I'm in the process of a complete engine rebuild on my 1967 327/350 hp. The engine shop working on the machining said that the harmonic balancer on it is an 8", but should be a smaller 6 3/8".

Is this correct?

 

No, it takes an 8" balancer; the 300hp takes the smaller one.

 

The '67 327/350 HP takes an eight inch damper, an original should even have fins on the back of it. The GM replacement should be P/N 3817173, pre 1969 timing mark.

 

They'r blowing smoke up your ****. That's no excuse to stop work on an engine. Examine your final bill carefully.

 

I'm not accusing your machine shop of anything, BUUUUUUUUUUUUUUUUUUUUUT, let me say this. If that were MY engine, I would be IMMEDIATELY concerned (I was going to say suspicious, but that is probably politically incorrect). If your machinist is the LEAST bit familiar with hi-perf small blocks, he KNOWS that the early/mid-60s hi-perf 327 came with finned 8in balancers. Also, the ORIGINAL finned 8in balancers are quite valuable. Again, if it were my machinist and he said this to me, I would be concerned that he was trying to swap out my balancer (translate valuable) for a common, low demand balancer. Also, if your balancer is the original finned 8in version, the timing chain cover is also somewhat valuable!!! The reason is because the 62-68 timing chain covers have the timing tab spaced out an additional inch to accomodate the 8in balancer, plus, the 68-earlier timing tabs are in a different position from 69-later timing tabs.
Personally, if it were my engine (and my machinist told me what he told you), I'd be going down to the machine shop and casually inventory the engine parts.
And, one last thing. Have you told your machinist NOT to surface your block???? If your 327 is the original engine to your car, and he surfaces the block, you will loose your matching numbers on the block. VERY, VERY seldom do small blocks really need to be surfaced. But many machinists like to convince you that it needs to be done so that the heads and gaskets will properly seal (a method of making a little extra money). BS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!! Just in case he should insist that your block needs to be surfaced, go down there and make him dimonstrate why it needs to be surfaced!
In 40yrs of building engines (and I've built many), I've only seen 2-3 engine blocks that REALLY needed to be surfaced. My machinist used to get a little upset with me because I wouldn't let him surface the blocks that I brought to him-------------------but he knows how I am now and never pushes it anymore. He just asks if I want it surfaced, I say no, end of conversation. I've never had a head gasket fail on an engine that I didn't have the block surfaced.
Now I mentioned all of the above in SPECIFIC reference to the fact that your engine may be the original, matching number block. Otherwise, it doesn't matter.

 

Just further info on block surfacing:

The orginal GM assembly used steel shim gaskets, which are far less tolerant of surface variations than later composition gaskets. Typical max. variation if using steel shim gaskets is .001". Composition gaskets can tolerate .003" variation (that's a lot on a block surface).

Only small blocks that I have seen that needed surfacing on a regular basis are those that have seen a very high overheat situation (read; run out of water - for a distance). Normally the heads warp way before the block does.

Now 400 CID SBC blocks are more prone to warping and gasket failure due to the thin cylinder to cylinder wall thickness and the siamese bores.

As DZauto stated, machine shops just love to try and talk you into extra work! Some of it is necessary, and some of it is pure gravy!

Plasticman