Will 390 high compression car piston work in a 360 truck engine?
 

I was looking at swapping out the 360 for a 429. It is too much work to get involved with at this time. I was wondering if 390 hi-comp pistons will help the anemic little motor?

The highest compression stock type 390 car pistons are the same as standard 360 pistons. Same part numbers usually.

Now, someone might make a domed piston or something.

The best way to improve your 360 is to put a 390 crank, rods, and high compression pistons in it. Silvolite 1131's would work great. It should also be noted that high compression 390 and standard 360 pistons are both Silvolite part number 1131.

Edit: Anemic? You can wake that motor up. Look for a 4 barrel intake manifold, a Holley 600cfm carb, and headers for it. I can almost guarantee you'll have enough power then, assuming the rest of the motor is in good condition. The headers are a must. Those stock type exhaust manifolds are IMO the worst design ever by any manufacturer.

Kurt, what kind of thickness of head gasket did the 360's come with from the factory?

I have no clue, I've never knowingly took apart a stock from the factory 360. I did take apart one from the junkyard, it has gaskets in it that resembled the standard Fel-Pro's. That's probably what they were.

I don't think you can gain anything useing the 390 pistons because the pin bores are
higher due to the longer storke of the 390. Unless you change crank compression will be lower.

yeah they will not work the stroke is longer in the 390 so the wrist pin is in a lower place from the 360 piston just like people put in a 390 crank in a 360 and dont change the internals and wonder why the piston taps the head.

First off, let me say welcome aboard :-X22

Secondly, the gang pretty much covered your thoughts. The 360 can be brought to life as a 360 with a cam/manifold/carb/exhaust changes. It will not get you near the fun factor that upgrading the internals (crank/rods/pistons) to those of a 390. If you decide to go the 429 route, you will need a new tranny, if it's an auto, and the engine stands from a late 70's truck running a 460. There are a few other little things, but a swap is a swap, not a replacement.

--Mike

Yea, if you change to a 390 crank there are several rod piston combos that you can use.
Don't use a 390 crank with the longer 360 rods and 360 pistons.

You can (I think anyway) a 390 crank with 360 rods and lower compression 390 (factory pickup truck) pistons. But I really think that is pointless because the rods aren't as strongs as the 390/406/410/427/428 rods.

You can (and should anyway in most of our opinions anyway) use a 390 crank with 390 rods and 360 flat-tops.

You could also get a 410/428 crank (3.98 stroke versus 390/406/427 's stroke of 3.78) and make your engine anywhere from a 410, 413, 416 and possibly a 419 or 422 with .040 and .060 overbores. Some 360 blocks can go to 4.13 bore which is the same bore as the 406 and 428 (.080 overbore) but I wouldn't bore the block anymore than it needs to clean up. If you are going to go above .030 you should probably get it sonic checked but a lot of people take theirs .040 and .060 over and don't really have any problems to speak of. I would say that if you are going to go anything over .040, get it sonic tested. I don't know what kind of shape you block and engine in general is. Has it been rebuilt recently, how many miles, never been rebuilt? You may get lucky and not have to bore it at all if you do decide to totally rebuild it.

What everybody is missing is the reason both engines use the same piston with a different stroke crank. The 390 uses shorter rods than the 360. The 390 rods are 6.488" and the 352/360 rods are 6.540", so the pistons are identical.

Well Bear, the higher compression car 390 pistons are the same as 360 pistons but the the 390 pickup truck (low compression - dished with 4 valve reliefs) are not the same. The pin heighths between the 2 are different also. I'm sure you know this but thought maybe someday I would get a chance to catch ya on something! (jokes)

Update on my 360
 

Forgive me for not giving more details on my 360. Here it goes:
71 F250 Camper Special
360 ( Appears to have been gone into at some point.)
New Cylinder Heads Driver Bank is a D2TE/ Passenger bank is C8AE
(DON'T ASK, THIS IS HOW I GOT IT!)
Headers
Edelbrock 390 Intake
Holley 600 on top of 2 inch Phenolic Spacer
Recurved Distributor- Not sure of total timing but it comes in relatively fast.
Blue Streak Cap/Rotor/Points Kit
ACCEL Steel Core wires
Jacobs Electronics Ignition
C6- Appears to have been changed and feels like a higher stall converter installed.

I bought the truck at an auction for almost nothing. You won't believe it if I tell you.
After getting the truck I switched out the Edelbrock 600 for the Holley,, added Phenolic Spacer and Ignition system. recurved the distributor. Then I added the headers and got rid of the glass pack exhaust that was on it. Put on dual Dynomax Mufflers and she sounds great. The truck runs BEAUTIFULLY! I was just looking for more POWER!

After all the great advice from all of you, I have decided to forgo the 429 swap. She will go into a Ranchero I have my eye on. I will keep the 360 and go with a cam and better exhaust. I have a line on matching cylinder heads(D2TE) that I will put stainless valves in. I'm going with a larger exhaust valve only. I did this on another 429 build and the results were quite pleasing. Lots of torque! I also will be going with a better than stock cam. Any suggestions? How much can I shave off of heads before geometry becomes an issue?

Now back to the 390 piston. I was looking at a set of domed 390 car pistons to put in the 360 block. From what I read the pistons are the same for 360 truck and 390 car correct? Well if I go with a domed car piston, won't it make up some of the compression difference?

P.S. Do your wives like your trucks? Mine loves this one and does not mind me spending a little money on it. She really loves the noise. She is a displaced redneck now. She is from Cali and now resides here in Ga and she is fitting right in.

Yeah, but we are talking about a 360 here and not the 390 truck motors. And yes the 390 truck pistons are different, but this guy has a 360 and was asking if the 390 hi-compression pistons (has to be car 390 because there is no hi-compression truck ones) would help him. In a 360 no, in a 390 yes, but I specified the 360.

Not sure, would have to see them and know the compression heighths. If they have the 360/car 390 compression height and a dome then yes, they could help a little (how big is the dome and does it have valve reliefs?) Not sure on how much you can take off the heads but I think .030 is the max and you will have to get the intake sides and ends machined down or the block ends and intake sides of the head I believe. Maybe could mill the decks of the block some too.

Most of the compression increase in cars is due to smaller combusion chambers in the 390's.

the pistons are advertised as 11.3:1. High dome w/ no valve reliefs. Not sure of compression height at this time.