I'm looking to RESTORE my 1970 L46 350. I've talked to a number of different machine shops. Before I can get in two words, I'm told everything that needs to done. Is this a common practice, I would think that block should be maged and measured to determine the scope of work.

Bob

 

It could also be the machinist has seen 11043583 small blocks and pretty much knows what he needs to do according to the mileage and whether it's be overhauled before to get it back in service

And yes they should be testing it for cracks, cylinder wall thickness etc.

 

Bob

It really depends what your looking for, We consider everything we sonic test first, clean, mag, line hone with an ARP bolt kit, deck, bore and plate hone and stroker clearance if needed and final rinse, some customers install their own cam bearings and freeze plugs. We do that if needed.

Then there are shops that will not deck the block first and then bore off an unsquared decks and no plate hone or line hone, they will magg and cleaning and installing cam bearings and freeze plugs ETC.

I really boils down to how good of job you want and how much money you want to spend.

Then we would go through the rods resize and check for bend and twist, check pin bore clearance in the pistons, hang the pistons if needed, grind crank if needed and balance the rotator and if its a standard we would do the flywheel and pressure plate as well.

Good luck with your build Carl

 

Would that mean in every case you would deck the block and others shops that wouldn't are inferior?
Reason Im asking is that the OP is restoring a 1970 L46 car and, if I were him I would not want my matching numbers decked off the block.

 

Ditto to 63mako about not having the machine shop milling the original numbers off. Fine a shop that can deck the block and not touch the numbers. Get it in writing that the numbers are not to be touched. Work to be done should be in writing. Don't go with the verbal agreements. Over time, people forget what was said and not said. Believe me, I know! Tony

 

No but your taking a chance with the decking GM does as we had a block come in the shop last and one deck was off .012 from front to rear and it was bored off the deck and the reason it showed up at our shop was it was using oil.

To straight it out we had to deck the block, bore it .060 over and he was lucky it sonic tested good, All we did was get him new pistons and rings, balanced the rotator, hang the pistons and plate hone it and that seem to take of the oil burning problems

Don't get me wrong if the shop knows the decks are right on there should not be a problem it they are boring off the decks.

We bore off the main line and don't need to the decks square for those that want there matching numbers to stay on the deck. Or we can deck and leave the numbers if needed.

If the 45's are off its not a big concern as the wrist pin will take care of that but haveing the bores a true 90 degrees to the cranks is a big concern.

We get a few jobs from other shops where they can't cut the decks and they can only bore of the decks.

Again how good of a job do you want and if its a performance build it probably more criticle to have the bores right. At least the rings would like to be square in the bores.

 

Most shops will tell you what operations in their experience are required, primarily to ensure you don't get "sticker shock" in the process. There's also often a discount for "packages" as for some operations a significant part of the cost is setup time.

If you're doing the build yourself then consider yourself the general contractor - you can ask them to clean, mag and inspect the block and "give you the numbers" to jointly determine what machine operations are required based on the power levels you want to achieve.

There's a balance between doing all the operations to completely "blueprint" a block and what's required for a decent street/performance engine. As long as you're making less than about 1.2 HP/CID you don't need to go crazy Factory engines ran well and reliably for many, many miles with tolerances that might make a blueprinter cringe.

As noted, you need to find a shop that will guarantee - in writing on pain of death - that they will preserve your stamping pad. Also look for a shop that is used to dealing with home builders.

If the shop is doing all the work including design and final assembly, then it's a different deal and you need to let them call the shots.

If you're headed for Gold in this restoration, you'll definitely want to work with a shop that has done restoration work - Corvette engines in particular have a very specific painting process that must be duplicated in order to get the right "sheen" on the engine.

 

BILLLA,
What is the special process to the proper "sheen". I am new and am restoring a 71 and have never heard of this.
Thanks

 

I have the fear of the numbers being removed from the block. How is the deck of the block measured. I just want to make sure that machine work is required. Cost is not a factor, I'm trying to sort this out before I take the block to a shop.

 

Deck height is typically measured from the crank centerline. As stated, some production blocks will be off from side to side or front to back.

IMHO, if you are doing a NCRS type restoration, I would ask the NCRS folks on the NCRS forum which BTW requires joining NCRS.

I assume Billa is talking more about the correct shade of color to use, different brands have too much gloss, the wrong shade etc. Quanta Products paint by the quart is usually pretty close.

 

Glad to see you not doing a budget build and doing everything right is the way to go.

The decks are measured of the center line of the crank to the top of the decks.

As we see a few budget build blocks a year where a guy sets the crank in the block and it binds up or they paid for the best job and we put a torque plate on the deck torque it down and find the cylinders distorted up to .004 all I say is how are the rings going to seal??? And we have leaked down cylinders that were not plate honed and have seen 16% on new builds, Not good when your paying to have the job done right. Leak down tests and bore gauges don't lie.

If your having everything done you should have a nice peice when its finished machined, square decks, true cylinders, main line housing bores all the same size.

Most guys don't understand the physics of machining and what needs to be done to get a good job.

I am sure guys that don't do this type of work will ay its BS as I know one that will reply for sure.

