Re: [Amc-list] Re; Suggested maximum long-term cruise RPM for 195.6OHV?

[Tom Jennings <tomj@xxxxxxx>]

On Wednesday 05 September 2007 18:35:55 John Elle wrote:

OK John, as usual you muddy up the waters with good observations and ideas/ 
Damn you! :-)

> To my way of thinking the way you have asked this question, the answer is a
>
> more based upon the performance curves of the engine than a mechanical
> limitation
> based on bore and stroke.
Oh I agree. I'm not afraid of the engine flying apart but where it's "happy", 
meaning unstressed, modern highway compatible (65mph all day long) and 
good/best mileage. 


> Using your numbers, 2250 
> for 65mph makes it 22.9 mph/1000 rpm which is about where my 1980 Spirit is
> geared at including taking into account the size of the rear tires
> (P245R60-14).

OK I made my spreadsheets calc MPH per 1000 rpm in top gear (all three top 
gears for this car:-)

3rd straight up 20.3 mph/1000
3rd OD             29.0
2nd OD            17.8

> Actually the Spirit and the AMX are taller at about 33 mph/1000 rpm
> That is very tall gearing.

Oh yeah.


> All the I6 engines I have built I have installed a cam shaft in it that can
> be considered a horse power cam, that is it develops horsepower at higher
>rpm's and there for torque peaks are raised also. These engines do not
> go dead at higher rpm's.
>
> My modified 258 cruises quite happily at 3200 rpm and will do so all day.

For some reason my Hornet 258 does really well about 3000, but my 63 classic 
(70 232 in it) goes flat much over 3000 (always did, not just the worn rings 
now). When I bought the 258 longblock from Mr. Rippe, he said that the friend 
he got it from put some cam in it. I had no inexpensive way to check that, so 
I just bolted it in and hoped for the best. I assumed it was stock because it 
idles fine, etc. Maybe it does have a mild cam, as it pulls like a small V8 
on the highway, and seems OK up past 4000 (not being a performance guy, 4000 
rpm sounds like a turbo to me). 

My Classic's 232 pulls fine up to low 3000's then goes flat. In that car, it 
sees that in 2nd, or rarely 1st, under load and about to upshift.



> To my way of thinking, it will be a function of the cam shaft primarily and
> not necessarily a comparison of how happy a 195.6 with twin stick is
> compared to a 4.0 with a 3 speed or a 258 with a torqueflyte. I see that
> as more of an apples and oranges comparison and has very little merit.
>
> Your particular engine will have a "Sweet Spot" so to speak and when
> you find it, the next question to be answered is does it have enough
> power to pull tall gears to obtain a maximum cruising speed with the
> weight of the car in mind or not. Or will you have to short gear it a bit
> to let it climb up the Grape Vine and settle for a less that legal
> speed limit cruising speed on the open road.

Well sure, cam plus the rest of the iron under the hood is stock, so I got 
what I got. Probably I can't beat the factory setup, as they had to know it 
was underpowered even then, and tuned the parts box as best they could. I'll 
probably end up with blackwall 195/17-R15's, 0.69% error from the original 
6.00x15's. That's the skinniest 15" tire I could find as readily available!


> Everything is some form of a trade off.

Yeah, but it's nice when you have something to trade (hp-wise) :-)

Tomorrow I assemble the suspension!

_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://www.amc-list.com/mailman/listinfo/amc-list