I thought about suggesting that, but every 70-up 455 still has the passage on the driver's side, and I've only heard of one instance where someone suggested that oil was seeping out through the head gasket (and I am skeptical of that).
Ok, I have a question then. I have a 75 block with 73 heads. I know its lower compression because of the piston dish. What spec pistons would I have to put in to raise the compression to 10:1 or so. Also does this lower compression really affect my perfomance that much.
Hmmm are the 75 heads "really" pieces of crap. Can't they be used in a boosted car. Turbo/compressor setup, due to the low compression?? I have a couple of them heads. Dont know what to do with them though.......anchors maybe :laugh: // Jan
Unless I missed it in this thread, what about having the '75-'76 (less desirable) heads milled down some to increase combustion? Is there enough material there to allow for this? Sidenote; great site, excellent info! :beers2: I am used to a couple other sites that are HIGHLY technical so I had big expectations. So far, my expectations have been met. Continue the great work gentleman.:TU:
no, scrap heap those huge chamber heads, by the time you cut them down to get a good cc, your valves would rub through the pistons into the crank:bla: I may have a set of 70 heads I would be willing to part with:beers2: :dollar: They need rebuild.
I have a 72 455. If I read your sonopsis correctly I can have the heads reworked with bigger valves and do some porting and I will have basically a stage 1 motor. What about the cam are they all the same between a Stage1 and a non stage1? :3gears:
Actually, just the bigger valves and you've got pretty much a Stage 1 motor. Porting is icing on the cake. From the factory the Stage 1 used a bigger cam, but you would not want to use either in an engine today. Technology has given us much better cams, and the stock Stage 1 cam is still very mild compared to what you can get today, with no downsides.
great post it answered a lot of questions i had i run a 73 lectra 225 on a 1/4 mile dirt track (worlds largest dirt car) it is a stock class last year i snuck in a little hotter cam 496 lift comp cam and it really helped . Next year we will be required to run a holley 500 2 barrell . keeping this in mind would i be better off to use the non stage 1 valves I am planning on building a new motor for next year and thought i neede a 70 model block and heads until i read your post any inside tips someone might have would be appreciated I need the most power I can get from a stock appearing engine we are requred to pull 16 inches of vacum at 850 rpms thanks for any info anyone might have
I am looking at buying a complete carb to pan 455. Comes with headers and is recently a stock rebuild. the block is a 72 by the casting, intake is 73 and heads are the 75-76 that you guys are blasting as being poor? He wants 700 for the whole setup, am I wrong in thinking I should be able to get this for 400? He originally bought it thinking it was a Pontiac engine and now can't use it as he wants the correct pontiac engine. If I keep the 75 heads on it, how much hp should I expect to get out of the engine if I throw a mild streetable cam? Great post, thanks for the info.
is recently a stock rebuild. is the rebuilder a known Buick guy? if he did a "Chevy" rebuild on it that engine is probably a grenade waiting to go off. If I keep the 75 heads on it, how much hp should I expect to get out of the engine if I throw a mild streetable cam? hard to say as we don't have any idea what pistons are in it. i wouldn't expect a whole lot out of it unless you plumb it for nitrous or a turbo or something.
I pulled the motor out of my stock 68 GS400 to rebuild and put in my brothers freshly rebuilt 69 GS400 motor (which I believe was kept pretty much stock) to keep my car up and running while I built mine. I used my stock carb on his motor and it never seemed to run just right. It didn't run horrible, but it didn't seem all that great either. Is there a compatibility issue with running a 68 q-jet on a 69 intake?
Ok here is a stupid question.. why was the "SF" motor rated at 370 hp??.. I pulled one fron a 70 Riv and that is what I'm running in my 71 Skylark..
In '70 the big car 455 was rated at the 370 number for marketing. To make the A-body cars seem a little safer they were rated at a lower rpm, thus less output. Or so the story goes, anyway. I don't put any weight in factory ratings to begin with. Devon