Need help with a 383 Build

[1969 beep beep]

Hi,

I just tore apart my original 383 from my 69 RR. The motor had 8.9:1 compression. With manifolds and cast intake it made 280 hp. It had 906 heads with flat top pistons 30 over.

I called Mopar performance, and they could not tell me what purple cam from the cam numbers. I would like to build something with a bit more power. Nothing crazy. I have a set of 915 heads and the flat top piston is 14th in the hole. The deck needs to be cut because it isn’t square. I would like to use the Edelbrock DP4b intake. The 915 heads and intake are slightly ported.

The 915 heads with new valves are around 83.5 cc.

I need some help with this build. I would like to use my stock manifolds with my Holley sniper setup. I am thinking around 9.5-9.6:1 compression. Any help would be great.

 

[Jerry Hall]

Are they the big valve 915 heads? Does the block need bored and pistons replaced? Sorry to answer a question with questions. Decking the block and possible piston to valve clearance needs to be checked. A 383 is a great engine for upgrades and you are heading in a direction that I like.

 

[1969 beep beep]

Yes they are the big valves. I have a set of Ferrea 2080x3/8x4875 and 1740x3/8x4910 I would like to use. The block doesn’t need to be bored. I am using the piston that where in it. They only have 5000 miles on them. L2315F 030 pistons.

 

[Jerry Hall]

14 thousandths in the hole on a 8.8 compression motor and changing to 915 closed chamber heads typically increases compression by a point. So we are saying 9.8 depending on how much decking is required. No valve reliefs in the pistons could pose a problem depending on valve lift. I have no idea on the cam by the numbers either, but I'm sure it can be measured if the specifications can't be found.

 

[Don Frelier]

So is the cam the question?
You can measure the lift and that would help give some idea. If you put it in the motor then you can get a whole profile.
Dial indicator and degree wheel.

 

[1969 beep beep]

Sorry I made a mistake. The compression was 8.9:1 and I used 14th as an average. The block is definitely not square. The front on one side is 11th and the back is 19th. The other front side is 15th a back is 13th.

I was curious to know what cam was in it. The engine builder measured the lift and said it was 305 on intake and exhaust. He mentioned to multiply that by 1.5. Which works out to 457.5.

I was thinking off reusing the same cam but not sure if it’s even worth it.

 

[Don Frelier]

Good chance it's a .455 272 cam. I would use it.

 

[1969 beep beep]

He is going to calculate the duration and let me know. Is that normal for the CC’s on the 915s to be at 83.5 with new valves. I guess they sit a lot higher then the stock valves.

 

[1969 beep beep]

What’s the stock 69 383 hp cam specs? If I remember correctly the original person that changed the cam many years ago said it was one up from the factory specs.

 

[mopar 3 B]

383 Roadrunner engine used the 440 hp cam. I have used all the way up to the street hemi grind with good luck. You will either need some in hole depth or thick head gaskets if using 915 heads. Nothing quite like slapping the heads with pistons of zero deck height.
If you really think you need zero deck pistons 452 heads would be a better choice.

 

[sabre67]

watching

 

[blue69runner]

Use the 906 head's and put half dome piston in the motor to give it more compression. Let the piston move into the head chamber for more. Valve relief's. Went to summit and call comp cam company and they set me up with the cam-valve spring's and lifter's. Close to the purple cam. Those guy's are spot on. The Kit is cheaper than buying all the parts by them selves.

 

[fratzog lover]

Good chance it's a .455 272 cam. I would use it.

The .455 cam is an excellent choice. Jack of all trades master of none? This cam comes close. Good MPG's, Nice sounding idle, good off the line, stock converter works, etc. The duration is 221 @ .050 not 231 like some older sites have listed. With the 2315 pistons and headers, you have a very nice street combo. Unlike some 383 cars with too much duration that sound mean, and get pasted by some high school girls Kia.

 

[Don Frelier]

Mine has always run well with the .455 here it still had the Carb on it.

 

[Nate S]

Does 14th = .014" in the hole for the pistons?
If so, with 83.5 cc heads and .030 overbore you'll be at 9.68:1 with steel shim gaskets and 9.28:1 with .040 fel pro. With that cam I'd go with the thicker gasket. Heads won't hit pistons, there's a gasket in between.

If you're above deck .014 you're at 9.93:1 with the thick gaskets.

Seems like a nice combo

 

[Don Frelier]

Just because the piston depth varies it doesn't mean the block isn't square.
You've got additive tolerances/variance with crank, rod and piston in each cylinder.

 

[blue69runner]

The .455 cam is an excellent choice. Jack of all trades master of none? This cam comes close. Good MPG's, Nice sounding idle, good off the line, stock converter works, etc. The duration is 221 @ .050 not 231 like some older sites have listed. With the 2315 pistons and headers, you have a very nice street combo. Unlike some 383 cars with too much duration that sound mean, and get pasted by some high school girls Kia.

We might be a master and a worker of trades but we do our darn best. Like the comment. I resemble that remark.

 

[fratzog lover]

I was referring to the .455 cam doing everything really well!
Seriously, if you have that cam, it's a winner. Overlooked often, but a good choice for a street 383 in my humble opinion.

 

[1969 beep beep]

I finally determined the purple cam is P4286676. (Adv 272 Intake/Exh, .455 lift, 112 lobe)

I need some help with making this combo work. I wanted to use my 915 mild ported heads 81.5cc, with Edelbrock DP dual plane intake, stock manifolds, L2315F 030 pistons, Felpro .039th head gasket, with the above cam. 4 speed with 3:91 gears

Should I get the compression to 9.5:1?

 

[Don Frelier]

I think around 9.0:1 would be good. Mine is 9.4:1 and after a couple years it started pinging on 89 octane.
But my quench height was not ideal either.
Higher octane was fine. That cam is excellent and so is a DP4B intake but they recommend a single plane with EFI.