Mopar Muscle Association UK

Asking for a friend. My guess is a 318 poly.

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Yep, 318 Polyspheric engine, known for some reason as a "semi hemi".....

Much obliged - I'll pass the detail on.

What are giveaways to it being a semi hemi and not a standard 318?

rocket70 wrote: ↑Wed Jan 31, 24 7:17 am What are giveaways to it being a semi hemi and not a standard 318?

It is an "A" Engine - easiest "tell" is the 2 bolt Rocker covers, as opposed to an "LA" - Light "A" - engine with a different design and Perimeter bolts on the rocker covers, very few parts are interchangeable....

Big block weight, small block capacity and hard to find parts for, boat anchor basically.

I recently heard that L/A heads will bolt onto the poly block and the poly block can go .100" over with no issues. The poly engines are heavy due to the size of the heads and cast iron intakes etc, the blocks alone are reputed to be only slightly heavier the the L/A blocks. Cranks and rods are interchangeable, though pistons / cam are a no due to valve placement. There's folk running stroked poly motors well into the 10's N/A and still using the poly heads across the pond. I've no real world experience of poly motor's but there are a few big small block strokers using these blocks out there.

https://www.motortrend.com/how-to/426-c ... gun-hemis/

They can work and do have thier fans but you can imagine what it costs compared to an LA or big block making the same power.

There was someone over here that was going to set the world alight with one about 15 years ago, I can’t hold my breath for much longer…

I was just surprised at the amount of parts that will change over from poly to L/A (and vice versa), I was always under the impression that virtually nothing did

I knew some parts interchanged but I didn’t know the LA heads could be swapped on.

yeah someone had plans to do a 4 inch bore one, might have been baccaman, opens up things on the piston front
with a stroker crank might be fun

the chamber shape, rather than the valve positioning is semi hemi, like the aussie 265
think you can fit a 2 inch inlet and a 1.6 exhaust in there and you'd need to get well acquainted with the ferrea valves catalogue, positioning is still on the diameter of the bore, not offset to one side or the other so all good on that front

definitely a "because i can" type project.

Dave