How high can I rev my m42 ???

[Danny318]

When its done, of course...

The head will be a fully built stage 2 head from VAC with the fancy dual valve springs and expensive retainers and all of that. It will have some 269/269 cams too.
will also have a .080 MLS gasket to drop the compression a bit.

The bottom end is stock components but will be fully balanced, the rods are being reshaped so they are round where the bearings are and also weight matched. the crank and flywheel and clutch and harmonic balancer are all balanced as well.. The bearings are high quality clevite ones too.

I'll be running megasquirt for everything so I'll be able to tune it well.

What are the weak points in the build, and I know there is no hard number, but what do you think i could set the rev limiter to and be okay?


Also yeah it will have the DASC on there with 7psi of boost.

[rwinter]

Hi

If they converted the lifters to solid, 8k should be ok. My hard rev limit was set a 8200, but I've backed off on it to 8000 to get more life out of the engine. I have also went to a solid crank damper. (so basically no crank damper) Supposedly at least on a E30 vintage the crank damper can fly apart above 7k rpm. For hydraulic lifters, I'm not sure.

How much power are you predicting?

[Danny318]

Unfortunatly I am using hydraulic lifters. Supposedly you need a different cam for solid ones?

I have heard things about the damper, but having mine fully balanced I would think it wouldnt care how fast it was spun as long as it was balanced.


I am hoping for 200hp at the wheels

I was also hoping for 7600-7800 RPMs but perhaps thats too much to hope for.

[Danny318]

BTW what are you using engine management? Full list of mods? nice

[rwinter]

Hi Danny
I'm using a electomotive Tec3 ems for ignition and fuel injection, no air flow sensor. Stock intake manifold and throttle body with 370 injectors. Its got 11:1 compression, solid crank damper of my own design with 20% speed reduction for waterpump and alternator. Stock connecting rods and crank. 1 1/2" custom header tubes to a 3" exhaust. (total overkill exhaust but hey I already had it for the M20 engine I was using before) Solid lifters. I don't have the cam specs but they are full race. Ports were flow benched but porting was minimal due to rules. It dyno'd at 232hp at 7400rpm, 176ft-lbs at 5900rpm. It is not streetable by the way. Not very happy below 4000rpm. Its seen above 9k rpms due to a bad shift (oops) with apparently no issue at all.

I don't know what the limitations of hydraulic lifters are specifically, only that Rebello racing, who built my engine said that they were necessary if I wanted to go to 8000 rpm. The solid lifters cost me $840.

[bmvw]

Don't miss shifts any more with stock rods unless you want to play "piston catch."

[Danny318]

I've never missed a shift so bad that i put it in the wrong gear. I've made it to no gear, but thats no harm.

Maybe I'll have to live with something like 7400, but I'd like to know how high the hydrolic lifters can go before I make up some number and stick to it.

Very nice sounding engine btw? Hows the bottom end, stock or ?

[rwinter]

Actually, I put it in the gear I wanted except that I wasn't going slow enough to downshift yet. Didn't do enough braking before the shift. Excellent way to explode an engine. Lesson learned I hope. Do you think the rods are a time bomb now?

[Danny318]

Originally Posted by rwinter

Actually, I put it in the gear I wanted except that I wasn't going slow enough to downshift yet. Didn't do enough braking before the shift. Excellent way to explode an engine. Lesson learned I hope. Do you think the rods are a time bomb now?

I bet they are just fine.