Bored and destroked??

itsa52

itsa52

Well-known member
Always popular to stroke a flathead, lots of torque but limited on RPM's.. Curious if anyone has played with de-stroking them.. Obviously need to bore them.

I know, I Know, I am bored but humor me please
 
Only advantage to destroking would be to fit in a particular racing class that limited cubic inch size. It's been done.
 
Barney Navarro ran one at Bonneville and the lakes that I think was destroked down to 176cu.in. Like 40 Deluxe said it was built to fit a particular class. Google this- "Barney Navarro, 3-71, roadster", something will pop up.
 
"Always popular to stroke a flathead, lots of torque but limited on RPM's.."

Another old wives tale.



323 ci, 6800 rpm twice a lap. (4 7/16 stroke)
 
6,800 rpm twice a lap with a 4 7/16" really big stoke -- wowzer!!

How long did the bottom end of that engine last?
 
jonf said:
6,800 rpm twice a lap with a 4 7/16" really big stoke -- wowzer!!

How long did the bottom end of that engine last?
Click to expand...

Last time I heard it was still running. It is about 5 years old now.
 

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I had a 3 3/8 by 3 5/8 stroke I sold to a fellow in Germany. Had it for sale her on the barn,but no takers. Had a Potvim 400 cam for it. still have that.
 
40 Deluxe said:
Pete, Are you willing to share any info on cam, port work, etc.? How about a dyno chart? Please??
Click to expand...

Some....
The cam was a #4 Offy. (similar to a 404A)
All ports were as big as they would go with a .090 wall.
.200 deep relief.
I don't release dyno info, sorry.
 
Pete said:
Some....
The cam was a #4 Offy. (similar to a 404A)
All ports were as big as they would go with a .090 wall.
.200 deep relief.
I don't release dyno info, sorry.
Click to expand...

Pete I find your knowledge and experiences to be nothing short of fascinating. Would love to "shoot the breeze" about all out Flatheads someday. I wonder what is the biggest bore you have put in a Flathead Ford? Which block do you feel is best for a big bore and why? Thanks!
 
One more de-stroked record setter. 1957, Tony Nancy's 22 jr., Had a 3&3/8 bore, de-stroked a 1/4" to 3&1/2" stroke, 256 CI. Built by Tommy Sparks, Sparks & Bonney. 10.86 at 131MPH.
 
Henry Floored said:
Pete I find your knowledge and experiences to be nothing short of fascinating. Would love to "shoot the breeze" about all out Flatheads someday. I wonder what is the biggest bore you have put in a Flathead Ford? Which block do you feel is best for a big bore and why? Thanks!
Click to expand...

I have built quite a few flatheads with 3 7/16 bore.
Several have been honed .010 or .012 over that at rebuild time.
Any block that sonic checks so you have about .090 wall at finish bore is ok by me.
The last two engines I built I stopped at 3 3/8 + .030
because I got tired of tearing down engines to find a good block. Of late I have used 8ba type blocks exclusively because of the ease of redrilling the back to take a Chev bell housing/scatter shield or a motor plate in the case of a circle track car that requires no flywheel.
 
Thanks Pete, I have an 8BA block that is bored to 3 7/16". I have a set of pistons and rings though it looks like the dome of a couple of the pistons have been banged on. These Pistons are for the 3 3/4" Ford crank. The block has a couple thinwall sleeves and someone butchered the relief job but I think I can save it. I'm gonna try. I've got nothing to lose at this point.

Thanks for the info.
 
Knew someone who worked at an engine re-conditioners. He wanted to see how far he could modify his car so he found longer 'rods and ground most of the crank journal away and built it up again closer to the main bearing with a welder. As it cooled the weld peeled away.

He gave up on that idea.
 
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