Part # help

[Mike H.]

I need some help in determining the history of part #12529015, and its application (small block or BB). Any known configuration differerence from original?
Thanks,
Mike

[Joe L.]

Re: Part # help

Mike------

GM #12529015 is an A/C compressor muffler and hose assembly which is applicable to 1969-72 Corvettes with 350 cid engines.

The original assembly for 1969 Corvettes was GM #3949927. This part was replaced for SERVICE in July, 1969 by the 1970 assembly, GM #3963760. This piece was replaced for SERVICE in October, 1970 by the 1971 assembly, GM #3992144. Then, the 3992144 was replaced for SERVICE in December, 1971 by the 1972 assembly, GM #3998438.

GM #3998438 remained the SERVICE part for all 1969-72 Corvettes with 350 until October, 1995 when it was replaced by the SERVICE-only GM #12529015. The GM #12529015 was discontinued in January, 1997 without supercession.

Each of the above-referenced parts have configuration differences, but I cannot tell you what they are, especially since there were so many different successive parts that the GM #12529015 replaced. I can tell you that the GM #12529015 included hoses that are compatible with both R-12 and R-134a. The earlier hoses were compatible with R-12 only.

[Mike H.]

Re: Part # help

Thanks, Joe. I thought it was for the 350 but wasn't sure. I'll keep looking for the elusive 454 A/C hose set.

[Jack H.]

Re: Part # help

The factory original part has a rather large rectangular 'chunk' of block aluminum that bolts to the rear of the A-6 compressor with inlet and outlet tubes heliarc welded to the bottom. The SB version has a short, unsupported, tube run to the in-line muffler while the BB vesion has an aluminum reinforcement welded to the interconnect pipe between the manifold block and the muffler to thwart breakage.

The original, as Joe says, has LONG been GM discontinued and factory correct original AC manifold assy's are QUITE pricey in the used market. Go figure $150-400 depending on source, condition, Etc.

The service replacement manifold resembles a pair of 'binoculars' with a bolt hole between the 'eyepieces' to attach to the compressor. These are known to have some reliability problems since the attachment point where the bolt mounts is rather thin. IF the hoses aren't properly strain relieved (attached to inner fenders with clips per the AIM), they can vibrate and cause the binocular manifold to fatigue fracture.

In passenger car applications where this form of A-6 refigerant manifold was used, a stamped steel strain relief was mounted between the aluminum binocular manifold and the mounting bolt to help reinforce the structure. Had one musician classic Corvette owner in California who'd gone through FOUR of these manifolds with complete refigerant loss each time the assy broke. Once I supplied him with a steel strain relief taken from a scrap yard Impala AND he properly routed the rubber hose lines under the clamps called for in the AIM, his problems disappeared and he was a HAPPY camper.

But, if you intend to use the service replacement manifold on a Corvette intended for factory concours judging, expect to lose about 20% of the applicable line item originality points for this parts VERY different configuration geometry.

[Joe L.]

Re: Part # help

Mike-----

For a 1969-71 427 or 454 you are looking for a GM #3949928; for a 1972 the number is 3998472 which is also the SERVICE part for 69-71. Unfortunately, the GM #3998472 was discontinued in August, 1985 without supercession.

[Mike H.]

Re: Part # help

Thanks, Joe. Those were the only numbers I could come up with, but incorrectly assumed there had been another supercession. Discontinued in '85 helps account for thier rarity, and as Jack pointed out, cost.
Mike