I'm looking for a good cam for my 383 LT1. I am going to be using a carb instead of the fuel injection. I have some fully ported heads with 2.02/1.6 valves, 11:1 comp. This is going in my 69 Camaro that will be a weekend driver/racer. I am looking at the GM 847 cam. Does anyone have any imput on this cam or another suggestion of a good combo. I also have all forged internals and plan on spraying mabey a 200 shot.

Thanks, Tim

What are the specs on the 847 cam?

What compression ratio, stall, and gear are you going to run?

Do you have flow numbers on your ported heads? I assume they are LT1 heads . . .

I can't find my flowsheet right now, but I know the heads flowed 286cfm @ .500 on the intake and I think 182 on the exhaust. They are LT1 heads. I want the most power I can get for a weekend driver/drag car. I don't plan on reving past 6500 rpm. I will probably use a 2500 stall and 4:10 gears with a th-350

The GM-847.

Hydraulic Roller Design
This hydraulic roller design contains eccentric for mechanical fuel pump. It is for off-road use only. The duration at .050" tappet lift (intake/exhaust) is 234/242; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 539/558. Valve lash is zero/zero and lobe centerline is 112 degree

Is this the one I need or should I go with a custom grind?


Thanks, Tim

" For off road use only" eh??? I wonder where they get this stuff. Unless thats a california emmissions thing, its a joke. That is a fairly tame cam, plain and simple. You could definately use more cam than that with 11:1 compression. I wont recommend an exact cam because i dont have alot of personal expierence with alot of different cams. But look bigger, alot bigger. If its only a weekend cruiser and you want this car to be fast. Id go AT LEAST high 240's-250's @ .050 and if your going to put up with a roller, go solid roller, why go with a heavy hydraulic roller? Thats my 2 cents. Just an opinion

The GM 847 cam should be quite sufficient for your needs. Joe Sherman used a smaller cam in his 600+ hp 365" Enginemasters entry. 4.10 gears and a 2500 stall converter will require good low-midrange torque. 6500 rpm with 28" tires, 4.10 gears and 10% converter slip equates to 120 mph, about a 11 flat quarter mile.

Your combo is a little tough to pick a cam for IMO because you are running 11:1 compression, a tight converter and have heads that will run to 6500 easy.

If it were my car I'd go with a little looser stall and more cam. You are pushing the limits of pump gas -- although I have heard that the reverse cooled engines can take a little more squeeze than the traditional small blocks.

I run 11.3:1 and manage OK on pump gas, but my cam is every bit of 250* @ .050 duration. A big cam bleeds off more cylinder pressure and if you want to run 11:1 and pump gas, you'll need a little more cam too.

Just my opinion.

The GM cam isn`t too far off the mark IMO.
I would get a UD/Lunati grind like ours I think it would work very well.
The specs are:
288/296 adv. 234/242@.050 .530/.530 lift. 108 sep.
Our compression is about 10.9-1 (+-)
Runs fine on 93 octane we have alum heads though.
Your LT1`s are iron right?

The cam suggested would work well on motor.
For spraying, 112 would work better.

Thanks for all the replies. I have not bought a stall yet, I will just get one that best compliments the cam. Before I ditched the fuel injection, this engine was in my 95 Z28. It was a six speed so I did not have to wory about stall speed. The only difference internally will be the cam. I was running a Comp 236/242 .550/.570 112. I do have aluminum heads and was running 11:1 cr with no knock retard on 93 octane.

By the way, just for comparison, the LT1's are 10.5:1 cr stock and will run fine on 87 octane.

Thanks, Tim

oneofakind67, Joe Shermans motor was hardly a pump gas motor if i remember, 13:1 compression wasnt it?. Yeah it ran fine on PG on the dyno but it wasnt subject to humidity, or load from a car or anything like that. take those jagged edge pump gas dyno's with a grain of salt, cause all it is, is an exhibition contest.

Neofaguy73,

You can view all the final dyno runs at:

http://www.popularhotrodding.com/enginemasters/dynopulls/

With proper combustion chamber design and quench you can run a lot more compression than most think. I run 10.3:1 compression with iron heads and a 224°/224° Comp HR cam on 91 octane pump gas. I tow trailers, drive everywhere and I'm not hoping for an 11-second time slip, I've got a bunch of them.

well first off either your trying to mock my screen name or you cant spell. Both of which make you look fairly stupid, 'cause all i did was make a very good point in my last post.
Second what the hell does you running an 11 second time slip have to do with Joe shermans dyno pulls on engine masters????? Please let me in on that one. Ahh it just hit me, you were trying to take a shot at my signiture....ahhhh, well the track dosent open up for a few more weeks here in iowa, so this spring/summer ill get my time slips, and then thats about the time you'll shut the hell up.
Now if we're trying to have a "who can run the most compression on pump gas" pissing match....I WIN hands down. I run 11.1:1 compression {according to Pat's calc.} and have been on 89 octane all spring with all my timing in before 2,500 and 36* total so suck my b a l l s.
So do yourself a favor, next time somone has a good objective viewpoint, which i must say i did, why dont you embrace it, and objectivly argue instead of trying to mock them.

