Is there any performance difference between romeo blocks?

53BigDog

Active Member
May 22, 2001
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Palm Harbor, FL
I just cracked my 97GT romeo block and am looking at new/used ones. I understand that all romeo blocks are interchangable but my question is specifically is there any major performance differences when swapping out a 96-98 romeo block as compared to a 2003 Cobra Romeo block?

I understand there are main bolt differences (2bolt-4bolt) but other then that are there difference in cylinder size, etc.

Which block would yeild the best performance on my 97GT with PI heads and 9cc forged pistons and forged rods. I am looking to stay N/A and gain about 10.5:1-11:1 compression.
 
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Any 4v headed block will not have the 2v head coolant passage on the driver side of the block. You will need to drill out that coolant passage.There arent any differences between the blocks, they can all handle the same amount of power. Also, all 2v cast blocks are a 4 bolt designed, the 4v blocks are a 6 bolt.

No mod engine is a 2 bolt design.
 
However when ordering ARP main Studs you must designate between 2 botl mains and 4 bolt mains. That signifies the amount of bolts that lock down the main caps from the bottom of the engine (not including the side bolts that screw through the block.