got my 383 back form the machine shop and I asked for a copy of the tolerances and bob weights for the job.. this is what they gave me..

not being an expert in this area I'm wondering if anything appears out of place here? or is all ok? Thanks


[click on image for larger view]







[Modified by BluByU, 6:53 AM 7/21/2003]

 

donno... I have no idea what to compare that info with.

I will be curious to read replies, too!

 

ttt

 

The numbers I could actually READ looked good (0.030" overbore etc) and your compression looks good for a 383 as well. But most of that is cryptic chicken-scratch from a guy who's probably done this so often he's writing down the norms for the sake of documentation( you know he torqued the heads to 65ft-lbs... but did he do it in steps? doesn't say). I.E. this is probably worthless for the most part.

You'll notice your compression is 215 psi? Well since when are all eight cylinders going to have exactly the same compression??? There's no range (210-217psi for example), and an average value isn't all that useful.... But keep it as a record of the work done, so if something breaks in 5,000 miles you can have a starting point. :D


But I wouldn't worry about it too much.
:thumbs:


[Modified by Ramanstud, 3:15 PM 7/21/2003]

 

yea,

im not to impressed with this machine shop.. i just realized they put a crank key on (so i have to replace it with the LT1 notched key now) and while i notice that i also noticed they had the cam 180 degrees out of time.. they had both the crank and cam gear marks at 12 o'clock like a normal chevy.. LT1's should have the timing marks at the 6 o'clock(cam) and 12 o'clock (crank)..
I should have just assembled it myself.. this would have also solved the problem of having them install those junk victor-renz gaskets instead of the fel-pros like i had asked for!!!

:smash:

ok well... I can fix it all.. it just goes to show ya if you dont do it yourself dont count on it being done right...


oh did i mention they tried to convince me to re-use the old cam timing gear with a new chain and new crank gear.. all because they didnt have the right part...:skep:


i didnt like that so i got a new gear from chevy.. 39 bucks.. i'll be riding along soon!!\]

:steering:


[Modified by BluByU, 7:47 PM 7/21/2003]

 

Don't forget that the crank turns 2 turns for every 1 turn of the cam, so if the timing marks are currently at 12 o'clock on both cam and crank, turn the crank one full revolution and you'll see the 12 and 6 o'clock that you're expecting to see.

 

Holy Crap! I'd be a little more than pissed! Frankly I would have absolutely zero tolerance for that kind of service. Hell, you're paying these guys $$$ because they're supposed to know what they're doing!

I was considering taking my ride to the "shop" for the first time [ever] for a tranny rebuild. Now I'm getting paranoid again... Maybe I should replace it myself like I was planning on doing?


:skep:

 

the crank is in the right postition (12 o'clock) its the cam that gear that needs to be turned 180 degrees.. its currently also at 12 and needs to be at 6

 

That's what I'm trying to say. Turn the crank 1 full revolution so that the timing mark is back at 12 o'clock. Because of the 2:1 ratio between the crank and cam, the cam will be at 6 o'clock with the crank at 12 o'clock. The shop didn't install the cam incorrectly, the crank is just one full revolution off of what you're expecting to see.

 

ohhh.... yea... ok so your saying they must have rotated the assembly during testing (obviously) and the marks just happened to be where they are.. is there a way to check to make sure everything is a-o.k.?

#1 should be at TDC and the cam mark should be at 6 and the crank at 12.. right?

 

You can get a keyed hub for the LT1. If you pick up an ATI damper, it should come with one. How do I know, when we were putting together my 396 I installed a new stock hub thinking the new damper would just bolt to it. Had to pull it to install the keyed hub. Anybody need a stock hub? :steering:

 

Exactly. Roll the motor over until the cam timing mark is at 6 o'clock, and line everything up. From what you were saying before, I think you'll find that everything's ok.

 

Actually if the cam mark is at 6 o'clock and the crank gear is at 12 o'clock, the engine is at TDC. BUT us distributor using guys (non- LT1) would have to rotate the crank one more time to install the distributor or it would be 180 out.

BTW- CorvetteZ51Racer is right about all of the above....

 

Well...I can't read it too well but what I can make out I have some issues with...

Main Brg. TQ: Is that 90 ft/lb??? That's more like BBC main tq; small blocks should be 70 inner/65 outer with studs and 70/65 on bolts with moly.

