I'm throwing this out to get some thoughts from guys who have run this combination before to get your feelings on how well it will perform on the street. I have a '60 283 in that was gone through and left to set for some time. I pulled it down and cleaned it up, (it was really clean already), and checked it out pretty well. I'm going to throw new rod and main bearings in just as a precaution. I have a set of 462 casting, double hump heads with 1.94 valves that are fresh with hardened seats. Also, I have a Comp Cams repro of the old 327/350hp Chevy cam and hydralics, all new along with the double roller chain. I'm using one of Bubbas point style distributors and a Melling high volume oil pump. The intake is an Edelbrock dual plane with two 94 Holleys, one primary and a secondary on a progressive linkage. All this is mated to a 78case Ford box with '48gears and a 7222 tower, (bacically what everybody calls a '39 Ford box). This goes to a '48 Merc rear shortened to fit my Model A chassis. The rear has 3.78 gears and I have some concerns. Your thoughts on...... How well will this combination run on the interstates, 65mph? Will the 3.78 gears just plain suck on a longer run? once or twice a year. Should I be running a different carb setup? Anything else I should think about? This is a fairly light car. I've been following Andregg roadster's thread and now I'm a little concerned.
Just run as TALL a tire as you can I had a warmed up 283 ( plus .060 ) in a 40 Ford coupe with the same rear end. I had 29 inch tall tires and drove it most anywhere I wanted to. At 70 MPH the little 283 was getting busy ... but never had any issues. With a 31 inch tire ... 70 MPH should be fairly easy on the SBC. A 3.54 ( from a Mercury ) or aftermarket ... would be BETTER
A 3.78 gear and a 283 will highway just fine at 65-70 MPH, its not going to be Ideal but its not going to hurt it either
RPM formula is: (mph x gear ratio x 336) divided by tire diameter in inches. So 70 mph x 3.78 x 336 divided by 31" = 2868 rpm. Enter different values depending on gear ratio and tire diameter. My Roadster with a Columbia rear axle is 3.78 and 2.72, so 70 mph in overdrive is 2064 rpm with a 31" rear tire.
Thanks guys. My biggest concern is the gearing. It should be nice around town but definitly will be tough on the way to Wildwood. I'm going to have to change those cogs. Like most people these days I'm pinching every nickel on this build and keeping what I can.
The heads are 1.94, small intake heads. They work fine on a 283 as opposed to the more common 2.02 heads which whack the bores. Also the cam is pretty mild actually and should pose no threat to the pistons. I think most of my internals are pretty compatable. I've never used the two carb setup and have my concerns. Obviously a four barrel would be vastly superior but not look near as cool. I will need to change those gears and probably limit how much I drive it, but what miles I put on will be fun!
The gear ratio may be ok, may not be ok, kinda depends on your preferences. In the old days 3.7x gears were "highway gears", compared to the 4.something gears that you ran if you wanted to win any drag races.
With your cam your 283 isn't going to want to run until you get it revved up anyway. It should really like running in the 2800 to 3200 rpm range. That is about what you are going to be turning @ 70 with anything over a 28" tire and that gear. You should cruise just fine.
I personally think the taller gear will allow you to drive it more, especially if $$ are a concern like the rest of us squeaking by. Youre in 1st 1% of the time 2nd 2% and high the other 97....so enjoy maybe a bit better mileage (maybe) and a bit of peace of mind with a few less revs....good luck. Ps really interested to see how you like your cam choice
If you run a 30" or 31" tire no problem. Just to give you an idea the standard ratio for Vettes in the 60's was 3.70 and they used a tire that was about 27.5 inches.
I'd like to run the 3.78s because it will save me a ton of time on the rear, basically I can just bolt it in and run, but the 3.54s are going to be a bit nicer no doubt. I'm going to try to have this on the road and running for Fall Wildwood. After that I can tear it down and have the whole winter to make it right. SneakyPete made it down last year, (barely!), with 4.11s in the GTO. I won't be quite that bad off and I can take my time and run with the flathead cars, Fryguy, YankeeDave and Hardtop57's sportcoupe, so I won't be pushing it. Some of the guys think there's points for early arrival. Time to assemble! Thanks guys.
