FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 63.5xl on April 27, 2015, 06:22:37 PM
-
I need to order pistons for my .060 over 390. I think I have figured out how to do the measurements (but I could be wrong) and get numbers, but don't know what to do with numbers, what works best together and what not. So I need some help to put this together the 1st time and be done with it. Going in my 3900 lb. 63 1/2 with close ratio 4 speed and 3:50 gears and 29 inch tires. Maybe some has a different piston in mind.
I am ok with 91 Octane, which is what we have here in Kansas. Weekend driver, and about a 400 mile round trip to my daughters every other month. Has 406 shorty headers and ford tri power.
Heads are 63 c3 heads with 69 cc chambers, block bored .060, std 6.488 rods. Cam research 291 cam, 540/565 lift, 226/234 duration @ .050 with 109 lobe separation. Using 2 different Felpro head gaskets 8554pt measures .051 compressed with 4.232 bore. Felpro 1020 measures .041 compressed with 4.400 bore. Using 10.170 as a deck guideline.
Pistons I have found are:
H304P dish cast piston with 12cc volume and 1.759 compression height. .033 deck height. 9:22 to 1 with 8554 gasket and 9:35 to 1 with 1020.
Quench then looks to be .084 with the 8554 and .074 with the 1020.
H395P flattop cast piston with 4cc volume and 1.759 compression height. .033 deck height. 9:94 to 1 with 8554 and 10:09 with 1020 gasket.
Quench is also .084 with 8554 and .074 with 1020.
L2291F60 flattop forged with 10 cc volume and 1.776 compression height. .016 deck height. 9:72 with 8554 and 9:87 to 1 with 1020 gasket
Quench is .067 with 8554 and .057 with 1020 gasket.
Thanks for any help.
Carl
-
Carl, nice to see you on the board. I'd like to run a dynamic compression ratio calculation on your combination, but I'm not sure what the advertised intake duration is. When you say it is a 291 cam, does this mean it has 291 degrees of advertised intake duration?
If that is the case, then any of those pistons is going to be fine, because your DCR numbers are pretty low with that setup. In fact, I'd be looking at trying to up the compression ratio to 10.5:1, to get the best performance with that cam. Maybe have the block decked a little?
-
Jay, Maybe I bought the wrong cam to start with I do not know. It is going to be a driver with some spunk to it and a lope at the stop light and highway driving every other month. I have not started to put the short block together yet but have bought the cam which I could sell and maybe get some of the money back if something different would work better. I have attached the cam card if I got it attached okay.
Carl
-
I think that cam looks fine for what you are doing. Of your piston choices, I'd go with the H395P with the 1020 head gasket, and maybe get the block decked at the machine shop, just to up the compression a little bit. I think with that cam you are safe to 10.5:1 or so.
-
How much should I have them deck the block, or would it be better to go with the L2291F pistons as they have a 1.776 compression height where the h395p have a 1.759 compression height instead of decking. What does a deck the block usually cost? Sorry for all the questions, No help local for the fe questions as every machine shop I have been too including the one who bored my block are all chevy people and admit they know nothing about what works for an fe. I had already sent the dist off to Faron Rhoads and got it back and he set it up for 38 degrees all in by 3200 rpm and to set the initial at 14 to 16 degrees
-
I'd have the block decked first; have them cut as little as possible to square it up, and then give you the deck height. A lot of blocks won't square up until you cut them to 10.16 or 10.15. Once you know the deck height, you'll be in a better position to pick the piston.
Sounds like Faron has your distributor dialed in just about right.
-
Thank you Jay, I will take it to a shop tomorrow.
-
Jay, how much can a person deck the block without affecting intake mounting
-
Usually you can go to a 10.15 deck without problems. Any more than that and you are probably looking at cutting the intake side of the heads, or the intake itself.
-
Got the block dropped off, told him just to square it up, said he should have it by next Friday.
-
Jay, lets say the block squared up and it measured 10.167 for example, would I want him to take a mimimum off. Say if it squared taking .003 off, would i want him to take .another .007 off for a total of .010 down to 10.16? In other words if the block is squared and we are not to 10.16, then take it to 10.16. I guess you know what I am trying to say Jay.
-
Not Jay but....
