Finally spent some extended time on the highway....but there are questions

Had the opportunity to visit some old friends around Dallas this holiday weekend - and put 450 miles of highway driving on the car. Although I put about 2,900 miles on the car doing shorter trips, I never really found a reason to take a nice high-speed run - as opposed to touring.

Jumped on I35 and spent about three hours at 70 - 80 miles per hour. (I know the speedometer reads a little low - at least according to the GPS.) Questions:

1) At 75 mph the tach reads around 3,700 rpm. Does this make sense? The mechanic I use told me it should be around 3,200 if the car truly has the freeway flyer / 3.88 transmission. (In any event, 98% of the 450 miles was at this speed.)

2) Will maintaining this level of rpm for an extended time hurt the engine at all? Should I vary the speed somewhat?

3) The mileage was around 30 mpg. This isn't any better or worse than around town (unless I'm trying to play around like I stole it - shade of Cory and his most recent video posts.....) Is this normal?

4) Finally, my gas gauge red lines empty and the tank only takes about 8.5 gallons to fill. Is it possible the gauge is screwed up or are some of the Vintage tanks that small. Maybe I should just take a gallon jug with me some time and let it run out, so I really know how much the tank takes?

Thanks for the help!

At that speed and RPM your transaxle has a 1 to 1 final drive ratio, just like stock. (Usually a Freeway Flyer has either the 3:88 R&P or a Bus fourth in order to drop the RPM down somewhat.)

You should always vary the RPM in an air cooled engine, the same speed/RPM over a long distance will over heat the engine. Is that RPM OK for an extended period? Depends upon the internals and valve train. Certainly not good for a stocker, or a small high performance miil built with stock valve train components.

MPG varies with every driver and engine, but 30MPG is probably around average.

The repro tanks are usually smaller than stock, although you can find a stock sized tank if you search around a bit.

I THINK anyway . . .

I'll agree with what TC said on all counts. Who built the transmission, any idea?

Post your tire size and the ratio of your 4th gear and I'll give you RPM's vs speed calculations.

Here's an example. If you're using 165 x 15 tires and have the common .89 4th gear, 3,700 RPM's equals 76 MPH If you have 205/60/15 tires, the speed would be 78 MPH

If this helps you any, my VS was also ordered with a 3.88; the other day I was doing 65 mph at around 3,500 rpm's. My tire sizes are the stock 165 SR-15's. With respect to the mileage I'd say 30 mpg is very respectable. And yes, the tanks on VS's are kind of small; a couple of folks here have replaced them with larger tanks from JC Whitney; do a search and you'll find the posts.

Thanks to all for the replies.

According to the build sheet, the transmission was a "rebuilt" as provided by Vintage Speedsters - with the 3.88. The next time I have the car in the shop I'll have the R&P pulled to check it out and get more information on the tranny. I think it's a real easy swap if necessary - right?

Based upon the concensus, sounds like I may have the stock gears - but we'll see.

The tires are the standard 165 X 15's.

At this point I'll have to live with the smaller tank. Even though I live in the middle of this great country - we still have gas stations within 50 miles, in most cases. (Plus at my age stopping every 100 miles or so for a comfort break has now become a requirement.)

Cal -

Didn't it feel GREAT to experience the wind and road noise at speed (whatever the RPM) in your top-down Speedy on the highway? That's what driving these cars is ALL ABOUT!!

Here's wishing you many more miles of safe open highway cruising!

Peace - Out!

Cal, Unfortunately, your mechanic is dead wrong. With a stock 4th gear (.89) and a ring and pinion consisting of 3.88 to 1 and 165 tires, your RPM's vs MPH is accurate. The example I posted above is correct. In order to achieve 3,200 RPM's at 75MPH with your trans ratio's you'd need 215/75/15 tires.

If you had less RPM's you run the risk of overheating the engine. The faster you go, the more cooling you need.

In closing, removing the Ring and Pinion is labor intensive.

I agree with Larry; even though it may seem that these cars need lower gearing when driving in the highway, the truth is they need the rpms to cool properly.

I am truly happy that I brought up the subject(s) - I think it may have saved me a bunch of issues (and dollars) later on.

First of all, the normal driving I expect to do with the car won't be several hundred miles on an interstate (unless Jim Ward decides to undertake another road trip in the future, invites some of us locals, and I find time to tag along).

Secondly, it sounds like I have the appropriate gearing.

Next, I'll be sure to run by any recommendations provided by the mechanic past the SOC folks before I commit to anything.

Finally, sitting in the speedster on a glorious mid-70's day with Bocelli cranked up (by the way, the car handled great at speed - I just wish my face didn't flap some of the time...), was more fun than an old guy should have....

Thanks, again, to all!
Cal

Cal, when I get through this recovery (hopefully by Feb.) we will get together with Justin and his Dad for a run. (P-mail coming and thanks for the card, neighbor. I may call after we get through a few tests this and next week).

Your trip to Big D sounds like it was fun and the weather was perfect. The music selection is perfect for a drive.

I installed a larger tank in Justin's VS when I owned it(see Knowledge section). It does make a big difference on the longer trips.... not so much in how long of legs you (we) drive, but the hassle of pumping fuel so often and at places that may not be our first choice.

Maybe a fun Trip would be to meet with the North Texas Tub Club in Bedford for breakfast on a Saturday and then take a tour of Zim's Autotek just across 183 (Airport Freeway). I joined the club this Fall and am wanting to get down there to meet with the members. It would be an easy drive and a chance to check out some steel.

Also, you and Justin might consider a drive to Vancouver in July. Yeah, it's a long ways, but just consider it about 68 short local trips, lol. IMs BBQ will be in early July and I'm sure we can make pit stops at some owners places along the way. Think about stopping at the Salt Flats to catch some land speed cars and bikes along the way. Owners of all types are invited to the BBQ and I believe Ron Leonard, Rick Davis, Bruce Gordon, Henry Resiner and others are planning a fun event, including a tour through the BC Rockies.

Jim and Cal, I am definitly up for a cruise sometime. I would be willing to brave the elements too. As for Canada, I would love to mae the trip, but the wife is graduating from post grad school this summer. The salt flats sound like an awesome experience.

Jim - it's really good to hear from you. The north Texas trip sounds like a very real possibility as long as the weather cooperates, it's 27 degrees out right now! As far as the trip in July, it would be great, but I'm certain my vacation allotment won't handle it - but a shorter version or partial trek up when you leave/return could be possible. I have a daughter in Colorado Springs that could probably put you/us up on one of the legs as well.

Keep getting better buddy - I look forward to hitting the road with you!