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BDodson5.0 08-09-2014 08:48 PM

302 Questions
I recently purchased a 66 Mustang. Car was originally a 289 car. Previous owner swapped in a 302. Came from a 86 T-Bird. EGR and all emissions. After doing some research, it seems this motor sucks. It's a tappet cam, hydraulic lifter motor. Is 140hp a legitimate number for these motors? What can be done to open these up? I have a high flow aluminum manifold without EGR I'm putting on, a 600cfm 4-barrell Holley carb, Hooker long tube headers, and that'll be all for now. I was thinking GT40P heads or a set of trick flows. Plan is a 347 build. Top to bottom. But with the newly found knowledge on this motor I'm wondering if it is even worth it. Or, if I pull all of the emissions junk off of it, swap what I have and do a roller cam swap, will it open back up to the 250-350hp these motors are easily capable of with basic bolt ons?

barnett468 08-09-2014 09:43 PM


the 140 hp is around the same as 180 hp or so. they changed the rating system sonce the old days.

nothing really wrong with it. it will be ok for a 347. but you need heads like afr 185 for a 347. if you go carburetor, an xe 274h is a good mid range cam.

the 185s are too big for a stock engine.

the gt40 heads need to be milled around .032" to get the compression up.

if you add a cam to the stocker i would use an xe262h. an xe268h is a bit big unless you get a lot of head flow like afr 165's and low gears like around 3.50.

BDodson5.0 08-10-2014 08:02 AM

Who makes AFR heads? Sorry, new to mechanically working on these cars, I've replaced every piece of sheet metal on about 6 of them haha. Also, XE for the cams? Appreciate the insight on the 140 & 180 basically being the same. Pulled my manifold yesterday to swap it out and found 6 bent push rods. Valves seem to be fine, put new push rods in lashed the valves, hopefully today I can put it all back together with the new parts and get the motor to turn over. Trying to get my motor build all drawn out for parts and everything, I have a buddy who has his own machine shop, hell do all the lower end work.

67mustang302 08-10-2014 01:19 PM

AFR makes heads. Air Flow Research. The XE cams are from Comp.

BDodson5.0 08-10-2014 05:00 PM

Thanks for the info! Sorry for all the questions. I'm just trying to gather as much information as I can. It had the cross over lines on the back of the heads. I pulled those off and was wondering if there is a company that sells some sort of block off plate to properly cover those up. I put my new manifold on today to do away with the EGR. Also installed my new carb, I need that and to figure out the heater hose situation. The old manifold had large 90 degree fitting that screwed into the manifold for one of the lines. It hits the runner on my manifold and wont thread in. Heater box is wrecked. I was going to do away with it for now. But I have no idea on how to plug the hole coming off the water pump for the other hose. I know a regular cap will blow off under all that pressure. Need some suggestions.

barnett468 08-10-2014 08:25 PM


need photos.

your push rods did not bend all by themselves for no reason. i would redo the heads. if you lay a straight edge across the top of the valves look to see if any are lower then others. if they are, the valves might be bent.

BDodson5.0 08-10-2014 09:10 PM

Did that already. I can completely spin the motor freely, complete rotations without any jerking stiffness or issues. I know it makes no sense what so ever. But I can't find anything wrong. It had a few massive vac leaks was the only thing ive identified that was mechanically wrong so far. I'm gonna attempt to start it next sunday I needed a few fittings and plugs. If it fails this time im pulling the motor for complete rebuild and will input damage I find.

67mustang302 08-10-2014 11:03 PM

You really should find out why the pushrods were bent. If someone over revved the engine previously, you could also have valve seat, valve and lifter/cam damage. If there was contact between the valves and pistons, you could have compression losses etc.

MonsterBilly 08-11-2014 07:42 AM

simple, put a blow through carb on it and a turbo and dont look back. it will be wayyyyyy less than a 347 and you can get similar power out of it. you wont need heads, exhaust or anything other than a cam. well you will need to do exhaust.

rmodel65 08-13-2014 09:23 PM

i dunno if you can swap heads on the tbird motor without doing piston mods. the 86 mustangs have a different piston compared to the 1985 and 1987-1993 engines.

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