Gentlemen,

I was lucky enough today to pick up two used crack-free (miraculous) heads. Valves look quite good, no burning.

Question: Should I use lapping compound and my drill or just install them as is?

Ken

PS my old heads were cracked across valve seats, hopeless.

 

i would take to shop to have 3 angle resurface on seats and machine resurfacing of valves....
modern valve seats and valves, especially the exhaust, are too hard to get a good seal by just lapping....returns old head seats and old wear unmatched valves to correct angle and perfectly round shape...will also find any slightly bent valve stems
poor seal causing burning and power loss....
job will be less than $100

 

Thanks 96

Ken

 

if you do decide to lap for cost reasons, try to get one of the diamond dust lap compounds, will cut the hard exhaust seats

 

I'm with 96_4wdr, Ken. Have the valves and seats cut. Also, they would resurface the heads if necessary. It generally is much cheaper if you would remove the springs first and just give them the heads with the valves in them.

Also, make sure the casting number on the new heads matches those of the old ones. There are several versions of the 4.0L heads. Best way to make sure is to compare the shapes of the area around the valves.

 

Thanks guys, big, big help.

ken

 

One of my heads was good, one was cracked. I had the good head rebuilt, all new parts for $35.00 at the machine shop I use. I already had the parts for rebuild, but for $35.00, I just kept the new parts I had for future use. I bought another rebuilt head that was ready to slap on, it cost me $100.00.



T

 

Just out of curiousity, why would you port and polish the heads? (I assume that is what you are talking about.)

Wouldn't you only want to make sure that the head is not warped and there are no cracks? I would think that would be enough, but I could be way off, if so, please explain?

 

No, they are not talking about polishing any ports. The area where the valves touch the valve seats must form a perfect seal. They have to be either polished (lapped) till they fit, or machined to perfection. On newer engines, they should be machined. You should never port and polish your heads.

 

ok, that makes sense, I just misunderstood what you weree talking about.

 

Dear KH,

I agree with your comments but am curious about porting and polishing. Mind you I didn't do that, but why do you say it is bad? what is wrong with smooth runners and ports that match up? But then, if rough is bad, why aren't golf ***** smooth. My god we are back into aerodynamics.

Ken

 

Golf ***** aren't smooth because the pits give it more lift, than a smooth ball. Engines don't really need lift.

 

Be careful to tell the shop you want a straight edge put on the heads and if the
surfaces are as tru as stated in the Ford shop manuals you don't want them resurfaced.
To many shops just go ahead regardless. I have a saying "all the bandits don't wear Masks. At least the racoon tells us what he is".

 

It seems that the entire auto repair industry could be described by Kotzy's post.

ken

PS. my heads are in the shop having their valves ground with three lovely angles. You guys made me do it.

 

Dear 93,

Isn't airflow over a golfball the same as airflow down a pipe??

ken