2.4 builks questions

[bgyglfr]

I just bought a 73.5 coupe a few weeks ago and it came with the original case but no other engine components. I want to build this motor up to use as a fun street car. It will be driven summers, spring and fall. Maybe an occasional DE. I have a couple motors at my disposal for parts and I wanted to ask the knowledge base for your opinions.

Starting with a 2.4 bare case, I also have a 2.2 long block complete and a complete 75 2.7 motor to steal parts from. My thoughts are to use the crank from the 2.7 and the pistons from the 2.2 with an E cam to make a higher compression 2.4. Simple enough until I start thinking what heads and intake to use. I have the 2.7 CIS complete or I could just pick up some webers or zeniths and jet them.

If i go with the the CIS, I am assuming I need the 2.7 heads but will the CIS be able to be tuned for this motor? Do I need to stick with CIS pistons etc?

If I go with 2.2 heads and carbs, do I need to do any porting other than just getting the valves done?

Would I use the 2.7 or the 2.2 rods?

I am leaning toward using carbs just for simplicity.

BTW, I was also thinking I might build a 2.5 SS down the road for my 68L with the left over 2.7 case and 2.2 crank etc. Might be a good idea to build one at a time.

Just looking for a starting point. I will be calling on you guys for more help as I start the build.

[nickyclyde]

Sounds like a fun and interesting build . Someday , I'll be able to chime in on such dilemmas. Til then , I'll read and learn

[Flat6pac]

Rods arent interchangable, crank and rods go together as 2.0/2.2, 2.4/2.7 and 76/77 3.0.
The 2.2 pistons on 2.4 rods increase power but theyre not forged so you cnat depend on them.
The CIS are specific cams and the heads are specific injected for CIS but can be plugged for carb use.
Bruce

[crummasel]

Plus you d need "bowled" pistons for the CIS

[bgyglfr]

I'm leaning toward using the 2.2 heads and carbs. It seems the easiest to build and the most tunable. If my pistons are not to be trusted, any suggestions on what to use?

What about an efi kit as an option in the CIS manifold?

[burtm5]

FWIW, I had somewhat similar decisions to make as I had two motors to make one. 75 rebuilt 2.7 with cis pistons and nikasil cylinders. and 2.2 built to 2.5 with nikasil c and 8.5 mahle p and L/E cams. I bought new JE 9.5 Ps (probably not necessary) and put 40 webers, E cams on 2.7 with ss and two in one out muff. Works very well. the point is you can mix and match the best of what you have. 2.7 for displacement and 35mm intake heads, carbs, exhaust and cams from prior years to make about 210 to 220 hp and good drivability. (not great gas mileage though) best henry

[bgyglfr]

Thanks for all of the advice. I have decided to go with carbs on the 2.4. I really want to use my 2.2 pistons for budget reasons. Since they are not forged, am I asking for trouble by using them? This is a street motor. Not for racing. Maybe one or two DEs a year until I get my 68 built. The 2.2 motor I am using for parts was a good motor before it was disassembled.

[Henry Schmidt]

The long hood cars are becoming so valuable that I think I would build the 2.4 CIS engine the car originally came with. Those little engines were a joy to drive.
I think I have some 2.4 CIS heads, injection and the piston/ cylinder situation can be worked out.

I fact many of the 73.5 CIS had 7R cases making a 2.7 conversion easy and desirable.
If you have a 7R case and a 2.7 core you have most of what you need.

[bgyglfr]

I suppose I could just rebuild the 2.7 and leave the original case on the shelf. I guess that way I'm not at risk of blowing the matching numbers motor.

[bgyglfr]

Ok. I have come up with a plan. Can you guys let me know if this is a reasonable route? I have decided that Henry is right. Since it's a matching numbers case, I plan to keep the engine a original as possible on the outside CIS and all. I want a street motor that is as lively as possible while dependable and still keep the CIS injection.

Than plan:
2.4 CIS case
2.4 2.7 crank/rods
Stock barrels
JE cis 9.5-1 pistons
2.4 CIS heads
2.7S cams from a 76
2.4 CIS system for original look

Questions.

Can I get a little more with a regrind or is the 2.7S cams max for a 2.4 motor with CIS?

Can I upgrade the 2.4 CIS system with 2.7 components (injectors, throttle body, fuel distributor, etc)? I have a complete base 2.7 CIS system from a 74 and 2.7S CIS system from a 76.

After all of this, will I really gain anything? I guess I have almost everything except the JE pistons so it's no additional cost to build it.

All opinions are greatly appreciated.


73T
68L