There's been a little talk about the Promaxx vs Speedmaster heads lately. I got my hands on a Promaxx as cast SBM head for the first time yesterday. Thought it would be interesting to compare the Promaxx vs Speedmaster vs Edelbrock stock castings. I flow tested all 3 back to back to back this morning using the same Speedmaster 30/45 valve and the same radiused entry plate for all 3 tests.
I've tested the SM vs the Edelbrock before and the slight edge usually goes to the SM. Not today. The Edelbrock head is the same as I tested about a year ago but the SM is a different head.
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