Thread: 427 Tall Deck Big Chevy

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I have a tall deck 427 big block chevy from a truck in the mid 80's with plans on turbocharging it with a turbo (not roots blower) from a 8v-71T detroit diesel (yes, the cfm and sizing work, determined by a ton of math). I am going low buck on this hole build.
I was wondering due to the fact that the tall and std. deck share the same bore,stroke & con. rod, the pistons pin to crown hight must be larger by 0.4". (Am I correct in stating this)
If this is true can I run a shorter std. deck 427 piston to increase the combustion chamber size and there for lower my compression ratio.
Two more questions, is there a 427 piston that is some where between the two because a full .4" increase in clearance would drop the comp. ratio to about 5.5:1 which is excesively low for the boost I wan't to run (mabe a high comppression std. deck piston)
Finaly if I do run the heaver tall pistons what is a safe RPM for intermitant runing (5500?)

Are you sure about the engine displacement? I thought the tall deck truck blocks were offered starting in the 80's as 454's only, and the 427's were last made in 1970?? Is this some type of hybrid the previous owner put together himself? I'd break it down to find out what's inside before going any further.

If it is a production 80's truck engine plan on pitching the heads, the ports are smaller than the average small block. No point in adding the turbo with those heads as a restriction plate.

You don't want the pistons set down 0.400 in the hole, you want to maintain a normal squish band. Use the appropriate pistons. You could choose to take the advantage of the tall block and stuff in a 3/4" stroker kit.

You might want to rethink the turbo choice, even if it was free. This was a big, heavy duty turbocharger which would have a horrible spool up delay in your application. The compressor side seals aren't set up for a draw thru, marginal at best on a blow thru setup. Find a generic TO-4 on ebay for $200, you'll pay a lot more trying to making the 8-71 turbo work.

Good luck, Mark

I agree with Mark, start from scratch again... The tall deck 427 is not a good one to start with anyway. Besides the issues you mention (you cant just switch pistons) you'll have problems with header fitting and other issues.