Who knows about rod/piston/crank specs?

[fords2fast4u]

So I had this used engine deal go wrong, and I came out of it with just a good set of eagle rods and a 70 351W block.

Now the Ross XL400 pistons were worn too much the shop says, and they recommended going with a cheaper piston anyways to replace it, since I'm not running a million HP. But I think i can have them turned down and still use them (i think my dad can mill them for free, so i might try that).

but this other guy has some pistons for cheap, but they're for a stroker. Can i use them with my stock length crank and eagle rods?

is there a source of info on what is interchangable and what isn't? or what compression will be produced by what CC/s in the pistons and head chamber?

yeah, i know i'm asking for stuff that people don't usually mess with, but I figure I'd give it a shot. thanks!

 

[seijirou]

So I had this used engine deal go wrong, and I came out of it with just a good set of eagle rods and a 70 351W block.

Now the Ross XL400 pistons were worn too much the shop says, and they recommended going with a cheaper piston anyways to replace it, since I'm not running a million HP. But I think i can have them turned down and still use them (i think my dad can mill them for free, so i might try that).

but this other guy has some pistons for cheap, but they're for a stroker. Can i use them with my stock length crank and eagle rods?

is there a source of info on what is interchangable and what isn't? or what compression will be produced by what CC/s in the pistons and head chamber?

yeah, i know i'm asking for stuff that people don't usually mess with, but I figure I'd give it a shot. thanks!

I can almost guarantee that you can't use the stroker pistons with your stock length rods.

Those stroker pistons almost certainly have a different compression height than stock. What were the pistons for? You might get lucky if they were for a 302 based stroker or something. But that would be LUCKY!


Have you concidered doing a 393? All you need is a 3.85 throw crank under $500, and some stock 302 pistons, which are pretty cheap. You use your stock length 351W rods, and you already have some nice ones.

Throw that together and you'll be holding on to the steering wheel pulling your face.

 

[seijirou]

Dude, I just checked Summit, because well, you gave me an excuse.

They have 3.850 throw Eagle cast steel crankshafts for $300 bucks.
8 hyper cast 302 pistons with rings 30 over is $175. Forged will run you $310

You can get individual pistons as cheap as $17 a piece.

Or there's always the used 92 - 87 302 piston route.

for the dollar I don't think you can beat a 393.

 

[DaSouthWon]

Are you talking about milling the tops of the pistons down to reduce your compression height or turning a +.030 down to say a +.020 piston? If it's the latter I strongly discourage attempting it. Piston skirts are not straight, their slightly barrel shaped. As far as milling the tops down, some pistons would be fine, and others are already on the edge of too thin to begin with. If you are looking for some inexpensive forged pistons google "blackjack pistons". I have never personally used them but looked at a set when I went to pick up some cranks from the shop the other day. I was really surprised, made in the USA, and looked to be decent quality. They may just be polished turds, but I think they're worth taking a look at. I believe they were less than $300 a set.

 

[fords2fast4u]

Well, as i said, the engine deal was all screwed up. I really got hosed. But this engine was supposed to be a 69 block 383W stroker, but it turned out that the block was no good, so i dove into tearing it apart and found out all this other stuff...

but i was talking about turning them down from a .060 over piston to a .040 over piston, since they're already worn quite a bit. I've heard of guys doing this years ago. And I thought that all pistons (no matter what size over) are forged from the same mold, and milled to specs anyways?
So if i could have them worked on for free, then its not worth it? I'd really hate to waste those expensive pistons!

but if they're not usable, then that's that. I'm not trying to throw together trash here, but I just heard that racing guys used to do it (like putting chevy pistons in a Boss 302 block and all that crazy stuff).

Anyways, Seijirou, you're sure that I can use my stock length Eagle H beam rods with this 393 build, so long as i get .040 302 pistons and this 3.85" crank? that would be just what I'm looking to do, since I've already got all the ARP bolts, a good block and rods. I considered selling all my good stuff and buying a longblock from CHP or DSS or something... but if what I have can work, it'd be cheaper to build my own i think. I just want it to be right!

thanks

 

[seijirou]

Anyways, Seijirou, you're sure that I can use my stock length Eagle H beam rods with this 393 build, so long as i get .040 302 pistons and this 3.85" crank? that would be just what I'm looking to do, since I've already got all the ARP bolts, a good block and rods. I considered selling all my good stuff and buying a longblock from CHP or DSS or something... but if what I have can work, it'd be cheaper to build my own i think. I just want it to be right!

thanks

If your stock length Eagle rods are stock 351W length, I am absolutely positive.

But don't just take my word for it

Strokers Wild: Part 4

If you're going to piece it together, you'll want to remember to get it balanced

 

[NIKwoaC]

With .040 over pistons, you'd actually be closer to 395ci... Just a thought.

Keep in mind that you want half your stroke plus your rod length and piston compression height to be as close to the size of your block's deck height as possible.

'70 351W deck height = 9.480"

Stroker Crank = 3.85"

Stock 351 Rod Length = 5.955" (I think thats right...)