That should work ok the way you plan on using it. The 283 I had in my T bucket and then put in the 48 ran at 3000 rpm at 80mph in the truck and loved it. That was with an M21 Muncie and I have no idea what gear rear end with N-50-14 rear tires on it.
My rear tires are L-78 15 with about a 30" diameter. That should put me right in there. I'm so used to my family truckster turning 1500 at 80mph I forget how high you can wind these old Chevys.
Koz, there's an easy fix for this, Quick change rear! Run the 3.78's during the summer short trip then when Wildwood nears, swap in the 3.54's for the run. Heck take the 3.78's with you swap them out once we get to Wildwood. Fryguy
Totally out of character for me, the reason for this dissertation is I'm trying to build this as inexpensivly as I can. (Kinda' leaves out a quickie). I'm getting tired of building something and selling it for half of what the parts cost. I can rather easily change gears myself but the gears and bearings are in the neighborhood of $800! The car will still be worth maybe 10G's, maybe less, no matter how well it's built. Over the years I've come to accept that sooner or later sombody is gonna want money and I'll sell the car. Maybe the solution is to change my line of work not my building habits? Actually, I know the 3.54 gears are near ideal. The set under your roadster is almost perfect. You could probably use a little more cam in the 283 which would help on the open road. If your running at 2000 rpm and punch it there isn't much room to head upstairs. I know I can make the shore with the 3.78 ratio, I'll just chew a little more fuel. Big deal. It will be a bit more snappy around town. In my build thread on the Goons site I origionally talkked about running the Rodsville center with 3.08/4.11 gears as an ideal. I since sold the center to a customer and decided to use the Merc rear as a cheap alternative. A lot of Mercs, particularly western cars had 3.54's from the factory. Too bad this one isn't one of 'em. It'll be an acceptable compromise and I can always change it over the winter if I want.
If my calculations are correct I should be just a hair under 9.5-1 with the copper head gaskets I'm using. I could bump it up a hair with steel gaskets but that would probably be a bad call. I think that is near ideal on the street. Anything more and I have isssues with detonation etc. I've built at least a half dozen cars using this combination in one form or another. The variable here is the gear ratio. I usually run the 3.54's which are easy to get, (Speedway, Getz gears). Fryguy uses this combination in his roadster and is right, it tends to be a little unresponsive on the open road. Actually after thinking about some of the comments in this thread, in particular Narlee's post, I think I may have been a little off base in the past and the 3.78 might be a good call. Also I've never run the 2x2 setup. I know a four barrel would be better but the twins will just be too cool. When I get it on the road I'll see if Fryguy and I can switch hit on the way to the shore or something which will tell me which gearing is right since they're both similar cars and weights. If possible before I throw the clutch together I might use an aluminum flywheel in such a light car which would wind up a lot quicker. I have one left over from my red roadster. It didn't seem to make that much difference but the '38 was a heavier car.
The 283 with Fuelie heads ( the first "F.I." heads were on the early 60's F.I. 283 and Vettes had 1.94/1.50 valves NOT 2.02's ) and 350HP L-79 cam was a VERY common combination in the late 60's on through the 70's and works great in a light car with a stick and 3.70 or so gears. You aren't going to see much mileage difference with a 3.54 vs. a 3.78, if anything mileage could potentially be a little worse with the 3.54's behind that combo. It's going to want to turn some RPM to be at it's best. When I was a kid 3.73's were considered tall you didn't have "low" gears until you got into the 4's or 5's. I know times have changed but you'll be fine.
As has been said before, your 283 will have no problem with those gears. I actually think it will be happier with the shorter gear. I know of guys years ago with early 283 Vettes running 4.11's getting close to 20MPG on trips. Look at the extra gas money on the trip to Wildwood as having more fun than spending it on a ride on the roller coaster!
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