2007 Lincoln mkz head????

[jred]

2007 Lincoln mkz 3.5 head anybody have any info,, I looked on Mitchell on demand and AERA prosis they give the stock thickness but no minimum thickness,, I was hoping some here that does dealer work could tell if there's a minimum thickness or its a no surface head and time to buy a new one thanks

[jed]

do you have a casting number??

[BillK]

Is it warped or corroded or other reason for resurfacing ? Most newer heads cant stand to be warped much more than .004 before the cams start to lock up. What I do when there is no spec in Prosis is to bolt the cam(s) in with no followers and just snug the end caps down by hand. If the cam spins easily by hand then I will resurface it up to .006 or so. Most of the time the cams will start getting tight at about .004 You can also put a straight edge across the top and see how it looks. Sometimes the head will not actually be "warped" but pushed up in the middle.

If the head is pretty straight you could also cc one of the chambers. Prosis gives a cc size for those heads.

I ALWAYS call my customer first and tell them what I am doing and give them the options and let them make the decision. I have not had a single problem that I know of using this method for the last 30 years.

[rebelrouser]

I don't have access to service info, but most OEM newer engines do not allow you to surface a head, when you surface the head you change the cam timing, and with the variable cam timing systems they will set codes with a few degrees in error. stretched chains and worn guides are setting codes on engines that customers say run just fine.The only way is to surface the head, and then get a shim to make up for what you took off. But with the expense and availability of that system, I do not use it much anymore.

[BillK]

Just want to add another comment. There is always production tolerances on the heads when they are new. There have been many times I have checked a head that I know for a fact had never been surfaced and found it as much as .010 "thicker" than the supposed factory spec. I had a set of 2.5 Mazda heads in the shop last week that measured about .006 larger than the spec shown in Prosis.

As far as affecting cam timing goes if you have a 3" diameter cam sprocket you would have to cut the head .026" to change the timing 1 camshaft degree. So I really do not think that is an issue.

[jred]

Don't have the casting number as I haven't seen the head yet , my customer the repair shop is trying to see for the customer if its new head time or if the head can be surfaced,,

Yes I am aware of the pitfalls of surfacing OHC heads increased compression late cam timing piston to valve clearance and such,

And I have done the same thing about testing the cams for rotation in a unloaded head,,

AERA MITCHELL on demand and the SBI web site gives the new head thickness but no minimum thickness and SBI does not show a head saver shim to repair the thickness of the head,,

Ford does the same thing on their 6.0 diesel heads and knows this but yet sends them over for surfacing and when there's a problem want us to pay for their mistake..

In todays day and age with everybody being so sue happy its important to have some sort of documentation on how and why you did what you did so you don't get sued,,

I would like to know how bill k came up with the formula as to how much needed to be surfaced to change the cam timing I would like to know this so I can use this to show customers some sort of proof..

thanks to everyone for their help on this

[rebelrouser]

don't have a formula, but the import forums all quote the same number, for every .012" you remove, cam timing is retarded 1 degree. And one degree retarded, most likely will not set a P0012 retard code for example, but if the customer is reusing a high mileage stretched chain, it may push it over the limit. Again I think the reason most factory specs now don't show a minimum/ maximum spec is they don't want you to surface a head.

[BillK]

Ford does the same thing on their 6.0 diesel heads and knows this but yet sends them over for surfacing and when there's a problem want us to pay for their mistake..

???????

Not sure what the mistake is. I bet I have done at least 100 sets of those heads over the last three or so years and every set has been resurfaced. As long as the valve recession is ok there is no problem at all taking up to about .010" off them. Most of the ones I have done have been for a couple of local truck repair shops but I bet I have done at least 5 or 6 sets for the local Ford dealer also. Have not heard of a single problem related to surfacing them. I did two sets last week. These are all your basic clean - check for cracks - resurface. Easy money.

[BillK]

don't have a formula, but the import forums all quote the same number, for every .012" you remove, cam timing is retarded 1 degree.

Thats about right in crankshaft degrees for a 3" cam sprocket but I would be willing to bet dinner that factory manufacturing tolerances are greater than 1 degree. Now I am not talking about a performance application but a strictly stock engine.

There a many, many late model ohc heads that give a new thickness and a minimum thickness that is at least .010" different.

[jred]

I was thinking about the 6.0 heads PROSIS says you can surface .006 with no problems and I have done that many times for walk-in customers,, the problems that we were having is the dealer will send the heads over to be checked out and do what's necessary ,,

Heads coming in leak down checked valve job if necessary, set stem and spring height, check for warpage and surfaced if needed guides and what not,,

Heads go back to the dealer and we get a call from the service writer,, what was the thickness on the heads , you tell them and they come back that the heads are below the factory spec and we want you to buy us a new set of heads

Anymore when dealing with the dealers it was to our advantage to call the dealer and talk to the tech that's doing the work and find out from the horse's mouth what they (the tech) are really wanting or looking for,,

Go's from the service writer to the tech to the parts department through the service managers though the P.O. writher sometimes by the time it goes though that many people something gets lost in what the tech wants or needs..