Plans for a 478 build.
 

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?

Re: Plans for a 478 build.
 

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.:thumbsup:

Re: Plans for a 478 build.
 

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.

Re: Plans for a 478 build.
 

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.

Re: Plans for a 478 build.
 

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.

Re: Plans for a 478 build.
 

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! :ahhhh: And thanks for the links!

Re: Plans for a 478 build.
 

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:upyes:

Re: Plans for a 478 build.
 

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

Re: Plans for a 478 build.
 

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

Re: Plans for a 478 build.
 

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.

Re: Plans for a 478 build.
 

Good luck with this one TJ! It sounds like it's going to cost a fortune :woowoo: but man if you got the money I got the interest! I can't help any but I'm subscribed to see how it turns out :thumbsup:

Re: Plans for a 478 build.
 

Don't have the money yet. haha! Don't even have a motor yet. Just planning for the near future. :thumbsup:

Re: Plans for a 478 build.
 

$40,000... Monster custom Ford's. With shelby block side oilers cost 35,000 . just did one 800hp. Big custom chevy w motors. $45,000. A monster chevy big block. Off the shelf. $18,000.

Re: Plans for a 478 build.
 

haha, nothin wrong with dreamin!


Yeah, I knew it'd be expensive. I was guessing around $20k with all the custom parts, but I didn't figure $40. I've seen guys order custom pistons at $1000 each for a small 6 or 8 run so that's $6000 right there alone in piston cost. Yeowch! If I didn't have a wife and kids, and want to retire some day (hopefully!) without eating dog food for breakfast I'd love to blow 40k on Cecilia. Man, that'd be sweet! :thumbsup:

I think we all have an addiction problem here! :lolsmack2:


http://www.crushable.com/wp-content/...iction-gif.gif

Re: Plans for a 478 build.
 

A 478 is more diesel like in it's construction (heavy parts/limited breathing). As such, I'd approach a build with only one idea..................boost! That will allow you to keep the engine speed within stock limits and take the high cost of making it live at higher RPMS out of the equation.

Perfect your fabrication skills and learn all you can about turbocharging. Over the years, I've built a few turbocharged engines and fabricated the setups. You'd be surprised on how much power you can make on the "cheap", relatively speaking of course.

I can easily see a 478 making 800 lbs ft of torque at 1400 to 1800 RPM's and about 400 to 425 HP at 3200 to 3400 RPMS with no more than 15 pounds of boost on a simple draw through carbureted fuel system with breaker points in the distributor and simple water/alcohol injection............with a single turbo.

With an good engine, this could be done for less than a couple grand.

Re: Plans for a 478 build.
 

I don't think there is a compromise either go lower RPM and boosted or higher RPM and Naturally Aspirated.

Re: Plans for a 478 build.
 

I think the hard part with big boost on a 478 would be finding one in any condition to use. As to high rpm. I am cleaning out the core motors at the shop. There are six v6 engines. Ones a 478. A couple of 401 and the rest are 351 engines. All have broken rods and one of the 401 has a busted crank. All of them came apart in the mid 4000 rpm range. I have an old Buick pull through turbo on a 305. Its set at 8lbs.

Re: Plans for a 478 build.
 

There you go TJ! A single turbo and a good 478 and you're in bid'ness! Time to start shopping
:woo:

Re: Plans for a 478 build.
 

Boost is in the plan for sure. But if I boost it I'll probably leave the internals stock as that engine has plenty of pull as it Is....then add 8 pounds of boost....sheesh! Sucker would pull a mountain.
If I stay naturally aspirated I'll lighten the rotating assembly and see about making it a 5500 rpm engine like has been done before. Course at that point I'd be putting a big 4 barrel on it, make a set of headers, and maybe try an hei with the msd box. Also would need to have a custom cam made. And many other things. lol
Be fun to make a twin 4 barrel high rise intake for it. haha

Re: Plans for a 478 build.
 

Getting good so far! Only thing is finding one near by! haha Closest one I found was in Washington and they want like $1700 for a 50 year old engine. :pullinghairout:

Re: Plans for a 478 build.
 

My thoughts exactly.

Re: Plans for a 478 build.
 

The biggest problem with the v6. And the main reason it's made so heavy is it's design can't be balanced. The rotational mass can. But the firing pulses can't counterbalance each other. The engine actually shakes front to back. Kind of like a rocking chair. This is why they don't feel smooth at higher rpms. The faster you turn it the more violent the rocking becomes. You could lighten up the rotational mass. And the rocking motion would be worse as the speed increased. Its the weight that makes these engines feel half smooth.

Re: Plans for a 478 build.
 