It would be helpful to mock-up the block with the crank, pistons and rods (say 4 corners) and with the selected head gasket check the quench distance. Hard to do now of course. Yet, if it's a streeter and not a race engine, I'd say save the $ on the 2nd pass. Still, if for example the pistons still end up in the hole with an assumed .047 quench distance, with .040 or so being ideal, then yes, a 2nd cut would be helpful. I guess it depends on money, as always, and time.
-
Carl, I'd suggest cutting the deck no more than absolutely necessary to square it up, and then see where you are at for compression ratio. Ideally you would like to have the pistons at exactly the deck height (zero deck) when they are at top dead center; this gives you a good quench distance of about the head gasket thickness, say 0.040". If you are down in the hole too much, quench distance is too big and combustion efficiency will suffer. However, if you are zero decked on the pistons and the compression ratio is too high, then you have to add volume to the combustion chamber somehow, and that can be problematic.
Square up the decks and mock up the crank, and one piston and rod, and see where you are at. You can make decisions from there.
-
Getting excited for next Friday to come and see where I am at.
-
Been over a month, been working on body, grandkids ballgames, honeydos, and what have you. Had block decked to just square it up. installed one piston and it came out to .031 deck clearance. That is the H304p dish with 12cc I mocked up that has the 1.759 compression height. Looks like the H395P flattop with 4 valve reliefs, which I am guessing at 4 cc, would be at 9.98 to 1 and the dish at 9.26 to 1
Any suggestions now.
-
So I have been playing with the online calculators at https://www.uempistons.com and it looks like I am right at 8.0 dynamic compression ratio with the cam I have if I did it right. It said use the intake closing at .050 and add 15 degrees. My cam is 38 degrees intake closing so I put in 53 degrees.
But with the deck height of .031 and gasket of .051, the quench is at .082, do I need to get the quench lower which will raise my compression to do this.?
Will it run on 87 octane with the H304p dish pistons at 8.0 dynamic CR. I was ok to buy 91, but the more money and time this is taking and gas creeping up on price again. I think I just want it to sound good, exhaust and cam, and drive it.
-
Carl, my only concern with your combo is 3900lb car, close ratio (2.32) 4 speed, 3.5 rear and 29" tires. Might be hard to get it off the line? Easiest and cheapest thing to change are the tire height(lower), second ,rear gear, 3.70 or more if you keep the tire height, (although bearing in mind your highway driving) With that current setup you will be doing about 2400 @ 60mph, which is fine on highway, but it's the initial takeoff in 1st gear (2.32) which might need some revs to get off the line and maybe chirp the tires pulling a heavy car? Others might have some thoughts on this?
-
I hear ya Machone, gearset is another $580 to change it over to wide ratio. I really like driving the close ratio, once you get moving, but it would make more sense to change it over to a wide. I just have to spend another $580 i don't have. Lol.
Unless i win the lottery and put a 4.11 with a gearvenders behind it.
-
Carl, even at only 8:1 DCR I don't think I'd run regular in it, you'd be a lot safer running 91. I think I would run a thinner head gasket (most are about 0.041"), which would give you a little more quench and bump the compression ratio just a little, and run premium fuel.
-
Jay or anyone else, I run the numbers again on the pistons with the actual cc number for the piston dome. I have the 304p's all ready but I called and I can return them, plus they were only $100 for the set, o which set should I stick with?
all the following with .040 gasket and the cam I have
H304p dish is 12.8 cc Compression Distance 1.759 Static CR 9.410 to 1 and Dynamic CR 8.131 to 1
JB 1116 dish 9.5 cc Compression Distance 1.760 Static CR 9.723 to 1 and Dynamic CR 8.396 to 1
H395p flattop 4 reliefs is 6 cc Compression distance 1.759 Static CR 10.039 to 1 and Dynamic CR 8.664 to 1
JB 1131 flattop 4 reliefs is 8 cc Compression Distance 1.760 Static CR 9.8.65 to 1 and Dynamic CR 8.516 to 1
-
I had based tge previous number from a ford 6051 gasket, should i go with a thinner gasket, i see they have some .020 gaskets at summit
-
You have cast iron heads, right? I wouldn't go over 8.25:1 for DCR with cast iron heads. I think I'd stick with the pistons you've got.
-
Thank you for your reply Jay. I will order the ford 6051 head gaskets and put it together,