6.75 rod 4.5 build

Has anyone done a 4.5 stroker deal using the 6.75 rods from Molnar? I am going to be selling my 4.3 6.8 rod and frank setup and switching to a 4.5 deal because I’m switching to an a460 instead of my dove. I’ve been doing a little research and it seems many suggest a 6.8 rod but many others say 6.7, also most of the kits that are sold (crank with rods) come with 6.7’s versus 6.8s. People say to use as long a rod as possible but the 6.8 will require support rails correct? I figured i could do a custom piston for the 6.75 rod with the compression height where I would be out of the pin? Or is that still not possible without going to a 6.7 rod? Or am I just being to picky? I have no issue paying extra for a custom piston, I just want this motor to last as long as reasonably possible and I figured this seemed like a good compromise to the 6.7 vs 6.8 debate if it’s possible. It’s an sr71 head deal for a 79 f350 street/snow/sand drag truck

.050 in rod length is going to make no difference what so ever.

I’d stick with standard part for replacement reasons.

My 557 has 6.8 rods and it still scuffs the pistons slightly. Its fine for drag racing but i definitely wouldn't recommend going any shorter. Apparently lots of guys get away with using 6.7. I personally wouldn't use either for a street or endurance engine. Just my opinion.

stanger68 wrote:My 557 has 6.8 rods and it still scuffs the pistons slightly. It’s fine for drag racing but i definitely wouldn't recommend going any shorter. Apparently lots of guys get away with using 6.7. I personally wouldn't use either for a street or endurance engine. Just my opinion.

Which block do you have?

D1VE with pro gram splayed caps added. We welded the main webs with nickel and machined them down flat with the pan rail to allow the use of the flat bottom main caps.

stanger68 wrote:D1VE with pro gram splayed caps added. We welded the main webs with nickel and machined them down flat with the pan rail to allow the use of the flat bottom main caps.

A D1VE block with its shorter cylinders using a 4.500" stroke does not like less than a 6.800" rod length but, it will survive a while in a short time, drag race engine before piston rock at BDC will cause ring seal to suffer.

I’ve ran 6.8 with 4.5 stroke with no issues. I don’t use ring support rails either but I do have 3mm rings

(Stand-by)

Paul Kane wrote:(Stand-by)

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