jackson

My first post here in some 2 - 3 years

Sorry you've had difficulties with dirty IRON blocks and IRON heads.

Next time choose an auto machine shop which has the proper equipment ... then specify your chosen method. ... but, in a nutshell, to clean:
First via BAKING then Followed via BLASTING. First time I saw baked and blasted heads & blocks I thought they were brand new.

Special care must be taken with ALUMINUM.

Baking = high heat oven
Blasting = high pressure wash

PLEASE READ this linked article on engine cleaning published in professional trade magazine ... a real-world comprehensive guide to cleaning. There's also a wealth of other articles there to help y'all out.

https://www.enginebuildermag.com/201...ds-and-blocks/

jackson

Buccaneer

This is what I would do as well. Sounds like you were taken for a ride IMO and wouldn't trust anything they did. Good luck with anything you decide to do.

NewbVetteGuy

I followed up on this and 4.5 thousandths for cast pistons is outside of the GM spec for cast pistons

Road Use: 0.0015- 0.0025
Street/Strip: 0.0025- 0.0030
Racing: 0.0030 - 0.0040


But the old forged pistons are a high expansion alloy and the specs are much wider:
Road use: 0.0040- 0.0050
Street/ Strip: 0.0050 - 0.0060
Racing: 0.0055- 0.0065


So I'm right in the middle of the range for road use; very happy with that.


Adam

NewbVetteGuy

I could use some help with bearing clearances.

http://www.chevytech.info/1c6o1.html

The link above says the main bearing bore spec range for Medium Journal SBCs is 2.6406- 2.6415, but it doesn't list the bearing clearance spec range for medium journal bearings (only small and large).

Can anyone tell me what the medium journal clearance range SHOULD BE?


The only two measurements I got from the machine shop say: "2.4482 / 2.4488" and "2.0985 / 2.0990"



Adam

stingr69

Adam,
Not 100 % sure but those numbers are probably for the bearing bores in the block where the bearings are installed. Not the bearing shell to crank clearance.

You need to be checking the bearing to crank dimensions. Check in several places on each journal so you can check for any eccentric "egg shaped" wear. We are double checking the work the shop should have checked.

The 350 crankshaft main journal needs to be 2.0985" diameter at a minimum in order to run a standard bearing shell. If your crank mains measures smaller than that, you will need undersize main bearings. If your journals are .001" smaller than that, run a .001" smaller bearing shell. They make .002" if needed.

The 350 crankshaft rod journal needs to me at least 2.4479" diameter in order to run a standard size bearing shell. If your crank rod journals measures smaller than that, you will need undersize rod bearings. If your journals are .001" smaller than that, run a .001" smaller bearing shell. They make .002" if needed.

The numbers the shop gave you could be the largest and smallest journal dimensions they found. Hope this helps you ask the right questions.

jackson

You can also mix undersize bearing shells.
perhaps you need to make up only 0.0005" ???
put a standard shell in rod cap and a "one" (undersize 0.001") into rod; same method for mains OK. Put the thickest shell in rod or block.
Many good race motors built this way SOP.

L88Plus

It's stuff like this that makes me very grateful and thankful for the machine shop where I have my work done. I know they're busy with high-end builds, so I take my junk in during their off season and tell them to call when it's finished. Spot-on work from the best in the business.

RaceShop at Scoggin-Dickey in Lubbock - thanks!!!!!!!!!!!!!!!

jb78L-82

Exactly^^^^^^^^^

Unless you really now what you are doing, I would not be experimenting on my own engine....................

Sky65

Nevermind.
Tom

NewbVetteGuy

Tom. You're not getting it, because you're missing some information and are jumping to some incorrect conclusions.

I don't trust anything the shop said.
I didn't get the piston to bore sizing recommendations that I posted from the machine shop, but reposted them from another source. -It would seem that Lars was talking about (and correct about) piston-to-wall clearances for cast stock pistons; the old forged pistons expand a lot more and need larger clearances. You can use the Google to look this stuff up. It's not that I'm ignoring the advice that I'm getting it's that I get a lot of different advice from a lot of people that conflicts and I'm taking ownership of getting to the truth and tracking things down when there's a difference of opinions. (Blindly trusting off-the-cuff advice from an internet forum without double-checking it doesn't seem like a good recipe for success.)

Some of the advice is focused on things I COULD HAVE done if my decision on what to have done at the machine shop was in the FUTURE, it was not. When I created this thread, the machining was already done, I was just picking things up. Its hard to take advice in the past; I have a Corvette; not a Delorean.

This is just supposed to be a cheapy refreshed stock bottom-end L82 rebuild with some good heads and a roller cam up top. I have no desire to put $2,000 - $3,000 in the bottom-end at this point in time. Later on when it gets rebuilt, I will either buy a CNC Motorsports GM 383 short block or a CNC Motorsports Dart SHP short block and strap all the top-end components on it. If I had infinite money and wanted to put infinite amounts of money into the bottom-end I could follow all the advice on here and just say "yes" to every machining operation.

-I'm not sure why you would expect someone to just start an internet forum thread and take ALL the advice and literally do an engine build that just does what all the posts of the thread say (especially when many of the posts conflict with each other). -Ever seen the Simpson's "Homermobile" episode?



Adam

NewbVetteGuy

Definitely jealous you've got Scoggin-Dickey down the street!


Adam

jim2527

NewbVetteGuy

That's a good point. I've definitely got some money into this thing.

I literally planned on just bolting my top-end parts onto the block originally, but then I decided I should pull the engine to make replacing the RMS and flex plate much, MUCH easier. Then I decided I wanted to paint the block and then new rings and a hone scope creeped their way in. Now I'm kinda drawing the line on any more scope creep and I'm just looking to get it reassembled well and run the thing.


Adam

jb78L-82

I guess I am confused since it appears what you are after is mostly what I did in 2014 ^^^^ using the numbers matching L-82 block and many of the OEM components BUT with upgrades along the way with pistons (because I had to ), roller cam and AFR heads. It was not cheap but it looks like an OEM L-82 cruises like an OEM L-82 BUT goes like stink at any throttle input of off idle and cruise...AND I mean GOES....

NewbVetteGuy

Yea, it's funny because I know we've been on threads discussing the merits of doing a rebuild with 355 cubes vs. 383 and I ended up very close to your build in the end. I've been slowly copying where you went with your suspension, too, so I guess I'm doing a JB78L-82 clone build (except for my intake and EFI).

I'm obviously using the stock pistons, though. I've got $998 Jegs Profiler heads, a fairly aggressive Mike Jones Roller cam, and a weird TPI-style FIRST Fuel injection intake to go with the Holley HP EFI. -Then crank trigger ignition with LS COP ignition coils.
Mine sure won't look remotely like stock, though.

Adam