I know enough to be dangerous
I have a 91 305 TPI with quite a few miles, so I don't wanna bolt on my Procharger just yet...

Along with the supercahrger, I have a TPIS Bigmouth base, AS&M large tube runners, & ported plenum for the build...

I'm getting a little confused as to what block I need (to keep using TPI system)....

I saw on jegs they had brand new GM blocks for $750... I thought, well, I can get a new one that starts out @ 350 and hasn't been bored / honed / 100+k miles on it, etc... good choice...

http://www.jegs.com/i/GM+Performance...5123/10002/-1#

I know that in 86 or 87, something changed, they went from 2 piece rear main seal to 1, and what else...??

I had thought the above motor was the newer one (I have But then I came across this block...

http://www.jegs.com/i/GM+Performance...2516/10002/-1#
It's almsot twice as much!

There is also an older 350 with 2 piece main seal, for $700

http://www.jegs.com/i/GM+Performance...6034/10002/-1#

Then I came across this site and info...

http://www.team3rdgen.com/modules.ph...=Casting_Block

I also see some people saying get a 2 bolt main and get the caps splayed (thus becoming 4)...

I want at least 500 rwhp....

So I get a 2 bolt main, and which block ???

Thanks,

Raf

Don't mind me, just talking out loud...

There is a guy locally that has a 90 TBI truck motor, I'm assuming it's a 2 bolt main, $100..

I'm reading that the 2 bolt converted to 4 bolt splayed would be stronger than the factory 4 bolt (and for sure 2 bolt)...

Any thoughts???

Raf

Your links all take me to Jegs homepage.

Truck blocks are typically 4-bolt. Check the main caps, there is no other way to know.

If you're building a supercharged motor, you need a good foundation. How much you pressurize is important, though. If mild, a factory 2-bolt with splayed caps will be fine. A factory 4-bolt could be as well.

The block has nothing to do with whether or not you can keep your TPI, though. What flexplate, what cam - that's what will be dictated by the block.

I'm planning on 15 PSI boost.
I know stock, the 350's are runnin 10 PSI intercooled, so a 4 bolt or 2 bolt splayed to 4 is fine...

I do want to keep my TPI, but cam will be specific for supercharger, I want aluminum heads too... Will my serpentine system bolt up to older blocks? Flex plate and rear seal??? I have a 5 speed and wanna keep it... ?

Raf

I fixed the links...

I clicked on more info and in reading some other sites... found out more info...

http://www.jegs.com/i/GM+Performance...5123/10002/-1#

This one is for 86-99 Gen 1 hydraulic roller... and is probably the one I want...

The other similar block that was $1200... was clearanced for a stroker crank 383..
http://www.jegs.com/i/GM+Performance...2516/10002/-1#

I'm thinking to go ahead and get the $750 block for my 350 TPI build... Is this block ok, anything concerning fuel injection / carb specific to blocks? Just want to make sure I make the right choice... Thanks,

Raf

I already answered that - no.

It should be fine as long as you don't go nuts on the power and fill it with good parts.

Actually, there is one minor one... many of the newer castings of the '638' block (350 roller block, 1pc seal) do NOT have the drilling and machining done to them to accomodate a mechanical fuel pump.

I have a '99 L31 engine sitting in a crate in my garage that is as-is out of the truck it came out of, minus water pump and intake manifold, and it doesn't have any of the machining done to the block for a mechanical fuel pump. The provisions were cast in, but the machining was never done. Was nachined for a roller cam, and even has all the roller stuff in it, but nothing was done for the mechanical fuel pump.

Using an electric fuel pump is the only way to use this block with a carb.

I don't know when they stopped machining the blocks for the mechanical pumps, but I know they did at some point during the '90s.

The blocks used for crate engines were drilled for the fuel pump rod. Although I can't say with absolute certainty, these bare block probably are, too.

Brand new blocks, yes they likely are, you're right. I know for a fact though that some factory installed blocks were not... just sayin'