Yep, again. I think I found the perfect piston. It's not in the KB catalog because they only make it for one distributor in Australia.
The application is the 351C using the 302C rods. I finally got the specs after convincing KB tech that it was theirs.

"That is our number, the3434H.That piston is for a stroke of 3.500, comp. height of 1.415, 4.00 bore std.,ring pack of 2-5/64 1-3/16. The pin dia. is .9122, rod length 6.025 and piston weight is 489, and pin 103g. The cc to head volumes are as follows for comp. ratios, 62cc-11.1,66cc-10.6,76-9.5. I hope this what you were looking for.
Thanks Tech Dept."

It's a flat top "claimer series" piston. $375 AU (about $207 US).

Take a 400 crank and off set grind the journals to a 4.17" stroke with the 2.123" 240 I-6 rod journal. The 240 rod is 6.795 long, 912" pin. Rods are $80 a set. They have to be narrowed.

10.297
-2.085 (half stroke)
-6.795 rod
-1.415 piston
--------------
=0.002 deck

 

Well just goes to show you what a little home work will bring you .. Now here's a low cost stroker Motor that will make an awesome street motor.

 

what would be the cr on a 400? this may be my build! awesome research!

 

You have to run your own numbers through a calculator like the one on the KB site.
http://www.kb-silvolite.com/calc.phtml

I came out with about 10.8:1 with a 76cc chamber. There are many ways to change the numbers. The 4.17" stroke can be reduced. The 240 rods can be shortened slightly with bronze bushings or resizing the big end.

The KB pistons can be shortened slightly or a dish added on a lathe. I used .041 for the head gasket thickness, but I think up to .060 is available. Polishing the combustion chamber will add about 3cc.

There has been a lot of talk about the benefits of using quench heads to fight detonation, but on a stroker motor this size, a very large piston dish matching the combustion chamber shape is the only way to make it work correctly.

I think the quench benefits on a street motor have been overrated. The only thing that should be avoided is a domed piston with an open chamber.

A note from the Australian Mail order company said, "We Ship all around the World, Internaional order can take our Australian GST
(10%) off the prices listed.
thankyou
VPW Sales"

Even better. Pistons would be $341 AU ($188 US) and their 3V Aluminum heads would be $2545 AU ($1400 US)
http://www.vpwmailorder.com/ieframeset.html

 

so, is this they way to go for 351m modified to a 400 with aussie heads? Thanks a bunch fellas!

 

>so, is this they way to go for 351m modified to a 400 with
>aussie heads? Thanks a bunch fellas!


this is not for a "regular" 400 - this is for a stroker motor with a custom offset-ground (stroked) crank, and 240 I6 rods.

 

sweet
the pistons i got to use would raise the comp to high anyhow. be good for the race motor i was thinking about though. this stroker option is getting cheaper all the time.



later.......:P

 

I ran into a lot of stumbling blocks while I was looking for pistons. Most of the stroker pistons are expensive. Usually $500-800. They all seem to use a .927 pin, probably because it's a chevy size.

There aren't many stock rods longer than the 400. An aftermarket 6.8" rod set is less than $400, but the 2.2" journal was too big. I couldn't off set grind a stock 400 crank to the 4.17" stroke I wanted. Custom long rods with a 2.1" journal were $800 and up.

The 240 I-6 rods were long enough, cheap ($80), and they use a .912 pin like the stock 351C. The KB 3434H is the only short piston I found with a .912 pin. I lucked out. I like the price too ($188).

If you want a race motor, quench heads will get you 13:1 compression with the KB flat tops. I think a 426 would be great with 4V heads.

351C open chamber or 400 heads would be 10.5+:1. I think there is enough piston thickness to allow for machining a shallow dish to get the compression down to 9.5:1. It's very easy to do on a lathe.

My mission is over. It's time to collect the parts and put it together.

 

where there is a will, theres a way

 

what kind of rpm's do you think the stock I6 rods could take. I would like to build this stroker but I want to make a hevy towing monster of a motor while still reving to 5000 or 5500rpm. I am thinking about using a dual patern crane cam with 260 intake and 272 exhaust duration. what do you guys think. I know the cam is a litle big for a real hevy towing motor but wont the longer stroke conteract that. I mean when you increse stroke more duration dose not negitively effect low rpm TQ gain becous the piston is moving faster in the bore.

-Jim

 

 

ttt

I thought this was interesting.

 

WOW I missed this:

If you want a race motor, quench heads will get you 13:1 compression with the KB flat tops. I think a 426 would be great with 4V heads.

351C open chamber or 400 heads would be 10.5+:1. I think there is enough piston thickness to allow for machining a shallow dish to get the compression down to 9.5:1. It's very easy to do on a lathe.

so um brian, can it take enought lathing to get the cr from 13:1 to say 11.7 with closed heads?

i am a stinker.....

 

Hmmm, this is a very interesting build... although quite a lot of custom machining. Do machine shops generaly have the ability to use the lathe to dish the pistons like mentioned above? And were might one look to get the 240 I-6 rods?

This may be my ignorence speaking here but how do these 'flat-tops' yeild such a high compresion. I thought flat tops on a 400 were only good for about 9.0:1. I see these pistons have close to zero-deck though as compared to the excessive deck clearence the stockers have so is that the difference, over a point and half compression just by zero-decking? Or I am probably missing something

 

well the thstock piston is .0565 down, this build is .002. thats the cr change