Good luck with your build. Carl

 

Good answer. My deck on the 1973 L82 block I used for my 383 was decked to get the head mating surface 45 degrees to the center and parallel with the crank. It took a .014 cut on both sides to get the deck correct. This motor originally ran for 100,000 miles like this with virtually no perceptable wear so for a stock rebuild it is generally not that big of deal. As for boring, a lot of shops want to go .030 over right off the bat. The 010 blocks are a high nickel block. Mine had no ridge and would have easily cleaned up @ .010. Problem being a .010 forged piston for a 3.75 crank is harder to come by. With a stock rebuild it is easy to find a .010 or .020 piston. Only bore enough to clean up the cylinders. Same with the crank. Most times you can polish the crank, Mic it and put new bearings in and your good. Sending it out to be ground .010 is not a requirement if it is in good shape but is a very common practice. Same with align boring. If this engine ran for almost 40 years with the same crank you are reusing why would it have to be done now. Only do what is nessesary for a quality rebuild. I was doing this 30 years ago and have freshened up a lot of truck motors with the block left in the frame. New bearings, Ream the ridge, hand hone the cylinders, New rings, valve job, reassemble and go. Good for another 100,000. A lot has changed in machining and blueprinting standards since then and engine builders always want to cover their a$$ but sometimes this is at your expense. Find a good local shop, educate yourself and as Billa said, be a good general contractor. If it ain't broke don't fix it. High Horspower race builds are a whole different animal.
Edit: Blockman posted while I was pecking. Let's say we agree to disagree and leave it there.

 

This is good advice. Take charge, know what you're getting and what's going to be done, and work with the machine shop so you're comfortable with all the steps.

 

You've not said what's specifically wrong with the engine- if anything.

Please note all the comments made that come from shops or people that talk about correcting machining 'errors' that have been there since the engine was first built. If these 'errors' have been there for 100,000 miles and caused no problems, why do they need to be fixed now?

99.9% of block decking is unnecessary- fixing something that is not broken.

 

As for paint, it's more than just the color. It's a matter of very careful dissasembly to get clues on how the engine was painted and ensuring the process is carefully duplicated. This includes doing a light spray-down with oil before the first start. I've done a few of these and it's a very involved process. I don't want to go OT with all the details of the cosmetic aspects of an engine restoration effort, but just ensure you're working with somone that understands this before moving forward.

As for sorting out the details, 63Mako's advice to educate yourself is the place to start. There are a few 'classics' that are a great foundation:

HP Books How to Rebuild Your Small-Block Chevy

SA Books How To Rebuild the Small-block Chevy

TALK to your machine shop after you've done some reading - a good one will make time to talk through the build and offer their advice. The right shop will tell you what needs to be done and specifically why - vs. "we just always do x".

 

Great advice, the motor has 72k, I'm in the process of rebuilding the entire car. I want a soild motor with stock apperance. I plan on HPDE/AUTOX. I would like to know that everything was checked and correctly upgraded. I had the cylinder heads pocket ported and CC. In addition to 2.5" exhaust manifolds,Cast iron LT-1 intake and modified oil pan.

Bob

 

It sounds like NCRS is not a concern I would consider is replacing the engine with a crate or different engine and keeping your numbers-matching engine carefully stored for the future. They don't take up all that much room on a rollaway stand. You can create a VERY factory-looking engine with modern technology underneath; I've done a bunch of these and they're a riot - it's fun watching people look under the hood and then do a double-take and lean in a little closer! Just a thought - recognize that if you're driving the beast hard, stuff breaks. It also changes the guidance a bit from a restoration engine in terms of the build level.

FYI, there is no cast-iron LT-1 intake - they are all aluminum. I don't believe that manifold will fit under the base hood with the stock Holley 3310 and air cleaner. Not posting a "for sale", but I have a correct 3310 and intake if you're seeking.

Finally, if you're somewhat serious about racing the C3, there are some great notes on chassis prep in an older version of the Chevy Power Manual - someone here may have them or I have PDFs I can email. You will find it hard to be competetive in a mostly-stock C3, but there's tons o' fun to be had!

 

If you want to beat on it get a different block, Roller cam and take the additional machining steps needed for a higher performance build. You can build to 400 to 450 HP pretty economically. Get past 500 HP and you are talking spending considerably more to build the motor and major drivetrain upgrades. Depends on what you want. I have a custom 63 and really like the custom High performance route but on a #s matching 1970 with 72,000 miles, if it is correct and numbers matching now I wouldn't modify it or beat on it much. It will depreciate the value considerably.

 

I don't plan on beating the motor to hard @ HPDE/AUTOX . I think that the car might see 2-5k miles a year. I don't want to expand my parts inventory anymore than it is now. This gives me something to talk about, do you think I'm making that big of a mistake trying to use the original motor.

Bob

 

It's all about risk and value. If you're going to autox and HDPE with any level of seriousness, you bet you're going to beat on the engine. If you don't, you're doing it wrong

If you seriously damage the engine such that the block or heads are unrepairable, you cut the value of your car in half depending on the options, etc. If that's not a concern - and IMHO it should be - then by all means use what you have. If it is, then an alternate engine is a better choice. Numbers-matching Corvettes are a blessing and a curse, and restoration and racing really don't go together unless you're going vintage racing