I tore down my 390 I bought off craigslist that I am going to put in my 75 3/4 ton hi-boy with C6 and 4.10s. Not a off-road rig, just a sunday driver.

I noticed that the motor that I bought looked to be a fairly recent rebuild. I also noticed it looked to be running rich, due to the black carbon that had been starting to build up on pistons/heads.(It had a 750 edel on it that I plan to replace with 600 holley) It's a .030 over motor with flat tops.(don't know which kind) The deck height that I was able to measure was right around .12" I plan to bring my digital calipers home from work to re-measure for a more accurate measurement. Also has a pretty new double roller.

My question would be what head gasket to use.(I have pictures of pistons and can email) I'm going to use C8AE-H heads, a crane 941(that has roughly 200 miles on it and If it makes sense to use with existing parts) and a performer 390. If I do pull existing cam and replace with 941, can I re-use pushrods and just throw in new lifters? I also plan to use existing non-adjustables rockers. I guess y'all have to know what cam is in it now? If so, I'll check. Shouldn't number behind on the front end, right behind timing gear?

I've got pictures of pistons, so I can email them.

Thanks for any info. I know I probably left some necessary info out, but if you let me know, I can get it. Just ask.

 

After some research on deck clearance, isn't that too much deck clearance? What do you suppose is the issue? These are 390 truck pistons. Should replace pistons with????

 

Did you actually mean .120" deck clearance, or .012"? That makes a big difference.

If it's actually .120", you've got a big compression problem there. It sounds like the rebuilder went with stock replacement parts. Nothing wrong with that if all you want is stock performance. I certainly wouldn't use the 941 with those pistons in there though. What do you expect this motor to do?

 

Nope, I really meant .12 inches. That is what is scary. So, by the sounds of it to you, then it is a stock rebuild with the deck clearance being .12"?

I don't have many options, I don't think. I suppose I can replace pistons, but then I suppose I'd have to clean up cylinder walls? (I believe I remember a slight rib at top of wall, where piston stops.) Could I spec taller compression height pistons without boring more? I really didn't want to touch bottom end, but will replace pistons, if need be.

My truck is not a thrasher for the woods, but is rather used for runs to the garbage dump and hauling hay every year.

Thanks for any insite.....

 

Truck 390's came with a deck clearance of .112". It sounds like the rebuilder got aftermarket "replacement" truck 390 pistons. Most replacement pistons have a slightly lower compression height than original factory parts for some reason.

It sounds like for what you're going to be doing with the truck, a simple stock rebuild would be totally adequate. I would make sure of the cam that is in the truck. If he used an aftermarket "stock replacement" cam you could have a problem. Some of those grinds are spectacularly bad, with advertised duration more than a Crane 343941, but very low .050" duration. So you'd get a motor that idles bad, with no torque and doesn't breathe up top either! If it's the stock camshaft you should be ok. If not, I have a couple very small Crane or Comp grinds in mind that would work good. Again, do not put the 941 cam in there with those pistons. Your best bet for camshaft identification is to contact the seller and / or rebuilder.

You could replace the pistons, but I think for what you're doing with the truck that would be too much work. You'd have to at the very least remove the ridge and rehone the cylinders to put taller pistons in it. You would have a more powerful efficient motor, no doubt about that, but for a garbage truck? Leave that to the racers and people like me with tires to burn!

 

Thanks for following up. Before I bought it, it seemed to run great. It idled good, and wasn't rough at all. As far as identifying the cam, shouldn't the front of it be stamped, or do I pull it out? I just got off the phone with the guy I bought it from and he had no info on the motor. He said he bought it from a guy that told him that someone went thru it, before selling it to him.

Yer probably right about the garbage truck. It'll be good enough and better than the 360 w/ logs and a 2bbl, that was in it. I've got headers that I plan to put on when I drop the motor in. I also wanted to clean up the exhaust ports a bit. I should touch the intake, with the exception of matching performer intake, right?

Thanks for your help
Mike

 

The regular Performer 390 should already match to the intake ports. That part should be fine. A good port cleanup always helps, so go ahead and do that if you have the time. With headers and a 4 barrel it'll work great for what you're doing.

I cant tell you much on the cam identification. I haven't really done much in that area. Usually with me it's stock cam out, Crane cam in. What I can tell you is about the two 360 cams that I have. Neither have any information on the front. Between the rearmost cam bearing journal and the rearmost lobe there is some information though. The cam that I pulled out of my old 360 has "CWC" with "25" cast underneath that. On the other side, it says "SF 63". There is also some information near the center bearing journal. It says "C2" on one side and "D2" on the other. On the other side of the center cam bearing journal, it again says "CWC". The cam that I pulled out of the junkyard 360 motor simply has two dots cast near the rear cam bearing journal. As far as I know, both are stock cams. I wouldn't be surprised, however, if one had been replaced at some point.

 

Thanks for the info. I looked at my cam tonight and i decided to yank her for identification. Here's the info I got; the rear of the cam is stamped 930718, with a J2 underneath it. I also spotted a CWC with a 12 underneath that, and directly 180 from the CWC/12 I spotted a SF63 with a D3 unerneath it.

