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Engine- what to do

2K views 15 replies 15 participants last post by  Woodchuck 
#1 · (Edited)
Hello all,
I am planning to probably replace the rusty cowl on my 1970 Mustang this winter, for which the engine will have to come out. It is a 2 barrel 302, the original engine I believe, though I haven't checked. I don't know if it's been rebuilt, but it runs strong, doesn't smoke, doesn't leak, and doesn't seem to burn much oil. I have not done a compression test. Only upgrade so far is longtube headers.

I don't want to do a full rebuild right now if not necessary (lots of money) but while the engine is out, I'm thinking about camming it. I'd like to gain some top-end power, it feels pretty gutless at higher RPM. I have a four barrel carburetor I'm planning to install which I figure should help, but from what I've read a cam would have significant additional benefit for not much money.

I have a friend who is trying to talk me into a 351W swap. I'm not exactly sure what the engine would look like or where I would get it, since I'm not currently in the mood to spend several grand on this (Maybe I look for a Lightning engine? Maybe a truck 351 with a cam and Explorer GT40 heads?).

It should be noted that I care about fuel economy. Right now I have a T5 and 2.79 rear gears. I get 24 mpg cruising at 80 with the windows down, which is really nice since I do a lot of road trips with this car. I know the T5 is a little fragile, and the tall final drive is hurting my acceleration (Though my 3.35 T5 with a 2.79 R&P has a lower 1st gear than a Toploader with a 3.25). I'm willing to sarifice a few MPG for power but not much (so no high-overlap cams blowing fuel out the exhaust). All else being equal will a 351w be significantly thirstier? (And of course it can't break the T5.) My rear axle is whining and will need a rebuild soon but I can't see myself going much shorter than 3.25.

I also care about handling. This car is surprisingly fun to chuck around as it is (fast-ratio steering gearbox helps) and I've done an autocross with it. I'm planning to do a suspension overhaul with autocross in mind. Will the greater weight and higher center of gravity hurt its handling significantly?

So, with that in mind, mild cam in the 302 or 351W swap? (Or maybe just put on the 4 barrel and leave the stock cam?) If I do go with a 351, what's the cheapest way to get/build one that doesn't suck? 5.8 truck engine with Explorer heads?

People keep telling me I bought the wrong car if I care about handling and fuel economy. They don't get it. I've had a lot of fun with the car as it is, but if I can gain some noticeable power for $300-1000 without breaking my transmission or destroying the MPG I think it would be worthwhile.
 
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#2 ·
If you are going to the trouble of pulling the engine and tearing it down far enough to replace the cam, you might as well rebuild the whole thing. Bigger cam you will probably need new springs, you can replace them with the head on, but again, you are that far into it might as well pull the heads. No easier time than now.
 
#3 ·
Power costs money, the real question is how much you want to spend.

Cams are 80% experience, 20% voodoo. Many a person has wasted money on an off the shelf cam in an otherwise stock engine to see no, or worse, results.

When it comes to engines, the sky is the limit, but the more significant changes you make, the more time and money are required.

For example, lets say you go with a 351 swap. It will defintiely fit, but a 351 will move the exhaust around - now you are redoing at least part of that. The headers are going to be different too. I'm not sure on the trans, but you might be in for a new bell housing now as well. Then the clutch linkage, motor mounts if it doesn't fit under the hood.....the list will go on!

Now is indeed the time to do it since half the work is done, but having just read your post on doing the rust this winter, I would greatly suggest you focus on the body, get the car running again, then focus on the engine.

I'd also add, it really sounds like you don't know what you want yet. Start spending cash on power when you have a better idea of what you want. For now, I'd sit on this guy, put it back in when the rust is fixed, buy another engine and build it on a stand, then swap everything at a later date.
 
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#4 ·
You can Autox successfully with a 351w @dobrostang however in stock form and in the stock location the added weight will affect handling. If your really considering doing something engine wise Don't rule out doing a GT40P swap bang for the buck is pretty high.I have the same 3.35 T-5 gear behind a GT40P short block with Edelbrock performer 5.0 heads and in front of a TJ built 3.40TL gets 20ish mpg even with an autox day thrown in
 
#5 ·
It doesn't sound like you have a pressing need for a rebuild. Save that for another time when you've got more budget. A more aggressive cam should be fine, provided you've upgraded the valve springs to match. As far as weight, 351's are great, and I don't think the weight would be significant. Plus, you'll be running an aluminum 4bbl intake either way which will help compared to what you have going on now, regardless of displacement. Warm up your 302 and have fun with it. Also, I think you're a ways away from breaking the T5 unless you're doing frequent, super-aggressive launches like with drag racing. I've got a roller 5.0 with lots of forged and aluminum goodies on it and my T5 is going on 10 years of trouble-free operation.