Stock 302 Piston Compression Height = 1.605" (again, I think...)

1/2(Stroke) + Rod Length + Compression Height = Deck Height

1/2(3.85) + 5.955 + 1.605 = 9.485 (about the height of the block deck)

 

[PUNISHER RACING]

junk the pistons and get a set of KB's or TRW's if you nat. asp. get a stock 351 crank somewhere and just build a nice windsor.

 

[fords2fast4u]

well my eagle H beam rods are marked 6200BS, so I think they're 6.2" ... so thanks for the calculations NikwoaC, but i think I'm a bit off from that.

then i read on another website about stroking windsors, that a stock crank can be ground somehow and with a .040 over piston be a 377 or with a .060 over piston be a 383. (this motor was advertised as a 383, and it was .060 over with a ford crank).

anyways, with 6.2" rods, I'll have to figure out what else I can use. Today i was looking at a probe catalog and figured on 6.2" rods, but I can see that I'll need to do plenty more research before I buy anything.

My cheapest out is to use this stock crank and buy some forged pistons. But I need to know how tough it is? I read that a steel crank is good to 750 in a 351, and that you only would need a forged one if you were pushing that... but that was steel. aren't the stock crankshafts nodular iron or something?

PUNISHER RACING - I'm not really N/A, as I'll be adding 150-200 shot, depending on what i push N/A. I want to be in the 650 FWHP range on the juice, 450-475 N/A.

 

[seijirou]

well my eagle H beam rods are marked 6200BS, so I think they're 6.2" ... so thanks for the calculations NikwoaC, but i think I'm a bit off from that.

then i read on another website about stroking windsors, that a stock crank can be ground somehow and with a .040 over piston be a 377 or with a .060 over piston be a 383. (this motor was advertised as a 383, and it was .060 over with a ford crank).

anyways, with 6.2" rods, I'll have to figure out what else I can use. Today i was looking at a probe catalog and figured on 6.2" rods, but I can see that I'll need to do plenty more research before I buy anything.

My cheapest out is to use this stock crank and buy some forged pistons. But I need to know how tough it is? I read that a steel crank is good to 750 in a 351, and that you only would need a forged one if you were pushing that... but that was steel. aren't the stock crankshafts nodular iron or something?

PUNISHER RACING - I'm not really N/A, as I'll be adding 150-200 shot, depending on what i push N/A. I want to be in the 650 FWHP range on the juice, 450-475 N/A.

Those 6.2 rods can be used for a 383 or a 408.

With the 383 you need a 3.75 crank, and some 1.4 or 1.405 (.005 in the hole or flush) compression height pistons, but I don't easily see that piston for a Ford on someone's shelf.

With the 408 you use a 4.00 crank, your 6.2 rods, and some 1.175 compression height pistons. That gives you a total stack of 9.375. The 1.175 compression height pistons are stocked pistons because the 302 based 331 stroker uses the same piston. Nothing wrong with being .005 in the hole.

If you wanted to utilize your nice rods with just a stock 351 crank, you'd need some 1.525 or 1.53 CH pistons.

 

[NIKwoaC]

Those 6.2 rods can be used for a 383 or a 408.

With the 383 you need a 3.75 crank, and some 1.4 or 1.405 (.005 in the hole or flush) compression height pistons, but I don't easily see that piston for a Ford on someone's shelf.

With the 408 you use a 4.00 crank, your 6.2 rods, and some 1.175 compression height pistons. That gives you a total stack of 9.375. The 1.175 compression height pistons are stocked pistons because the 302 based 331 stroker uses the same piston. Nothing wrong with being .005 in the hole.
If you wanted to utilize your nice rods with just a stock 351 crank, you'd need some 1.525 or 1.53 CH pistons.

+1. Thats just that much less concern about valve-to-piston clearance and it won't hardly affect your CR.

 

[fords2fast4u]

wow man! how did you figure all that up? doing the math or referrring to a reference?

thanks!

I'll check around for some specific piston numbers now (P/N and CH numbers)

 

[NIKwoaC]

wow man! how did you figure all that up? doing the math or referrring to a reference?

thanks!

I'll check around for some specific piston numbers now (P/N and CH numbers)

Once you understand the basics of engine design geometry, its really not very complicated. Check out Coast High Performance's website or Probe Industries' website for some common stroker assemblies and part combinations. Good luck! Let us know how it goes!

 

[fords2fast4u]

Yeah, i was looking at Scat's P/N lists with their kits and saw the rod length I already have in there a couple times. Now I'll go back with some more serious intel as to what I'm looking for and know what to keep a look out for!

And you bet I'll be posting how it all ended up~! I haven't been around this site for 6 or more years, and owned 5 mustangs, to walk away yet! ha!

:SNSign:

 

[fords2fast4u]

one more thing, so the CH of the piston, where do i measure that at? is that a number i can go to a search for that required spec for what I need, with other options such as CR varying?

just checking.

