2.4 conversation to 2.7

[Allen,N]

I am currently rebuilding a 73.5 2.4 CIS engine.
I have the option to bore the case to 2.7

Would like to tap into the huge amount of experience and expertise on here.

A few questions.
Can the 73.5 CIS system handle fuel and air delivery needed for a 2.7?

Does the case cylinder seats get too thin if I bore out?

I would go with a bigger oil pump and case savers.

Nathan

[NZVW]

Hi Nathan, not being an engine builder bloke can I ask if you have a T E or S?

[geneulm]

Just pitching in…

Q: Can the 73.5 CIS system handle fuel and air delivery needed for a 2.7?

A: Yes, absolutely. However you will get a very nice power bump w a shift to carbs, mfi and an even slightly more aggressive cam (E, S or one of the more modern variants)

Q: Does the case cylinder seats get too thin if I bore out?

A: Boring the spigots has been done for years. Since you have a 73.5, that means you have the 7r case, which outside the early sandcast alum cases is the best.

I would go with a bigger oil pump and case savers.

Def case savers. Bigger pump isn’t needed but a later 4-bar pump would be a nice addition.

[Allen,N]

It is a T car

[Allen,N]

Geneulm,
Thank you. This is helpful.
Have you done this before?
Do you know the increase power estimate?

[RickWhite]

Make it an RS.



Other, wiser folks can chime in, but you should be able to get up toward 225 hp with a thorough reworking to 2.7 RS specs + carbs + exhaust.

[geneulm]

Have I done this before? Yes. It was an ok motor… it didn’t last long in that spec as it was taken apart for E cams and Weber 40 ida. Which was a great motor

[RickWhite]

Interestingly, I have a 2.7 with e cams and a 2.7 with s cams. The e cams definitely have more low end torque, but get really flat at high RPMs, sort of the opposite of what you want from a LWB engine.

[Richy]

'73 T's have 30mm intake ports , unless some head work or different heads are in the plan everything else is a waste of time .

[geneulm]

Getting the ports brought out to 36mm is a simple and effective mod. Should be done. W this. Even if you keep the CIS injection.

I’ve done both E and S cam engines. The E cam was def faster on the typical auto x course, although it ran out of steam in 2nd, where you spend a lot of your time. I do def like the zing and umph of S or Mod S engines. Especially when the compression is more like 9.5/9.8. GE60s are one of the best all around cams ever.