Lastly, on the rear end: I would at least consider 3.55's. I have 3.73's and am pushing about 2,200 RPM at 70mph. Tire height can have an effect here as well. The best thing you can do for MPG is to have the carb dialed in, and it's common for gas milage to improve when going from a worn 2bbl to a newer, well-tuned 4bbl. As long as you keep your foot out of it, that is.
 
#7 ·
Just my opinion, but it sounds like you are basically happy and just want a little low cost improvement. If that is the case then I recommend (just my opinion) that you:

Skip the cam, get a dual plane 4V intake manifold and install the 4V carb. Then replace the rear gears with 3.0 set.

Both the carb and the gears will increase the seat of the pants feel off the line, and the carb will improve the top end a bit as well.
 
#11 · (Edited)
I agree; however if you feel the need to install a camshaft... I would recommend the Comp Cams 260H Hgh Energy Camshaft. It is a great all around camshaft and will not require any other mods to the engine. But for the slight gain, I would leave the current camshaft.

You already have headers, as said about a 4V carb no larger than 500 CFM would help. In addition, I would have your distributor check by a reputable engine shop and have them curve it correctly. Tell them your specifications, they will probably lighten the advance springs and recommend advancing initial timing. I had my factory distributor recurved and it felt like a 50 HP gain, it was a remanufactured unit with really stiff springs.

Enjoy the car, keep it running, your engine compression numbers are fine. You can always acquire another engine and build it to suit as time and money allow. If you are going to build a 302, I would not waste your time with your 70 engine. I would acquire the GT40P heads and then find a 5.0 short block with roller cam and one piece rear main seal. Those are very reasonable and there are plenty of proven combinations and the benefits of a roller cam.
 
#8 ·
Manifold, carb, plugs, wires, dist. and air filter, added to the headers that you already have, and enjoy the car while you do the cowl and floor yourself.

Save the rebuild or 351 swap for last.
 
#10 ·
I'm bringing this thread back, finally about to pull the engine. I did a (cold) compression test yesterday and got:

140 158 158 145 170 145 135

I'm going to redo the test today with a little oil in the cylinders, then pull the engine. I am still thinking about doing some work to it. I found a good, inexpensive machine shop, and if the bottom end needs a rebuild I can do it. I'm hoping it doesn't need it though. Either way I am strongly considering some GT40p heads from my local junkyard, which would only cost me $38 each (plus whatever it costs to build them). I'm going to try to price out what my total expense would be after buying those heads and preparing them for use. If they're in good shape, could I just buy them, change the valve springs to match the cam I choose, and call it good?

How can I calculate what compression my 1970 302 would make with a different head? I know the GT40P heads are 61cc. According to this article, the 1968 2V heads are 63cc.
https://www.diyford.com/ford-cylinder-heads-valvetrain-interchange-small-block/

Are my 1970 heads the same as the 1968 heads? If so they would bump my compression, correct?
@Israel I already did all that except the carb, which was rebuilt by the PO. I haven't neglected basic maintenance.
 
#13 ·
I'm bringing this thread back, finally about to pull the engine. I did a (cold) compression test yesterday and got:

140 158 158 145 170 145 135

I'm going to redo the test today with a little oil in the cylinders, then pull the engine. I am still thinking about doing some work to it. I found a good, inexpensive machine shop, and if the bottom end needs a rebuild I can do it. I'm hoping it doesn't need it though. Either way I am strongly considering some GT40p heads from my local junkyard, which would only cost me $38 each (plus whatever it costs to build them). I'm going to try to price out what my total expense would be after buying those heads and preparing them for use. If they're in good shape, could I just buy them, change the valve springs to match the cam I choose, and call it good?


@Israel I already did all that except the carb, which was rebuilt by the PO. I haven't neglected basic maintenance.
Yeah. No.

