ED69ray

My sb 350 setup looks final now as i talked to the engine builder today:

.060 over 2 bolt 1973 block
10.25-1 flattops
GM alum high rise intake
Holley 650 DP mech sec
Edelbrock performer alum 2.02 heads 64cc chambers w/170cc runners
Comp hyd roller cam in the .490 / 220 (@.050) range
Comp roller rockers
MSD ignition w/rev limiter

I have been told this is a 380-400hp setup.

Anyone has any comments about going .060 over on a two bolt block? I plan to use it between 1500-5500rpm - with either a M20 or M21 4 speed/3:70 rear ratio

Thanks, Ed

Durango_Boy

I hate to throw a wrench at your current build but did you entertain the idea of building a stroker? The crank and cam are the big differences and realistically if you are already doing what you're doing the cost is barely even any more than what you are already doing.

63mako

Sonic test the block. Some blocks can't go .060 over. If you have to go that big of bore I would consider another block that will clean up @ .030. They can be found cheap.

ED69ray

Good point and I have considered it, the cost is only around $800 more than I am already spending - $300 for additional machine work and $500extra for forged pistons (vs hyper) and the cost of a Scat crank. Already planned to buy I beam rods. Block will be balanced and assembled with ARP bolts.

My only concern with the 383 setup is the potential stress (425hp/450tq) put on the .060 2 bolt block. I need to get some miles out of this thing - this candle needs to burn for a while before being replaced.

Thoughts?

Thanks, Ed

ED69ray

the block is gonna get tested this weekend - sould know by Monday if its good or not. It is already at .060 over but has very fresh bores and is very clean inside. I had no history on the motor - it ran ok and did not use oil.

My builder was not concerned about the overbore - he remarked that an early 70's block at .060 over still has more meat than a standard bore 1980's equivalent block - he thinks it will clean up with a nice hone and plans to use hyper flatops to get compression at 10.25-1 with the alum 64cc heads.

If the block is questionable at all I plan to source a 4 bolt block for the build.

BLOCKMAN

Cylinder mold placement on the older blocks is not a good as the late blocks as the later blocks they are better beacuse of up dated technology.

We sonic test every OEM block that goes through our shop and on the average blocks old or new the thickness is the same for what we have seen. We have seen vey few blocks that will go .060 over that could be used in a performance build.

On a .060 over bore the block should be plate honed as with the bigger bore the cylinder are weaker and will distort more when the heads are bolted on.

Most guys prefer their cylinders round when the cylinders are hone with no torque plate but I prefer them round when the heads are bolted on.

Here is a link to a guy that broke a cap on a 2 bolt 383 on this site.
http://forums.corvetteforum.com/c4-t...ps-1992-a.html

Little Mouse

Reading the above posts I had a hard time believing there would be a difference in the cylinder wall thickness in an early block and a later block they were known to be thin back in the 60s if the factory would have made them any thinner in later blocks they would have no cylinders .

63mako

Same block design, better cylinder placement during casting. I would find a 4 bolt block that will clean up @ .030 over. The 1970 through 1974 010 High nickel blocks are made of better material. That would be my choice. I used a 1973 L82 block when I built mine. You could tell the technology used to machine it originally was dated. To square up the head mating surface it needed .008 off of it before it was cutting all the way across. The bores were not centered with the crank so boring machine was cutting more out of one side of the bore than the other. If I had it to do over again I would have probably bought a new modern GM 4 bolt 1 piece rear main seal block that would take a factory roller cam with no machine work and stock bores. By the time you machine the old block and buy a retro roller your $ ahead buying the new block.

63mako

88962516 383ci Stroker, after machining. Used for the 383ci partial engine block. [Old P/N 88959106]
This bare block is the same as the 350ci Bare Block P/N 10105023 except the pan rails have been machined so the 3.80" crankshaft clears the block. It has 4.00" diameter cylinder bores and four-bolt main bearing caps. This block is machined for a 1-piece rear crankshaft seal. (Does not include rear seal or adapter.) These blocks weight 181 lbs.
Technical Notes: Cylinder wall thickness is the same as current production engines. The lifter valley is machined for hydraulic roller and flat tappets. Crankshafts with 2-piece seals can be installed with adapter P/N 10051118. Main bearing torque specifications for all Bow Tie blocks are 65 lbs. inner bolts, 60 lbs. outer bolts, and 40 lbs. on 3/8” front bolts with light oil. Block castings are P/N 10243880 and 14093638.
Here you go. Under $1000 Takes a stroker crank, Stock size pistons and roller cam with no machine work.http://gmperformancepartszone.com/ba...16-p-5635.html

BLOCKMAN

REREAD MY POST as the later blocks seem to be better as far as cylinder wall thickness as the molds are better then the molds 40 years ago.

On the later blocks its more common to find them more centered and see the same thickness from side to side then an older block were one side will be .400 on one side and .125 on the other side.

If ever get the chance to sonic tests blocks you can see what I have been taking about.

I had a 327 in the shop late last year and it was .040 over and one or two of the cylinders were .130ish on the thrust side and that one went on EBAY I believe.

BLOCKMAN

We buy alot of GM blocks and have sent a few new ones back because of thin cylinders maybe 1 out of 20. But they still need to be checked.

Ironcross

Lawrence Jewel of Jewel Tool Co. in Taylor Mi. was making crankshafts for early Chevy blocks {283} 4 1/8 by 4 1/8 for a total 416 ci for drag racing in the early 60`s and Moldex Tool built the connecting rods. The 327`s were not available yet. It can and was done. So a .060 over is not a bad engine to work with.

I wouldn`t want it though. My engine of choice are Chryslers...

63mako

Here is a 383 rotating assembly internally balanced, 4340 6" rods, ARP rod bolts Forged pistons. bearings, rings complete, under $1000. You would need the piston in a flat top instead of the dish piston to use in the above block and the 2 piece seal adapter. Probably bump the cost up a little but not much. Think Motorhead used one of these Scat cast cranks in his 550 HP 406 with no issues..
http://cgi.ebay.com/ebaymotors/_Car-...1%7C240%3A1318

ED69ray

Thats probably the most telling statement.

Its staring me in the face - just get another block dummy I would have to agree it would be best to start fresh with a nice 4 bolt block.

Having to source a 4 bolt block will eat up some extra cash and may put the 383 out of reach - that can come later - a 380hp 350 will still be a lot of fun

Thanks for the input, Ed

63mako

I would still consider the new 383 GM block. You can build it to a 350 now and later bore .30 over and upgrade to a 383 with minimal machining and an inexpensive roller cam. By the time you buy the 4 bolt used block and add in machining costs it is almost a wash. Good luck on your build.

Little Mouse

Blocks are just like the foundation of a house you would not want to stick a good amount of money into building a house on a weak or qustionable foundation.

I have three four bolt blocks one is a 74 high nickel content the other two are earlier 4 bolt canister. Have not talked to a good machine shop
on what all the costs are to check a block and machine work. Don't think I would even mess with them for what the cost of a new block is and I already have the blocks don't have any expense to buy a used block.

I like 63mako suggestion to buy a new block.

Little Mouse

The post that I was concerned with is when he said his engine builder told him earlier 73 block was thicker cylinder wall then the later model blocks all the blocks I had anything to do with were late 60s early 70s blocks so I did not know for sure until you confirmed what I thought. If chevy would have made later blocks thinner there would be no cylinder walls in them.

BLOCKMAN

From what I have seen when sonic testing is if the cyliders are some what centered tou should see appox. .230 ish on the skirt sides and at the pin side .130ish is a good cylinder on most OEM blocks.

I see this on newer blocks and older blocks as well.