Nevermind, i figured that out. Promlem is now I'm thinking that the 6.2" rods i have, have a different rod journal size, because the crank i have, may have been an offset ground one. it was stamped 3.700 and the CH on the pistons i have were 1.4 i believe if i measured it right...
that would have worked, (3.7/2)+6.2+1.4=9.45

but if that crank's stroke is 3.7, that means that it must of been offset ground, which also means that the rod journals must of been smaller ( I read about being an option where "eagle makes a rod for this with "whatever" size rod journals... blah blah")

bottom line, i think I'll just need to find another set of pistons that match my crank and rods... i think that'll be the best bet. Now to find a piston with a 1.43 CH for a zero deck height... hmmm...

 

[fords2fast4u]

that guy who's selling the pistons says he bought them for use in a 69 block with a 4" stroke and 6.2" rod combo, but the CH is 1.285?

I have the full specs on them, but that number is off from your reccomended 1.175" CH?

 

[fords2fast4u]

With the 408 you use a 4.00 crank, your 6.2 rods, and some 1.175 compression height pistons. That gives you a total stack of 9.375. The 1.175 compression height pistons are stocked pistons because the 302 based 331 stroker uses the same piston. Nothing wrong with being .005 in the hole.
QUOTE]

ok, i used the formula NicwoaC stated earlier, and i came up with 4.00" stroke, 6.2" rods and a 1.28 CH (2+6.2+1.28 = 9.48)

in the quote above, you said that I'd be .005" in the whole, but that equaled 9.38, not 9.48? maybe a quick mistake?

I'm sorry to be posting so many questions, but I think I'm close to figuring this out, and I'd be real happy if these pistons will work for me, since they're new and pretty cheap compared to my other options.

his 1.285 compression height and a 4" crank puts me a 9.485. I'm assuming though, that since I'll be using a more than likely milled block that this won't work?
Maybe if i had a later model 9.5" deck height block?

thanks again, for educating me here!

 

[fords2fast4u]

well this is getting more interesting than I ever imagined. Now I'm learning about Quench distance? (distance from piston top to head deck surface), and it looks like those pistons will work, with them coming out of the hole .005". Some guys with LS1s were running .007 out or even up to .012 out of the hole (with a .054" gasket). So I'd just need a .045" thick gasket to acheive the optimal .040" quench distance an I should be good.

then there's the 22.35" dish volume, with a 60cc head chamber should yield 10.6 compression with a 4" stroke (assuming a 4.040" bore and head gasket diameter).

there is some info our there and calculators and stuff, but i haven't found a really user friendly site yet. this is the closest one that had what i needed to know i think. United Engine and Machine Co.

it was a really useful site, and then i searched other sites to find acceptable clearances here and there, and learned that optimal quench distance is .040" for best, most effecient fuel burn and all...

cool

 

[fords2fast4u]

ok, after a couple hours of searching, reading and measuring, I've got a handle on this whole deal... and learned so much, so fast!

So my crank and rods are normal 3" mains and 2.1" rod journals (i miked them).

step 1, these pistons are 4.040 exactely pistons... and my block is machined to the same size. Can i just have it honed .005-.006 more for the nitrous and will that be enough room for them to put a good crosshatch on it? i think so since people were saying that they can hone a bore taking as little as .0005 out... so, assuming i can use these brand new, but cheap Ross .040 over pistons in my already .040 over block...

my two options with the 6.2" rods and 1.285" CH pistons are, as i see them are:

1. 3.85" Eagle cast steel crank, which will put me at 9.41" (.070" under my deck height, so I'll have to have it decked down to about .001" in the hole for the optimal Quench, taking off a total of .060" with a .030" gasket)... in then end, bringing a CR or 9.9/1 with 60cc head chambers. Not bad, so long as i can have that much taken off the top.

2. 4.00" Eagle cast steel crank, putting me .005" out of the hole on an undecked block, meaning I'll need a thicker head gasket (about .045" i'd say). maybe even mill the top of the pistons if i wanted to use OE gaskets or see if .025" is enough room (who knows, but i don't want to push it until i know for sure how close i can get) bringing a CR of 10.2/1 with the same heads and quench distance.

what do you think? ha!:SNSign:

 

[seijirou]

With the 408 you use a 4.00 crank, your 6.2 rods, and some 1.175 compression height pistons. That gives you a total stack of 9.375. The 1.175 compression height pistons are stocked pistons because the 302 based 331 stroker uses the same piston. Nothing wrong with being .005 in the hole.
QUOTE]

ok, i used the formula NicwoaC stated earlier, and i came up with 4.00" stroke, 6.2" rods and a 1.28 CH (2+6.2+1.28 = 9.48)

in the quote above, you said that I'd be .005" in the whole, but that equaled 9.38, not 9.48? maybe a quick mistake?

Maybe nothing, that's a flat-out mistake. When I saw 9.375 for some reason I was thinking 9.38 deck height, not 9.48. Good catch, and I'm sorry for not being more careful in making recommendations! Seriously, that's not cool. Major apologies!