Need a little help picking cam for my 383 combo

[tattooedblue]

Ok, Right now I have a 74 RoadRunner, it is a 4 speed car, and has an 8-3/4 rear with 3.91s..

Current combo is a 383, crappy pistons way down in the hole (they are old TRWs I believe that were new in the early 90s) it is fuel injected, Edelbrock RPM intake, XE268 cam, MSD6AL, 440 Source Stealth Heads, and of course headers and dual exhaust..

The old combo was the same other than steel close chamber heads, and a Mopar 509 cam.. and it ran OK once the RPMs came up, but it was a dog down low.. The new combo is not much better, I think because I killed my compression with the new heads..

SO... I am now looking at a set of KB400 pistons to bring compression up, keeping the Edelbrock RPM intake, and out of the box 440 Source Stealth Heads. What would you suggest for a cam? This is a street car only so I am more concerned about torque than high RPM HP.

 

[lewtot184]

don't over cam!!!!!!! 383's can't handle the duration. i've said this in many replys here and i'm sure it falls on deaf ears; a small to moderate mechanical can is best. they are far more flexiable. you might want to contact the folks you got the injection from and ask if there are cam limitations with what you have. when i was hot rodding 383's the more cam i went to the slower the car went. 383's don't make torque. a lot of cam grinders will tell you to treat them like small blocks when it comes to cam selection.

 

[robinsonwr]

My preference for a street car now days would be a hydraulic roller. Concidering that oils today do have what it takes to keep a flat tappet running. I would recomend an XR280HR, grind # 23-711-9 from Comp Cams. The XR280HR has 230/236 @ .050 with 541/537 lift with 1.5 rocker ratio. The powerband on the camshaft is 2200-6000 rpm. It will work well with the performer rpm intake and the stealth heads. The initial investment is pricier than a flat tappet but I fel a more reliable peice.
I am using Stealth heads on my 440/512 build with a custom Comp hydraulic roller that specs 230/236 @ .050, advertised duration 281/286 and 622/625 lift with 1.6 rockers. I wanted a camshaft that used the available flow of the heads @ 600 lift. The duration is very mild and should make good vacuum for power accessories and have great throttle response for in town driving. My car is going to be a dedicated street car with the occassional blast at the track.

 

[robinsonwr]

Crane Cams have hydraulic roller cams ground on 114 lobe seperation which fuel injection engines like. I also saw you lost compression using the stealth heads. Aluminum headed pump gas motors like around 10.5:1 compression. My pump gas 440/512 will have right around 11:1 compression. Low compression aluminum headed motors leave alot of power on the table.

 

[tattooedblue]

don't over cam!!!!!!! 383's can't handle the duration. i've said this in many replys here and i'm sure it falls on deaf ears; a small to moderate mechanical can is best. they are far more flexiable. you might want to contact the folks you got the injection from and ask if there are cam limitations with what you have. when i was hot rodding 383's the more cam i went to the slower the car went. 383's don't make torque. a lot of cam grinders will tell you to treat them like small blocks when it comes to cam selection.

Ya, I have made that mistake in the past, that's why I am asking for advice with this one, it's already been apart twice, I don't want to do it again after this time, lol

 

[lewtot184]

call some cam grinders and get some good advice. these internet websites are the wrong place to get a good cam recommendation.

 

[robinsonwr]

Ya, I have made that mistake in the past, that's why I am asking for advice with this one, it's already been apart twice, I don't want to do it again after this time, lol

It is a great idea to contact an expert. Have a good idea of what you want the engine to do before calling. Like the power band you want 1500-5500rpm, compression ratio, daily driving, or good all around performance. I suggest calling this guy:
*William Hood*
Technical Sales & Support
COMP Performance GroupT
3406 Democrat Rd.
Memphis, TN 38118
Toll Free: (800)999-0853
Direct (901)795-2400 ext 724

 

[Sublime440]

The Stealth heads should be a closed chamber design, so I wouldn't worry about the KB400's just to get the compression up. You should be able to go with Speed Pro 2315's if I remember the part number correctly. Cutting ~.010" off the block should give you pretty good quench and ~9.5-9.7:1 CR with .039" head gaskets. The thing I don't like about the KB400's is the dome impedes the flame travel.

I'll second the "don't over cam it" comment. With a 383, compression is going to be difficult to get over 10:1 anyway, so I'd stick with something not much bigger than the stock HP cam, which is pretty much what the XE268 is. I'm actually running that cam with a 727/3.23's and it pulls good for a basically stock, almost, engine.

 

[tattooedblue]

The Stealth heads should be a closed chamber design, so I wouldn't worry about the KB400's just to get the compression up. You should be able to go with Speed Pro 2315's if I remember the part number correctly. Cutting ~.010" off the block should give you pretty good quench and ~9.5-9.7:1 CR with .039" head gaskets. The thing I don't like about the KB400's is the dome impedes the flame travel.

I'll second the "don't over cam it" comment. With a 383, compression is going to be difficult to get over 10:1 anyway, so I'd stick with something not much bigger than the stock HP cam, which is pretty much what the XE268 is. I'm actually running that cam with a 727/3.23's and it pulls good for a basically stock, almost, engine.

I usually run Speed Pro's in my small block Chevys, but in this car the Stealth Heads are listed as 80CC chambers, and the Speed Pro's are showing 8.94 with an 88cc and 9.77 with a 78.5cc. KB shows 11.6 with a 72cc, 10.6 with an 80cc, and 10 with an 85cc.

I would like to get close to 10.5 which is why I thought about the KB400s

Wonder which would be better, an extra point of compression, or better flame travel.. :thinker:

 

[Sublime440]

It seems like I've read the KB figure you're talking about and they didn't make any sense. I think I calculated it when I did mine and with the KB400, shaving the block for ~ zero deck, .030 over and .039" head gaskets with the Stealth heads was barely 10:1. The small bore and short stroke make it hard to build compression out of a 383. The 2315's are a flat top and no valve reliefs, you wouldn't want to use them in an open chamber style head (88cc) anyway because you wouldn't have any quench. The problem with 383's is aftermarket piston selection sucks.

 

[tattooedblue]

It seems like I've read the KB figure you're talking about and they didn't make any sense. I think I calculated it when I did mine and with the KB400, shaving the block for ~ zero deck, .030 over and .039" head gaskets with the Stealth heads was barely 10:1. The small bore and short stroke make it hard to build compression out of a 383. The 2315's are a flat top and no valve reliefs, you wouldn't want to use them in an open chamber style head (88cc) anyway because you wouldn't have any quench. The problem with 383's is aftermarket piston selection sucks.

I am realizing that now, lol.. That KB figure was taken from KBs catalog