knock knock

[Dr.Jass]

I long considered the prospect of using Mopar Performace Super 60 parts on a 273, way back when the Super 60 stuff was readily available. I would think the fuel/spark mapping would be pretty close, since a 273 is size-wise very close to two 2.2L engines. The only trick (and it's not much of one, really) would've been convincing the ECM to fire twice as often. Considering the full-boat Super 60 package made for a 300HP 2.2L, I would imagine you'd be within a reasonable +/- margin of doubling that number with the smallest LA engine using similar cam timing worked to the V8's advantage. The Super 60 cam was pretty mild, too, meaning off-boost you'd have a reasonably economical engine.

That being said, I wouldn't attempt it with the puny stock 273/early 318 connecting rods, which are part of the reason 273s are so willing to wind--its pistons and rods are very light. Those dinky rods would never live at that kind of output.

 

[Dr.Jass]

that IS the exception to the rule...but as i recall...with your speficis it was oddly better on smaller cubes but only maginaly?

From the endless simulations I've run, for some reason on the boosted applications it seemed the shorter stroke engines work better. I have no idea why that is, but the flip side to that is that with the better off-boost torque of the 360 you'd probably end up with a better overall combination. Better pull out of the hole pre-boost and more usable torque in everyday driving would probably offset the rip-your-head-off higher level power gains. It'd probably be quicker in the quarter, too.

Just to clarify, by the way: the 372 (373) is not a stroker engine. It's a 4.070" bore with a stock 360 stroke @ 3.58". Putting a factory 360 crank into a 340 isn't advisable. The aftermarket has stepped up to make such a crank available but I question its value since all you're getting is a slightly-large-bore 360 when all's said & done.

 

[69.5CUDA]

i think that was my take on your turbo build too..the torque of the 360 would take up the turbo lag

considering the 2.2/2.5 turbos used race desgined rods....thats where they made up for the boostability.....but...i cant help but wonder what a 273 rod looks like compared to a 2.5 rod....hmm would a 340 rod work on a 273?

 

[Dr.Jass]

The main reason I'm ultimately going with a 318 is economy. Less cubes = less to feed, and the plan is that the turbocharged engine will be docile enough for daily-driver use and get 20+MPG. We'll see, I guess.

The 273/early 318 rod is tiny compared to a 2.2L rod. The 273 rods look like twigs. Seriously, they're really small. The later 318 ('71-up) and all 360 rods will work in a 273, and they're all the same forging as a 340. The only difference is that the 340's small end was reamed and bushed for full-floating pins. The late 318 and all 360 rods have press-fit pins but can be reamed for the full-floater bushings, and virtually all aftermarket pistons not only have the grooves for the circlips, but the circlips usually come in the box (my Wiseco forged 318 pistons did).

 

[69.5CUDA]

ive had the rods in my hands a few times..and yeah they are a bit skinny...hmm ive got some 73 318 rods with trw 10:5's around somewhere...those rods in a 273 with a pair of S60s oh yeah baby....if it was setup to wastefire....and was driving 2 coil packs...problem solved

 

[Dr.Jass]

Well, you can't make the 10.5:1s fit, but that's not really an issue since the static compression's too high. Bleeding off cylinder pressure via the camshaft isn't an option, either, since that would very negatively affect your turbochargers.

Firing two coil packs in waste fire wouldn't work either. You'd need four (assuming two plug terminals each) and have to fire each of them twice for every two revolutions. Even in a wastefire configuration, you still need 4 individual firing events per revolution of the crank rather than 2. However, the solution is even simpler: run the Super 60's ignition trigger wheel directly off the crankshaft. It normally runs at the same speed as the camshaft, which turns at 1/2 crank speed. The crankshaft mount means full engine speed, so twice as many events per rotation. Interestingly enough, this would also solve the issue of firing the injectors, which I believe are batch-fired in the 2.2L MPFI. Boom. Next! Obviously, it's not that simple, since you'd need a custom trigger wheel large enough to fit on the crank and a matching sensor to pick up the pulses, but realistically that's not a tough fabrication job: one piece of flat sheet steel, preferably 14ga, and a very short chunk of large exhaust pipe (5"?) welded to it with notches ground imitating the 2.2L trigger wheel.

Realistically, this configuration would work with the more-common 2.2L Turbo II parts, giving you a probable 350-400HP 273 that would drive better than a stock two-barrel engine with a considerable increase in fuel economy. The only trick to making it work, of course, is having the exact same camshaft lift and timing (especially LSA and center) and running a similar compression ratio, though probably lower with the iron heads. I think you could probably manage that last part by just using a set of open-chamber heads, preferably X/J/308 castings for their superior flow. Wire it all into a stock SMEC for a Turbo II, or if you really want to turn the wick up on it, an MS2 (which would throw half of what I just wrote out the window ).

 

[69.5CUDA]

nah i didnt mean the slugs i ment the rods...funny i have a pair of 2.5 turbos...and a full brain from a stock 89 caravan and harness...the old parts van..aint no super 60 but the same brain setup has been super 60'd before..if you want over 14psi of boost you have to fool the brain..again ..easy

as far as the cam goes..."if" one had the specs of the 2.2/5 cam profiles ive got a cam place neer me who does custom cams for fairly cheep...and yeah dropping a set of J heads would be OBVIOUS not just for flow..but for compression drop too

maybe ill have to build such a beast..i do have a spare 273

 

[69dart340]

I know the super 60 specs were 260/260 adv, 218/218 @.050", .499" lift, 112 lobe separation, 112 intake centerline