cam for a stock 383

[custom880]

How far can I go with a cam in a stock 383 before I run into valve problems with flat top pistons? I have a 1970 block with 906 heads and want to beef up the cam, but I dont want to go with new valve relief pistons.

[cuda66273]

Not really you can't compress the valve spring down enough to get a true measurement of the clearance. The cam timing events will affect the clearance, you may have a problem when the valve starts open.

The 906 head moves the valve way up from the piston and because of the quench area in the 906 you probably have lost alot of compression.

By installing a bigger cam you may hurt yourself, with what I can tell you probably need a cam that won't bleed off any more cylinder pressure and a wider lobe center may be in order. I've done several of those motors and we've had good success by carefull cam selection based on true calculated Compression ratio's and building the power at the bottom end...they just don't want to pull much past about 5K, but under 5k they're a mule.

Racer Brown is real familiar with this combo and can grind you a stick that will pull hard.

You also may want to consider changing the head gaskets to the Cometic .027 thickness and cut to specific bore to maximize your compression ratio, this will allow you to run a slightly bigger bump stick and make some more usable RPM.

If you need more info I'm around the shop today and I'b be happy to try and help you out with any further questions.

Don

[custom880]

Don great info thanks. Basically what I am doing is putting a 1970 383 in a 1966 Polara and I am looking for a little more grunt for the car. What I used to do way back when is put a 440 6 pack cam in the 383 and that usually gave it some good power. The car is a vert and I do want to be able to run it a little bit. No track stuff but the Polara is a heavy car and it will need some good power. The original 1966 motor had the 516 heads and ow compression pistons. That combo is a dog in my experience. I have used this particular 383 before in another car and it is a very good motor. There was a rebuild done on it about 5K ago. I was thinking about a Mopar Purple Shaft cam set up. Cam and lifters. The springs should be pretty good.

[cuda66273]

If you think it was low compression with the 516 heads wait untill you run the numbers on a a set of 906's......

MP Cam?...I wouldn't put one in my wifes kitchen blender. But's that's my opinion based on computor profiles on actual delivered units and what's that worth?

If you want that motor to have some grunt you need to spend some time grunting over a calculator.

If I can help you know how to reach me.

Don

[custom880]

Don I didnt mean that the 516 heads are low compression. They are in fact closed chambered heads. The pistons in the 66 are low compression type. Dished pistons. The 2 barrell motor to be more specific. I have a set of 516's on my 361 and they do just fine, for a 361. I dont think that I would use them on my 383. I like the 906 heads, especially the ones that I am using. They were redone with new stainless vales and guides. The heads seem to flow very well. I never had them checked for flow. Racer Brown cams are well respected thats for sure. I have had very little sucess getting a hold of them. MP purple shaft should have a good Mopar grind. Have they fallen behind the other manufactures? What about Huges? I am not going to get to radical, I just want a decent set up for a street motor that wont break the bank. lol

[71383bee]

The price is not that different. The point everybody is making is that RB will make your cam to your motor for about 20 bucks more than the other guys. MP was had HUGE quality control issues and there designs are outdated. I may get flak for that, but the truth hurts. Hughes and Comp do make good cams, but they are going to give you a cam that on average works good for your combo. What I mean is that you tell them your basic specs and they look on a chart and pick the cam that fits. RB starts at that point, but customizes the cam to your specific issues like body weight, gear ratio, idle range, calculated compression, stall, etc.

It's worth a call...I am talking to him already about recomendations for my 318.

[custom880]

I have dealt with Huges before and have had very good results. They have set me up for my 400 HP in my 73 Charger. Just like you said they asked specifics about the motor and what it was in and the intended use. I had a very good result dealing with them. To bad about MP and their outdated specs/designs. Wonder why they dont do a little research to find out what the competition is up to. I am mostly concerened with valve lift. I have the flat top pistons in my 383 and I dont want to have any trouble with clearance.

[71383bee]

With 906 heads and stock 1.5 rockers I am willing to bet that you won't have a problem. Actually the 383's have a pretty low compression ratio. Did you mill the intake or heads at all? What gas are you running?

[weerem]

880------ you want answers!!!! Here's mine. cam- xtreme 284 -.507/.510 lift (great cam I might add) stock pistons .084 in the hole, 516 heads, the trick with these is grind the exh ports for forty days and forty nights, heads milled .060, mopar steel shims .020. Now, I've got 10:1(+/- .34%) and a healthy .120 exh clearance and an int of .100. This is with NO valve releifs. From what I understand you will have less cam etc etc . If it were my car and you didn't mill the heads , I wouldn't worry about it.

[custom880]

The 383 was a junkyard motor with 98K on it. I had the block lightly honed (didnt need boring) cleaned and magnafluxed. I had the mains aligned bored and the crank polished. The heads were gone through magnafluxed checked for straighness (o.k.) and new valves 2.08 and 1.74 stainless steel. New keepers and springs and retainers. New guides (cast iron) along with a three angle valve job. No porting was done. No milling was done. The cam that we put in the motor after the rebuild (new Molly rings full grove bearings) was a 440 six pack cam. The motor ran very well with a stock cast iron mopar 4 barrell intake and a 625 Carter carb. The exhaust was stock dual with turbo mufflers. I always ran 93 octane with that motor. I also used a Mopar electronic stock ignition set up. All in all it was an o.k. set up. The cam pushrods and lifters were taken out of the motor and used on a friends 440. I thought that the 383 would sit for a long time but it is now needed. I am now looking to replace the cam lifters and pushrods. The motor will be getting a better manifold, and headers. Probably and Edlebrock carb as well.

