I'm doing some homework on the SBC 3991492 angle plug cast iron heads with 2.02 /1.60 valves. An article in C/C mag. rates these heads as #2 behind the old 461X fuelie heads. So far I've gathered an application for the 70 LT-1. Good points are screw in studs, guide plates, good ports. Bad points is a close proximity of water jacket to spring pockets with large spring use. Also talk of Grumpy Jenkins using them on his 331 pulling 700 hp. I know there are some head guros on here that can share some info. possibly if you ran these heads, best cam, value, etc. I have a set and am deciding their destiny. Thanks for reading.
turbo heads ....or thats always what i have heard them called. think the other casting is a 292. i'd have to think they'd be better than a camel hump....never on a production car , been a few years since i have had a pair.
I remember when CarCraft printed some porting templets in one of the magazines for us to cut out and use for "fine tuning" the intake and exhaust ports on the "292's... That was back in the late 70's... I might still have that magazine somewhere..??
As Brandon said. The 3991492 angle plug was an "over the counter" part. Straight plug version (same part #) came on 1970 LT1s. I am pretty certain of this, but some one correct me if I am wrong.
Your correct on the 292's being an over the counter set.... They came out in??? '76-'78 I think... There was so much ink in alot of car mags back then about those heads. Not sure about 492's
My date codes reflect 1970, always thought the LT-1's were angle plug but I guess this would be a good time to clarify that controversy, could be over the counter? I imagine the 70 Z-28 crowd would have a dinner meeting to discuss the issue.
The angle plug 492's were never production heads. They were an over the counter head that used the same ports as the straight plug 492's (which were production heads). They were pre 292 Turbos, which were completely redesigned. You can't use the 292 porting templates on the 492's without ruining them. Larry T BTW, LT-1s were straight plug.
Larry T has it right. The 492's are not "turbo" heads as most people know. The 292 casting were called "turbo" castings and thay are much better overall design than the 492 angle plug head. The 492's are comparable to the 461X "fuelie" head with a better designed exhaust port. The intake port is virtually identical to the 461X. They are thin in the spring pocket area, but with moder "beehive" springs it is no longer an issue. There is absolutely no reason to enlarge the spring pocket anymore. These heads are excellant heads for high rpm smaller cube motors...Grumps 331 was just over 700 horse with worked over 492's, and I still have my 335 that was 688 hp with minor port work, close to .600 lift solid cam, 12.8-1 compression and edlebrock tr1y tunnel ram. I've built a few 377-416 ci engines with the 461X and 492 heads with very respectable results. There are better cast heads out there, but for a $! If you have them, I'd say use them. They are very capable of supporting 600+ horse on just about any small block as long as the whole package is built accordingly. It all depends on what you are planning on, but those heads will work for most anything hot street/strip application. If you are thinking about something 420+ ci then I'd say you'd be further ahead selling the 492's and buying a head better suited for a big inch small block. As far as I know, there was never a "production" angle plug head on a small block.
Take this for what it's worth (CRS could be in full swing), but I think Chevy actually followed the aftermarket on angle plugs. Seems some of the dragracers figured out that different plug placement could make a little better horsepower, so the hot setup was angle plugging their straight plug heads. Someone (Crane or ???) sold a kit with plugs and fixtures to rework straight plug heads. Chevy started selling the overcounter angle plug shortly thereafter. I'm not saying that Chevy wasn't working on their angle plug heads before that (and lots of technology was passed through the back door of GM back then), but I think people were running angle plug heads before they available from the factory. Larry T
I don't think Jim Hill will mind if I share this post he made on the Gas/FX group (Byron's Gasser Madness) Larry T "Yes, Crane used to produce modified cylinder heads. From the early 60's until the late 70's they were called Super Port-Flow heads, and were kind of like the "state of the art" for their day. These were serious race heads, made from ported and polished, new Chevy 461 and later, Turbo 292 castings. Later we offered the FireBall heads for small-block Chevys and Fords. These were originally based on the Turbo 292 Chevy head. Later heads were based on a World Products casting that was mildly modified, but in the most critical places, such as chamber bowl, inlet and exhaust gasket size, etc. They were very popular and reasonably priced and were delivered complete, ready to bolt on with springs and retainers and assembled for either a roller cam or flat tappet. We haven't offered these heads, or any kind of heads, since about 1994-95. The reason is that there are just too many good aftermarket heads available today, and many flow better numbers right out of the box, untouched, than the best "race heads" used to! Add to that today's very scienced methods of CNC port modifications (available usually from the same company that makes the head) and you have great heads that are the same as the first hand-ported heads, whether you buy one pair or 100. -Jim Hill"
Thanks guys, plenty of good information for a direction to go with these heads. I think they will work well for nostalgic purposes and will probably draw some conversation as well as performance.
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