I've got the custom cam specs for my 478. I'll have to send you a copy of the custom cam specs for my 478 along with the part number for longer valve springs from Comp Cams , they are actually Ford 390 valve springs:thumbsup:

Re: Plans for a 478 build.
 

The cost of making a 478 (or any other GMC big block V6) make power at high revs will be much higher than making the same power at low revs by boost. I can certainly see the limited breathing of any of the V6 heads nullifying some, if not much of the gains made through headers, 4 bbl carbs and cams.

In addition, to make power at high revs will require tons of money to be spent on either making the heavy parts in the bottom end live, or be replaced with custom/aftermarket stuff. Aside from that, you'll still have to buy/source/make the headers and intake as well as pay for a custom ground cam.

Under no conditions would I try to make a 478 run at over 3600 RPM with the stock bottom end or valves, even in new condition.

Re: Plans for a 478 build.
 

I would say 3700 rpms is max for the 478, mine is good for 4500 but only if I get rid of those hollow stem sodium filled exhaust valves which I will absolutely have to do. Some 478's back in the day had the governors blocked and would get over revved and end up sucking valves.:ahhhh:

Re: Plans for a 478 build.
 

I thought you used cat valves in your 478. Not sure which. I looked at all the cat specs and none are close to a v6 gmc

Re: Plans for a 478 build.
 

Never used Cat valves, someone else on the site did and gave me the part numbers which I can't find, so I'm thinking of going with some custom stainless steel valves from Manley.

Re: Plans for a 478 build.
 

Are these the ones?

http://6066gmcclub.com/showthread.php?t=38705

Re: Plans for a 478 build.
 

Beerman, those most likely are the valves, thanks for digging it up:signthankspin:

Re: Plans for a 478 build.
 

I never rev my 305 past 3500! I wouldn't dream of reving a 478 past that either. haha

Another thing I was considering was fuel injection. The MSD injection is spendy, but a sweet unit. Be great on a motor that size. I've been wanting to make headers for my 305 for the cool factor, but haven't gotten around to it.

Maybe I'll just do nitrous on the 478. :lolsmack2:

Re: Plans for a 478 build.
 

For fuel injection on the 305 you can go with the Howell TBI most likely a 305 Chivy unit along with an HEI. I talked to Howell a few years ago and they said it would not be a problem with the 478. They do highly recommend running an HEI with it:thumbsup:

Re: Plans for a 478 build.
 

Never hurts to have more spark. HEIs have been know to increase mileage and performance. It did on my 305. Cold starts and warm up are much smoother and the mileage is even better! I'm gonna be trying out that MSD box and see what it does.

Re: Plans for a 478 build.
 

Did they say what ecu they would use to drive the injectors on the TB? Although aftermarket standalone controllers are nice, I like the idea of retro-fitting a GM system on it. I have an extra Procharger head unit sitting around and I thought about looking into the SY/TY 1227749 ecu (keeping it all GMC) which could handle boost. The problem with the SY/TY setup is that it would require an intake manifold and probably some sort of crank hub mounted reluctor. Maybe it's time to search the third gen.org site.

Re: Plans for a 478 build.
 

Be some fun fabricatin!

Re: Plans for a 478 build.
 

The wiring would be easy (you could probably even buy a standalone harness) and the sensors are readily available. They sell generic Prochager mounts, you'd only need to machine up some standoffs, maybe clock the head unit, run some tubing, add O2 bungs and make a mount for the reluctor. Plenty of room for an intercooler and bypass valve. LOL I even have tunerpro with romulator for tuning on the fly. I'd make a 329 ( put the bigger stroke in a 305) or a 379, because I'm still not totally sold on those extremely large bores. Of course I still need to put a floor in my cab but if your dreaming I'll dream with you.

Re: Plans for a 478 build.
 

Speaking of over stroke....can you put a 379 crank in a 305? Direct swap? The added stroke and a .060 overbore would be pretty cool. Bump in compression and bigger cam would be sweet to.

Re: Plans for a 478 build.
 

2 factory crank sizes 3.58 & 3.86
CID Bore Stroke
478 5.1250 3.86
443 5.1250 3.58
432 4.8750 3.86
401 4.8750 3.58
379 4.5625 3.86
351 4.5625 3.58
329 4.2500 3.86
305 4.2500 3.58

Re: Plans for a 478 build.
 

Old Bore 4.250
Over Bore 0.060
New Bore 4.310
Stroke 3.86
New CID 338

Re: Plans for a 478 build.
 

338 would be nice! I just wonder if the cranks will swap without issues on the 305. They are all different blocks from what I know.

Re: Plans for a 478 build.
 

Here is a 4bbl manifold design by Andy Harman, I think it is a dual plane design rather than single plane as all our V6 engines have. He also has one for EFI if I can get it to upload:pullinghairout: