I have 2 390 engines that I'm making one good one from. I have a 1975 F150 that the block was cracked so I bought another 390 engine. The donor 390 has a block with C6me on it and the one from my 1975 truck has D3TE. I believe I understand the differences of the two which as I understand it, they are the same except for the years difference. The cranks from the older block has is a 2U and the newer block from my truck has 3U. Now here is my question:
The cam from my truck has only an NA or Upside down "U" and "A" with the number 24 between some of the back lobes. The donor engine has a cam with the same "NA" or "UA" with the number 29. I mic'd the lobes on both cams to see if there was a lift difference and it does appear that the "29" cam has more lift. I'm not sure if that is fact or just a worn out cam from my truck and the one from the older engine could be a newer one??? The lifters are different length as well with the older cam having actually slightly taller lifters. The pushrods and rockers are all stock original.

Can anyone tell me what cams these are?

One more question on pistons. The pistons out of my 75 truck block has 410 on the pistons and the ones from the donor engine as 390. They are the same diameter and the pin is in the same location so I assume they are the same piston. There is a difference in the centers of the pistons where the 410 marked pistons has an extra raised area between the valve reliefs where the 390's go dish flat in that area. One other issue, the 390 pistons apprear to have the same compression ring thickness for both compression grooves. The 410 pistons have a larger second compression ring thickness. Why is there a difference? One of the pistons from my original block was replaced with a flat top piston and I want to swap it out with one of the 390 pistons. Will this work or do I have to use all of the 390 pistons instead??? I would think the 410 pistons might give a slight better compression ratio and if so could I purchase a replacement piston if I can't use the 390 piston??? I know this all sounds confusing and I hope it's not. If there is anyone that I can talk to about this over the phone to make it easier I'd be glad to call.
HELP I'm really confused here.
George

 

Would have to get home to a book to help with the cam ID(think there are other IDing marks on them). The pistons, don't mix them and depending on the condition of the block (taper) could create one hell of an issue for you. Take the two different pistons and lay them top down on a table and try to push a wrist pin out of one and into the other. A 410 piston has a wrist pin height of 1.65 IIRC and the 390 1.76 so there is .10 difference. Using a 410 piston with the same crank at 3.784" stroke would give you a lower CR much lower. Someone else will be shining some more lite on this thread for sure...

 

OK then in regards to the pistons, I could just use all of the pistons marked 390 and that would solve that issue then. Now to solve my cam issue. Where else would there be markings? I've looked at both ends of the cam and found nothing.

 

Reusing a cam is not a good idea. First of all, it is important that you keep the lifters in the holes that they came out of, "so they go to the same lobes on the cam" if you did reuse the cam and lifters.
Best choice is to buy a new cam and lifters. If these engines have a lot of miles on them, you can expect wear on the cam lobes, possible stress cracks, etc.

What do you plan to do with this engine? Is this a farm truck, or are you planning on driving it on the street? Are you planning on using the used bearings?

 

Ummm, you want to keep the pistons and crank together as a set. That is how they are balanced, as a set.

I'll be following the cam marking info.

 

My truck will be used on the street, to tow a vehicle trailer, camper and all around normal use of a truck. The engine in my truck was rebuilt and had, so i was told about 5000 miles on the engine when it was parked 10 years ago. The rod and main bearings look good and the crank checks out good. Both main and rod journals are still in spec. I'm trying to avoid spending large amounts of money on this rebuild. I'm not looking for a race built, perfect balance engine. Just a standard all around normal use engine. It's not going to be used as a daily driver either, just as it is required for use only. I've been building engines for 40 years and I do understand about the balance of it. I know I can use different pistons and rods with different cranks. It's not a 100 rule of thumb that you have to order an entire rotating assembly balanced unless you're using it for high end horsepower. This will not be used for such. Balance issues like that are more inclined to be an issue at higher rpms. This truck will never see redline much less 5000rpm. I keep looking at the ring sets available and I don't see any that have the two compression rings the same thickness as the ones on the 390 pistons. So I'm not sure where to go with that issue. I've been looking at Summit for parts, is there another cheaper place to look?

 

C6ME Camshaft: Upside down (Inverted) is correct for the A only, which comes first. The other letter is a U.

A C6ME 390 block could have used two different camshafts with like markings.

C6AZ-6250-A / Marked: Inverted A followed by a U and a dab of WHITE paint / Hydraulic lifters / 15 tooth dizzy gear / Induction hardened.

Fits: 1966 Ford, Fairlane, T-Bird (2V, 4V) / 1967 Ford, Fairlane, T-Bird 4V / 1968 Ford 4V, Mustang 2V-Premium Fuel / 1969 Torino GT, Mustang 4V.
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C7AZ-6250-A / Marked: Inverted A followed by a X or Inverted A followed by an U with a dab of GREEN paint / 15 tooth dizzy gear / Induction hardened.

Fits: 1967/71 Ford, Fairlane/Torino with a 2V / 1967 F100/350 352 2V w/o T/E / 1968/72 F100/350 360/390, AND > >
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C7AZ-6250-A is the only camshaft listed for 1973/76 F100/350's with a: 360 2V / 390 2V or 390 4V.

Info sources: 1965/72 Ford Passenger Car Parts Catalog / 1964/72 Ford Truck Parts Catalog / 1973/79 Ford Light Truck Parts Catalog.

 

As others have mentioned, do NOT mix the pistons from the 390 and 410, they have different piston pin compression heights.
Speaking of crankshaft ID's. The 2U and 3U cranks are both 390 cranks, see Big block Ford engines by Steve Christ page 52. So this makes it easier. Take 8 good pistons all the same type with rods attached. Take your best crankshaft. Reuse your main bearings if they look OK, but consider new rod bearings because they are the weak link. I would suggest having the rod big ends checked for out of round, but find an honest machine shop or check yourself. You could take your best set of used rod bearings, put em on the rods, put crank in block, check crank main clearance with plastic gage, then check rod clearances to the crank with plastic gage. Maybe get away with using all the old parts you have. I have even seen used rings "stretched" out a bit and reused in fresh honed cylinders, the car ran fine for what the owner wanted. For plastic gage clearance you would want about 2-3 thousands clearance max. Consider maximum piston to cylinder wall clearance about 5-7 thousands. Some folks will insult me to no end, but I've put em together a lot looser than that depending on what the customer could afford. Did a loggers truck engine, must of had 0.020 or more piston to wall clearance, they took that fresh rebuild out the night I gave em the truck back, they drank like crazy, tried all night to blow up my new rebuild and couldn't do it.
Remember the cam bearings are worn too, so oil pressure could be down. Could consider a Melling high volume oil pump, or put in your stock pump and a mechanical oil pressure gauge with copper tubing, NOT plastic tubing. Need only about 10-15 psi oil pressure at idle and about 50-60 at 4000 rpm. I would absolutely buy an ARP oil pump drive, I think summit has them. The stock drives you have are flimsy pieces of tired metal.
I have a used 390 truck cam in good shape I'd give you for free if you paid shipping. It would need a set of new lifters. Be sure to use Rotella oil for initial start up of your rebuilt engine, also consider adding a bottle of comp or crane engine oil supplement. These products all add the zinc and phosphate back into the oil to help the cam break in correctly without wiping out the lobes and lifters. All the new oils are EPA friendly so the old style cams get ruined easily.
Don't be talked out of using the old parts you have, as long as you check them correctly, clean them like your going to eat them, verify fit and function as you assemble everything, and be clean clean clean as you go together, I mean serving supper out of the oil pan --- that kind of clean. hopes this helps.

 

How much would shipping the cam be to 30135? It appears that I can't use either set of pistons as both sets have issues, so I will be purchasing a new set. I found a "Master Engine" rebuild kit for sale in NY for $339.00 complete with everything I need. I am most likely going to get that kit as I can get everything I need including cam, lifters, pistons, rings, oil pump, bearings seals, gaskets, timing chain set, and freeze plugs. I already have new cam bearings and freeze plugs installed. I had the block done at a shop and had the cylinders honed and there is only .003" wear so I think the cylinders will be fine. I've built engine with more wear and made over 500rwhp so I'm sure I'll be fine here. The kit also comes with an RV cam. I'm going to check to see which cam is used and I'll let you guys know. Pistons are cast which is fine for my application.
One question though: The guy offers two different kits, one for 68-76 "Truck" 390 and a kit for 66-71 "car" 390. Would the difference in the kits be the cam and pistons? I believe I can ask for the better compression pistons if the truck kit comes with lower compression pistons. I just think the stock 8.2:1 compression is a bit low and the higher 9.5:1 car pistons (assuming that is what they are) would be a better choice. Any thoughts?

 

The cam I have to give away is a used truck cam. One of the ranchers I know says he likes to put the car cams in his trucks. More torque and still works well in a 4x4, so you might consider getting the "car" 390 kit, which hopefully would come with higher compression. The car kit might come with flat top pistons, meaning compression would be 10:1. This still might work out ok depending on combustion chamber volume, deck height, etc. Could set ignition timing at about 10 degrees max, to help avoid detonation, also could retard the cam 2 degrees if needed, but try the setup the way they send it to you first... could work great as-is. Don't foreget the ARP oil pump drive.
Smokey Yunik recommends doing an engine mock up at least once before actually assembling the engine to run.
You know about chasing all bolt hole threads with taps. So you could install crank w/ main bearings (no rear main seal yet), then verify crank turns freely at each torque setting as you torque bolts in 3 or 4 steps. Then install each piston w/o rings. torque rod cap nuts, verify crank with piston rotates freely. Keep adding another piston, verify smooth crank rotation. So now rotating assembly turns freely. Much goodness. Take everything out of the block, and now check the cam. Put cam in block, Dove performance says cam should rotate without much resistance in new cam bearings. May need to scrape bearings one by one to loosen up cam rotation.
Now you could do short block finaly assembly.
Now time to check valve job. I have seen more than once a bad valve job, where some of the seats were NOT cut, or very poorly cut. Many times now I lap the valves in with a light amount of lapping compound, verify a good pattern on valves and seats. Be sure to CLEAN ALL the lapping compound off the parts. This is a must or trouble will happen.
I just put a 390 together where the 3 top oil passages were not drilled thru correctly. You should be able to look down the length of the passage without restriction. Might want to check this. Sorry to ramble, Hope this helps.

 

I ordered the kit with the car pistons for the higher compression. They do come with the valve reliefs and I'm getting the RV towing cam thrown in at no extra cost. I'll let everyone know what it all looks like when it comes in. Should get it by Thursday.