Here is what the machine shop replied:

You need the pistons to know what size to bore the block to. Cast pistons,
hypereutectic pistons and forged pistons are made differently and also
require different clearances to operate properly. Also, different brands of
pistons may be slightly different in size and clearance specifications.

 

Might as well Make sure you're getting springs that can handle .500 or so of lift "while you're in there".

 

 

Will do.

 

Ok lets slowwwwww down here Wilson.

First: that rings comfirms a forges stock crank and don't let it go - look for a quality shop to polish or turn it, maybe radius the journals too.


Don't worry, Chevy sb rods are all forged. Always get the ends resized and quality (ARP) new rod bolts installed. Check the cost of shot peening and if affordble ok but not nessesary. If u want to be resourceful u can polish the beams before or after peening but maybe not for u this first try at overhaul.


I'm sorry but u will need to research and choose yourself for running w/o hardend seats. I have read the need for hardend seats is overemphized and I take Bill's advice serious - but again those ain't my heads.
Be sure u have "PC" vlv seals installed as Bill will just send u the stock O-rings unless requested (i had to install umbrella seals on mine and work fine but PC's are the trick here). Also important, make sure u request the vlv spring seat and open press specs so u can choose a compatable cam.
BTW Bill will beat anyones price on parts (please don't tell the forum vendor i said so).

One more thing on heads, u can remove, tap and install studs your self for cheap $$ as Jeg's and Sum... sell the tool for it.

Again go for the big vlvs.

If they won't bore the block without the pistons then find someone else. This is good practice for u. When u can't get the service u need then take your parts and walk before its too late.
That old 327" block will bore .060" and parts houses carry .080" pistons on the shelves for it. Get the block bored at least 0.030" and have it "zero" decked.
U can shop for pistons once the heads are back and u have measured the chamber volumes.

One more time, don't shop for a cam yet. Just get the spring pressures with the head work.

Whew! Thats a bunch'a typ'n but i can tell u serious and know its not going to waste.

Sounds like your into this build up to your eyebrows.
Good luck,
cardo0

 

Viton oil seals S5325 www.competitionproducts, these push on the
stock guide no machining. To zero deck the block you will need the pistons
you are going to use find out exactly how far things are down in the hole
so the right amount can be taken off the block, if you zero deck the
stamping numbers on the front pad will be gone. Machine shop needs
the pistons to do the final honing.

 

The people I've used for rebores for years insist that you, or they, supply the pistons before they do the bore. That way they can bore to the size of the actual pistons (plus clearance!) & get it exact. I know another place that will rebore without the pistons, just going by the size listed in the book. Usually this is OK (I've used them occasionally), but every now and then a rebuilt engine that they've bored is a smoker due to too much clearance. This is a total pita to fix. It would be nice to think that manufacturing tolerances are now so good that the min & max acceptable finished sizes of pistons are extremely close. Is this the case with all pistons for GM V8's?
I'd say good practice is to give the machinist the pistons prior to him (or her!) doing the boring. That way you'll get a bore size that is correct for the piston being used. If you're going to the trouble & expense of getting it done, then why not get it done right?
I'm not being argumentative, I've just learnt the hard way

 

Sounds to me that matching the pistons to the bores can be nothing but good and a safe bet. So I will do it.
BUT I'm not quite sold on the need because after all isn't that the purpose of one of the rings to allow for 1) the heat expansion and 2) slight differences in the piston and bores. After all the rings are "springy".
I think out of round conditions are a real danger. The rings can'tmake up for that.

 

I feel like I have to jump in on a few things here. I'm not trying to be contrary, and I'm limiting comments to areas where I've got a strong opinon As you're finding, every decision is interrelated as you look for the right system (combination of matched parts) to deliver what you want for power and driveability.

• Definitely price new aftermarket rods and compare to the cost of overhauling your existing rods.
• I'm completely opposite of cardo0's comments regarding the shop's desire for pistons in hand before machining. I'd bolt if the shop just decided to bore to 4.030 and leave it at that. You'll have to make your own decision, but I think you've got a good shop there.
• I would wait on the shop to determine what to bore rather than just going .030 right out of the gate. Sonic testing is always a good idea to ensure the wall thickness and verify the bore centers.
• The springs MUST match the cam - IMHO it's not possible to get the heads done until you know the cam.