Ring End Gap: Are these file fits?? There's only one gap shown and you have two rings which have separate gaps. On a naturally aspirated motor they should be: Top- .012 Bottom- .014. If you plan on running over a 200 shot of N2O they should be .018/.020. What I'm seeing is a single .019 which is way too loose; the motor will have poor leakdown characteristics.

Main Brg. Clearance: .0025" is right where you want it...With a high pressure pump and synthetic oil I like to see them in the .0020"-.0025" range. But the Thrust Bearing clearance (#5) is too much... .0030" is ideal and you have a loose .0040".

Piston Clearance: What is this figure? Is it piston to wall clearance? If so, and you're running forged slugs, that's TOO TIGHT! It should .0040"-.0045". If they're cast or hyper pistons you can run them tighter but .0025" is too tight.

Rod Clearance: A little loose at .0025" but not bad... I try to set them at .0020".

Rod Bolt TQ: 50 ft/lb? They didn't use a stretch guage? No biggie but what are the torque/stretch specs w/moly on the bolts/studs in your rods?

Another thing I'm not seeing here is your crankshaft endplay (ie., your thrust); it should be around .006"-.008", but nowhere is it listed. Nor is the rod side clearance (between the rods on the journal); it should be in the .010"-.015" range.

The bobweight card looks typical for a small block Chevy but what was the final balance? Ie., +/- how many grams? Neutral? Split? External?

Too late now for second guessing but I'll give you the best bit of advice anyone can possibly give you... Don't ever skimp on machine work; find and use the best shop available to you. You'll pay more but quality and piece of mind are worth it. The sad fact is that with all of the comments I've made above; and your own comments about your confidence in them- you're never going to have a free mind when it comes to this motor...There will always be something in the back of your mind that second guesses it.
-Jeb

 

I'm thinking that might be an "In the hole" measurement for qwench. You know, how far below the deck the piston is at TDC. If that's the case, my memory tells me that's pretty much on the money. Not sure though.

 

No...That would be "Piston Deck Height" which he has listed as .011", meaning the pistons are .011" in the hole.
-Jeb

 

oh great... this tops my day.. :nonod: are the specs you listed for LT1's by GM? although some things may not be ideal is everything within acceptable factory tolerance? and yes i'm using KB hyper pistons

 

Well, to paraphrase Smokey Yunick: "A small block Chevy is a small block Chevy..."

Yes, everything I listed pertains to an LT1, aside from the reverse flow cooling and the Opti-Spark system they are virtually the same in every other way to the old Gen1 SBC; including main torque specs, bearing clearances, rod end gaps, etc...

I hate being a harbinger of bad news, but it just needed to be said. My suggestion would be to either have him go back through the whole assembly and do it right or simply pay him and install the motor and hope for the best. It may turn out to be a decent motor (notice I said decent not good) but you'll have that nagging in the back of your mind. IMO this machine shop has done just a slightly better than "rebuilder" job; not an excellent job for a high performance mill. I'm sure what I'm saying will **** off your machinist (it would me); but the truth hurts. The main deal here is that you're the customer and you want it done RIGHT; don't feel bad over the whole situation. I'm sure this may be the first time you've ever had a high performance engine built; this happens to a lot of people so don't beat yourself up about it...Go beat your machinist up (unless he's real big :D ).
-Jeb

 

I'm kind of surprised to see 215 PSI crank pressure with .019 end gap except for the .011 deck height...thats pretty tight. They must have really cut the block down to get that, and if so, what is your real compression? 11.5:1 or so? What is your valve to piston clearance? As for the .019 gap...either the bore is slightly over the .030" size (if they used presized rings,) or they over cut file to fit rings.

As for timing marks...they would not be lined up if the shop did a compression test. Brings another point...how would they have turned it without the flywheel? I hope they had your flywheel, because unless you want an internally balanced motor...you have to have the flywheel to balance it, as well as the crank hub.

BTW: because it's keyed on the hub, it means it is externally balanced. (The key locates the balance weight and timing mark).

Does it look like a starter was bolted to the motor?

I think they just wrote stuff down on a paper to make you happy.


[Modified by BBA, 12:41 PM 7/23/2003]


[Modified by BBA, 12:43 PM 7/23/2003]

 

yes, they had my hub, calancer and flywheel.. The block wasnt cut down at all as far as I am aware of. and yes 215 does sound high considering that .019 is right at the tolerance limit for the ring end gap... .020 being max according to my book..