393 Guys HELP!!!!

[Jerrod4567]

OK so I started assembling the 393 today. I have a 9.503 deck heigh block, Eagle 3.85 "Cast Steel" crank, 5.95 351W rods and Speed Pro 272AP 302 pistons .030. I mocked it all up and discovered I will need to notch the pan rail for the rod bolts (no biggie) But what I discovered next was that the Piston skirts hit the crank throws. Whats even more weird is this. The piston at TDC sits about .045 down in the hole. Something here is not right. I'd appreciate any advice about this situation.

 

[Jerrod4567]

OK I just did the math, and this makes absolutely no sence whatsoever. Alright, here are the facts:
Block: 9.503 Deck Height
Crank: 3.85 stroke 1.925 distance journal will travel from centerline
Piston: Compression Height 1.6"
Rod: 5.956"

5.956+1.6+1.925=9.481

9.503-9.481= .022 The piston should be .022 in the hole. Yet it is .042

Somewhere .020 has been lost. Now since Eagle doesnt make a 3.82" stroke crank I know it cant be that. Also I am pretty sure for didnt make any 1.58" Compression height 302 pistons so.... Im at quite a loss on this one.

 

[BUCKETOBOLTS]

You could have the block decked .020". Speedpro also makes a piston for a 393 stroker, H132CP, that has a compression height of 1.615.

 

[BUCKETOBOLTS]

Also I am pretty sure for didnt make any 1.58" Compression height 302 pistons so.... Im at quite a loss on this one.

A 350 chevy is 1.56". Still a 4.000 bore. Are you sure of the piston set you have? Something just doesn't seem right.

 

[Jerrod4567]

yeah, its a Speed Pro 272AP 302 Piston. The counterweights on the crank smack the skirts too.

 

[broncnaz]

I'd suspect the pistons are the wrong ones and also question your actual deck height. I'm no expert on strokers but most of the 393 kits I've seen use pistons with a 1.615 pin height putting the piston .007 below the deck

 

[Madgyver]

I'm ready to mock mines up so I'll be adding to this thread. This has got me thinking. I'm also using a scat 3.85 crank so I'm hoping I won't get the same problem. I'll see if I can do it today before the kick off of the big game...

 

[blksn8k]

According to the chart on JE's website your pistons should be at -.019 with a 9.500 block, 1.600 deck height piston and 5.956 rod so your -.022 sounds correct for a 9.503 block. I'm with BUCKETOBOLTS on this one. Sounds to me like somebody sold you Cheby pistons.

http://www.jepistons.com/pdf/2002-srp-ford.pdf

 

[BUCKETOBOLTS]

What pistons are you using Mad?

 

[Madgyver]

What pistons are you using Mad?

KB364 + .030 with valve reliefs cut into it for Cleveland type heads. I had to get dished pistons to bring my compression down for pump gas, with the quench heads I'll be using and flat tops combined with the stroke on the crank it would of come out close to 12 to 1.

 

[Madgyver]

OK so I started assembling the 393 today. I have a 9.503 deck heigh block, Eagle 3.85 "Cast Steel" crank, 5.95 351W rods and Speed Pro 272AP 302 pistons .030. I mocked it all up and discovered I will need to notch the pan rail for the rod bolts (no biggie) But what I discovered next was that the Piston skirts hit the crank throws.

I got the crank in to check clearances and all is good. I'm using ARP rod bolts so it should clear. I read that also the 351W truck rods with the football shape head on the rodbolt should work fine also.
You can see I had brought out the kids TV so I can watch the SuperBowl game while wrenching........... Got to make use of my time.....
Is the crank throws hitting the skirt itself or is it hitting all that casting flash on the bottom of the skirts?

 

[Jerrod4567]

I have the truck rods with the football shaped heads. Though I only installed the number 1 and number 5 pistons in mock up, number 5 smacks right into the pan rail. I have the Eagle crank as opposed to the scat. Anyone out there running an eagle crank?

 

[bronco italiano]

How much engine building experience do you have? If your not a true pro, I would leave it to the pros. A stroker motor have so many variables in regards to clearance and setup that it can drive a non pro builder crazy. And if something is missed or miscalculated all that time and money will be for nothing. If your not absolutely sure take it to a pro. Good luck, BI

 

[Jerrod4567]

How much engine building experience do you have? If your not a true pro, I would leave it to the pros. A stroker motor have so many variables in regards to clearance and setup that it can drive a non pro builder crazy. And if something is missed or miscalculated all that time and money will be for nothing. If your not absolutely sure take it to a pro. Good luck, BI

I have quite a bit of stroker experience ;D I have a fully built (by me) 408W in my drag car. This problem I'm having is very strange. I have verified that all of the parts are what they are supposed to be etc.... Hmmm.....

 

[76Broncofromhell]

I was looking at a 302 piston vs my old 408 piston and noticed that the skirt is significantly longer on the 302 piston. I know the 393 uses different pistons than the 408 but I would assume the 393 ones would be closer to the 408 pistons vs the 302. Could it be related to rod length? Have you tried Coast yet? I'm pretty sure the 393 uses a different height piston with a shorter skirt to clear the crank eccentrics even on the 393. Speedomotive also has some good info on their strokers.

www.coasthigh.com

www.speedomotive.com

 

[BUCKETOBOLTS]

yeah, its a Speed Pro 272AP 302 Piston. The counterweights on the crank smack the skirts too.

Did a little researching...

272AP compression height is 1.585"
273CP compression height is 1.605"

I believe Eagle suggest using the 273CP piston with their set up. I helped a fella I work with put his 393 together and I know these pistons worked with out any hassles.

 

[Jerrod4567]

Did a little researching...

272AP compression height is 1.585"
273CP compression height is 1.605"

I believe Eagle suggest using the 273CP piston with their set up. I helped a fella I work with put his 393 together and I know these pistons worked with out any hassles.

Wow thank you. Let me ask though, where did you come up with the numbers? I looked all over and finally called the engine shop I bought the pistons from and they told me the 272AP's were 1.605.

 

[BUCKETOBOLTS]

I found the info on the Federal Mogul web site. Federal-Mogul When you choose your options choose Sealed Power, pistons, ect...

They are good quality pistons, though. When "Bubbles" my buddy was building his engine. He bought the crank and pistons from Summit. And for some reason that number just stuck in my head. So when you started the thead, something just didn't sound right to me. Hope you get it together soon.