Compression ratio

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71DartGuy

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Can some of you gurus tell me what my compression would be with these numbers? I've tried a bunch of different calculators online and am getting answers all over the place. I've also put the cam specs here too for some opinions. Thanks!!

383:
Bore- 4.31"
Stroke- 3.38"
Head cc- 88cc
Head gasket dia.- 4.40"
Compressed thickness- .020"
Pistons- .030" in the hole (Hughes #2050 I think)
Effective dome volume of pistons- -5.0 cc

Cam:
Crane 693802
Adv Duration- Intake 278, Exh 290
Lift at valve- Intake .467, Exh .494
Duration at .050- Intake 224, Exh 234
114 degree lobe separation
Seems to be a decent street cam but would just like a few opinions on how to build the rest of the engine around it as far as convertor and induction.

Let me know if there is anything else you need
 
A 383 has a 4.25 bore. At 4.31, the engine size is 394.

9.25 - 1 is the ratio.

What are the valve sizes in what head with anywork?

Headers? Intake? Carb size? Oh and anything else off the cam card?

I fudged what I could in the Desk Top Dyno and it came up with over 400 HP @ 5500 and approx. 446 lbs. of torque @ 4000.
 
Yeah, it appears to have been bored .060. I believe the heads are stock, rebuilt, maybe some aftermarket springs but havent looked at them too close yet. They are 452 castings. I would like to go with an M1 intake, not sure of single of dual plane yet. It will get TTI's or Schumaker headers. As far as the cam I dont have the card. I pulled the cam and got the part number off the back and the specs I gave are right off of Summits website.

Thanks Rob!
 
I would suggest a RPM intake for this since the cam is mild and a 750 cfm carb. Ethier header will do, your choice, though I like the tti's a little bit more than the others, but what ever works.

I don't remember what size valves came with a 452 head, I jotted down 2.08 and 1.73 for the program run. The valve sizes being off but in the general ball park of stock will not reflect a big change on the results....which should be taken with a grain of salt since it is a simple dyno program.
 
I was thinking this thing shouldnt have a hard time making 400 horse and 425 foot pounds. Definitely not opposed to the RPM intake either. I want to say that the 452's had 2.14 intakes but not positive...
 
8.684733558225307:1


I thought you was going to stroke it?

You mean 3.31 on the stroke don't you?
 
Correction! I pulled the pistons this morning to make sure everything was clean and it turns out I have KB 162's in there. I think that should help a little.
 
Essentially you've got a 9 to 1 compression 383 and that is low. If you've still got the block stripped I'd get her shaved and shoot for 10 to 1 to 10.25 to 1. Can't be sure with KB pistons but aren't they +5 cc (2 large valve pockets machined in to the top) but at the very least you shoud be zero deck to .010" proud. Yes go with the Performer RPM as it's the best all round out there and beats the crap out of a few single planes. Your 452's (2.08in x 1.74ex) tho they are a good flowing head in stock trim should be pocket ported and the bowls worked on or they will be the cork with TTI headers and the RPM manifold. Also at the very least your 452's need dampener springs inside the main valve spring for any moderate lift cam like the one you're going to run.

Terry
 
Thanks Terry. I guess with a zero deck would you use a .040 gasket to get a tighter quench so you could still run on pump gas? Oh yeah the KB's are +5cc.
 
71DartGuy said:
Thanks Terry. I guess with a zero deck would you use a .040 gasket to get a tighter quench so you could still run on pump gas? Oh yeah the KB's are +5cc.
Click to expand...

You're going to have to do a ton of actual measureing cuss you can't assume someone in the past hasn't messed with the sealing faces of the heads. They essentially need to be cc'd on one combustion chamber on each head. If you haven't physically measured the deck height of the piston rod comb (without rings) in the block bolted to the crank you need to do that to ensure someone hasn't messed with the block. Talk to Hughes and see what they recommend. I'm running 10 to 1 flat tops on my 383, 0 deck, ported iron heads and run 92 octane with no problems and timing is 12 and 38. I'm probably right on the edge tho. Oh yea, she'll make 400HP easy maybe closer to 450 with some head work and unless you're on going for the jugular with a wilder cam don't let anybody talk ya out of the cast heads into aluminum ones, at least that my opinion for what it's worth.


Terry

6 (Small).JPG
 
I went ahead and cc'd one of the chambers on one head and came out to 87.5 cc with my measurements so I'll call em 88's. I saw that KB says these pistons should be sitting .027 in the hole but I measured .030. Can you enlighten me as to why you would measure without the rings? I havent heard that one before.
 
71DartGuy said:
I went ahead and cc'd one of the chambers on one head and came out to 87.5 cc with my measurements so I'll call em 88's. I saw that KB says these pistons should be sitting .027 in the hole but I measured .030. Can you enlighten me as to why you would measure without the rings? I havent heard that one before.
Click to expand...

Cuss you're only going to take the deck measurement then remove the piston rod assembly for complete installation later with all the rest.
 
mullinax95 said:
8.684733558225307:1


I thought you was going to stroke it?

You mean 3.31 on the stroke don't you?
Click to expand...

The compression ratio based on the numbers given is 8.68:1. Any other number is not taking into account the head gasket bore/thickness, piston effective dish or piston position below deck. If the stroke is 3.31 then the compression is 8.52:1.
 
You're right Ax, i was going to do a stroker but came across a 383 at a decent price so I'm going that route instead. Big Block here I come!!!
 
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