alexb76

Curious if anyone has tried to convert the GT3 RS 3.8 engine to 4.0 spec?

If so, what's involved, costs, etc...

Charles@dundonmotorsports

Crank
Rods
Oil pump
Outer plenums
Lower manifolds
Cylinder heads (sorta)
Cams
Air box
Decklid

It's a lot of money for that slight little change. Labor varrys between shops as does parts suppliers if you don't go all OEM.

My advice

From a 3.8, go to a 105.4-106mm bore. And the crank, lighter steel rods, custom pistons, 4.0 intake or better, our headers/exhaust, our air box, decklid if you want,

Really depends on your end goal and budget.

sccchiii

Call autometrics motorsports in SC. I've driven one of there 4.0L conversions and it's a beast.

The Greek

Curious to see the responses. 4.0L motor is on my radar in the future.

Jamie@dundonmotorsports

Stay tuned... 40R (4.0L) and 42R (4.2L) Ti rods, Ti Valves, solid radiussed cam followers, 2 ring short skirt pistons. Throwing the book at it. Neil at Performance Developments and Dundon Motorsports working on it together. My 4.2L will be the 42R specimen

We offer stages, from mild all bore 4.0L build to Crazy 9000rpm 42R variants... Bottom line is goals and budget.

alexb76

Thanks guys. Mostly interested in using as much OEM as possible.

My previous experiences with mods has been a hit and miss. Problem with most typical aftermarket upgrades is that while it can provide some good gains in a dyno run, it's often NOT very reliable and almost always fail on track days. Hence, curious if it's easy to get to the 4.0 level with as many OEM parts as possible, but it sounds like it maybe too costly.

Charles@dundonmotorsports

More often than not it has to do with the engine builder more than the parts. Anyone can "slap it together" but not knowing all the finite details is what makes it last, especially on the track.

One of my 3.6RS built out to 4.0 is on its 4th track season now. I think It is on about 60hrs right now and still strong, actually going back to the dyno with it soon to compare some other bits for more power soon. Leak down at the 50 hrs track use was still 3-5% when COLD. This engine is setup to run 100% when at full hot opperating temp such as 230-240 coolant and 250 oil temps, not just put it to C&C. Anyone who has tracked with him would say it is strong, solid and beyond bulletproof reliable.

Using OEM parts is not a bad thing or wrong idea, just that there is or can be more out there if you want it, Several shops that have tried to do big engine builds and have failed sometimes go back and do the OEM 4.0 build and leave it at that.

Tom@TPC Racing

We've done it using all OEM parts. Cost depends on current pricing of OEM 4.0 components. Ballpark 40K...

tcsracing1

The cost to take a 3.6 or a 3.8 and push it to 4.0 is expensive.
Especially in CDN dollars. You would want 30k u.s minimum in your jeans to do it.

There is a .1 GT3RS for sale on Rennlist for $140k
It has a Champion $$ built 4.2L that was mirrored from the Manthey RSR.

You could buy that car and be ahead money compared to buying a stock car and converting it to a 4.0L.

FJSeattle

Is it power you are after? Or just to have a fun project?

For example, I am having DMS give my 3.8 more air through the 4.0 Plenum, DMS intake and headers, tune. We are confident this will get us close to 4.0 power without the cost and huge modification.

alexb76

Thanks, I guess one should stick to a reputable shop, and hopefully they know what they're doing so it could stay reliable.

alexb76

Thanks, and overall it works just fine on track with no reliability issues? How do OEM parts compare to aftermarket? Could the same performance/reliability be gained by aftermarket but at a lower cost?

Tom@TPC Racing

1. Works as good as any 997cups with OEM 4.0 in 24-hour racing.
2. No comment since we've not used aftermarket parts for this type of build.
3. No comment since we've not used aftermarket parts for this type of build but I'm sure the reputable engine builders on this forum select the finest aftermarket parts to bring value to their customers.

Charles@dundonmotorsports

The aftermarket stuff you have to get custom parts for top notch reliability and quality, or weed out all the junk. But again most of it comes down to workmanship and knowledge and detail of the builder.

OEM parts are generally easier most of the time because the factory tries to take out all of the user error when assembling. Such as bearing clearances, ring gaps, piston wall clearance machining tolerances, etc etc etc. cleanliness is Another important factory that no one talks about. Engine parts are either -A) clean. Or -B) not clean. There is no gray area, this is one of the biggest areas where failure or early wear on the engine begins.

As for cost, there is no "cheap" engine build. Good parts cost money, good labor costs money, correct prep work and assembly costs more money.

Have a budget in mind, leave about 15-20% extra in reserve as stuff comes up and or you decide to upgrade other bits along the way.

alexb76

Thanks, what do you mean by "cleaniness"?