I walked into a killer deal from a core dealer on a late model roller 5.0L with the GT40P heads out of a 2001 Explorer that was replaced under warranty. Cheap, cheap, cheap! Apparently, Ford replaced a few thousand engines in these trucks chasing a powertrain vibration that was eventually pinned on too long motor mount bolts that were bottoming out before the mount pulled completely tight against the block. Oops! So in a nutshell, I've got a nearly new longblock with less than 35K miles that essentially has nothing wrong with it. It's extremely clean inside and out and I've checked a couple bearings and everything seems to be in excellent condition. I bought this engine for my project car and the temptation to slap the carb manifold and other external parts on and slide her in as-is is very high. BUT! I'm concerned about one thing. The engine I'm replacing is a solid 289 that is overall in good shape and really only needs valve seals to continue to give good service. It's a little on the wimpy side, though. If I'm going to go to the trouble to replace it, the new powerplant had BETTER make it worth my time in performance. The Explorer 5.0L specs 9:1 compression and given the 59cc chambers on the GT40P heads, I'm guessing that the lower compression comes from dished pistons. With this few miles and this little wear on the block, I'm considering pulling it down, giving it a quick clean-up hone, and putting in new std. size flat tops and a fresh set of rings to bump the compression up to around 10-10.5:1 - assuming the bores are in good shape. I'm thinking that a little more compression, a cam better matched to the vehicle, and those heads would make my ride a whole lot more interesting long term without costing me a bunch of cash that needs to be invested elsewhere right now. I don't know that it matters, but the induction will be a dual plane intake with a 600 CFM carb and exhaust will be through repop hi-po manifolds. Tubular headers in this chassis with the oddball GT40P plug location are not an option, but the iron headers fit OK. We're going to be staying on the street and the emphasis will be on torque in the cam selection given the 2.70 gears and no overdrive. I can't get an AOD underneath it without a torch, so the gears have to stay. Might go to 3.00's later MAX. So what do you guys think? Swap the cam and put it in or change the pistons too?

 

Well I think the cam and pistons are great together but if i had to pick one or the other i would go with the cam. You will get a greater return on the cam.

What vehicle is this for?? I have a 1980 F150, and it had a 2.75 rear gear and a C-4 transmission. The 302 in it produces about 315 ft/lbs of torque and significantly less horsepower (i'm thinking around 240 or so.) With that gear I could run down the highway at 65 runnin about 2,200 rpm's. I swapped the transmission for a 4 speed I got for free and turned the same rpm's in 3rd at 65mph. I put a 3.50 gear in my 9inch and found that in 3rd at 65mph I was turnin only 2,800 rpm's. That's about where my motor ( and most 302's from my experience) like to run. Most literature I've read says that 302's like to run about 2500 rpms. This was a HUGE improvement. I would suggest looking at swapping gears and doin the cam. You would be pleasantly suprised with the result, I guarranty it.

On another note, I'm looking for an even lower gear for my truck. I'm thinkin a 4.11 or maybe even a 4.56, but I want to know if a gear that low would make first gear useless except in towing. I don't care about towing, I just like to cruise and burn out. I'm building a 460 for the truck and I plan on saving my 3.50 carrier for the motor so a low gear would not be a problelm right now. Oh and with the 460 will come a C6 so I'm not at all considering using the 4 speed trans.

 

sgt pepper is your 302 stock motor?

blue, leave the pistons alone. but a cam upgrade would be better. but it would help us if we knew what the motor was going into.

 

289's have 54 cc chambers and you say those ones are 59. that should be the only reason for the lower compression., no biggie though

 

This is going into a '65 Falcon 2 dr hardtop. Yeah, yeah, I know. This is a truck board, but this is also where all the best advice I've gotten in the past has come from, too. It's the first car I've messed with in awhile. Been in the truck mode for some time. I originally wanted to build a 347 for it and keep it dressed in the stock 289 covers and accessories, but this came along and I couldn't say no. I'm still trying to wrap my mind around what to do with the cam and gears. It MUST be able to comfortably cruise on the interstate and an AOD won't fit in the narrow tranny tunnel without a hammer and some creativity. Consequently, I'm going to try to get as much torque out of it as I can off idle from the cam and hope for the best. I don't have a tach in it yet, But I drove it 1000 miles home after I bought it and it seems to be turning plenty fast at 75 already without dinking with the gears. I've NEVER messed with roller cams, so any advice here would be welcome, too. I guess I could call Comp's tech line and ask what they think, but the profiles are so different from flat tappet cams that I don't even really know what I'm looking for. Sounds like the general consensus is to leave the pistons alone. I can live with that. I don't mind swapping them either, but the gain would have to be worth about $400 and a week's worth of work.

 

I've only dealt with roller cams once and I regret to say it was on a C#evy. Then again I wouldn't have had to repair the motor if it were a good ol' FORD. I think you should install a tach and see exactly what kind of RPMs you are turning. You can also check on google for an RPM Calculator. All you have to do is put in tire height, transmission type, rear gear ratio and mph and it will tell you the rpm. I seriously think that a lower gear would do you well. Even a 3.50 would do wonders.

My motor is not stock. Most of it is, however, I have bored the cylinders out .030 and I've had the crank turned .030 also. The heads are stock and the cam is just above stock, any more and it would lope. I've got a 289 Edelbrock intake and a 600 Edelbrock (which I hate.) Finally I finished the exhaust off with some shorty Mustang headers and 2 1/4 " pipes back to the rear axel and into two mufflers (generic turbo mufflers) and then they just turn down.

I'm looking for some late sixties Windsor heads right now. They have a decent compression gain, but their real advantage is bigger, better flowing valves. Also, I'm gonna go to a bigger cam sooner or later. Something with a lope. When I do that I'll change my intake to an open plenum Edelbrock Torquer 2. I'm rebuilding a Holley 600cfm vacuum secondary carburator right now which will replace the Edelbrock. Finally I would really like some full length headers and two Flowmaster 40 series mufflers (not the delta flow pieces of crap.)

BTW: I've heard some good things about 289 heads on a 302, but I think they are crap. The combustion cambers are soo small that the compression goes up, but the valves are also so small that they don't flow worth crap. If an engine is a giant air pump then it would be more beneficial to have slightly larger combustion chambers and big, flowing valves. Just my two cents.

 

the more flow = hp, if its a tad restrictive it will produce trq.

sgt. your crank is .30 over. that is not good. anything over .10 is conciderd a worn out crank ya know

 

my bad. it is .01 over.... I hadn't thought about it in a while but diggin out the old rebuild kit reassured me that it was .01 over. Thanks. Oh btw what do you drive???

 

I think your calculation is a little off. Wouldn't more flow just equal more torque at a higher rpm?

 

its hard to explain. but more flow will create more power higher in the rpm band so i guess that would include Torque. but to much flow and you will lose all bottem end until 2000 rpms which for my FSBronco that dont work well.

 

Yeah I getcha. I understood what you meant but wanted to clarify for anyone else reading. Btw what is an FS model truck? You said you had an FSBronco.

 

Full Size Bronco.

 

ahh not a bronco 2.

 

thats why I stated that. everyone gets them mixed up. its awful

 

ah maybe you could help me on another problem though. Today I ran my 302 to 4500 while on the secondaries and i had a terrible knocking right around the peak rpm. it wasn't pinging, it was a definate knock. what could cause that?