The Silver Buick's well Silver Buick!

[Scott Liggett]

Re: The Silver Buick's well Silver Buick!

On my second leg of my trip north yesterday, I drove 161 miles at 85 mph which is about 2400 rpm and I got 16.77 mpg.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

Here's the Stat's of the Trip. The GPS was on 99.9% of the time, I might be missing a few miles from turning it on and driving before it locked in plus it was off when I took it in for an alignment and the tech test drove it twice. No major issues, just an alignment (which worked fabulously!) and the alt belt stretched enough to squeak when cold, but I left that alone. If I'm not too hung over in the morning I'll write up more about the trip.

[milner351]

Re: The Silver Buick's well Silver Buick!

Nicely done Randal - You've got to feel good about proving out all the work you did with a long cruise - and no break downs... well done indeed.

So - what gear were you in when you hit 99mph? do you recall the rpm? That might give you a good data point to extrapolate from and estimate your top speed at a land speed event.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

Thanks John. I didn't look at the rpm, somewhere around 3,500rpm I think in Overdrive. I was loafing along when I set that keeping three Escalades and a new Camaro from tailgating me. I think I'll eventually be re-gearing the axle down to 3.42's or so (currently 3.70's and .64 OD) to bring the cruising rpm down 500rpm.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

Because I'm killing time at work (sundays....) I was checking out ring and pinions. I originally intended on getting 3.42 gears for the car but Jays67 hooked me up with too good a deal to pass up with the 3.70 gears and the carrier that I had to run the 3.70's for at least a while. Now that I've got six or seven thousand miles on the 3.70's I think I definately want to drop them down a bit.

I am thinking between the 3.42's and the original 3.23's that were in there. With the other engine I felt the 3.23's kind of lugged the engine down at 70mph, at ~1850rpm, but with the EFI and computer controlled timing I'm thinking I might pick up some torque at the lower rpm and that become a non-issue. The 3.42's would only bring the rpm up to a shade under 2,000rpm (or 80mph/2100rpm and 80mph/2250rpm).

Now an interesting note on pricing! Looking at Randy's Ring and Pinon site (where I got the bearings and shims, etc) there is surprisingly quite a difference in price between the two sets of gears. The 3.23 gears are $310 :o (http://www.ringpinion.com/ProductDet...px?ProdID=5307) and the 3.42 gears are $230 ??? (http://www.ringpinion.com/ProductDet...px?ProdID=5308) I kinda wonder what gives on the price differences. Their listings for the GM brand gears are pretty much the same price for either ratio.

I'm just kind of window shopping for now, I want to get the EFI done first, but I'll end up with the 3.42's based on price alone when looking at a 100-150rpm cruising difference.

[squirrel]

Re: The Silver Buick's well Silver Buick!

I'd be looking for some used 3.08s

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

I'd be looking for some used 3.08s

That would be sliding it down to just under 1800rpm@70mph and 2000rpm@80mph. I'm not sure I want to go that low at 70mph. The first gear ratio of my trans is 2.87, not exactly a steep first gear and no converter to build rpm against. Of course if some free gears land on my door step I'm willing to give 'em a try :P ;D

[Scott Liggett]

Re: The Silver Buick's well Silver Buick!

You're an interesting guy. You build a 455, but are really concerned with mpg. I'd go with the 3.42's.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

You're an interesting guy. You build a 455, but are really concerned with mpg. I'd go with the 3.42's.

I figure I could build for MPG and let size worry about the power :P I said early on my ultimate goal would be N/A 400+Hp (450??) and 30mpg. Looks like I'm a long ways off, but I still have lots of options to play with.

[squirrel]

Re: The Silver Buick's well Silver Buick!

I'm just sayin.....that crown vic we had ran 3.08s with a little bitty 280 cube engine, and got 27 on the road. It was quite a bit more aero than your brick, and with that tiny engine it had to run with the throttle open a ways at highway speed, so it was working pretty efficiently.

I did some work on a guy's 57 chevy a few years ago, someone had put a T5 behind the LT1 type engine, and it had 3.70 gears. Not enough overdrive, too much gear, first gear was useless, and I didn't enjoy rowing thru the gears at all. I guess your transmission is quite a bit different than a T5 though.

[Scott Liggett]

Re: The Silver Buick's well Silver Buick!

The EFI can really help the mpg in the cruise mode. You can sure tweak it to be on the ragged edge of lean and not have a problem. Carbs, at best, are just compromises. Tune em for mpg or tune em for hp. Insanely hard to do both with any accuracy especially in your neighborhood and severe altitude changes every time you hit the road. My primary jets are on the lean side with my Holley. That's fine, but the engine really doesn't like going over 3500 rpm without the secondaries open. I can even hear how it changes it exhaust note. I think if I push it over 4500 rpm without the secondaries opened; I will start getting lean out backfiring.

Out of curiosity, what's the gear ratio's in your box?

[squirrel]

Re: The Silver Buick's well Silver Buick!

The neat thing about efi is that you can get the engine to run smoothly at low rpm under load....which is how you get mpg....

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

The ratio's are:

1st: 2.87
2nd: 1.89
3rd: 1.28
4th: 1.00
5th: 0.64
Rev:2.56

[squirrel]

Re: The Silver Buick's well Silver Buick!

That's a pretty hefty overdrive...nice. Although it's also a big rpm drop when you shift into it.

Have you watched the tach on the late model work trucks when you're putting around on level ground?

[Scott Liggett]

Re: The Silver Buick's well Silver Buick!

The ratio's are:

1st: 2.87
2nd: 1.89
3rd: 1.28
4th: 1.00
5th: 0.64
Rev:2.56

Do you have a pretty big rpm drop from first to second? My trans has a 3.06 to 1.82 shift. It's pretty big, but the planned up to 3.73 gears should help a lot. Can you start off in second?