Some driving impressions of the 3.7 MM sport motor

[Jeff N.]

Have about 280 miles on the new engine. For those of you following, this is a clone of the Metric Mechanic 3.7 "sport" engine. I have the MM ported head and cam and just installed a short block with the 95mm overbore pistons that bump the compression to 10:1.

Here's the bottom line so far. I like it. While it's hard I think to tell the sum of the improvements from having a fresh bottom end vs. the bump in compression and increase in displace, the end result it really good. Is this a tire burning type upgrade? Nope. Not that. But this is the motor that I've wanted to have for a long time.

The car has big time roll on the freeway. 3rd gear pull is stout and the car gets up and really walks away nicely at 75mph. Hit 4th and it just keeps on going. I'm still keeping the revs below about 5200 RPM or so I can't give an upper end report but I'm working it that way. Off cam, where it was really sluggish before, the car is much more driveable. Doesn't have the big torque bulge the stock motor has at 3k RPM but you don't feel like your driving a jekyll and hyde car like it was before. Tip in power is sufficient at 2k RPM and if you want to get up and go, drop it a gear or two to hit 3.5k+ on the tach. There is still some "waiting on the cam" effect from 2.5k to 3.5k, especially when you compare it to say...Martin's car.

As many of these changes have been incremental, it'd be fun to go back and drive a stock 535 now to see how all this plays out side by side.

I think the big question I have right now it where the powerband is situated. By design, the MM cam comes on a 3.7k and keeps going. I'm not sure that where you really want for a city/street car. I'm going to let the motor break in and drive it for a while but there's still a thought in the back of my head to swap the current cam for a schrick 282 which should drop the start of the torque curve down to about 3k. I will have to give kudos to the MM cam in that the car idles dead smooth and runs very well overall. You have no clue the motor's been modded at all idle.

With the new engine, the 3.73 gears in the back feel maybe a little short. I could see a really nice combination being the schrick cam and the 3.64 gears vs the 3.73 gears. Not that I'm complaining mind you!

So...here's the current setup:

10:1 forged pistons, MM variety, with 92 ---> 95 mm overbore.
Stock stroke
Ported head from MM
MM "rally cam", low overlap, high lift and duration about 275 or so??
MM adjustable cam gear, cam at +4 degrees at the moment
Port matched intake
Balanced engine assembly
Racing King (Pro Flow) MAF conversion
19lbs Mustang injectors
Stock exhaust from manifolds back
22lb E28 flywheel with E28 clutch
3.73 LSD (shortened from 3.46 stock gears)
Stock chip

Still to dos

Finish up the break-in
Try tinkering with some other chips to see what happens
Try some g-tech runs to check output
Consider having the flywheel lightened up to about 14lbs or so (should have done that during the motor job...my bad)
Consider installing a wideband o2 sensor (LM-1 kit from Innnovative)
Enjoy the heck out of it!

More reports as things progress.

Cheers!

Jeff

[632 Regal]

Great report Jeff! Do you have the specifications for the MM cam in comparison to the Schrick?

[Jeff N.]

I wish I had some basic information to compare/predict the cam performance.

Jim R. is a bit strange when it comes to discussing his cam. It's a bit like talking to the mad scientist; a bunch of jargon and stuff that likely makes sense if you're a tuner and cam grinder. To me, it's a bit like swahili. Anyways, it's an assymetric grind and he only modifies the intake lobe. Welded up vs. just a grind. Trying to get the lobe centers and overlap and the .050 degrees is a trick. I was going to measure it out when I had the head out of the car but didn't have a good bench to so I could really secure everything.

Schricks have better physical information but I haven't seen a published profile ala (...works with h/c, tuned for peak torque at ... )

Martin has an old stock cam in his garage. I think getting that profiled would be the first item. Then you can measure what you're planning on putting and compare the changes and try to anticipate the impact.

Some days...chevy's are good.

Great report Jeff! Do you have the specifications for the MM cam in comparison to the Schrick?

[Hector]

this is gotta give ya a great sense of accomplishment and satisfaction. I'll be looking forward to your dyno results. Thanks for keeping us posted.

[Paul in NZ]

A guy here in the car club who has what he calls a 3.7 "tourque" engine in his 3.0 csl......can you comment on the difference Jeff?

[Jeff N.]

To get from the 3450 cc (thereabouts) displacement of our motors to 3700 cc's, you overbore the block. He's likely got an E24/8/32/34 M30 and installed the larger pistons (if he's running FI vs carburation).

If you get a chance to ask him, see if you can find out the source of his pistons. Be interested to know that.

From there, you'd have to ask him what else he's done to the head (porting, etc) and what cam he's running.

I can suggest that running a 3.7 engine like mine in a 2800 lb car would be a HUGE AMOUNT OF FUN!! That car would totally fly!

A guy here in the car club who has what he calls a 3.7 "tourque" engine in his 3.0 csl......can you comment on the difference Jeff?

[Maximabello]

As many of these changes have been incremental, it'd be fun to go back and drive a stock 535 now to see how all this plays out side by side.

Thanks again for letting me watch/help! You are welcome to drive my car if you want, stock except for EAT.

Erik

[Ted K]

Thanks again for letting me watch/help! You are welcome to drive my car if you want, stock except for EAT.

Erik

Good write up Jeff.
I am down in Olympia, member of the club here in Puget Sound. Have a stock 90 535 5 speed with EAT chip for ya to check out. We should try to get together some time. Would love to see yours and Martins cars.

[bahnstormer]

how far do u expect to spin the motor after break in? 6500rpm?

also regarding the e28 swap, how much torque can that setup hold?
i'm planning on FI and am considering doing a m5 clutch/flywheel assembly
for greater holding power and then putting the uuc light weight flywheel for
the m5 in there....

[Paul in NZ]

If you get a chance to ask him, see if you can find out the source of his pistons. Be interested to know that.

From there, you'd have to ask him what else he's done to the head (porting, etc) and what cam he's running

I beleive jeff its a full MM job......