[weerem]

What's the weight? What's the gear? Dual plane? Edelbrock carb??? 383 pushrods in a 440? 516's and dished pistons? You have to open the exh ports with the bigger valves. They are like 1.40 holes behind the 1.74 valves. It hurts H.P,torque, effiency, M.P.G , well, everything.

[71383bee]

With the 66 low compression pistons and 906 heads I bet you are around 8.5:1 compression. You can probably get away with 89 or maybe even 87 octane gas. You don't necessarily need to run 93 octane unless it pings.

I say an Edelbrock perfromer RPM intake and a 650 mech secondary demon from Don and a good Racer Brown cam would really wake your car up. The only limiting force is your compression and your heads.

[Glen440]

The stock heads badly need to be opened up under the valve. You pull the valve out and the hole is like 1/4" smaller than what it should be. Gotta see what it looks like when you jam a 1.81 valve where a 1.60 was........lol. I coulda filled a 500ml pop bottle with metal after I ported my 452's never mind my 516's.
Cam choice is mainly for what you want to do and how much power. I tuned the stock cam into the 13.9's before I went to the .528. 8-1 engines have alot of clearance with pistons .115 down the hole. When you hit .500 lift and 290 duration you are really pushing it for clearance on that engine. My bro put the .509 in his 69 383 and a valve touched a piston, it didn't do it right away but the first time he thrashed it. Clearance was too close.
That was one way of destroying an entire engine. when you pull an intake and you find piston ring in it you know you did something big and it travelled to all cylinders somehow and smashed all the plugs and bent valves, what a mess.

[custom880]

Originally posted by 71383bee
With the 66 low compression pistons and 906 heads I bet you are around 8.5:1 compression. You can probably get away with 89 or maybe even 87 octane gas. You don't necessarily need to run 93 octane unless it pings.

I say an Edelbrock perfromer RPM intake and a 650 mech secondary demon from Don and a good Racer Brown cam would really wake your car up. The only limiting force is your compression and your heads.

There seems to be some confusion on the motor I am talking about. The motor I am using is a 1970 383 with 906 heads and flat top pistons. This is not the 1966 motor. The 66 motor has dished low compression pistons. That motor is under my bench and will not be used. The 70 motor was out of a Newport and is all stock. The cam that I had in it I gave to a friend along with the lifters and pushrods. The pushrods he is using in his 361 Charger car. The cam and lifters he is using in his RoadRunner. The 906 heads on the 1970 383 came with the motor. The car it will go into is a Polara Vert and it weighs in at 3800+. The manifold will be a dual plane Edlebrock with a Edlebrock or Carter carb (same thig) the rear end has a open 8 3/4 with 2:76 gears. This is a highway cruiser for the family, but I am looking for some real power without a lumpy cam. He I want everything. LOL Thanks guys for all your input.

[71383bee]

Ohh ok sorry about the confusion. A 1970 stock motor with 906 heads should not have valve clearance problems. I am currently running a Comp cams EX268H cam and a plain ED Perfromer intake and Holley 770. It is a bit over carb'd but the cam pulls good low end and decent power all around. I know I can get better with a RB cam, but I didn't know that back then. It is a great cruiser motor and it will put you in your seat. It also runs just fine on 87!

I would suggest a Thermo quad on a perfromer intake and an RB cam then for your vert. Looks stock, but runs much better.

[custom880]

Thanks Bee. Sounds like a good combo. The reason I mentioned the Carter Carb is because I have one. I also have an intake (factory) that would work for a T Quad but I never had any luck with those carbs. I have a double pumper Holley 650 but that carb doesnt thrill me either. I seem to have the best luck with Carters and Edlebrocks. Probably because I cant tune the other types!! LOL Racer Brown is a little pricey for this motor, but maybe. The vert wont be a ground pounder by any means but I do want it to pull hard. Thanks again for all the help.

[71383bee]

Demonsizzler can tune your TQ carb for a reasonable price and from those who have used him it is a bolt on and go.

When compared to other cam companies RB is worth the 20 bucks, but if you aren't going to use him then be sure to use someone who grinds true mopar cams that utilize the larger lifter diameter. ie Hughes, Ultradyne, and Comp Cams will if you specifically ask for it, but that costs extra and then the cost of that RB cam doesn't seem to high...etc

[Eats4dz64]

In stock form 500lift and 240dur @ .050 is the largest you can go with out doing a full clearance check (But should be done anyway). I ran the purple shaft 284-484 with 2.14 1.81 valves and a 1.6 rocker and stupid me didnt check clearance and bent all exhaust valves. I am still running the 484 with a 1.5 rocker, but with the weight of your car and the mainly street use you wanna keep the dur @ 50 around and below 230. That way you wont need a high stall converter. I totaly agree with looking for a more up to date manuf. Especialy with your application. By the way all the praise that Ive been hearing about this cam company, How do I contact them?

[custom880]

Contact Racer Brown...Good Luck. I have a phone number but I can only call during the day (I work nights) and you can only get a hold of them after 7 or something like that.

[cuda66273]

Jim answers the phone after 2PM EST. and is usually there until about 7PM