I'm starting with a std. bore block and building a second engine. Motor will be going into a turbocharged streetcar and produce ~700rwhp at <6500rpm. Water jackets will be short-filled.

I am curious about the need to sonic check an LT1 block that will stay below 0.030" over - If it was your money you were spending on a build. Understanding it makes sense to confirm a good foundation, is this activity typically worth the effort?

What is considered minimum wall thickness for a high horsepower build. For those that have sonic checked LT1's, how do they normally look?

Do many engine builders use sonic data to offset-bore the cylinders and what are the pros & cons of doing this?

Thanks,
Scott.

 

According to the book, "The Racing Engine Builder's Handbook", you want a minimum of 0.25" wall thickness for naturally aspirated engines. From what I have read, LT1's tend to be in the 0.320-0.350" range from the factory and do not vary as much as the older blocks do. I would recommend having all cylinders checked at multiple depths in the cylinder, particlularly the thrust position.

Most good engine builders sonic test before any machine work is performed to avoid wasting time. If you are buying a block these numbers should be available.

 

If you have a shop handy that can do it at a reasonable price, AND it is a very high end build than yea, otherwise I wouldn't loose sleep over it.

Rich

 

I suppose as part of the block validation process it makes sense for $110 - before putting another ~$1900 into a stock block

I believe D. Vizard has recommended 0.200" minimum for a SBC assuming large overbores. I'm hoping to not even go 0.030" over on this block and run a custom piston.

Thanks,
Scott.

 

I don't know where you pulled those LT1 block numbers from, but I always see them as low as .090" on the front/back and .110" on the thrust, that's on standard bore blocks.

 

$1,900 is a lot for block prep. What all are you having done?

Rich

 

Rich,

Essentially the following:

>> Hot tank (bake) block
>> Magna flux block
>> Sonic check block
>> Shortfill Block
>> Machine for splayed caps-Flat bottom ProGram (plus steel front)
>> Stroker clearance
>> Bore and hone w/ deck plates
>> Deck block
>> Install cam bearings and plugs
>> Balance Assm.

The shop has a good reputation and has experience doing the splayed conversion, however wants $2500 to do the above (plus $70 for front cap +160 to fill block = $2730 ). Because they want to clearance for the stroker on a mill, that operation alone is quite expensive. I could probably do the blockfill & clearancing myself to offset some cost.

I have a few other quotes but do not want to use stepped caps and/or do not feel comfortable with a shop doing the main conversion for the first time. I actually had a gentleman in CA quote this as well (I'm in MI) at a more reasonable ~$1400 - but then there is 200-250 in shipping one-way.

Thanks,
Scott.