I thought some of you guys might have an interest in a 403 CID LS2 build I was recently involved in that just may fit the bill for some of you looking for more power but not wanting to sacrifice alot of drivability to get it....it can be done...it just takes $$$ and the right combination.

It started back in last August....just another phone call with a potential customer discussing AFR heads and his wanting to build an engine that really placed on emphasis on usable power, but something that would also make enough grunt to propel his 4000 lb GTO to a respectable time slip when he and his wife occasionally take it to the track.

Fast foward five months....Roy decides to allow me to build his GTO dream engine with the goals being set forth mandating a combination that had "stock like" perfect driving manners (his wife drives it more than him) and a powercurve that has tons of usable torque and really focus's on area under the curve. Roy was looking for huge grunt in the lower and middle part of his powercurve....the area which accounts for most of your driving conditions....not just WOT. Peak HP would actually be secondary (no dyno queen with this combination), but I had a hunch with the right selection of parts and completely optimizing every component and clearance in the build, making good power would still be possible.

I told Roy going in that with a very optimized build and the 402/403 CID we had already agreed on building that I was hoping for an engine that would ultimately produce close to 550 ft/lbs, generate at least 500 of that at an early RPM where it could be appreciated every day, and hopefully knock down close to 575 HP at the same time. Also, like some of you, Roy had overcammed a few of his other projects and he was adament on not doing the same here which obviously makes producing a big HP number a lot more challenging. A "smoother" idle was also the order of the day.

Here's a quick rundown of the parts (and a few extra machining op's) which helped us achieve the numbers we did...

LS2 Block honed .005 oversize with TQ plate and ARP head studs (hence the 403 CID displacment....not a 402)

Premium rotating assembly which consisted of a Dragon Slayer Callies Crank, Callies Comp Star rods, and Diamond pistons (which were also hard-coated as well).

ATI Harmonic Balancer

Painstaking time spent on shortblock clearances including bearings, piston to wall, ring end gaps, cylinder wall finish, etc., etc. I bring this up because it will have an outcome on the total power produced.

Static CR was kept at only 11.25 to 1 with a quench distance of .031 (pistons .010 out of the hole.....041 thick Felpro Head gaskets).

Ported GM Hi Perf Oil pump

Comp Custom ground cam 232 / 232 on a 114 LSA +1 (113 ICL)

GM Cadillac Racing lifters set to .100 pre-load.

AFR 205 Heads with reworked chambers to take advantage of the larger bore and light porting on intake and exhaust (minimal increase in cross section). Killer "area under the curve" gains with the mods performed allowing alot more average air to enter the cylinder on each gulp....especially useful at higher RPM's when the engine has only a tiny fraction of a second to fill the cylinders....none of the airspeed was reduced, in fact increased due to all the additional airflow passing thru essentially the same size hole....a very lethal combination. I have included the actual flow number down below the dyno charts.

FAST 90 ported as well as a ported NW billet TB

Yella Terra "Ultra-lite" shaft rockers 1.7 ratio

QTP 1.75 headers which made the same power and ten more ft/lbs of TQ over a conventional dyno header at 3000 RPM's.

That covers some of the quick basics....I'm sure a few more facts and figures may find its way to you over the course of the thread.

We dyno'ed this engine a little over a week ago at the same facility (Westech) I have tested all of my personal engine builds you guys are familiar with (the 346 and more recently my solid roller 383). Needless to say we were all very pleased with the results....

The engine idled almost stock like at 850 RPM where it was producing about 14.5" of engine vacuum. What I thought would be a light lope was barely audible....(in hindsight I might have bumped the cam a couple of degrees....the engine was even smoother than I expected). The curve was about as pretty as I could have hoped and looked like this....



Here is all the data in chart form where it is easier to see at a glance the TQ and power this engine produced...



And here is the flow information from the reworked 205's....again noting that most of the serious work was performed in the chambers and the rest of it assuring that the ports perfectly copied the prototype there were copied from.



Last but not least a quick video of some of the last few pulls we made with this engine....the original video was a little clearer but due to keeping the vid a reasonable file size its a bit compressed. If your computer has a small subwoofer you may note the engine idling smooth in the background between the two pulls you see featured....

Enjoy!

http://www.youtube.com/watch?v=OHXJx5MXlIk

Look foward to seeing the actual results in Roy's GTO.....unfortunately its an A4 car so we wont see any hero numbers on the chassis dyno but you can rest assure this car should run pretty well at the track....while I know Roy would have been thrilled to run low 12's on moter (about what his former combination ran on spray), I have a sneaking suspicion his car may crack into the 11's assuming decent traction at a reasonable D/A....

Catch you guys later....
Tony Mamo

 

Nice..
What is the right combo $$$ wise.

 

This exact combination left no stone unturned and would be expensive to duplicate...there may have even been a few small items I forgot to even mention. Lets just say the parts and machine work alone would easily get you close to 12-13K (no engine assembly labor included).

Anyone who has seriously priced (or purchased) a combination of this caliber with all the bells and whistles could vouch....there are also thousands in extra's not typical here or "required" but make no mistake about the fact they helped the end results which speak for themselves and is worth the price of admission to someone truly looking for the have your cake and eat it to scenario. Alot of the mods we spent extra coin on also add to the reliability as well. I built this engine as if it were my own (selecting the parts and extra machining op's) and I have to thank Roy for allowing me the creativity to do so....it was a really cool project that slightly exceeded my expectations when the smoke cleared from the dyno cell....

Tony M.

 

Awsome Tony!! I am happy with the combo you helped me with not exact but very similar. The only thing left Id like to do is swap out the headers and let you rework the heads a little.

 

I can't wait to post up my 403 L92 #'s!!!! Those are nice #'s you have!

 

Great post thanks for sharing. if anyone can make a mild mannered monster its you!

 

Awesome

 

Very Nice!

 

Please post the chassis dyno numbers when you get them. There's so much speculation about how much loss there is on a higher HP configuration. This is the perfect apples-to-apples comparison.

The QTP header information was interesting, too. Made me feel a little better about my headers.

 

Any chassis dyno numbers yet?

 

 

Not yet....but I hear the engine is in the car and finally running.

I think in a few weeks we will finally have some data back.

Not expecting hero numbers thru the A4 and aftermarket converter but mid 400's or thereabouts would be nice. It's always a crap shoot dyno'ing a car with an auto trans....some are just alot more efficient than others. The kicker will be the RWTQ which should be close to the same figure as the HP (or a little less) and the very usable power curve bringing most of the big power early right where a primarily street driven heavy GTO needs it the most.

Stay tuned....

Tony M.

 

 

 

There's nothing like driving a - drives like stock - torque beast. My mild build LS2/L92 403 makes 380 RWT at 2200RPM and hits 500RWHP at 6k. I drive it around like an automatic. Stick it in 6th and cruise.

Well done!