I was reviewing the Silvolite website again tonight, trying to figure out what to do with those two old 360's in my garage. Lame, yeah, I know. I'm bored. But anyway, I've found a possiblility for raising compression on the 360's affordably and to good effect.

Take a look at the Silvolite 3144d pistons. They say they've got a 1.902" compression height, and a 2.6" diameter, .190" deep dish.

Dish? What's he talking about a dish for? Hold on, I'll explain.

When we convert the numbers to centimeters, we get a 6.6cm wide, .4826cm deep dish. So we figure the area. 6.6 X pi = 20.7345cm^2, and then we multiply that by .4826cm and get 10.0065cm^3, or 10cc. This gives us a piston with 1.902" compression height and a 10cc dish!

So what's he getting at?

I put these numbers in Desktop Dyno, and assuming a 70cc combustion chamber commonly found on 360's, using a .043" thick head gasket (I measured a used one), and 6.54" rods, I came up with -.022" deck clearance, and a compression ratio of 9.60 to 1. IN A 360!!!

But that leaves the piston above the deck! You cant do that!

I beg to differ. With the .043" thick Fel-pro blue permatorque head gasket and .022" above the deck, we are left with .021" of clearance between the piston and the cylinder head. Read this article.

It would appear, from where I'm sitting, that we have a viable alternative to the 390 conversions that we've been recommending wholesale recently.

Thoughts on my ramblings?

 

You need to take a deep breath, take your fingers away from the keyboard, and step away from the computer. Do you have a woman? If not, get one. Otherwise, it sounds like a good project just to see. You might be on to something.

 

Looks great on paper, I guess. If you like a motor that winds up quick, the 360 is great. If you want more grunt at lower RPMs, look to the longer stroke of a 390 or 428 crank.

I'm not discounting any ideas, it's cool that you're looking for ways to get more snap out of the 360. For someone who doesn't work their truck often, or go off road, the drive around town could turn into a whole lotta fun.

For my truck, and my use, I miss the 390 that the 360 replaced. When I finally do have enough money to rebuild, I'll be looking for early torque and a transfer case that actually has a low range.

JMO, Mike

 

It does look good on paper, but you would have to put it into play in a block to see if your numbers come out correct. One thing you can also ponder would be to use a .020 shim gasket with your .040/.043 FelPro, that would put you pretty close to 0 deck (don't ask how I know this...). Definitely need to do a valve clearance check on those.

--Mike

 

Any suggestions on exactly HOW this is done? I havent had much luck.

Oh and Mike, if we increase the head gasket thickness to .063", the compression goes down to 9.13. Still better than stock 360, but kinda low if you ask me.

 

Hey thanks for that lesson in math ( my math sticks)
I have been looking for an alterntave to sup up my 360 ( IE other then buying new rods and a 390 crank - even thought about building a 410)
thanks again - here in Connecticut finding a 390 in a junkyard is like finding a needle in a hay stack ! - pleanty of 360's though

 

I know, I was up to the local junkyard today and must have seen at least 10 360's up there. I know theres more than that up there, probably around 30-40 if you looked hard enough. There was only one 390 I found though.

Now it looks like we have a way to get some serious power out of all those 360's out there.

 

not only that but doesnt the 361 FT piston use 3 compression rings ?
That should add to the durability of the already stout ( low rpm use 1500-4500) 360 truck engine.

 

The 360 is merely a 390 with a 352 crank. Basically a de-stroker. I had a rebuilt 360 with 10:1 flat tops(small dishes in the pistons for valve clearance) and it performed rather well. I did, later on, change out to the larger 390, and found it to be the preferrable engine. The 360 was a bit quicker for acceleration, and better on fuel(after the rebuild) but it didn't idle up the rough stuff with the stump pulling power the 390 provided. In a 4x4, touque is king.

 

I totaly agree that torque is better but in my neck of the woods I would be better off switching to a 400 as they are everywhere ( wont happen though, I love my FE) The 390 just doesnt seem to be avaliable .
Secondly as you said about mileage - with gas prices the way they are 1.99 a gallon for regular , I need to take that into consideration as my 1975 F100 4x4 , np435,dana21 pickup is my daily driver .
So in that sense I would rather improve what i already have .
Belive me I have priced out a new 428 crank from scat ( to make a 410) and I cant seem to justify the cost for a truck that does what I need it to do already with a STOCK 360 (stock air cleaner ,egrvalve,stock exhaust,and holley 350cfm 2bbl.
So in saying that I think that when my engine is up for another re-build (last one was just rings bearings and timing set on a still standard block D4TE mirror 105 ) I am going to try those silvolite pistons on an otherwise stock engine .

 

No, the ones I linked to are the 2 compression, one oil ring pistons. They do make a 4 ring piston, its the 3142d. It's got a 12cc dish with the same compression height.

In addition, both of these have an iron top groove, which should help durability. As for the 4 ring piston, I dont know if it would help performance or not. On one hand, the extra ring creates drag, but on the other it helps seal up the chamber better. I do know it would help durability by stabilizing the piston in the bore.

 

I was thinking more as a heavy duty engine , in our lite duty trucks
I wouldnt want the 4 ring piston in drag racing but in heavy towing applications it might be benifitial.
I wonder what the difference is in drag between the two pistons .
I think these engines have a prestty good rod ratio , I dont think the 360 persay is known for piston slap so I guess it is an idividual's choice on the extra ring .That being said I have read that the wrist pin bore is offset 0.0625 toward right side of the engine on the FE piston .
The 4ring FT pistons are NOT made with this offset.
More compression and friction cause heat as we all know so I would surmise that the regular 3 ring piston(3 rings total) is prolly ok?

 

Personally I'd use the 3 ring piston for regular street duty, and the 4 ring for towing.

I just wish they made these pistons in something other than just plain cast.

 

Great idea rusty...I just found your math to be a little off: Area = pi x radius^2, 6.6 is your diameter so 3.3 is your radius, thus Area = 3.1416 x (3.3^2) =34.21194 cm^2, now take 34.21194 x .4826 cm = 16.5107 cm^3...or about 16.5 cm^3.

Someone please correct ME if I am wrong...it has been known to happen before!

 

Yep you're right. According to this online calculator, it comes to 15.66cc's.

However, in the picture it shows that the dish has a definate chamfer to the bottom of it, so it's probably less than what the calculated value is.

I'm going to send 'em an email and ask. That way we'll know.