I also brought home my digital calipers and came up with a measurment of .118 inches for my istance between top of piston and deck.(Deck height, right?)

OK...... let's say with what we have to work with, and in using existing pistons and cam, what else could I possibly tinker to get the most out of this motor? Is it going to be beneficial to go ahead an pay the extra money to get thinner head gaskets, rather than using the ones that I am going to get when I buy a gasket set?

That sounds good about the performer matching up with the heads. That part is covered. Should I go ahead and gasket match the headers, and if so, which gaskets would you recommend? Sorry for all the questions. You've been very helpful and I appreciate it. :thumbsup:

Lastly, I noticed right above the exhaust ports there are drilled an tapped holes, with set screws installed in them.(refer to page 62 of Steve Christ's book. Top left photo.) What are these for? I noticed them on these heads and they are not on the other 3 sets of heads that I have.

OFF TOPIC: (Please reference page 125, center photo.) Notice the ribs on the side of the block? I have another 390 block with these ribs. Is this a service block of some sort?

Thanks again for your knowledge. You've been very helpful in my ignorance of FE knowledge.

Mike

 

I would guess from the D3 that the cam is a stock FE cam (as in D3TE or some other Ford number). Mine had a D2 on it.

Yep, .118" is your deck clearance.

A set of thinnner head gaskets would be beneficial from a compression standpoint; it'll still be low though. However, you want to make sure your block and heads are absolutely perfectly clean and flat!!! Also, use the Permatex Copper Spray-A-Gasket stuff on 'em. Give 'em a couple coats, let it get tacky, then install.

Dont match the exhaust ports! There is a reversion dam and intentional mismatch. Again, just clean up the ports. Use whatever gaskets come in the set that match the port size. Normally they'll ship a few different sizes.

As to the holes in the exhaust ports, these are AIR injection holes. This was an early emissions device. What it did, was inject air into the exhaust ports through these holes in an attempt to burn off any remaining hydrocarbons. Yours have the plugs in them, so dont mess with 'em! Also, on the inside of the port near these holes there should be a giant bump. Grind that sucker off of there and smooth it up with the rest of the port. Breathing is improved this way.

Lets see, what else to get the most out of it... A good head porting job would be about your best bet right now. You're putting a 4 barrel carb and headers on it, so that part is taken care of. There is power to be had in getting it tuned correctly, but you're not that far yet. Anything more would involve pistons and a cam.

Oh, and that block. I think it is either an FT or a service block. I'm not 100% certain though. I do know that none of my blocks have those ridges. This includes two "mirror 105" 360 blocks, and some mid '60's 390 and 352 blocks.

 

OK, thanks for the info again. BTW, I see summit offers fel-pro, selaed power & Mr. G. Is there a preference as to which set?

What do you think about this? I thopught about installing studs in the heads for the headers, rather than using bolts. Does this seem like the way to go for you? I figured if I did that, then I can install brass nuts.

 

I'd say either the Fel-Pro or the Speed Pro, as the Mr. Gasket set doesn't include new valve stem seals.

I like the idea of studs for the headers. I usually just go to the hardware store and get 16 grade 8 bolts of the appropriate size though. I'm cheap like that.

 

Do you have an approximate CR for this motor, using the different head gaskets?

Am I going to be able to tell the difference if I went with the .041" gasket, or the .02"?

 

Well, assuming 8cc valve reliefs and 73cc combustion chambers like my old 360 heads had, and assuming it's at a .030" overbore, with a .020" thick Mr. Gasket head gasket you'd have 8.28:1 compression. With the .041" Fel-Pro it would be 7.93:1.

 

OK, thank you for figuring that out for me. BTW, I've also got a set of D2TE-AA heads sitting on the shelf in the garage that have been magnafluxed and are clean.(They are bare and are just the castings)

I was thinking about runnning these heads, instead of the C8AE-H heads that I pulled off the motor, since they have the hardened exhaust seats. Can't I not port the D2's, then trasnfer valves/springs, ect. from the C8s onto the D2s, or is it not that simple?

Thanks,
Mike

 

Well, you could port the D2 heads. I would. What I would do is get a full new set of valves. You could measure your existing ones and only get replacements, but it would cause fits for your machinist to try and set valve to guide clearance, and you'd have to keep them straight as to which valve goes with which guide. Then, take the heads to a machine shop and have all new guides put in and the seats touched up. Bronze guides are probably the way to go. Take the new valves along so they can set valve to guide clearance as specified in the book. Be sure you take the book along and specify the clearance you want; I got burned once when my machine shop left them too tight.

If you have a little extra cash, you could get a set of 2.09" / 1.65" CJ size replacement valves and have the machine shop fit those to your heads. This will improve performance. They will need to install hardened valve seats though.

If you just transfer the valves over to the other heads, some valves will be more worn than others, and some guides in the D2 heads will be more worn than others. This will cause you problems, like oil burning. Also, the seat may be in a slightly different location on the D2 heads and the other valves may not seal right unless refaced.

When I put heads together, I like to hand lap the valves. Not to improve sealing or anything, although that may be marginally improved. I do it so that I can look at the resulting wear pattern to be absolutely certain that the valves will seal in the engine.