ScottyRS

iTrader: (2)

Okay I finally got my block back from the machine shop and I'm starting to piece together a rotating assembly. I already have SRP forged aluminum flat-top pistons. And that's it.

What I'm looking for now are some connecting rods and a crank. I intend to push 500hp out of this thing so I need quality parts. And I've read mixed reviews about Eagle and Scat.

So I need some good 5.7" rods and a 383 crank. (And I'm on a budget).

Thanks in advance.

izcain

Sounds to me like if your going to be pushing that much power out of that engine your going to have to take most of the parts BACK to the machine shop for balancing and such.

I have had good luck with most of SCAT's products they have always seemed to be good quality.
SCAT sells a pretty nice quality crank for the 383 for a affordable price for the budget build and these have proven to take 500 hp.

zrated57

I would buy Eagle over Scat any day of the week. When I hear someone say they are buying a SCAT part, I picture someone buying a Dual CD player instead of buying a quality part.

Anyway... I would get some Eagle "ESP" forged 5.7 rods and an Eagle forged 3.75 stroker crankshaft, which would make a bulletproof bottom end. You can easily pound out 500 or 600 horsepower without the worry of bottom-end failure. I would agree that SCAT products are cheaper, but I have only heard bad things or mixed reviews about them. Don't take my word for it though, wait for some more replys on that subject. Sounds like your pistons are good to go. That's my two cents.

What are you plans for heads and camshaft, because that's my next purchase as well.

-Erik

shaggy56

Funny thing is both companies get their parts from China even though Scat still has their parts machined in USA.

jbenge

iTrader: (2)

The American made parts are higher quality but its hard to beat the price of the Scat and Eagle stuff. If you use Scat or Eagle just be sure to have the machine shop check your parts to make sure they are machined correctly. My Eagle crank was ground wrong from the factory. The surface where the bearing rides was slightly convex causing premature bearing failure, it didn't happen suddenly but would wear out bearings sooner than it should. I went through 2 rebuilds before I figured it out. I've heard of this same thing happening to a few others too with both Scat and Eagle so it does happen occasionally. I wouldn't hesitate using Scat or Eagle stuff (its great for the money)but have the maching shop check it out carefully before installing it.

ScottyRS

iTrader: (2)

I'm planning on using the GMPP aluminum fastburn heads with a Vortec intake. And I haven't even gotten around to looking for camshafts yet. But I may have found a project car to drop the engine into and it's a T-top. So I'm toning the power down to 450hp.

And I was looking at the GMPP 3.8" crank (which would make a 388, but close enough) and the catalog says that the crank can only be used with a "1986-and-later one-piece crank seal design flywheel or flexplate". If I'm not mistaken, my '73 block is machined for a two-piece seal. I'd like to get as much GM Performance Parts on here as possible because, frankly, I trust the General. But I'm not sure if that crank will work or not. Can anyone chime in on that? Thanks a lot for the input so far, it's greatly appreciated.

Sonix

iTrader: (1)

that's a 1 piece RMS crank, won't work for you.

2nd, which pistons do you have? are they 383 pistons? When I hear "flat top" and "383" I get leery, that should skyrocket your CR into race gas territory. What's your CR that you're shooting for?

Try Ohio crankshaft. Some H beams (all rods are forged), and a cast steel crank, balanced locally to your pistons and rings and, should work out just peachy. Internally balanced then?

Apeiron

The price you'll pay for most GMPP parts isn't worth it. Stick with the aftermarket stuff.

Air_Adam

He hasn't bought heads yet, so it could work just fine with heads with the right chamber size.

I'd suggest a set of AFR 210cc heads, competition ported, with the larger chambers (can't remember if its 72cc or 76cc though, you'll have to look). It would be right around 11:1 with a .040" gasket.

The GMPP Fastburn heads have chambers that are way too small for a 383 with flat tops.. 62cc chambers IIRC.