I just installed GT40P heads on my kids fox, and there are some issues. A set of junk yard heads will likely need some work before they are ready to install. I think the shop charged me $150 for a valve job. But the biggest issues with those heads are the spark plug angles are different. They probably won't work with your existing headers or exhaust manifolds. In my case, I ended up buying GT40P specific shorty headers AND had to get work at the exhaust shop to get everything buttoned up right.

I know you are concerned about money, but if you are looking at rebuilding the bottom end and upgrading the top end....I would be personally be looking at my budget, trying to make it bigger, and thinking "crate motor".

Phil
 
#12 · (Edited)
It is generally not a great idea to put a new, more performance oriented cam in an engine that is not done but well worn. The 3.25 gear will give you a sense of more power.



I just swapped my third member in my truck again and went from 2.79 to 3.25. It felt like I added a couple of cylinders but I already have a 268 duration hydraulic cam in it and mildly ported heads. No headers or 4 barrel though. I can't justify the expense for an engine that has 70,000 miles on its last life time and a Cleveland is sitting on the stand for it. Headers and intake wouldn't transfer.



The 4 barrel intake and carb should improve your top end up to the limit of the rpm range of the engine. Both the gear and 4 barrel carb may also decrease your mileage a bit especially if you expect to cruise at 80.

You can't have it all if you start to change things. There will always be trade offs to deal with.
 
#14 ·
I’m successfully running a GT40P and on the cheap side. The last non P head 5.0 made was 22 years ago. The last 5 years years of 5.0 pushrod motors ended 17 years ago in 2001. A little bit of a wake up call on how long it’s been. Like it or not, the GT40P at this point are going to be the more commonly found and newest 5.0. The good is that they last a very long time, 300,000 miles is common. So if you’re not stuck on a new motor but can live with a good used motors, the GT40P can work out great. They respond very well to simple mods. Even with just a used Mustang 5.0 cam they haul butt.

I bought a GT40P with a trans and all the efi equipment out of a wreck for $450. Sold what I didn’t want for $175, net cost of motor was $275. Used 5.0 cam $60, used Wieand Stealth $80, used 600 Edelbrock $125. I did buy a valve spring kit and new seals along with a shim kit for the springs. I think that was around $180 but that expense was for a free E303 cam I was going to install but didn’t as I discovered late on the cam got wet somewhere along the way and had severe pitting on several lobes. The bottom line I couldn’t build even a stock rebuild this cheap and I know a reputable company built the motor, Ford. I also knew it ran. The P head is worth about 30 hp over a typical sbf head. My motor pulls hard well past 5000 and does it pretty quickly.

I believe in Phil’s case it wasn’t a vintage Mustang swap. Yes the plug angle can be problematic but it’s not impossible. You basically have to pick the right header. I used common, off the shelf MAC long tubes. While they were not designed to fit the P head, they do. There’s nothing special about them. About $250 for them. They have great ground clearance, they clear the clutch linkage, starter and will fit a PS car without a drop bracket for the ram. They weren’t hard to install either. Your stock cast iron exhaust manifolds will work easily with some minor grinding or filing. Over all maybe not a perfect swap but under some conditions, a killer swap! I’m very satisfied with the P motor. The only way I would put aluminum heads on my car is if someone gave me a set.

Bottom line, you have to look at everything and see if it’s what you want and can live with it. While I’m a fan of the P head the reality of it is like any other common, mass produced sbf head, what you’re going to spend rebuilding them, you’re going to be into them for close to what you can buy new set of very good aluminum heads. This whole thing works if you find a good set of GT40/GT40P heads that cheap and useable as is. There’s a ton of good useable roller motor parts out there like camshafts. Guys buy a performance roller cam then move up and sell the slightly used cam at a good discount. Unlike flat tappet cams, it’s not a issue with using a used roller tappet on a different cam. This works out cheaper then a swapping a flat tappet cam.
 
#16 ·
If it runs good, don't mess with it. Clean it up, replace any leaking gaskets or seeping expansion plugs, maybe drop the pan to clean the gunk and replace the oil pump pick-up and strainer, check the timing chain & sprockets and RUN it. As a matter of fact, I'd probably leave the original 2V on it since it seems to be doing a great job with fuel mileage. If I was going to do ANYTHING, it'd be to send the distributor out to Dan Nolan and have it checked and recurved. If you have good low-end torque and throttle response now and, most likely, spend the vast majority of your time below 5,000 rpm why mess that up?
 
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