[jdmerk]

Im gonna be buying a cam in the next few days, but i really have no idea what would be best for my setup maybe you guys can help me out...
the car is a 1972 LeMans with a 400 and th350 behind it. the engine had obviously been rebuilt before i got it and from the casting numbers i know it is a late 70's block i think it was 76 or 78 (6x heads), i can say for sure but i believe it has a higher conpression ratio than those engines did stock. maybe the pistons were swaped for performance pistons and/or the heads were milled im not sure but it runs pretty strong already...up to 5k. it has 6x heads on it, headers, a 750 holly and an edelbrock performer intake (which i will be swaping for a performer RPM along with the cam). my problem is that my engine runs out of steam right at 5k, i dont mind lope at all (actually i would like some) and im looking for a nasty street car, this vehicle will see about 90% street and 10% track but i want as much as i can possibly get out of it and reasonably expect to drive it on the street.

thanks guys

[jdmerk]

oh yea ive also heard really good things about rhoads lifters...increasing low end torque and vaccum with radical cams, whats your take?

[JKGTO]

More info needed on your combination. What converter, gear ratio, tires stock or larger? If possible you might take the engine down to the shortblock to see what you actually have now for a cam and pistons and CC the heads to figure out the compression. You are going to have the intake off anyway so you may as well take off the heads to check things out. All the parts have to work together with the cam. Jim

[jdmerk]

running 26" tires, stock converter, 2.73 open gears in it now...soon to be 3.55 or 3.73 with a locker. so im gonna need to pull the heads while im in there? ok, but how can i tell what the CR is jsut by the top of the pistons?

[John Milner]

If your engine has flat top pistons in it, I would look for a set of 16 or 62 heads to get about 10:1 compression. If you switch to 3:73's I would look at the summit 2802 cam (224/234 .465/.488) or something like the crower 60916 cam (221/229 .455/.470). You may also want to look at getting a higher stall, something like a 2500rpm. Either one of those cams should have a choppy idle. If you want a nasty idle I would look at the comp XE274 or the Ram Air 4. As for rhodes lifters, I am not a fan of them because they are noisy. But, if the noise dosent bother you, I am sure they would work well with a bigger cam.

[jdmerk]

how necessary is a higher stall on those cams you listed? also hows the vaccume on those choices? and can the 6x heads handle that lift?

[John Milner]

I have ran the Summit 2802 in a 400 with 10:1 compression. I was running 3:23 gears at the time, and it had plenty of power all the way to 5700rpm or so. I also ran a stock converter. It had plenty of low end torque to smoke the tires. I'm sure it would have ran a lot better with a 2500 stall and 3:73's. I am not sure on the vacume, but it had plenty to run the power brakes. I would say that if you switched to 3:73 gears you could get away with either the crower 60916 or the 2802 with the stock converter. If you ran a ram air 4 or the xe274 you would need a 2500-3000rpm stall for sure. I would invest in a new set of valve springs. Also, unless you are running a domed piston, the 6x-8 heads on a 400 will yeild around a 7.6:1 compression ratio, a 6x-4 head will yield an 8:1 compression ratio. To run any of the cams that I suggested I would recommend atleast 9.5:1 compression, with 10:1 being the best.

[jdmerk]

ok so your saying i need to switch heads to make this worth my time...which stock heads would net the type of compression your talking about (provided i have stock pistons)

[jdmerk]

nevermind i see the above post 16 or 62

[Ron H]

What ype of 6X head, 4 or 8? Probably 8. You don't have to swap heads. XE cams are made to help with ow compression heads.You could shave down the ones you have to increase compresson. You need to confirm what pistions you have. Overbore will also increase cubes, compression. Do some homework and search combo/cam threads. There is alot of threads on this.

[jdmerk]

ok so i guess ill pop the heads off next time i get a chance and cc the heads just to be sure whats in there...it was killing me not knowing anyway

[jdmerk]

OK so i was told that im runnin on all stock internals. So assuming that info is correct what would be the best cam selection for me?

[69birdboy]

Assuming that is true, you need to get your heads milled because compression will be 8:1 or even as low as 7.6:1 with those heads. Otherwise you'll need a much smaller cam and you wont get a nasty idle without killing your performance.

[*67firebird*]

jdmerk, you and I are going through the same situation, i am using a 400 head, performer intake, but i am sticking with my q-jet i've heard that it sometimes better than some out-of-box 750 carbs. I am going to be using my stock 670's and those heads keep me at a high compresion like 10.75:1, im going to be using the 2802 summit, with 3.55 gears and a converter that can stall between 2500-2800. The combo works out great with the intake and cam, both have the power range starting at 2500 rpm, so any converter that starts at 2500 would be a good setup, some people tell me to use a 3.73 for a better kick in the pants!!! but with the cam having a LSA of 114, the 3.55 can save me a few bucks on fuel. Otherwise if money is not the issue go for the 3.73. JMO

[jdmerk]

what if i got a set of #46 heads, they are 75cc heads which should put me somewhere between 9.5:1 and 10:1 but they have a smaller intake valve 1.96 vs my 6x's 2.11, i can pick them up for about $200 but would they benefit me even with the smaller valves or should i stick with the 6x's

[69birdboy]

I would tend to build for compression before flow. Compression increases power at all rpm. Why not just mill the 6x's and have the best of both worlds? You can mill off .060" (12 cc's) no problem, and Geoff has told me he milled his 6x-8's .110 no problem.

[chiphead]

If you do have heads milled over .030", you'll have to have the intake milled to match, and use shorter pushrods. Not a big prob, but you need to know... You can find a set of 6x4 heads and use them, they require less shaving, which can reduce fitment headaches. They'll have screw in studs, big valves and late style accy holes. If you don't want to use a stall converter or deep gears, I'd suggest the XE262 and matching lifters. If you want more power with less than 9:1 compression, use the crower cam and rhodes lifters. Mr P told me not to use rhodes with an XE cam, the lobes are too aggressive with fast bleed lifters. If you had more compression, you could use the XE274 or a more aggressive Crower cam.

And I wouldn't suggest spinning engine above 5500, since you have stock connecting rods. Try to build power between 1500-5000 RPM.