Rod stretch?

[Fordman500]

I am building a 302 for a non 4x4 related vehicle, but I know there are some smart guys here so I will give it a shot. I am using dart windsor junior heads, stock cc is 58 but I am unsure if they are cut or not. I am trying to cram in an SRP 18cc pop up piston into these (they claim they fit dart heads) and I am having a little bit of piston contact. I had massaged the cylinder head a bit and got them pretty close. With NO gasket on I would say its just barely nicking the chamber somewhere. I cannot figure out where its hitting now, I have tried grease and clay and it doesnt even make a mark. COmpressed head gasket thickness is .041 so I figure I have roughly .038 piston to cylinder head clearance. Expected RPM for the motor was around 7500-8000, but if I need to turn the rev limiter down a bit I guess that will work too. I have a forged steel crnak and forged scat rods. ANyone have an idea of how much the rods will stretch at 7 or 8000 rpm?

[Jrod-13]

what rods are they? I know steel rods don't stretch much, even at those RPM's, but I didn't really find much searching other than one company that states "aluminum rods will stretch up to .008" more than steel rods at high rpms"

What are you building the motor for? thats what, almost 14:1 compression? hell ya..!

[Fordman500]

It is going into a road race shelby.. Its my dads car he just makes me do all the work.. They are Scat 4340 rods, I would think that the head gasket would make enough room, but I also need to use some plug indexing washers to pull the electrode out of the chamber, or find a plug that fits with he electrode in the right spot. Here is the car, its got some good history back till the 70's.

[Totalled]

So, ah... I'm gonna need to know more about that '73 and the '68 Torino also.

[Fordman500]

The 73' has got a 351 cobra jet in it.. Pretty cool car I guess. The 68' is a Torina Talladega with a 428cj. Our shops got some crazy stuff in it (shop owner has some nice cars). How about a 61' starliner with a 427 SOHC..

[leadmic]

Originally Posted by Fordman500

The 73' has got a 351 cobra jet in it.. Pretty cool car I guess. The 68' is a Torina Talladega with a 428cj. Our shops got some crazy stuff in it (shop owner has some nice cars). How about a 61' starliner with a 427 SOHC..

Pics please
Leadmic

[larboc@hotmail.com]

Originally Posted by Fordman500

I am building a 302 for a non 4x4 related vehicle, but I know there are some smart guys here so I will give it a shot. I am using dart windsor junior heads, stock cc is 58 but I am unsure if they are cut or not. I am trying to cram in an SRP 18cc pop up piston into these (they claim they fit dart heads) and I am having a little bit of piston contact. I had massaged the cylinder head a bit and got them pretty close. With NO gasket on I would say its just barely nicking the chamber somewhere. I cannot figure out where its hitting now, I have tried grease and clay and it doesnt even make a mark. COmpressed head gasket thickness is .041 so I figure I have roughly .038 piston to cylinder head clearance. Expected RPM for the motor was around 7500-8000, but if I need to turn the rev limiter down a bit I guess that will work too. I have a forged steel crnak and forged scat rods. ANyone have an idea of how much the rods will stretch at 7 or 8000 rpm?

if you have rods that are stretching .038" you have bigger problems.

[Fordman500]

Some pics . All aluminum 468 with too much horsepower.. And the 427 SOHC.

[MC]

Sounds like you have achieved a zero deck. .035-.040 is optimal for a zero deck situation and a felpro head gasket will easily give you this measurement. Check your camshaft next to make sure you dont have to make your valve reliefs deeper.

[Fordman500]

Yup thats exactly what I had planned. Get the pistonts to clear with no head gasket, then with my .041" compressed thickness head gasket I should be OK. Now I have to degree the cam and check for valve clearance.. Hopefully it checks out. WIll let you guys know how it turns out..

[Fordman500]

Since the rods dont stretch that much is it because of piston rock that you need that clearance???

[MC]

Its really more for rod stretch than it is for piston rocking. With the compression height you have you probly dont have a extra ring land for the wrist pin hole (Where the oil control ring would ride on a small compression height setup) and therefor a generous skirt since its not a stroker so more for rod stretch.....rods do stretch and cranks flex under load.