Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
If the heads for both engines are usable (not cracked), and the heads are the correct match for the block, then there is no advantage to using one engine design over the other.
For an "ultimate" cost-no-object, puller or tow weapon engine, where ya have someone to do some heavy cutting on the heads so they can actually breathe and ya want to make some serious hp, then I'd use the ic motor. Your talking in excess of $6k to make either version do serious hp, ...at least $2500 just for the head work and very few folks who do that kind of stuff will even mess with those heads as far as port work.
But a "standard" machine shop head operation on those is no more $$$ than doing any four chamber head.
Let me say this...I don't care "how good" any previously machined engine component set "looks", I consider that stuff no better than a pile of parts and it's buyer beware. I've been involved with four similar motor situations in the past year alone...and in every case, the supposedly "fresh" parts were for the most part shit! The pile of parts was a pile of parts because someone scruud up or overlooked some critical piece and the financial trickledown exceeded the ability of the "customer" to complete the project. In some cases it's outright fraud!
I'd dam shore rather tear a runner motor down and start from scratch where I and the machine shop control the end result,...than deal with someonelse's scruuovers.
The engine you describe with "crosshatch", must be torn down and inspected in every detail! Who knows if the cylinders were properly clearanced to each piston after the rough bore. Who knows if the ring end gap is correct? Who knows if the cam bearings were properly aligned and installed? Was the block and heads magnafluxed, every hole and thread and gallery sterilized??? Have the rod and main journals been checked? Are the rods bent/twisted?? How was the water jacket on the block and heads treated?
If there is "paperwork" on the motor, it should have a detailed, line-item description of all work performed including post-machining clearances of critical interfaces, etc. Go talk to the machine shop that did the work, they should have a "file" on each job they do (usually electronic with a print copy) which serves as the control document for the pile of parts that was worked with.
I've learned my lesson this year, I'll not deal with anyone's motor that I not personally inspected/measured, and where I personally supervise and control the machine shop process in conjunction with the machinist doing the work.
The motor Robert is doing right now is a classic example! Someone spent major dinero on the wrong parts...and it was not Robert!