I have been through the archives and noticed, if you flip the H gearset it will give about .56 for the final drive.

For fuel economy, this would be great for freeway driving( I'm sure this has been talked about before but I couldn't find the thread).

At 65mph my engine spins 3400rpm. now, I know if it spins too low in rpm's there are heating issues.

so what is the minimum rpm at highway speeds the engine could turn without causing issues?

I like 3000 RPM minimum. Too low and you have no grunt to make a move quickly, not to mention the overheating problem.

beat I can figure is, with a flipped H gearset with a final drive of .56 @ 65mph I will be in the 3000rpm range. The 1.7 peak torque runs abour 87ft. lbs @ 2700. That will still keep me in the ball park of safe.

Does this sound about right?

lugging is not only rpm dependent, but load dependent.

cruising at 1500 rpm isn't lugging the engine, if you are putting little load on it.

True,

I'm wondering if the flipped H gear setup will work or if it will pull the engine rpm's down too low at highway speeds.

The stock gearing gives you a little over 70 mph at 3000 RPM. That's with stock tires or tires of equal to stock diameter. Empirical test way back when show that gives the best gas mileage, too. The Cap'n

Thanks Cap'n, I have 60 series tires so the rpm's are higher

I would like to keep it around 3k.

Am I reading it right about the flipped H gearset giving .56 final drive?

i think 3000 is a little low but probably fine for cruising - i think that a type4 can cruise all day long at 3800 or so, too. my question is at what temp would the engine be at after an hour of steady cruising at 3000 vs 3800 ????? jim

Unless you are going uphill on the highway your car really needs very little power (so its almost like coasting) to maintain speed to I think you should be fine.

If you are really concerned about temperatures, you should install a CHT gauge.

I will have a CHT gauge installed.

I am hoping for 35mpg from this motor. I have the Raby 9550 cam and with the inj. mod and MS I should get it. Lower highway rpm will help also.

I just took the tranny apart because 2nd gear was getting difficult to get into. Now that it's open I can change things.

I just want to make shure I will be going in the right direction with the gearing

Just drive faster to avoid lugging the engine!

ask Jake about where his cam is most efficient. my car lives at 4k all day and gives 34 mpg at that rpm. SD to Lancaster trying to keep up with Herb M's truck

keith

we got a great deal on e-bay for a real nice westach duel CHT for kennys new motor. its 2.125", it'll really be a nice addition to his gauges. the way you can dig in anylize i think you'd really benifit from a cht! hows the engine and injection system coming? i am interested in the eficientcy rpm range for the 9550 too. yours of course is a bit different than ours will be?...

mike

Good idea, I was reading about Jakes super 2L and he runs that engine on the peak of the torque curve and highway speeds. i thought i might try the same with this engine.

What engine is in your car?

My old motor with the big cam loved to run 3400 RPM for best cooling and 29 MPG.
I got slightly better MPG after the wing and splitter.

Head temps were always my guide. can't afford Exhaust temps gauge. YET

i need some "schoolin'" in reading EGT's. what exactly are you looking for and can/or does it tie into CHT's

MIKE

I'm not sure what good EGT's are yet. McMark installed a EGT gauge recently, he would have a better idea.

Also a great Q for Jake. I think there is some EGT info on his site. I have a freind who is a Ford mech/ tach, he say's, about 400* @ idle

I have a Dakota digital CHT gauge that will be installed.

The motor is going a bit slow. It's together and there are a few things left to do on the wire harness.

I also took the tranny apart to fix a second gear shifting prob.

I hope to have it in in about a month, Duck seson is slowing things down