Thread: 2.5 or 2.6
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Shuie Shuie is offline
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2.5 or 2.6

The thread blue72s started about the 2.6 performance figures has got me thinking. Here is blues thread I always like to learn about different engine configs and neither of these has been extensively documented here.

Short stroke 2.5 - 66mmx90mm

-Tyson recently built a hotrod 2.5 for Scruffy. His old posts gave a pretty good idea of what it would take to build this motor. Basically a destroked high compression 2.7 RS using 2.2 crank and rods. MFI induction, of course.

Short stroke 2.6 - 66mmx92mm

-Henry has mentioned this engine before. It basically sounds like a destroked 2.8 RSR (or a destroked version of Grady's 2.8 S) engine using the 2.2 crank and rods. Iíve never seen an actual measured CR for the 92mm Mahle RSR pistons when used with the 2.4 or 2.2 heads, but the indication in the very few old posts about this motor is that itís going to be well over 10:1. Twin plugs would be required for pump gas, and Henry has already mentioned needing a custom distributor or a crank fired ignition.

Iím trying to weigh the positives and negatives of each engine. Obviously both of the engine would need to be built from the bearings out with case mods etc. Neither will be cheap, but nothing about these cars is. There is not a lot of documentation available for either of these engines so Iím asking for your thoughts on either here.

Main question:

Is there a big difference between the two engines?

Is there a 'best' core motor to start with if someone wanted to have one of these engines built? Would it be better to start with a 2.2 crank and rods and either a 2.4 T or a 2.7 CIS motor? Or would it be better to start with a 2.2 motor and do all the case mods. I already have a 2.7RS MFI system and a set of core stacks and throttle bodies from a '69e, so please assume MFI for the induction.

Thanks for the help!
Old 01-30-2005, 07:39 AM
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