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I have a 1972 monte carlo with a 402. It has air and power brakes. The heads on the eng are 62272292 open chanber oval port heads. I'm looking to add some horsepower for some mild quarter mile racing. The compression is only 8.5 to 1 unless someone added different pistons. The engine does look fresh( new gaskets). Some Ideas would be helpful. thanks
you can do some work to it .a cam change a hi torque cam and a dualplane in take. work on the heads bowl them out and cut them to 9-1 or find better heads to get it to 10to1 the older O ports will do this you could get it to 400 hp with out to much work more can be done but .how much do you want to spend
The car is all original so I don't really want to hack it up. I ran the car on what I think is the stock motor and it didn't do very bad; 15.67 at 91 mph. This is with exhaust manifolds, cast iron intake, and 2:73 gears. I think the engine has been overhauled mainly because of how clean it looks. It runs beautifully and revs nicely. Even the stock quadrajet doesn't miss a beat. I think that someone may have installed a small cam, say a 260 duration, just because the car does pull pretty hard around the 3000 rpm range. I think that I will add a set of 3:55 gears, a small street converter, a set of headers and an aluminum intake. Most of these are bolt-ons and I'll bet that that will alone, bring me down to the 14.40 range. Not really worried about cost( i have a very undrstanding wife). But I would like to do as much with what I have. The compression may be higher than stock and unless I pull the heads, I have no way to know. I have air and power brakes so 108 LDA on the camshaft is out of the question. I would like to get the car around the high 13 range but more importantly, I want a good sound with some lope...since it is a showcar. I may pull the eng and or just the heads to see what's under there. I don't drive the car very often so I don't mind higher compression or steeper gears. The camshafts i have been looking at are: a crane 226/236 534/553 112 LDA , comp xe 268, 224/230 515/520 110 LDA and comp 274 xe 230/236 552 lift. A friend of mine has the crane grind and it sounds really good and is somewhat vaccuum friendly.
I have always been a pontiac guy and really don't know much about chevys. From what I have been told, it doesn't take much to build these up to powerful mills, even the 402. I appreciate any info as well as criticism you can give. thanks
It would seem some porting and flow bench time on the heads, along with the parts changes you are considering would do the trick. Getting the compression up to 10 will also help a lot.
if you do some work on the engine and the headers will help a lot with a good ex. on the cam i would go hydraulic roller and the 402 and 396 can be made to run very good i have had some of them with out alot of work.i beat up of alot of guys with alot more than i had . on the heads keep the money down on them if you go over boad on them you will have to much in them and at that point you can buy new . just a bowl job a good set of ss valves and if the heads need guilds go to 11/32 stem and a very good 3+ angle valve job if you drop the cc of the head you do not need new pistons. oh yes the rear gear is killing you 3.75 will work good
I really appreciate the replies. I have 2 1/2 inch exhaust with dynomax mufflers. Do think I should replace the 2.06 intake 1.77 exhaust valves with 2.19 and 1.88? I have heard that I may lose some bottom end. Do you think that these camshafts are suitable? I plan on getting the compression around 10 to 1. YOU GUYS ARE LIFESAVERS!!! THANKS FOR THE REPLIES.
if i tell you what i would do i am shue there will be 15 guys telling me i am nuts . but the big valves may help on hi rpm hp but they mite not work on the small bore that good. were they work good better on the big bore stuff have put them in but never see much but if you think you need them put them in i would not just use ss valves the same size and go to 11/32 if thay need guides and a good bowl jobQuote:
Originally posted by flanker1970
I really appreciate the replies. I have 2 1/2 inch exhaust with dynomax mufflers. Do think I should replace the 2.06 intake 1.77 exhaust valves with 2.19 and 1.88? I have heard that I may lose some bottom end. Do you think that these camshafts are suitable? I plan on getting the compression around 10 to 1. YOU GUYS ARE LIFESAVERS!!! THANKS FOR THE REPLIES.
So you're saying I should add 11/32 diameter ss 2.06/ 1.77 valves? thanks for the info Pat
they will help the flow this is if you think you want to do this and keep the old heads and do some work on the bowls and a good valve job and back cut the valves
Im nowhere near as experienced as some on here. But you did say money is not of a big concern. Instead maybe take those original heads off and shelf them if you sell and need original parts. Then get some after market heads. You can choose cast or aluminum. The aluminums are more forgiving on the compression and can typically run 1 point hight on pump gas than cast. You can get the heads they way you want, the valve sizes and stems you want, and even mill them for compression. Bolt them on and they will most likely flow a hell of a lot better than any work you put into your old heads. Maybe a set of Edlebrocks oval ports with 110CC chambers. Maybe Brodix race rites or ARFs heads. JMO. Im sure the experts on here can elaborate on this better than I can.
if money is not a big deal pull the engine out and bulid a 496?? and buy a good set of heads? the stock heads will work very good for what he wants the edelbrock will work good but out flow ?the stock heads for a mild bulid up will work good. this would be up to the guy with the wallet.a good set of iron heads will work just as good as the aluminum heads. theO stock ports work very good. do not be putting a lot of money in them like i said the aluminum will be ligther as for cutting the heads you can cut the stock heads to . for the money on the edelbrocks heads . if you heads do not need a lot of work take the money you would spend on the heads and run a roller cam . big valves for the smaller big blocks are better for hi rpms i have never seen it or felt it by the seat of the pants on the 396-402 but every buddy and there brother think they need big valves. the in take big valves may not be so user friendly on the small 396-402 bores