New member. Questions.

[Torinojts]

Hello everyone. Great information. I am restoring a 75 f350 4 door. Installing it on a 94 f250 frame. It has a 7.3 idi factory turbo engine. I took block to have machined .020 over. Balance internals and new exh valves and guides. The machine shop decked the block .07 with out telling me. I already have Mahle ceramic coat pistons. The problem is they stick above deck to .041 now. Can I run this? I have read where 1 guy ran his .052 above deck with no issue. I did order a cam to lower compression to run more boost. If I shave tops of piston, should I recoat tops or run without ceramic tops. Or clay the pistons and run pistons .041 out if no issues? Thanks

 

[79jasper]

I have no technical data to back it up, but I believe your pistons will be making sweet love with the head.

Also have you had the cylinder wall thicknesses checked, after the boring?

Last but not least, welcome to Oilburners.

 

[Torinojts]

Wall thickness was good and no cavitation. I know spec is .010-.031 stock. But I have seen where someone ran his at .050 and really no issue. Will this raise compression and with 10-15 lbs boost, heads studded, will I have head gasket issues with the raised compression?

 

[79jasper]

With raised compression, I believe you will have all sorts of problems.
But once again, no hard info to back that up, just what I've read here and other forums.

You should be able to mill the pistons to bring it back down, and have them recoated.

I believe we have a few engine builders here, so hopefully they can chime in and give you definite answers.

 

[HiHorse]

Are you certain the took 0.070" off your block?! I would believe more like 0.007" to square it up. Double check that number before doing anything else. If the machine shop doesn't know how to make this work you may want to consider another. I want to see your project!!

 

[Torinojts]

I meant .007

 

[hesutton]

With modified cam timing, that certainly may be an issue. I'd be temped to sell the pistons you have and get Mahle's reduced compression height pistons. The wrist pins are 0.010 higher on the piston, dropping them down in the bore. They are designed for use in decked blocks like yours. You could assemble the engine and clay it out, but if it is not going to work, you'll have to pull the thing apart again and start over.

Even without mod'ed cam timing, that could be a problem, with with it...... the risk increases.

Again, my two cents.........change the pistons or clay it and see.

Heath

 

[Torinojts]

I check with the parts store where I got the pistons. They said they would take back. But also said mahle doesn't make such a piston. I even Check there web site and none listed

 

[icanfixall]

My question has to be how do you know the shop cut off the 7 thousands they claim they did. This is the factory specs... From the centerline of the crank to the top of the block deck the measurement is 11.137 to 11.141. So we have 4 thousands to work with. I'm the member that ran a set as much as 54 thousands hig but every piston had a valve mark. I could see it but not mearsure it and I'm a retired machinst with all the years of experiance and tools to meaure. So it was way les than 1 thousands. Now my suggestion is use this tool after every rod and piston in installed, torqued without rings on the pistons.
http://www.bing.com/images/search?q...&id=52DBF3C02D71BCDC0E3BDC4AD0EFB789CA065F3D#
Then you will know for sure what the piston comes out of the deck of the block before running around thinking oh my... What to do. Many here will guide you along this trip if you ask. But fixing something after its broke is a problem. If you can't or don't want to buy this tool ask me for it. All you need to do is pay shipping both ways and of course cover any damage. I know I'm sitcking my neck out there again after some members have ruined my timing meters and a seat reamer but I want to trut everyone and help them out. I have nearly every tool needed to work on these engines. Its the tool kit designed by Ford for these engine overhauls.

 

[riotwarrior]

Gary is right, I'd be very cautious about the measurements without first confirming. As well any shop that does work without being asked to do so is not a shop that's worth your money IMHO. A phone call would have been all it took to get that to be OK'd that is unless you said something like do what ever it takes....

Honestly Contact Mahle directly and ask them about the lower compression pistons available web sites are known to not have accurate info. Especially for some older stuff that's just not got volume of purchase.

What cam did you get and from where?

Take a look around the site, Theres some great tech articles in that section some good FAQ material, and the Hall of Shame to help keep your money away from known vendors with bad reputations.

Take a moment and fill in your signature please, top right go to settings, down on left to edit signature, fill it save it and done!

Sounds like going to be a nice build btw, we need pics of this!

Welcome to OB

Al

 

[Torinojts]

I do have access to the gauge you slide across with a dial indicator on it. I measured with the rings on. I will remeasure with the rings off. Thanks for your offer thou.

 

[icanfixall]

If you installed the pistons with the rings on and got the demensions you posted. then there is no reason to guess what you have. The red tool I posted just has two rare earth magnets on its leggs. they hold the tool to the block so the dial indicater has a solid place to measure from. The center of the piston is where the indicter should touch. If all what you posted is correct about the reach out of the cylinders, The milled block and the ceramic coatings. Well it time to do something else. Like get low comp istons and creamic coat them AFTER you mill about 15 thousands off the tops. These heads have no combustion chambers like a gasser does. All that seperates the piston from the heads is the thickness of the head gasket. I found the felpro head gaskets are thickest of what was made 7 years ago. They are around 75 thousands thick before compressing. Its nearly impossible to claculate the compressed thickness but I fel I got close at around 45 thousands or so. I understand this does not allow any room for a piston that reaches 31 thou out which is the factory max but I'm erring on the caution side too. To get the actual compressed demention the head will have to be on the block. The block bolted down to a flat table. A dil indicater placed on the valve cover pan gasket rail and the head towqued down Thats a lot of special work going into this job. I know of no claiper that can measure this demension because of the angles of the head and oil pan rail at the bottom of the block... Even finding what the deck height is will be a major tooling. A try bar will have to be machined to be bolted inplace of the crank without bearings. Then an 10 inch depth gauge rod on a depth gauge with a 1 inch measure on it has to be used. Then subtract half the diameter of the try bar that acting as the crank to know where the center is. The try bar to fit the crank bores needed to be 3.3152 to 3.3162 diameter. So useing the middle ground of 3.3157. Take away half of that and you have the center of the crank at 1.6578.. If you wanted to get that precise.

 

[hesutton]

I check with the parts store where I got the pistons. They said they would take back. But also said mahle doesn't make such a piston. I even Check there web site and none listed

They need to have a closer look at their Mahle catalog.

Here are the Mahle part numbers:
144171 - Reduced compression (0.010). Standard, 0.020, 0.030, and 0.040 over sized.
144171HA - Reduced compression (0.010). Standard, 0.020, 0.030, and 0.040 over sized with hard anodized crown.
144171WR - Same as 144171 except with rigns.
144171HAWR - Same as 144171HA except with rings.

Heath

 

[riotwarrior]

I do have access to the gauge you slide across with a dial indicator on it. I measured with the rings on. I will remeasure with the rings off. Thanks for your offer thou.

Rings on or off does not affect how much piston protrudes out of the bore, it allows an easy assembly of the piston and crank for measurement purposes. Each piston should be checked individually IMHO.

This sounds to me like a calamity of horrors in the making too....

Al

 

[Torinojts]

Now that I know the part numbers I think I will get different pistons. Thanks Heath.