Plans for a 478 build.

[TJ's GMC]

So I'm planning on building a 478. When/if I can find one I will be doing a 4 barrel mod 1st thing and dual exhaust and HEI. Then I'll turbo it. Maybe twin turbo? lol. That might be just a tad bit of over kill. Anybody have any info on that 478 build with hemi pistons and caterpillar valves or something to that nature?

[bigblockv6]

The first thing to consider with this build is to lighten on the rotating mass, going with lighter rods and smaller piston pins which will require custom pistons. Basically you can use Chrysler 426 Hemi connecting rods and have the rod journal diameters turned down and at the same time even have it stroked to get over 500 cubic inches and the advantage to that is the crankshaft can be fully internally balanced. You will be able to get that V6 screaming safely at 5500 rpms but of course those hollow stem sodium filled exhaust valves need to be replaced with solid stem valves. I did at one time have the part numbers for the Cat valves but have not had any luck finding them so a custom set of Manley stainless steel valves would be best. For ignition I'm really thinking about a 3 coil pack from the Buick V6, Thunder V12 has a 6 pack setup for the 702 V12, I'm sure they can figure one out for the V6. As far as induction I'm thinking more of a belt driven roots type blower but it's up to you if you want twin turbo's.

[beerman]

IMHO and believe me I'm no expert but with a 5.125 bore that is a lot of piston to be moving.

Here is some Hemi bore and stroke data
http://victorylibrary.com/mopar/rb-bs.htm

and some BBC data
http://billygrahamracing.com/BBC.asp

My biggest concern would be at that bore and being boosted is flame propagation going to be an issue?

Detonation will more than likely eat those custom pistons long before you can get the blow thru carb tuned.

[bigblockv6]

It's been done before with success, this is basically Babe Erson brother to Sig Erson of Erson Cam's formula for building a performance 478 that would a safely turn 5500 rpm and give a moderately built 454 a run for the money. One other member of this site has done basically the same thing but has taken it further with custom Crower rods and stroked the crankshaft which now displaces 523 cubic inches.

[TJ's GMC]

Originally Posted by bigblockv6

The first thing to consider with this build is to lighten on the rotating mass, going with lighter rods and smaller piston pins which will require custom pistons. Basically you can use Chrysler 426 Hemi connecting rods and have the rod journal diameters turned down and at the same time even have it stroked to get over 500 cubic inches and the advantage to that is the crankshaft can be fully internally balanced. You will be able to get that V6 screaming safely at 5500 rpms but of course those hollow stem sodium filled exhaust valves need to be replaced with solid stem valves. I did at one time have the part numbers for the Cat valves but have not had any luck finding them so a custom set of Manley stainless steel valves would be best. For ignition I'm really thinking about a 3 coil pack from the Buick V6, Thunder V12 has a 6 pack setup for the 702 V12, I'm sure they can figure one out for the V6. As far as induction I'm thinking more of a belt driven roots type blower but it's up to you if you want twin turbo's.

Ok, I keep forgetting about the custom pistons. Man I'd love to find that build one day.

Super charger would be really neat. I like having a hood though. haha But that would be something you never see everyday! And that 478 would eat just about any stinking big block chevy alive!

Even a 6 coil pack and a bigger carb on a stock engine outta do something. Maybe 600 to 750 cfm.

[TJ's GMC]

Originally Posted by beerman

IMHO and believe me I'm no expert but with a 5.125 bore that is a lot of piston to be moving.

Here is some Hemi bore and stroke data
http://victorylibrary.com/mopar/rb-bs.htm

and some BBC data
http://billygrahamracing.com/BBC.asp

My biggest concern would be at that bore and being boosted is flame propagation going to be an issue?

Detonation will more than likely eat those custom pistons long before you can get the blow thru carb tuned.

Jetting that carb up and more octane outta fix that problem. lol And heck....could even create a custom manifold and go to two 4 barrels! And thanks for the links!

[bigblockv6]

Yes a custom manifold is a great idea! Andy Harmon who built the stroker 523 V6 has some designs made up. I may have the drawings and I'll post them later

[atomman]

For the ignition system check with electromotive http://electromotive.com/ They have it for the V-6
Atomman

[TJ's GMC]

Originally Posted by bigblockv6

Yes a custom manifold is a great idea! Andy Harmon who built the stroker 523 V6 has some designs made up. I may have the drawings and I'll post them later

Awesome! Post those up for sure! Be sweet having twin 600's on a 478! Maybe even do a high rise!

[beerman]

I get the additional performance with N/A motors but when you start boosting those hair dryers are going be moving a lot of air. That means a lot of fuel and just the thought of boosting through a carb with our intake scares me. The intake charge will favor the side by side ports and starve the single port. The roots style blower would definitely be a better option.


I agree that you could play with the stroke and rod length to obtain more performance. I think you would want to try and reduce the compression height of the piston and that will get this motor to tolerate higher RPMs by reducing piston mass. Plus you'd need something to handle the strokers harmonics.