Happy Easter

Mocking your screen name? Far from it, I just spelled nova the same way you did. You wouldn't be mocking mine, would you?

For a 383 with a 2500 stall converter, 4.10 gears and a 6500 rpm rev limit you certainly don't need a 250° cam. Not enough low end torque to operate the equipment, you're giving up 80-90#ft at 2500 rpm. If you're gonna spray it, the 847's 112° lobe centers are in your favor.

i think 80-90 ft-lbs may be a bit excessive, but if i read right he said his converter choice was not set in stone. Now im going to leave the converter thing alone cause i dont know them well enough to make a call {im a stick shift guy}, but im just saying that with 11:1 and 4.10 gears he could stand to use more cam than 235@.050. If im not mistaken eric68 has a nice little 11:1 383 combo that runs a a healthy 250@.050 solid cam and a mild converter, with 3.55 gears and has some very nice timeslips behind it.

Shermans motor ran with 11.4:1 compression and a solid flat tappet with 236 @ .050.

I think the GM 847 cam will do fine, especially on N2O. I'd prefer a little bigger cam, solid roller, in the mid 240's and a 3000 stall.

I don't have any 11 second timeslips. :mad:

Like I said earlier, this combo is a tough call -- 11:1 is pushing the limits of pump gas reverse cooling or not. Especially with a 234/242 @ .050 duration cam. What is the seat timing anyway?

A 250* cam will not necessarily kill low end -- especially in a 3.75" stroke motor. It depends on how low in the RPM band you want/need big TQ. How much TQ you can put to the ground anyway? If your chassis can put down 500 lb/ft TQ with street tires more power to you, but mine cannot -- not even close. In fact, even with a single plane I cannot mat the gas in 1st gear at all on street tires without tire smoke.

Joe Sherman's combo was interesting to say the least. While it did make awesome power, it was clearly never intended to be an example for selecting compression ratios for a street car. They even stated at the beginning of the article that these combos would need to be tamed a bit to run on the street and as I recall they specifically mentioned compression ratios.

Also, low end TQ and vacuum for power accessories will be affected more by seat duration that by 050 duration. If you have a high intensity lobe with say 285* seat duration and 248* duration at .050 it will be much friendlier down low than something like the magnum lobe with 294* on the seat and 250* @ .050.

Lobe separation angle with a manual transmission is an important factor too. Tight LSA'a make for peakier power and are very noticable when an engine comes "up on the cam". This makes life on the street with a manual tranmission a bear if you have a hair too much cam and a tight LSA. On the other hand, a wider LSA widens and flattens the power band helping a manual trans car out when engaging the clutch. In this application I would go with a 110-112 LSA cam.

For this car I would look at a cam with mid-280* advertised duration and mid-240* duration @ .050 on a 110-112* LSA (about 10 degrees larger all-around than what you are looking at now). With 4.10 gears you will NOT miss any low end TQ.

Originally posted by Eric68:
Like I said earlier, this combo is a tough call -- 11:1 is pushing the limits of pump gas reverse cooling or not. Especially with a 234/242 @ .050 duration cam. What is the seat timing anyway Seat timing int: 39* btdc 69* abdc 102
exh: 79* bbdc 37* atdc 114

Onenovakind has a hyd roller in his 406 that sports 224 @ .050 with 10.2-1 comp on lesser gas, 91 octane I believe

Big Red -- that timing is for the UD 288/296 on a 108 . . . that would be pretty good for this car but I thought the 050 numbers were bigger than that.

Comp cams 12-609-5 :D

Between theese two which one would be better?

Comp 235/242 .565 and .570 113lsa

Crane 246/254 .558 and.558 either 110 or 112 I'm not sure yet.

The second one is what Crane suggested for my engine. I will also be using 1.6 rocker arms instead of 1.5

Thanks, Tim

Both cam specs are with 1.5 rocker arms. The Crane cam is a 110 lsa. I'm leaning towards the Comp cam because it is cheaper and Crane won't answer their tech line. If nobody here tries to talk me out of the Comp Cam I'll buy it tomorrow. Thanks for all the help.

Tim