Need help with a 383 Build

[67charger383]

A single plane intake like a Holley Street Dominator and long tube headers would really wake up that combo.
As for compression, if you are fine buying 91/93 pump gas than I'd go for 9.5-1 or even 10-1. Detonation shouldn't be a problem for you with that small of a cam and under 12-1 compression.

Is your 383 still standard bore? I have a used set of '67 factory flat top pistons and rods that make 10-1 compression with closed chamber heads (915's or 516's) that I'd give you a great price on.

 

[blue69runner]

Look into a half dome piston that will give you more compression. That is what we put into my 383. It sound's grate on idle. Has that choppy sound.

 

[Outsider]

Just out of curiosity what were the CCs of the 906 heads you had on? Back in your post #8 you asked about "normal CC's" for a 915 head. I just CC'd a set of what I believe were originals and I got 78 CCs.

So this made 280hp on a chassis dyno? That sounds about right for a stock build with cast manifolds. I would think those almost new pistons have would be good enough for some mods and performance improvement. As for decking, I don't think that's something your are going to get much bang for the buck in terms of performance at this level.

That cam or one of the newer grinds like from Lunati can work with ex mans, but of course headers would be best and let you run a bigger cam. Biggest seat of the pants feel, put in the 3.91 gears.

 

[1969 beep beep]

Good point on the single plane vs dual plane with EFI. I will look into that.

67charger383 thanks for the offer but the block is 30 over.

My 906 heads are 88ccs. The 915s when I originally measured them they where 78 CC’s. The heads need new valves and now according to the engine builder they are at 81.5cc’s. Has to due with bottom valve design between the original valves and the Ferrea valves.

 

[Don Frelier]

Detonation shouldn't be a problem for you with that small of a cam

A smaller cam (less overlap particularly) will have a higher tendancy to predetonate than a large cam.

 

[1969 beep beep]

Update on my original post.

Bore-4.280
Rod-3.375
Piston-L2315F

The short is together with a flat top piston and it’s .008th in the hole.

Cam is an MP 272 adv & .455 lift & 112 lobe

915 Heads are slightly ported they flow 233 @ 500.

Db4p slightly ported single plane intake

Going to run stock manifolds.

915 Heads are at 83cc after valve job and new valves.

I was planning on using Felpro .039 head gasket 4.50 bore

What is a good compression range for this combo? Not sure if I should leave the heads at 83 or cut them.

Street car, 4 spd 3:91 gear

Thanks

 

[BSB67]

Update on my original post.

Bore-4.280
Rod-3.375
Piston-L2315F

The short is together with a flat top piston and it’s .008th in the hole.

Cam is an MP 272 adv & .455 lift & 112 lobe

915 Heads are slightly ported they flow 233 @ 500.

Db4p slightly ported single plane intake

Going to run stock manifolds.

915 Heads are at 83cc after valve job and new valves.

I was planning on using Felpro .039 head gasket 4.50 bore

What is a good compression range for this combo? Not sure if I should leave the heads at 83 or cut them.

Street car, 4 spd 3:91 gear

Thanks

Everything sounds good. Still hard to believe that the heads are 83ccs. Everytime I put new valves in a set of 915s they end up about 78cc.

With the 4 spd, you could go with a little more cam. My 383/4 spd/3.91 really likes the MP 280 cam.

 

[1969 beep beep]

I am going to double check the cc’s on the heads tomorrow. Should I keep the compression under 9.5:1?

 

[Nate S]

I am going to double check the cc’s on the heads tomorrow. Should I keep the compression under 9.5:1?

I would, or close. I find that my factory magnum cam 413 with 9.25:1 verrry rarely lets out a click with 93 octane but will notably ping on warm days with 89. That’s with proper 37-38 all-in mech timing and something more than that putting around with the vac advance going. If you go for more compression but back off the timing you’ve just lost more than you gained.

 

[Diodedog]

I would, or close. I find that my factory magnum cam 413 with 9.25:1 verrry rarely lets out a click with 93 octane but will notably ping on warm days with 89. That’s with proper 37-38 all-in mech timing and something more than that putting around with the vac advance going. If you go for more compression but back off the timing you’ve just lost more than you gained.

Way too much timing, should be 33-35 max

 

[Nate S]

Way too much timing, should be 33-35 max

The dyno and every iron head report I’ve ever seen from Direct Connection to Hot Rod dyno runs says 36-38. Where’s your info from?

 

[BSB67]

Did a lot of track testing with my iron headed 440. It ran best with 39 degrees total. There were track regulars that were running 40 plus. 36-38 was the typical starting point.

 

[Diodedog]

The dyno and every iron head report I’ve ever seen from Direct Connection to Hot Rod dyno runs says 36-38. Where’s your info from?

50 years at the Dragstrip and hundreds of engines built in my machine shop and everything from bracket race engines to my Max low comp NHRA stocker. There are situations where more timing would be best but not this one.

 

[Nate S]

50 years at the Dragstrip and hundreds of engines built in my machine shop and everything from bracket race engines to my Max low comp NHRA stocker. There are situations where more timing would be best but not this one.

Interesting but certainly out of sync with everything I’ve ever seen and tested myself. Clearly it’s working for you but you’re on an island by yourself. Just for the heck of it I did a search for 440 timing, the vast majority of iron head people are at 36-38 with the aluminum head folks around 32. The only <35 instances I saw were due to knock (iron heads). Dunno, it’s working for you but as a recommendation for the average build I guess I’ll stick with the crowd at 36-38 and leave your 32-35 for the “experiment here as you wish” part.

 

[mopar 3 B]

Interesting but certainly out of sync with everything I’ve ever seen and tested myself. Clearly it’s working for you but you’re on an island by yourself. Just for the heck of it I did a search for 440 timing, the vast majority of iron head people are at 36-38 with the aluminum head folks around 32. The only <35 instances I saw were due to knock (iron heads). Dunno, it’s working for you but as a recommendation for the average build I guess I’ll stick with the crowd at 36-38 and leave your 32-35 for the “experiment here as you wish” part.

Ok so believing what you read takes precedence over experience. I would take both into account as the only way your really going to know is by experimentation after it's together. Just to many variables to say one or the other is correct