ScottyRS

iTrader: (2)

Yeah they're 62cc but GMPP recommends using flat top pistons with them. And they are SRP Pistons: SRP-138089 - summitracing.com.

And those Ohio cranks look decently priced, anyone have any experience with them? I might give them a call.

But one more stupid question: Should I get the block decked? And what exactly does that do?

Apeiron

Decking the block corrects any flatness and alignment problems in the deck surface. If there are no problems, then you don't necessarily need to have it decked.

ScottyRS

iTrader: (2)

Thanks, that's what I thought. Guess I'll go check the block with a ruler or something.

Apeiron

A ruler isn't straight enough. You'll need a machinist's straightedge to check flatness. The deck should also be checked for parallelism.

ScottyRS

iTrader: (2)

Well then I guess it's back to the machine shop. I found a different one closer to home though, hopefully they don't suck as much as the last one.

Sonix

iTrader: (1)

based on the compression distance, those are indeed 383 pistons, but pop up domes (5cc in the positive).
Watch that CR while choose heads, and considering decking the block, your CR will be astronomically high if you aren't careful.

ScottyRS

iTrader: (2)

Other people have told me the compression ratio will be anywhere from 10:1 to 11:1. And as far as I know, those will allow me to run pump gas. Would a thicker head gasket be enough to solve minor compression problems?

Air_Adam

A thicker one can help somewhat, but its not really the best way to go about it. Do you know how deep the pistons are in the hole at TDC? Stock is usually around .025", and if left with that distance, can drop the CR quite a bit, compared to a 0-decked setup.

11:1 compression is just fine with pump gas if you use the right cam and a set of aluminum heads. If you are really careful with how its set up, then you can even get away with 11:1 with iron heads, like me.

Does GMPP reccomend using flat tops with those heads with a 383 or a 350? With a 350, it would be just a little over 10:1 CR, but with a 383, it would be quite a bit over 11:1... not really very good with pump gas.

gettin_er_dunn

with aluminum heads he will have no prob running 11.5:1 cr he will still be able to use pump gas all he has to worry bout is if ends up using cast iron heads then you will want no more than 10.5:1 thats max u can run pump gas with cast and not gettin detonation..but as for crank id go with scat thats what ive used and never had probs out of if u look at my other post i have a block scat stroker crank eagle i beams and speed pro pistons and a bunch of other stuff for sale but scat will work out fine for ya...

ScottyRS

iTrader: (2)

Well I'm definitely going with aluminum heads. And the ZZ383 uses the fastburn heads (62cc chambers) with flat top pistons, and only puts out a 9.1:1 CR.

Should I look into getting new pistons before it's too late?

1badrocZ

iTrader: (1)

"The GMPP Fastburn heads have chambers that are way too small for a 383 with flat tops.. 62cc chambers IIRC."

This is what i am using on my 383 im building right now. My engine builder said the compression would be around 10.5:1

Scotty, Doug Herbert has a 383 pro-street kit that is reasonably priced. The kit includes: Scat 4340 forged steel crank, wiseco pro-tru forged pistons, pro-tech 4340 "I" beam rods, plasma moly rings, clevitte 77 H rod/main bearings. This is what i went with, you shouldnt have to worry about your bottom end. Price $1359.99
Edit: just seen you already have pistons

1badrocZ

iTrader: (1)

If you decide to get a scat crank be prepared to fork out some $$ to have it balanced. They make a decent product but usually require alot of drilling and/or filling to balance em.

ScottyRS

iTrader: (2)

Well the machinist said he needed the pistons to bore the cylinders, so I kinda rushed to get them. Had I known he was going to take over a month to do it, I would have taken my time, saved my money, and found a good kit.


If worst comes to worst, can't I just have some dishes machined into the pistons to drop the compression ratio?

Sonix

iTrader: (1)

yes you can, not very economically feasible though, but hey, for $500 pistons that you already have, why not eh? (You said you're doing this on a budget... I don't really believe you or it's a big budget)

Here's my math on your combo, using your 5cc pistons
10.7 if you leave it with .025" deck height, and .040" gasket thickness
11.3 if you 0 deck it.
United Engine and Machine Co.

I think .060" quench and 10.7:1 is bad, and I think 11.3:1 is too high. IMHO you're not in a good place. I'd open up the chambers on the heads with a die grinder, or choose bigger chambers. I don't know what cam you have picked out, but on a street driven 383 with AL heads, I wouldn't go much higher than 10.3:1 IMHO. Some guys on here think that's low, but going higher on CR doesn't give you much HP, compared to risk factor. Do the math on your dynamic CR as well, shoot for 8.5:1 or so. I'd go for a .040-.050" quench, either using a thin gasket or decking or both.

I don't know how the ZZ383 has 9.1:1 CR, that kinda confuses me, something doesn't add up.

Air_Adam

You can't return the pistons? Or sell them maybe?

Why do you want GMPP heads so much... the AFRs I suggested would work much better with your existing parts, and make more power too, since they flow better than the GMPP stuff.

remltr

iTrader: (4)

I have those same pistons and they are flat tops with valve reliefs cut into them not domes. -5cc according to srp.

ScottyRS

iTrader: (2)

Because the fastburns are cheaper and I can use a Vortec intake on it.

Sonix

iTrader: (1)

right, I should have corrected myself, summit shows +5cc, which means valve relief, compared to -5cc would mean pop up.. strange convention.

anyway Scotty, what are your plans then?

ScottyRS

iTrader: (2)

I don't know anymore!

So will those pistons give me a huge compression ratio or not? Do I need to get new ones? Which pistons would you recommend?

Air_Adam

I doubt they are cheaper by much... and if you don't already have the Vortec intake, then why do you want a Vortec setup over the traditional setup? I bet the cost of the Vortec intake plus the GMPP heads will about even out with a regular intake and AFR or TrickFlow heads.

I forgot to suggest this before, but TrickFlow also makes a 72cc cylinder head, and its a good bit cheaper than the AFR stuff too, although I think its a 195cc head, IIRC.

If you do want to use the GMPP heads though, use a piston with a 12cc dish. With a 12cc dish and a .040" gasket, it makes for 9.94:1 CR. Right where you want it to be.

ScottyRS

iTrader: (2)

Okay so stepping aside from my piston problem for a second...

Eagle forged cranks: are they good? I know the cast ones are made over seas and get mixed reviews on the boards.

Eagle Forged 4340 Steel Crankshafts: ESP-435037505700 - summitracing.com

Or should I drop the extra $100 into a Lunati?

Lunati Sledgehammer Crankshafts: LUN-AJ115AN - summitracing.com

1badrocZ

iTrader: (1)

For 450hp, the eagle would be more than enough. I wouldnt drop the extra $100 for the lunati, youd be better off using the extra $100 on the heads. (AFR) Ive never used eagle but from what ive heard they make good stuff.

Mkos1980

iTrader: (8)

Hope you clearanced the pan rails before your final wash from the shop.

Sonix

iTrader: (1)

If you can return the pistons, that'd be wise. But assuming you can't (since it'd need to be honed again perhaps, etc), and selling them would hit you with a big loss, i'd just look for 70ish cc heads or something. Work with the variables you have left, which are heads.
and yea, that eagle crank should work fine.

ScottyRS

iTrader: (2)

I didn't bother having them clearance it. I just wanted my damn block back before they lost it. Hell, they lost my pistons...twice!

And I'll look into returning the pistons, or perhaps trading them with someone. Thanks again guys.

Air_Adam

You can always just clearance the block yourself, its not hard. The Eagle crank is probably more than enough for only 450hp as well, you should be fine there. Don't bother with the Lunati peice.

ScottyRS

iTrader: (2)

Yeah I've already asked about clearancing the block and it's nothing I can't handle. I'm looking into getting some forged Scat rods off a user on here that are clearanced for strokers. Hopefully that will save me some trouble.