Mopar Action On-line – Tech Questions


Tech Question

Gary torbey , massena, NY, 1969 plymouth road runner 440

Are siamese engine blocks ok for street use? I understandthat there is no water jacket between the cylinders and they run hotter. Arethese blocks reliable for street use? If they are ok for street use, isthere anything that you recommend to keep them running cooler? What’s thebottom line?


Very good question. Mopar guys have always ridiculed Chevys for theirsimaesed 400 smallblock. Then MP came out with the siamesed Megablock, andwhat could we say?

I have heard stories of guys who have drilled a seried of small holesbetween the bores on those blocks. I can’t see them being large enough tohave any significant effect. The bottom line is that it doesn’t seem to be aproblem. Thousands have been sold, I am aware of no specific flaws orhassles, I personally know of several that have been street-driven for quitea while. When you think about it, the vast majority of heat rejection occursthrough the heads anyway.



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