383 piston choice

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slyhog2007

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i was wondering what pistons would help my comp ratio out the most im using 906 heads and looking at a MP cam with .484/.484 lift. want about 10:1 if not just a lil more.
 
i went with a KB 400 piston - its a dome but got me to 9.4:1

It was a 383 mag, that was supposed to have 10:1 - it actually had 8.6:1 after I measured it
 
no sadly i got myself a 2bbl 383 to start with, it was a bargin at 280 bucks complete carb to pan with everything on front too
 
cool...

I had the option for speedpro pistons but they had no valve relief in them and I didnt like that option. so the KB 400's were the next one, and still alot cheaper then custom
 
yeah i figure i could poss got 400-450 if not more of it with the right combo, i tor it down today and plastigauaged one rod and main and found the rod at 0.002 and the main at 0.003.
 
but im also stuck between using the edelbrock rpm or the wiand action plus intake...
 
I just put one together with a stock style, (no valve relief) piston set. At .020" in the hole, and using a .039 gasket, I still would not have room for that .484" cam you wish to run. The 75 CC heads I have did keep my compression up to just under 10:1. If you are looking at trying for 400+ HP, I would choose the RPM intake over the Weiand. Good luck.
 
well shoot, i dont wanna spend money on sumthing that wont work....
 
DJVCUDA's idea sounds like your best solution if you want to run the .484 or bigger cam. I put in a .465"/.488" cam, (Summit $89 one), and had about .080" clearance on the intake once it was degreed. .080" was about as tight as I felt comfortable with. If I had pistons with notches, I would have gone with a larger cam.
 
ok so with the relifes in the domes i can get away with .484? i like the idea of the dome because of my 906 heads
 
I took a peek at them, and they appear to have some healthy valve reliefs in them. I don't see a problem with clearance using your .484" cam. As DJVCUDA mentioned, even with the domes, they still don't produce a high compression ratio, 9.4:1 in his case, which isn't a bad ratio for pump gas at all, in my opinion.
 
yeah 9.4 isnt bad but i figure imma have to get my heads surfaced so that will raise it but not anything noticable. if i had closed camber head im sure those pistons would probably get me in trouble at the pump. im only looking for a fun car to drive on the weekend, and blast down the track in local bracket compitition. but would also love 400+
 
Why not just get a custom made 13.5:1? If you want over 10.1 with iron heads you're not gonna be runnin pump gas, so you may as well build a race gas motor.
 
slyhog2007 said:
because race motors arent fun on the street
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You missed my point. I was saying that over 10.1 you will have to have race gas at least mixed with iron heads. Unless you plan to run a camshaft with over 100 degrees of overlap, to bleed off ALOT of cylinder pressure.....which would defeat the purpose. At that compression level, you may as well run 13.5:1 because race gas will have to be involved. Get me now?
 
Nope. No way no how. Not without a camshaft that's way too large for the engine. a true blueprinted 9.5:1 with a matching camshaft even requires premium fuel and still may detonate in really hot weather. An honest to goodness 10.1 engine is a high compression engine. With alloy heads, no problem on premium fuel....even perhaps to 11.1, but no way with iron heads. It's misinformation to think that. If someone says they have done it, either one of three things is true. Either they are running a camshaft with gobs of duration to bleed off cylinder pressure, or they did not blueprint their engine. Or both. It would take a camshaft of about 250 degrees [email protected]" and 108 lobe centers or less to bleed off enough cylinder pressure to run 10.1 on pump gas and that's way too much camshaft for that compression level. Sure, it can be done, but you will NEVER, EVER achieve the power level that you could at a lower static compression with a properly matched camshaft. I'd rather have a good blueprinted 8.5:1 engine with a mild cam any day on the street in comparison. I'd smoke that overcammed 10.1's butt, too. Done it many times.
 
If the motor is setup with quench it can be done , I did it with a 440 with KB quench dome pistons and off the shelf Comp cam , 10.3 compression runs fine on 93 octane. this build was a copy of a build another guy did , I did this for a friend , the other build is only 9.3 , not good quench and more head Cc and it will not run on anything less than 93 , something is not right with that build in my opinion.

He's not going to do it with 906's without a custom piston and a lot of machine work .

The KB400 is probably the piston to use , will get you over 9.0 compression and give you a huge valve relief to clear a bigger cam, also there are much better cam choices now than the MP .484 cam.

The only stock rod aftermarket for the 383 is the eagle rod , BUT i am not sure is the
KB piston is setup for pin locks which you will need because the eagle is a floating pin rod .

Diamond sells a piston that has valve reliefs but it's a 1.916 CH , a little short and it's not cheap but for a little more you can get the pin height moved so less machining will need to be done in the big picture .
 
StrokerScamp said:
Nope. No way no how. Not without a camshaft that's way too large for the engine. a true blueprinted 9.5:1 with a matching camshaft even requires premium fuel and still may detonate in really hot weather. An honest to goodness 10.1 engine is a high compression engine. With alloy heads, no problem on premium fuel....even perhaps to 11.1, but no way with iron heads. It's misinformation to think that. If someone says they have done it, either one of three things is true. Either they are running a camshaft with gobs of duration to bleed off cylinder pressure, or they did not blueprint their engine. Or both. It would take a camshaft of about 250 degrees [email protected]" and 108 lobe centers or less to bleed off enough cylinder pressure to run 10.1 on pump gas and that's way too much camshaft for that compression level. Sure, it can be done, but you will NEVER, EVER achieve the power level that you could at a lower static compression with a properly matched camshaft. I'd rather have a good blueprinted 8.5:1 engine with a mild cam any day on the street in comparison. I'd smoke that overcammed 10.1's butt, too. Done it many times.
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gee that's odd. the motor in my truck has a towing cam and 9.9-1 compression and runs fine only on 93 pump gas. it has a tad over 11,000 miles on it now. may be this cam is the answer, you tell me.
 
Static compression has little or nothing to do with running pump fuel. I've done it with up to 185psi. that engine was a 383 with stock replacement pistons and the stock RR cam. What you will fail to find is many "10:1" pitsons or engines that actually exist. Because the blocks are so tall naturally none of the pistons' advertised ratios are close to reality like JohnRR has said. In any event, running the 284/.484 there wont be any cylinder pressure to worry about...lol.
 
yes you are correct about the pistons but i purchased 12-1 pistons so i would end up with as close to 10-1 as i could. after cc'ing i was pleased to find out i had 9.9-1. she just didn't get along very well with regular fuel at all but pulls and runs great on high test.
 
Ha Ha Ha, i'm running 11.2cr at 205psi cyl pressure on 93. the only way to go!! tons of torque, idles right at the hit of the key, and a nice POP out of the tips!!
 
EL5DEMON340 said:
Ha Ha Ha, i'm running 11.2cr at 205psi cyl pressure on 93. the only way to go!! tons of torque, idles right at the hit of the key, and a nice POP out of the tips!!
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You must be running alum heads , I don't think you could do that with iron heads .
 
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