Looking for advice from Mustang Guru's - 1983 GT Re-Build

The two things I see that are "out of line" are 400 hp from that engine, and the weight of the car. First the only true way to get a weight is to put the car on some scales. I just use the local truck stop when needed. I think your going to find the car is heavier than you think. Second while a 302 can make 400hp it is going to be a high rpm power, and 3.27 gears are not going to get it wound up to fast. If your going to build an complete new engine I would suggest some type of stroker. You need crank rods and pistons any way plus you sound like the type that would want good parts so its really not going to cost that much more. As the old saying goes "there is no replacement for displacement." Also I would ditch the F cam. In the cars that I have had experience with, the F cam has been less than thrilling.

For the 400 hp goal I'd go with a 331 or 347 cid, AFR 185s and probably one of the Comp cams Xtreme cams. The 270 if you need to get thru emissions or the 274 if you don't. I'd also go with 3.55 gears as well.

I personally have had real good experience with the Coast High Performance

MadDAWG

Thanks for your thoughts. On the HP issue, that is projected, and I am not sure it will get there. I am trying to keep this car street and emissions capable. To be honest 350 HP is double what it used to be. I thought about the 347 stroker, but decided against that. As for the weight, that was calculated using the weight on the door and then subtracting the difference in weight from the new heads etc. It is only an approximation. So if I am off by a hundred pounds or so, well them I didn't account for all of the chages properly. But in the end, it will be a couple of hundred pounds lighter with the new heads, rear seat delete and all. From what I am being told, the 1983 is several hundred pounds lighter than any of the years after it. So I am not really tied to the 400 HP, it is just a target goal. Realistically, I think we are going to tap out somewhere between 350 and 375. And that is more than enough to get into trouble with.

As for the rear end. Gosh you are right! So I am actually going to step up to the 3.73 gears.

But the thing that I am most curious about is the old engine. Is it really junk or could it be re-built? The 306 is a completely new motor. My crazy thought is to have a second motor. One that does not have to worry about emmisions. I have this idea in the back of my head to do a little driving in the Silver State Classic. So I would use the old engine on steroids for that and use the 306 as the 'Daily Driver'. Again I may be nuts!

Thanks for the help!

David

Side-impact door beams were introduced in 1959. My '82 has them.

That isn't to say that a FOX chassis car is as safe as any car produced in the past 10 years.

Another bit of information.....

In changing the rear end, the shop wants to migrate me to a late model version (SN95). I was told that this would fit in my early fox body, but others have said it will not. The other thing involves the number of splines. I beleive they are using a late model Cobra rear end. Would that be a 31 spline setup from the factory?

Respectfully,

David Eaton

Do not go by the weight on the door tag. That is not "curb" weight. That is GVW (Gross Vehicle Weight) which is 'curb weight', PLUS all passengers, PLUS all cargo. Curb weight is not listed anywhere on the vehicle. FYI, my 'factory stripper' '83 GT hatchback with its factory longblock (rebuilt to 306 w/ a performance cam and hypereutectic pistons), transmission, rear, interior, T-roof, and non-stock long-tube headers, dual exhaust, and 16" Pony wheels and tires weighed

An F-cam and lifter set (or any other cam and lifter set meant for a 'roller' block) cannot be used in your factory block. Either stick with a flat-tappet cam and lifter set or employ a "retrofit" roller-tappet cam and lifter set for flat-tappet blocks. Or you can employ a 'roller' block and go with your roller-tappet cam of choice.

Okay, I guess I did a poor job of explaining. The new motor that I have purchased is a roller block probe motor at 306 cubic inches. I am trying to figure out what to do with the original block. I have seen a conversion kit on Ford Racing site to make it a roller block. But what I was most concerned about is that the 1983 block is or is not useable in any way, shape or form. I was wondering because I was thinking of making the 83 block into a 347 stroker. I talked to an engine guy toady and he said that there was no problem re-using the old block or making it a roller block. He brought up another interesting point though. For about the same money (+/- $200) we could build me a 408 stroker from a 351 block. So now it becomes the senitmental idea of using my original engine, or get a balls out 408. Luckily, that decision is further down the road.

