383 cam suggestions

[patmckinneyracing]

Ok so I'll start off with what I'm working with here. Bare bones, #'s matching stock 71' Roadrunner with a HP 383, 4 speed, 8 3/4 3.23 sure grip posi, and air conditioning. The engine has 346 stock heads and I have a pair of 452 heads as well. Also have power steering and manual brakes. Good overall setup since I dont have to worry about a torque converter or vacuum for brakes.

I am going to try and bump up the compression a bit and hoping to get it up to 9 to 9.5 to 1. Is this possible with stock heads? I don't want to shave the heads too much cause I will be using the stock intake, but may consider a DP4B intake. I will be using a Carter AFB 750 cfm carb and HP manifolds. Still deciding on whether to keep my stock exhaust or put it on the side for safe keeping (Yes the stock exhaust from 71' only has surface rust, reusable).

So this is what I've heard so far. Easy to overcam so I'm not going for any rediculous lifts or durations. I've narrowed down my choices to a few so far and here they are:

1.) Mopar performance 280/280 .474/.474
2.) Comp cams XE262H (their recommendation)
3.) Lunati Voodoo 60302, possibly 60303
4.) Hughes Whiplash cam

I will be using the stock stamped roller rockers, but of course I will be upgrading the springs. So I need feedback on what would be my best option here. Naturally I want something that sounds great and is good for torque numbers. Yeah they kinda contradict each other. I'm a little flexible as far as gears as I might bump up to 3.55 gearing to give a little more giddy up.

So what do you guys think? All opinions appreciated!:gah:

 

[63RedFury]

Comp Cams are real nice cams....

 

[Meep-Meep]

71 383 pistons are down in the hole compared to the earlier versions so you may benefit from the 915 or 516 closed chamber heads, which will give you around a half point increase in compression (pistons must be below or at zero deck). You will need to have hard seats installed in the old iron heads and most likely general rework that can cost hundreds of dollars. 915's can be pricey but 516's are almost free. Or for a little more money you can just pop on a set of Eddys or 440 Source.

Using the 452's will be a cheap alternative if the seats haven't lost the hardness through over grinding, but your compression will be the same.

The absolute cheapest way out to improve performance and reliability on a low compression engine will be to use your unleaded 452's (assuming not a lot of work is needed) and install a cam that is specifically designed for 8.5:1 CR. I have run the Edelbrock and Crane cams in FE Fords and an Olds 455 and they are great. These cams are not very aggressive and may not have much lope but the car will run great. You should expect about 150 PSI of cranking compression. The DP4B will work well too but perhaps better with a 625 carb. Regular fuel should work just fine with this combo.

The .474 cam is good with headers and 9.5 - 10:1 CR. It will also want more gear and works very well with a single plane intake and a 700 CFM carb. Cams similar to this one have lots of mid range power but you will need to do more work to the engine to take full advantage of them. Needless to say you will need to run premium fuel.

 

[patmckinneyracing]

I know the 452 heads are off an RV 440 and only have approximately 30k miles on them. So they have very few miles on them compared to my 346's. The whiplash cam is supposed to work real well with 8:1 to 8.75:1 compression motors. I'll probably be able to go with pop up pistons to work with the 452 heads. Unless I find a set of closed chamber heads somewhere

 

[Meep-Meep]

Pop up pistons aren't necessary for getting the compression you need. You can just use the 68-69 flat top pistons (higher compression distance) or the KB quench dome pistons with the open chamber heads to easily get up to 9.5:1. I like the closed chamber heads because of the quench but you can duplicate the effect with the KB's and 452's. The only reason I suggested the closed chamber heads is to get more CR without dealing with the short block, but since you're going there might as well get it spot on.

I would rather see a quench dome piston with the 452's for your combo while keeping the compression around 9.0:1. Keep in mind that balancing most likely will be required if you go with the KB's. I don't think they are the same weight as the OEM pistons.

 

[patmckinneyracing]

I still need to pop the heads off to check and see if there is a considerable ridge at the top of the chamber or not. Need to check for forged or cast internals as well since mine was built so late in 71' I'm worried they just chucked a cast crank in my HP 383. I also have a winnebago 440 but I think it came out of a 77 or 78' so I doubt it has the six pack rods.

The KB pistons your mentioning, are those the KB400's? I think some guy over on moparts mentioned them before.

 

[Meep-Meep]

For what you are doing (assuming you are making a good street driver) I wouldn't worry about a cast crank. If you have a good steel crank lying around with nothing to do then pop it in but otherwise don't kill yourself to find one.

I'm not sure what the KB numbers are but the piston top will have a small dome that fills in the shallow part of the chamber. It's recommended you check this area for head clearance and relieve as required. I have zero deck (really -.005") forged flats in my 68 383 but I built that long before I heard about KB quench dome pistons. I also have the 915 heads. It ran great on pump 92 circa 1988-ish but haven't run it with the current gas.

I'm currently putting together a 77 440 for my 66 Bel with KB flats and 915 heads, and it didn't have the six pack rods. I think those were found on 72-ish year engines - perhaps trying to use up old inventory? I CC'd my 440 setup and it's exactly 10:1 CR with steel shim gaskets.

One thing I noticed about my 77 block is the huge bore chamfer. I read this was done to relieve the annular space above the top ring for emissions reasons. It was found at some point that the space trapped a sufficient amount of fuel vapor that didn't get burned thus producing extra hydrocarbons. The hypereutectic pistons (same alloy as the KB) are really an emissions era piston design that allows for very tight clearances, especially the area above the top ring. Less volume in that area leaves fewer gases to get trapped.

 

[daredevil]

saw a dp4b on houston craigslist today for 50.Since you said you were considering it I figured i,d throw it out there.