Cylinder Head Swap

[KJEfting]

My '93 Bronco 351W is in need of a new set of heads. At least one valve isn't sealing up and I'm losing a lot of compression up into the head. I've come across what seems to be a pretty good deal. A guy is selling me a set that came off a 73 Mach 1 Mustang small block for $100. He said it had a Windsor engine, so will the heads bolt right up? I am going to get them milled and I will rebuild them before I install them into the truck. Also, I've heard that replacing the heads without rebuilding the bottom end will cause accelerated wear. More specifically, I've heard that it causes an engine to throw a rod. Is any of this true? My rings seem to be in good condition and I'm not burning any oil at all. I really don't see a need to rebuild the bottom end. Any info would be appreciated. Thanks fellas!

-Ken

 

[Broncosaurus!]

no truth to the accelerated wear due to new heads. Well more airflow means more power which means more stress but rebuilding the bottom end won't help if youre just rebuilding it with stock components. The power gains you'll get from those heads won't hurt the bottom end anyway. 15 lbs of boost from a blower on the other hand is a different story. And yes I think the heads will bolt up fine if they came from a windsor engine. I could consult my ford parts interchange bible but i shouldnt even be spending the time away from my homework to write this message.

 

[Yardape]

they will fit fine, only concern would be that some newer engines have the smog pump lines entering the back of the heads. If yours is like this, the lines entering the back of the head, then you will have a problem. The 73 heads will not have accomodations for this.

 

[KJEfting]

Is the smog pump necessary for proper operation? Can I just disregard these lines and use the heads anyway? Thanks for the help guys!

-Ken

 

[BLADE262US]

Valve seats may be soft in those heads due to leaded gas at the time should have your machine shop check before bolting on . /emoticons/[email protected] 2x" width="20" height="20" />

 

[KJEfting]

Thanks for the info. What's a fair price for a mill job from a machine shop? I've never had any machine work done on a set of heads before, so I'm just trying to get a feel for everything.

 

[mbtech2003]

if they need a mill job then are they warped?? might be better just to rebuild yours then... u know they will fit. and port and polish for more power

 

[KJEfting]

No as far as I know, they are not warped. I specifically asked the guy if the engine they came off of died of an overheating problem and he said no. He told me the engine threw a rod, but the heads were fine. The bronco is my daily driver and I'm trying to avoid taking it off the road for more than a day. Can I skip out on the mill job? I've never worked on a set of heads before, so I'm pretty new to this scene.

 

[Yardape]

If you are worried they could be warped, find a machinist or fabricater that you know and trust that could check the heads for warpage. I would trust him, not everyone wants to rip people off, but it does happen. They only need to be milled if there is a problem.

 

[KJEfting]

What about the smog pump? Can I just remove it?

 

[KJEfting]

Also, Are the head bolts the same size? I'm not sure if these heads came off a 302 or a 351, and I've heard that the bolt sizes are different. Thanks again for the help guys. I'm supposed to go pick 'em up in two hours, so any info is appreciated.

-Ken

 

[Yardape]

You have to know if its off a 302 or a 351, they have different bolt sizes, sounds like your getting in over your head here. I would recommend either fixing yours or getting a factory replacement, try a save a buck and you will pay for it triple I guarantee it. Not worth it.

 

[KJEfting]

Yeah I may have bit off more than I can chew, but I've got the heads now. If it turns out that they won't work, I'll just dump them off on e-bay. Turns out they did come off of a 351W and as far as I can tell, my 93 doesn't have a smog pump. I'm going to tear them down and take them to a machine shop next week. Any other tips I should know about?

 

[shuagriz]

You can check for warpage yourself with a straight edge and a feeler gauge. Its not hard. You just have to know what the maximum limit is.

 

[shuagriz]

Yeah I may have bit off more than I can chew, but I've got the heads now. If it turns out that they won't work, I'll just dump them off on e-bay. Turns out they did come off of a 351W and as far as I can tell, my 93 doesn't have a smog pump. I'm going to tear them down and take them to a machine shop next week. Any other tips I should know about?

Are you sure it doesn't have a smog pump? If you are looking under your hood the smog pump will be on you left hand side towards the bottom, just follow the belt down to it. It should be there unless some one took it off, which I would think is realy unlikely.

 

[Yardape]

I think he means that the smog pump doesnt go into the back of the heads, thats what we were talking about before. What was wrong with the original heads? why are you going through all this work?

 

[KJEfting]

Few reasons. A couple of vavles are chattering pretty loud. Low compression in one cylinder, but I'm not burning any oil and the plugs are still clean. The truck has 230K on it and I'm pretty sure a valve job won't hurt. The main reason I got a second set of heads was so I could have them ready and just do a straight swap. The truck is my daily driver and I really don't want it to go down for more than a couple of days.

 

[KJEfting]

Got the heads. Going to take them to a machine shop later today to get them cleaned up and pressure tested. I figure if they seal up pretty good, I won't even bother rebuilding them. They're going on a motor with 230K on it, so these heads will probably out live the bottom end anyway. I've attached a few pictures. Let me know if you see any glaring discrepancies in the pics. Can you guys can think of anything else I should know before I drop them off at the shop? This is by far the most in depth project that I have tackled on the old bronco. Thanks fellas!

-Ken

 

[bobstrat]

wow thats alot of work when you consider the factory rating of a 73 302.. personally i think youd have been better off finding a set off a 5.0 explorer. cast iron version of the gt40 heads.