As for the weight, I am not sure now what to say. I will just have to wait and see how it weighs out. I know the aluminum heads, water pump, intake and radiator combine for approx 200 pound decrease in the weight. Other things are lightening the load like the removal of the A/C system. The condesser and evaporator coils and the compressorr add up to another 50 pounds or so. Now drop the 80 pound rear seat and we have droppeed the weight nearly 400 pounds. So using your car as a guide, I am at 2500-2600 pounds. There may some inaccuarcy here to, I am just explaining where my numbers started to come from. As I will admit, the inital calculations were faulty. So I am interested in seeing where it all ends up!

Respectfully,

David Eaton

I just looked at my SVO catalog and the same rear end is used from 79-98. The 99+ are 1-1/2 inches wider. So you could use the SN95 rear end in yours with no problems.

MadDAWG

By chance is your orignal engine one of those 255s? Ford made them for a few years in the early 80's, but I'm not sure when. They had a smaller bore than a 302, and with the thin wall castings you can't get back out to a 4" bore. I thought they were gone by 83, but I'm not sure. Maybe yours was an early 83 and got a left over one from 82.

As for the 351w setup. More is always better. :) However there are a few drawbacks. There will be more weight up front, and it will sit higher as well. Also its probably not to practicale if your lokking at swaping back and forth because you'll need different exhuast, and front drive brackets. Also you'll most likely need a new hood as well. All that torque is hard on a tranny as well, but it sounds like you should be ok with that.

MadDAWG

Whether or not the block is useable would be up to the machine shop, after it has been checked out thoroughly, to see how much of an overbore it needs, if it needs to be decked and sqaured, align-honed or -bored, etc., etc. But to say that it's not useable just because it's and '83 block, if that's indeed what the machine shop is trying to convey to you, is malarkey. Yes, you can go with a 347 in that block, but you must educate yourself on the positives and negatives of doing that. Same goes for a 408 in a 351W block.

I do believe your weight estimates and totals are a bit liberal. For example, there is no way the rear seat (upper and lower) weighs 80 lbs. Aluminum heads will save about 25 lbs. each over cast iron.

FYI, My '83 GT never had AC. It weighed in at 3160 lbs. with me and a half tank of fuel.

An update for the discussion......

First for MadDawg, it is a true 302 block and not a 255 per your discussion. Also I apprecaite the heads up on the mounting and clearance issues of the 408.

Mick,

Well the weight issue is still a up for final weighing. According to my calculations, the AFR heads are about 40 pounds lighter (each) than the heads that are on the car now. The aluminum radaitor is almost 30 pounds lighter. The rear seat in my car is heavier than a fabric because it is the heavy leather upolstery. Having lifted the seat, I may be off a little but it is about twice as heavy as the 40 pound bags of dog food I toss over my shoulder. These are not what I would call real accurate, but as I said, my initial calculations were not correct. I am hoping to have a dry weight, no gas , no passengers of

Respectfully,

David C. Eaton

So with all of the help, I have started to finalize the project.

First, I am going to stay on target with the 306 and just get what I get as far as horsepower and weight. As for the other block, well I am going to let it go. I thought of making a 331 of a 347 out of it, but in the end, that would be a between engine solution for the road racing. So I am looking for another mustang to build as a pure race car. In that I will be looking at a 351 based engine, most likely a

I am interested in getting a better understanding of the advantages/disadvantages of the stroker engines. I understand that the early strokers wore down on side of the cylinder because of the geometries of the shaft and crank arms. I also have seen that Probe and other companies now have offset crank arms and re-designed pistons so that this is no longer an issue. So what is left in the good versus bad discussion?

Respectfully,

David C. Eaton

Well the results are in. Certified scale says my car weighs 2575 pounds with a few gallons of gas in the tank. So the removal of the seat etc did produce a profound reduction in weight. So now I have a

Respectfully,

David C. Eaton