I need help in valuing a pair of NOS GM LT-1 angle plug heads that I'm looking at. They're in the GM boxes and are part number 3995784 and casting number 3991492. There is a sticker on the end of the boxes that says in effect that these parts are 'For Off Road Use Only" The heads have the valves, springs and retainers installed but no rocker studs or guide plates and appear to have never been used. Also I remember reading back in the day that these heads were over the counter only. Does anyone know if they were ever installed on a Corvette at the factory. Thanks Rich # 2276
-
-
Re: LT-1 Angle Plug Heads
I have always understood that angle plug heads were over the counter only and never used from the factory. -
Re: LT-1 Angle Plug Heads
"LT-1 heads" is a mischaracterization. No production Gen I SB ever used angle plug heads. They were strictly over the counter/offroad use only since they were not emission certified.
The head part number and casting number don't jibe. According to the Chev. Power Manual the 3995784 cylinder head assembly is based on the 340292 casting.
The 492 casting was used to produce the 3987376 service replacement head assembly and 336746 off-road head assembly (circa 1971), which sounds like what you are looking at. These were the first "angle plug" heads that were produced by relocating the plug on the standard 492 casting. The 784 head was the next interation, released in 1973, and was produced from the dedicated 292 casting. I think these were referred to as "turbo heads" back in that era.
It sounds like you are looking at a set a set of 746 heads in 784 boxes. Assuming they are 746 heads the value would probably be no more than the cost of a set of aftermarket cast iron replacement heads.
DukeComment
-
NOS parts?
Here's another case where the part in the box did not match the part number on the box. Recently I was shown what the owner believes to be an "early" Duntov camshaft assembly, 3734077, that was produced for the '56 engine. The rear journal has a centered "flat" about a half inch wide, so it's not clear across the journal. It's not actually a flat because if feels like an arc of inverse convexity to the journal, and it was gouged out with a fairly rough tool that left a lot of tooling marks.
The cast in number is ground off and "078" is hand stamped, which are the last three digits of the finished '56 Duntov camshaft (less pin) otherwise known as the "ID number". The lobes are Parkerized and it's clearly never been run.
A check on a Cam Pro Plus cam analyzer clearly showed that it is a hydraulic lifter design, and further investigation revealed that the test data matches the engineering specs for the 3896929 '67-up base engine camshaft!
The cam was originally acquired in a parts inventory purchase from a dealer in the East who closed down circa 1972. The current owner was given the camshaft by the person who bought the inventory in return for helping move all the parts, and it's been in the tube ever since. The tube and parts tag look old but the corner of the parts tag with the processing date is missing.
This cam has splotches of blue and green paint on the front journal face, a band of green paint splotches between the first and second lobes, a band of green paint between the distributor drive gear and rear journal, and slotches of YELLOW and green paint on the rear journal face.
I have no idea what's going on. If anyone can ID this cam by the paint markings, please chime in.
DukeComment
-
Re: LT-1 Angle Plug Heads
Rich-----
As Duke mentioned, the heads and the boxes they're in don't "match". Also, as others have mentioned, these heads were never used on any PRODUCTION LT-1 (or, any other engine that I'm aware of). However, they are excellent heads; I used a set for years.
One other "irregularity": these heads were never supplied with valves, springs, and retainers. Someone must have added those. Plus, as I recall, they were supplied with rocker studs and guide plates, so I'd say someone removed those. It's a good trade, though; the valves, springs, and retainers are worth a lot more than the studs and guide plates and especially if a good valve grind was performed when they were installed.
How much are they worth? I couldn't really say. However, since they were never used in PRODUCTION, they're really not going to bring "big restoration parts dollars". Still, they're new and they are good heads.In Appreciation of John HinckleyComment
-
Re: LT-1 Angle Plug Heads
Thanks everyone, good information as usual. RichComment
-
Re: LT-1 Angle Plug Heads
I bought a set over the counter in the mid 1977-8 years. They came complete with guides,studs everything but rockers. They will increase your compression a little because of the cc size in the chamber depending on what heads you currently have. If you plan on running a set of headers make sure they fit with angle plugs. I had to modify a couple tubes back then to clear my new plug angle. Good set of heads but consider the plug angle,wiring to the plugs and type of exhaust manifold or headers to make sure they fit or clear without doing what I did back then.Comment
Comment