Twin Turbo Pistons

[Frankster]

Pulling my engine for a rebuild so I have an opportunity to replace the stock pistons with something optimized for a twin turbo setup.

Thinking of doing around 1000 HP plus or minus a little.

What is the best compression ratio for this power level? Also, should I replace the stock rods?

Any recommendations on piston and rod brand?

 

[dun4791]

Pulling my engine for a rebuild so I have an opportunity to replace the stock pistons with something optimized for a twin turbo setup.

Thinking of doing around 1000 HP plus or minus a little.

What is the best compression ratio for this power level? Also, should I replace the stock rods?

Any recommendations on piston and rod brand?

Oliver or Carillo billet rods
CP pistons
Billet main caps

8.6cr

 

[BOTTLEFED]

sounds good to me

oh, and heads and cam as well

 

[plumcrazy]

best thing you can do is decide now what TT setup you like and want. go talk to that tuner and get his input.

 

[Frankster]

Thanks for the info, guys. I was thinking of Carrillo rods but hadn't ruled out others like Manley. Aren't there some others out there just as strong?

I've written (emailed) a few outfits that do twin turbos for Vipers. Seems they're not too interested in my business as it's been over a week with no response. I'm a hot rodder from way back so I'm not beyond doing it myself. Looking at mounting the turbos near where the headers connect to the exhaust system but that will take some serious mods in that area. Anyone got pics of where to mount the turbos?

I'm wondering about lightening the valve train and rotating parts to get more revs, say, 8 or 9 thousand revs along with the twin turbo setup. Any sage words of advice in revving a Viper engine? Not sure I'm going to go there but am thinking about it.

So then at the risk of ****** off some, Thinking of going automatic for the street/strip. Don't want the 2 speed powerslide but more something of a 4 speed auto. Any suggestions on a unit that can handle the HP and fit on the back of a Viper engine?

Decisions, decisions.........

 

[plumcrazy]

good luck spinning the motor that high....

carillo are the best rods, CP has the best pistons, ross are good pistons too

i see nothing wrong with an auto for the strip but not a preference for me on the street. just not as much fun for me.

 

[Frankster]

As I write this I'm ready to pull the motor.

Should I do it with trans attached or removed?

 

[Joseph Dell]

As I write this I'm ready to pull the motor.

Should I do it with trans attached or removed?

This is a personal preference. The shop manual says to pull them together. the back tranny bolts are a PITA to get to, so it is definitely easier if you have the space to get the entire thing out.

RE: revving the motor higher: you will need a dry sump and solid lifters. I've only seen one viper spin to 8k RPM... all others die much earlier. Stock oiling stinks. As does the stock rod/stroke ratio.

 

[Disturbed]

Joe forgot to add the intake is a POS too for high revs. A ported Gen 3 is your best bet for the price.

RE CR ratio: 8.5 is low for my taste, I'd go with 9:1. But any of those will work fine, both have pro's and con's.

Tuning is more important than the CR with these power levels. The AEM is ***** to learn. WOT not so bad, idle and part throttle...not fun. Trust me...get a good tuner.

 

[Joseph Dell]

N/A, even my stock ported intake crapped out at 5800rpm. Engine dyno proven! It is all about the combination and not just slapping parts together. Plan it all out (bore, stroke, gasket thickness, cc's of the heads, pistons, etc...) And then you should be fine.

On the other hand, it sounds like you know enough to be dangerous!!!

 

[Frankster]

Pulled the oil pan.

Looks like the 3'rd rod back from the front of the engine is the culprit (not sure what cylinder that is, yet).

The bearing is completely gone. I can move the rod back and forth almost 1/4 inch. Amazing that it held together.

The engine did spend allot of time at extended revs on the race track in the hot desert heat.

Guess I'll have to take a close look at the stock oiling system.

Any thoughts a high pressure, high volume oil pumps? From some of the posts I'm reading the later engines run high pressures.

Any thoughs on salvaging the crank? Or has it been pounded too much to be considered reliable?

 

[Joseph Dell]

Pulled the oil pan.

Looks like the 3'rd rod back from the front of the engine is the culprit (not sure what cylinder that is, yet).

The bearing is completely gone. I can move the rod back and forth almost 1/4 inch. Amazing that it held together.

The engine did spend allot of time at extended revs on the race track in the hot desert heat.

Guess I'll have to take a close look at the stock oiling system.

Any thoughts a high pressure, high volume oil pumps? From some of the posts I'm reading the later engines run high pressures.

Any thoughs on salvaging the crank? Or has it been pounded too much to be considered reliable?

The crank can be machined depending on how much damage there is. .020 or .030 is pretty normal for crank cleanup. On this coast out here it is just a few hundred $$$'s to clean it up.

stock oiling system stinks. the only other choice is a dry-sump (for the most part). expect to spend 4k + lines + tank if you go that route.

3rd rod back from the front is the #3 rod... the rod that happens to be the one that normally fails on a viper that has been driven hard, even in stock form.

 

[plumcrazy]

definitely go with a billet crank. especially if you're gonna spin it as high as you say you want to.

but listen to this dell character, he knows what he speaks.....

 

[Frankster]

Joe
I was thinking along the lines you suggest (that this is a rod with a high failure rate).

Is it because of oiling issues or is there a crankshaft harmonic causing it?

 

[Joseph Dell]

Joe
I was thinking along the lines you suggest (that this is a rod with a high failure rate).

Is it because of oiling issues or is there a crankshaft harmonic causing it?

Do a search on this forum for "spun rod bearing". #3 comes up all the time. It is the oiling. and the stock oil pump stinks.

I'll give you a dollar if you call me Joseph instead of Joe.

 

[Frankster]

Joseph (Sorry bout that)

I looked up "spun rod bearing" and indeed there were numerous posts about spinning the 3/4 rod journal bearings.

So then oil cavitation and oil pressure loss can be cured with a dry sump system, but what about the 3/4 journal being the last combo to get oil? Have you heard about grooved bearings being used? What's your opinion on using them?

 

[Joseph Dell]

Joseph (Sorry bout that)

I looked up "spun rod bearing" and indeed there were numerous posts about spinning the 3/4 rod journal bearings.

So then oil cavitation and oil pressure loss can be cured with a dry sump system, but what about the 3/4 journal being the last combo to get oil? Have you heard about grooved bearings being used? What's your opinion on using them?

There are numerous ways to address the oiling. Some well-known tuners cross-drill the crank. I'm not a fan of it, however. There are other tips and tricks on how to do it which i can't publish on-line. Talk to your engine builder if you have one. Mitech race engines is in your coast... talk to Mike there, for example.