 

1) Agree - Right now I think new is the way to go, but I will check out the overhaul cost because I got nothing but learnin to do!
2) Agree - To me all things being equal if they want the pistons whether or not I buy them from them or not, then they are probably pretty picky about their quality. So again even though I don't quite buy it yet, I will stick to the theory as it is safer for me.
3) Agree on the bores. I think I should go to the minimum material removal necessary to minimize any wall thickness issues. Again, cores can move. And thicker walls should be more stable and handle more heat.
4) ?? I am confused on the heads now. I was going to get them sent out this week. Shouldn't I just make sure they have .500 or better lift springs?

 

Springs match the cam - for example, if you look at the CompCams catalog you'll see springs for each cam, or at least "family" of cams.

 

cardo0

 

I have changed back to the 383. I think thats the final decision,,,,like the last final decision, and the one before that

I have been reviewing the mind boggling amount of cams between Crane and Comp. My idea is to pick some out, see what you guys say, then see what Crane and Comp tell me. Then make a decision. It will be interesting.

Selection considerations:
Street performance car. I want the best performance I can get without sacrificing too much drive ability. I guess that means the idle can't be too rough. I need the power and torque at lower rpms as most driving is under 3000.
The stock 291 heads will be opened up to 2.02/1.6.
383 cid
about 9.5:1 Cr
3.7 rear end, M21 trans. (But may switch to a Richmond)
Hydraulic lifter, no rollers because it seems that most of the extra power you get from them comes in the higher RPM's which is not where I will be as a street engine. But I want hydraulic so I won't be making adjustments.

It seems like keeping the duration low relative to the lift. is better for torque and low end power.

Here are my Cam selections:
Comp:
11-242-3
12-242-2
Crane:
133941
133801
114142
113941

Feel free to offer your thoughts. I will advise what the mfg's recommend next week.

 

2.02
11-242-3 comes out to a BBC cam (?) so this would be a bad choice

Comp
The 12-242-2 looks like a perfect choice; you could consider stepping up one grind to 12-246-3 for your 383 - larger displacement has a tendency to make a cam "milder".

Crane
133941, 133801 are also BBC cams
114142 seems a bit mild...
113941 seems like another good pick.

I'd need to dig a bit deeper here but I think you're in the ballpark on both choices.

 

If you don't mind I would appreciate you doing that digging. Sounds like the concensus is I have done a pretty good job getting close and not falling for the temptation of going to big. Would love to see both the 12-242-2 and the 12-246-3 run on your computer simulator. It would be educational.
Another thing, there appears to be controversy over these Comp Extreme Energy cams. Many say they are noisy. Billa, do you have any insight?

 

I'll have a chance this weekend - I'm leaving tomorrow AM for a business trip.

The XEs have a steeper ramp, almost like a roller cam. This means they're more agressive, but they are harder on the valvetrain and noisier. IMHO, XEs really aren't designed for a daily driver engine making < 1.2 HP/CID - but that's just IMHO

 

Billa, Please clarify, you had said the 12-242-2 is a perfect choice but that the Extreme Energy cams are not made for my application? I'm a little confused here.

 

Ok, The manufacturers have spoken.

Comp:
XE284H with a small base circle. I think the small base circle helps for clearance in a 383. The 284 is MORE aggressive than the 262, 268, and 274 that forum members have suggested. My guess was that the manufacturer would be conservative. So I am surprised. They said the information provided is based on 350. The 383 will make the cams seem less aggressive. Which I already knew but to jump 2-3 cams to make up for it may be alot IMHO.

Crane:
113511
This IS more conservative than my choices, 114142, 113941. That's what I expected them to do.

The take away to me is that other than the controvesy over noisy Comps Xtreme Energy cams there is a consistent view that the cams you members and I chose are in the ball park.


Interesting! Comments?