TheMysticWizard

iTrader: (1)

Okay... I am beginning to plan out building up a 383 to replace my 305 TPI, I will be porting my base and adding aftermarket Runners, maybe an aftermarket Throttle Body also.

Anyways, I think I understand the majority of the 383 correctly, but please correct me if I am wrong.

A 383 is a 350 Block taken .030 over, with a 400 Crank which has either had the mains ground down, or the block has had the main enlarged... correct?

I've seen 383 rotating assemblies with both 5.7" and 6" rods, so either can be used, with the correct pistons right? What would be the benefits of using 6" rods over 5.7" rods? I hear H-Beam rods are a better choice for 383's as they usually have enough clearence, although they are heavier.. which rods would be better, I Beam or H Beam... or would I want to find some LT1 rods?

Now for my main question... are 383 Pistons just plain .030 over 350 Pistons, or are they special?

I was thinking of finding a 350 block, and taking it .040 over, then getting pistons that were .040 over and continuing to build it like a 383... but I got confused about the pistons.

Thanks Guys!

five7kid

iTrader: (14)

The 400 crank mains have been ground down to 350 size.

The location of the wrist pin has to be correct for the stroke and length of rod. 6" rods reduce the side loading on the pistons, and there are other differences they make with regard to the piston motion.

You need special 383 pistons whether you use 5.7" or 6.0" rods. I beam will be fine for a street 383. .040" over pistons are available for 3.75" stroke.

Don't forget block oil pan rail clearancing, external balancing.

TheMysticWizard

iTrader: (1)

Ok that's what I was getting at for the crank...

I guess I beam rods are where I was going anyways.. 6" would be better for higher rpms or not?

So lemme get this correct about the pistons.. all 3.75" stroke pistons will work? or do they need to be designed specifically for a 383 engine?

xpndbl3

iTrader: (5)

3.75 stroke is an 383 piston.....


you mean 4.030 bore piston made for a 383 not 3.75 BORE piston

TheMysticWizard

iTrader: (1)

Just making sure I understood correctly.. oh and btw never said anything about 3.75 BORE, I said 3.75" stroke, just wanted to be sure 3.75" STROKE was the key to 383 pistons... if ya get what I mean.

Thanks guys!

ZZ28ZZ

If you go with I-beams, you may have to grind the heads on the rod bolts. All depends on the cam.
In my case, I had to replace the I-beams with H-beams to clear my cam (LPE 74211).

If you buy a pre-balanced stroker kit with I-beams, and you have to grind the rod bolts, it will need to be re-balanced.

383 pistons are special, no matter if 5.7" or 6" rods are used.

The performance difference between rod lengths is more thoeritical than practical, but yes, the 6" is better for higher RPMs.

Also, when I was still planning on running I-beams, I had to grind a little on the bottom lip of the cyl walls for clearance.

BTW: The generally accepted min clearance for rotating assy-to-block-to-cam is .050", but some report suscess with less.

TheMysticWizard

iTrader: (1)

That's disappointing, I was planning on either the LPE 74211 or the LPE 74216. Maybe I will look at other cams first, although I am beginning to think there are clearance problems with most cams?

cp87GTA

There are now 5.7 I beam rods with cap screws on the market. Should help with the clearence problems. If this engine is mostly a street then go with the 5.7 rods, as the wrist pin goes right through the oil ring for the 6". They do have some steel rings that go below the oil ring for support, but I still wouldn't use them for a street engine. Just my 02. There are some kits out there offering cast cranks and forged pistons and rods already balanced, for up to 600 lift cams. I'm running a 600 lift cam in my 383, had to cut .080 off of the rods to clear, and that is a small base circle cam.

TheMysticWizard

iTrader: (1)

Ok, It's starting to sound better again... 5.7" rods with cap screws... sounds nice... I'm not looking for a cam with that much lift, although it's close, the one cam i am looking at (LPE 74211) has 560 lift (with 1.6 rockers) on the exhaust side. If I don't go with that cam, It would still be something along the same lines. with Probably around 550 life on 1.6 rockers.

Think the majority of 383 rotating assemblies would clear that?

TheMysticWizard

iTrader: (1)

.

ZZ28ZZ

If the rotating assy uses stock style I-beams, probably not. Not without grinding on the rod/rod bolts.

If the rotating assy came with Eagle H-beams, then yes it should clear without grinding on the rods.

I don't have any experience with the cap-screw type I-beams, so I can't comment on that.

I was using 5.7" stock style I-beam rods when I ran into cam clearance problems. I switched to Eagle ESP 5.7" H-beams, (which use cap screws), and they cleared my LPE cam with room to spare. Dirttrackthunder.com was selling them cheaper than everyone else I found.

Something else to consider, if you go with pressed fit wrist pin type rods (like stock rods) then switch to Eagle H-beams, you will need a different type of piston. A floating pin type piston. Then you get to re-balance it all over again.
Learned that one the hard way..

I tried the cheapest stroker kit route (enginekits.com I.E. Powerhouse) first. Wound up only using the crank from that kit.
If I had it to do all over again, I would just buy an Eagle rotating assy with the H-beams.

cp87GTA

Get on ebay, type in 383 crank. There are kits on there for 800.00 with the cap screw sir rods, already balanced and clearenced for 600 lift cams. Come with balancer and flexplate too. Eagle rotating assys.

TheMysticWizard

iTrader: (1)

My thoughts exactly... although I thought about buying stuff seperately, as it might be a little cheaper, but balancing would probably drive it right back up.

zippy

the days of using a 400 crank are long gone, this isn' the 80's.

cp87GTA

I went that way too. when all was done, I had more in it than if I'd have bought it together. I wanted the coated sealed power pistons, probably not any coating left now, after a season at the track. But I watched my balancer do his work. Not that I don't trust um. When he told me he'd get piston/rod within a 1/4 gram I had to see it. He did an excellent job.

Mkos1980

iTrader: (8)

Do not get the new Eagle I beams with the cap-screws. I went through 2 sets and both were out of round. Eagle said their may be a recall on this. The rods are not torque properly when getting align. I ended up sending my rods back and getting H beams. My machine shop has also seen these eagle I beams poorly made.