Hey all,

I am finally starting my 360 to 390 build but I wanted to run some things buy the group to make sure that I am on the right track since this would be my first ford rebuild (say a prayer).

Performer RPM Intake
Holley 600 cfm 4 bbl vac sec carb
D2TE-AA Heads with some mild porting
Crane Cam #343941 and the lifters to match
Adjustable Rocker arms (Crane part number CRN-34772-16)
427 Adjustable Pushrods
New Crane Springs (Crane part number CRN-96801-16)

I have the 390 skirted pistons that have the dish in them.

Rods and crank will be comming....

Comments? Thanks for any input you all may have...

 

First and most important:

What exact pistons are they? More specifically, are they car or truck pistons? What is the compression height? If you got the truck pistons, you will have an exceptionally low compression ratio and I can guarantee the motor will be a dog. We need specifics on these pistons.

Second, you will notice the ports are bigger on the intake manifold than on the heads. Obviously, you'll want to match 'em up. Dont go too far back into the runner or you'll hit water. You want to go the same distance back into the port as the distance the intake manifold overlaps the cylinder head port. Radius it off.

Otherwise, looks good...

 

Ah yes the pistons. You will have to excuse my late night post for the lack of information.

They are the pistons from the 360, with the slipper skirt and the flattop with "eyebrows."


thanks again all...

 

From a 360? So, you're just going to hone the bores and put those pistons back in? Are you sure it hasn't got too much taper?

 

Word of advice from someone who just learned the hard way... "NO RIDGE REAMER" ;( coulda saved myself lots of grief...

 

why should the taper matter, as far as I know we are talking about the diameter of the slipper to the piston diameter. I wouln't think that this would cause any problems, but then again this is the first ford build for this guy. As far as the reamer...the machinist told me that they would be grind gingerly...otherwise I suppose that it would be a .030 build up, but again see the above comment.

Please oh fe gods set me straight. I would hate for this time and effort to be waisted.

 

the best advice I would give you is get the book How to rebuild Big Block fords by Steve Christ..18.00 and when you get to the part about the ridge reamer..skip it!!!..

Taper is the wear on the cylinder at the top just below the ridge compared to the std bore found at the bottom. If excessive the rings will be doing the mojo while riding the walls and not last as long as you will want. if the taper is within reason... hone it and go..according to the book max taper .005 or less and glaze breaking to rering is good for a 50k life ..you decide...I'm paying 120.00 to bore .030 over and hone after the ridge reamer stunt..all in all I'm happy I'm going with the overbore now as the assembly cost almost the same either way-in the long run this should be worth it.

 

Am I correct in assuming you're converting from a 360 to a 390, and using the stock pistons that came with the 360? If so, you cannot use those pistons anyway. They would work fine, IF, and this is big, IF you have clean 4.050" bore! If the 360 had more than about 10,000 miles on it, you do not have a clean bore. If not, you'll need to have the block overbored and new pistons anyway. Reason is, if there's any ridge or taper left on the bores from the 360, it will either quickly break or wear down rings with the longer stroke of a 390.

I hope you meant new replacement 360 pistons.

 

so for clarification purposes...

Prelude) I am trying the bone stock 360 to a rippin $#!& 390 build up (I don't care about gas prices, but I also am not going to pay $1000 for the rods alone so use your imagination). I have the Christ book, and have been following it thus far...

1) I have the stock 360 pistons, and was going to have the cylinders honed. I was under the assumption that as long as they were slipper skirted, and had the eyebrows I would be good to go with reusing them.

2) What I am hearing now is that I should just have the cylinders bored .030 over and get oversized (and new) 390 pistons. I was planning on getting the rebuild kit from larry's performance out in CA.

3) Will the cam and lifters that I mentioned before be applicable?

4) I realize now that this rebuild is forcing me to start drinking in the morning . Good lord, please someone please make a tech article and sticky for this process (hint hint)

 

When I get some time I'll work on that tech article. I've got to put mine back together yet!

If you're sure those pistons are in good shape, you could find a 352 block and bore it .050" to 4.050". Then you could use those pistons.

But yeah, you'd be better off to just bore it .030", get replacement pistons, and be done with it.

Now, you're going to have a few options when you go to get replacement pistons. Here's a selection:

1. Keith Black KB150 piston. 1.78" compression height, 20cc dish. Gets you somewhere around 8.8:1 to 9.2:1 compression, depending on head gasket. Probably too low for what you're doing.

2. Silvolite 1131 or 1131h. 1.76" compression height, 8cc valve reliefs. Gets you somewhere around 9.4:1 to 9.9:1 compression, depending on head gasket. This piston and a steel shim head gasket would probably be ideal for what you're doing.

4. Silvolite 1130. Same as above but with 19cc dish. Gets you somewhere around 8.5:1 to 9.0:1 compression, depending on head gasket. If you were building a low rpm torque motor with a small cam you'd use this piston.

5. TRW L2291 (forged). 1.776" compression height, 10cc valve reliefs. Gets you somewhere around 9.55:1 to 10.1:1 compression, depending on head gasket. This piston would be ideal if you're going to run nitrous or forced induction. Also good if you like bulletproof pistons. I have a set in my 390. I recently had a valve sieze in it's guide, and the piston smacked it. For the most part, aside from a small scratch, the piston was undamaged.

There are some others that I did not list, that are similar to the Silvolite offerings. The compression ratios I listed assume 72cc combustion chambers. The lower ratio uses Fel-Pro head gaskets, the higher one Mr. Gasket steel shims. Not all of those are realistic in the real world though. For instance, the KB150's and steel shims would only leave .030" between the piston and cylinder head at TDC. If you were to rev it up too high, the pistons could smack the heads, with disasterous consequences. You should try to leave at least .035" between the pistons and heads at TDC. Try not to go over .060" as you'll lose all benefits of the FE's combustion chamber design.

For your application, I would suggest either the Silvolite 1131 pistons with Mr. Gasket steel shim head gaskets, or the TRW L2291 forged pistons with Fel-Pro head gaskets.

 

I would choose door number 2

but this brings up a second question...

Would I still use the Crane Cam (#343941 and the lifters) or would there be better recommendations?

the follow up would also be where can I get those pistons and how much are they going to run me?

Thanks for all the help

 

the follow up would also be where can I get those pistons and how much are they going to run me?

 

I tried to base my recommendations above around that cam, so yes, they'll work fine.

The part number on www.summitracing.com is UEM-1131-8. If you need an oversize, like .030" over for example, the part number would be UEM-1131030-8. They cost $82.99 for a set. Also, their listed compression distance on Summit is wrong. It should be 1.76". Here's a link to those pistons on their manufacturer's site:

http://www.kb-silvolite.com/spistons...tails&S_id=143

 

bless you rusty....the build woudn't be anything without the FTE group!

 

I just built a 390 with the kb150's and the same cam. This makes for one one heck of a motor. I used the felpro permatorque gasket and have had no problems runs fine on regular gas but alot better on premium.