6.5 Chev conversion questions for Bilbo

Mine was a PITA with too many revs at cruise speed. The 6.5 is not relaxed at those revs. I'd prefer 1,800 RPM at 110kmh.

Greg,

I got your email. I've just been a bit busy with my social calendar - mainly drinking beer and yakkin'! It's not east being retired!

I run 285/75/16 tyres - they were on the truck when I bought it and I'm not obsessed with tyres, I'm more obsessed with wallet. So "Black, round, holds air in" will do me.

I run 3.9 diifs which I find just about right for round town driving as long you don't mind using only 3 gears in the 5 speed box and it's about right to keep the 2 tonne van going uphill without the speed dropping off top much. Anything lower and the engine would revving too high to be optimal. You could go higher but I wouldn't. It'd be a tad too high for slow bush work and GOD FORBID you may even have to use LOW RANGE when trolling through the scrub just to slow it down!!

Scotty 'n Greg are pretty good at judging these engines and what a customer wants to do with one.

My road speed when towing is 85kmh to 110 kmh. Depends on what mood I'm in. The engine will hold 100 to 110kmh all day long, up hill and down dale. I may have to drop back to 4th for the long hills but 98% of WA hills I do in 5th without too much hassle. I don't drop below 90 kmh when towing uphill. The "towing fuel figures" that you've got reflect that road speed. I don't know Roland Hill or how steep is the gradient. I'm talking about the long hils of the mian arterial roads of WA.

I would hate to call Scotty wrong, although being an ex-dosel mechanic I did catch him out once - but I reckon he's wrong about those 3.54 diff ratios. If it had 3.54 in it those revs wouldn't be that high at that speed. That's my estimate of things using the car speedo/tacho observations and not GPS readings.

Thus, if "it wouldn't go up Roland in 5th or 4th" then Roland Hill must be bloody steep or it was indeed a very tight motor. Mine was extra tight when it was first fitted. It's a different car these days after 16,000 kms since new. Mine's till improving and performs much better than it did when new.

Where is this Roland Hill, I'd like to try it out? Perhaps it is "bloody steep" and you are asking too much of it. I'd like to give it a go.

Your 4.11 ratio is way too low. The engine doesn't need to rev that high to keep it in it's torque band. I reckon (without calculator) you'd be up around 2400 rpm and that's too high and totally unnecessary to hold 90 to 100 kmh without straining or lugging in 5th gear.

From memory, and using non-gps method, I seem to remember it does 2000 rpm at 100 kmh, I'll take it down the freeway and get back to you.

If you want the car for round town, shpooing troley stuff, good towing and bush performance at low RPM go the 3.9 ratio as good all round compromise. I certainly wouldn't go 4.11 unless I was 4WD cross country racing!

Bio-diesel? Scoty may not recommend but I would beg to differ. the 6.5 Chev is a Military Spec engine. That's what they were built for - mainly. As MIL_Spec motor it'll run aon aything from jet fuel (JP% jet Fuel which high quality kero) to cooking oil - as long as it's well filtered.

Diesels, particularly low tech motors such as the Chev will run on aything with no ill effects. Using bio-d however, demands far better filtration of fuel the dino-diesel.

Being a high capacity but relativly low ouput motor for it's capacity, the Chev doesn't suffer the same fuel quality vs perfomance constraints of the newer high tech, diesels. Although, these same, smaller capacity, high tech engines in Europe run bio-d without any issues. Bear in mind that in Germany 45% of the diesel fuel pool is bio-d. We're a bit behind the times here in 'Oz" ;)

With Chev vs a high tech motor, it's a bit like giving a race horse ordinary hay - it'll run but not as well as it should. But the Chev is a big agricultural horse - it'll run on ordinary hay fer years, do it's job without complaining. It's a big, ulgy, cast iron brute of a motor that'll just "DO IT" all day long fer years.

These engines are MIL-Spec and they are designed not only to run on top quality US Military Spec fuel but also to run on whatever the troops can find in any other country ion the world, and not all countrys have the same fuel quality. Some if it in places like outback Kazhakstan is not much better than straight crude oil!!

Using bio-d is topic that is too big for the here and now. I'd use it, no probs, I've used in a TD42 Nissan and the latest IHDT-Fe 100 series TD "Cruiser' with no ill effects.

Hope this helps,

Bilbo - "The tired typist hobbit"

Well, here we go. Greg asked about RPM vs Road Speed. The figures below are as accurate as I can get whilst driving and looking at tiny graduations on the Nissan tacho. They are speedo readings and not GPS corrected.

40kmh - 800 rpm

50kmh - 1000 rpm

80kmh - 1600 rpm

90kmh - 1900 rpm

100kmh - 2050 rpm

105kmh - 2150 rpm

110kmh - 2200 rpm

On reflection I reckon a higher diff ratio would enable me to make use of 1st gear when not towing, whilst giving me better top end fuel economy than I get now.

However, it may detract from the Chevissan's tractability in the slow bush work type towing. It could be a tad too high a gearing for that.

Hmmmmmmm,,,,,,,,,,have to have a think about that one.

Bilbo

Hi Greg, when I had the chevy (6.5ltr) put in my Troopy back in 96 I was told by Scotty & Glen the economical rev range for the Chevy was 2000 rpm. Since I do a lot of long distance travel & like to cruise anywhere between 90 & 110km/hr it was suggested I go for a diff ratio of 3.7 : 1, which ideally puts my cruising speed in the ball park & the diff gears for my Troopy (1990 model) were readilly available off the shelf. I can sit on 110km/hr @ 2000rpm in 5th gear running 235x85R16 rubber. If I'm towing then depending on road conditions I can cruise @ 90km/hr in 4th. gear. Also it gives a nice torgue range in 3rd gear for sand driving. Hope this helps in your decision.