nowhere to be found but they did turn up months later. They are 186 casting double humps that we were going to use but one has a crack in a very awkward spot that makes it risky to repair. Our first preference is to keep the car as original as possible but we are not talking full numbers matching.

The problem: All of the replacement double hump heads we've found so far don't have bolt holes. The 186 castings we have do have bolt holes. As the top and front of the engine were already disassembled when we bought the car, it is not clear if we need heads with or without bolt holes for the accessory (alternator, A/C compressor, power steering pump).

Additional information: Based on the numbers decoding, this car should have the 186 or 041 casting heads, both of which seem to come with accessory bolt holes, but it is possible that these heads are not the originals. Based on the assembly manual it looks pretty clear that the alternator and power steering pump brackets mount to the block or exhaust manifold. This also appears to be the case for the A/C compressor but there are two bolts (labelled 8 on UPC C60 C3) that may mount to the head.

Can anyone shed any light. Photographs of the set up would be greatly appreciated.

 

Working from memory, for the power steering two bolts go through the cradle and the two front holes of the adjusting bracket, and into the front of the block. The side of the adjusting bracket attaches to one of the motor mount bolts. The two holes for the ps brackets are down low on the front of the bolt, near the bottom of the timing cover.

Still working from memory, the alternator lower bracket bolts to the exhaust manifold on one side and the top bolt of the water pump on the other side, but instead of it being a regular bolt on the pump it's a bolt with a threaded stud on top. The bottom of the alternator adjusting bracket goes on the stud and gets a nut on it to secure it. Alternator brackets weren't attached to the head until 1973.

Again working from memory, the cast front bracket for the compressor is attached using the two water pump bolts. The compressor lower support bolts to the exhaust manifold and a bolt goes through the lower outer hole of the front bracket into the lower support. The front adjusting bracket bolts to the front of the compressor with one bolt going through the upper most hole of the front bracket, through the slot in the adjuster and into the compressor. The three hole triangle shaped bracket bolts to the rear of the compressor and to the rear of the manifold mounted lower support.

Neither the AC or the PS bolt to the heads, as near as I can recall. If my memory is failing me (again), I'm sure someone will post a correction to what I've posted.

 

I have (had) a 186 head off my 70 Corvette for sale here on the forum in the parts section. If you can't find it send me a message. I still have it.

 

Many thanks Glenn. This is consistent with what we can glean from the assembly manual. We gathered all the brackets and accessories this morning and, even though the block is at the machine shop, it appears that everything hangs off the block or exhaust manifolds. It's just odd that the heads have bolt holes in them that aren't used. Seen the same thing on at least one other 69 from an internet photo. So I think we are back on track and I can go with the heads we sourced that don't have bolt holes.

We will need to work out the brackets that mount on the exhaust manifold, as one manifold is broken at the exhaust pipe flange and has a broken bolt in a hole for the alternator. We were planning on going with headers anyway. I'm sure someone has modified brackets.

 

Thanks. Sadly we are in Australia so the shipping would be horrendous. We'll go with non-186 castings we've sourced here.

 

I'm not 100% sure, but I think some other Chevrolets may have used the holes in the heads to mount the alternator, maybe starting around 1969?

Because of the packaging issues involved in getting everything to fit under the hood of a Corvette, the accessory brackets used on Corvettes were sometimes unique to the Corvette and not shared with other Chevrolets. Also, Chevelles, Camaros, etc used "log" style manifolds instead of the "Ram Horn" manifolds, and used different brackets. The 68-69 era was also when A.I.R. pollution equipment use became more wide spread, and the holes in the heads may have been used to mount the A.I.R. pump in some Chevrolet applications?

 

Alex_67-327
If you can get the heads with forward holes you're better off, especially if you're not going numbers matching. When I bought my car ages ago it had some horrible contraption holding up the alternator.....had to keep fixing it. Noticed that the driver side head had holes so I bought the lower alternator bracket 3951337 and started using that. Cast Iron and solid as a rock.
Alternator Bracket 3951337 is a LOT better than those header bracket contraptions. I recommend it. You can probably find one cheap on flea-bay.... or from early 70s Chevy pickup trucks. Cast iron and sturdy.
Don't buy the first one you see....there's a ton out there and some of these scam artists are charging outrageous prices for them. Go look on fleabay. It's cast iron so it'll last forever.

See this post... attached below: https://www.corvetteforum.com/forums...post1605205735

 

Here's a pic of the 72 alternater bracket it is the only bracket that bolts to the head.Non of the ac or power steering brackets use the heads for mounting.

 

carriljc
Many thanks for the advice and link.

 

alt66

Thanks. That's a solid looking bracket but alas we are likely to go with heads that don't have bolt holes. They seem to be far easier to source here in Australia.

 

Alex_67-327
I am surprised. they made SBC Heads with holes a lot longer than without holes. I even bolted the same bracket onto my newer Vortec heads.....

 

carriljc

Yes, and I must admit my comment is not based on an extensive survey. It is just that we found three sets of double hump heads without holes and none with holes when we found the crack in our set and started looking for replacements. These are not numbers to say anything concrete!