[donmlewis]

I am trying to decide on a suitable engine/transmission for a project that consists of a 1946 Chevy panel body mounted on a 1945 pickup frame with a '74 Monte Carlo front end and a '89 Firebird rear end. The frame setup came from a friend's rod project that he lost interest in and the panel body came from a farm without an engine or transmission. I intend this to be a daily driver with considerable long distance driving. I want maximum engine reliability and fuel economy with reasonable power. I have a '74 small block 400 that I believe is rebuildable but I don't think I could get much more than about 12-13 mpg. Another friend has suggested installing a late model Vortec 5.3 to get the benefits of computer control. Has anyone done such a swap or does anyone have any opinions about it or the use of the sbc 400?

[darom]

Here is a good reading on a setup with semi-computer controlled ignition/injection :-) (carburetored). I am not sure about the mpg with it:
http://popularhotrodding.com/enginem...e/0409em_gmpp/

and here is the part from Scoggin Dickey's site:
http://www.sdpc2000.com/cart.asp?act...fac_catid=3541

I was in the same boat. I got a late model used block LM7 with alum. heads where the crank spun a bearing. I bought used coils-over-sparks, fixed the crank, new sets of bearings and rings for pistons, LS6 corvette camshaft. Now I just need $$ to buy that expensive intake with a MSD controller module.

Good luck with your project!
Denis
'67 Camaro RS

[Bumpstick]

I have kinda the same issue right here...

Going from BBC back to SBC(2) will have questions...


I have a very nice 5.3ltr with just 34 miles on it and am wanting MPG and performance too but want to retain the computer mild manners also (so the wife can drive it... )

I`ll check the links you provided and please anyone else chime in...

[PatM]

I don't know, but I've got to think 18-20 mpg is doable with a light foot, and a good carb or aftermarket EFI setup. Holley ProJection comes to mind as simple and straightforward. The key is in the gearing. If you use a 700R4, you are factoring the RPM by .7, not to mention the lock up converter will halt that slippage. Using a 29 inch tire (say, 255/65-16) and a 3.50:1 differential, you'll be turning only 1988 RPM at 70 mph. I think with a decent engine package (nothing too radical) you'll do way, way better than 12-13 mpg with that 400 cu in small block.

Pat

[donmlewis]

Thanks to all for the pointers and suggestions. I like the idea of using the 400 since I already have it and a LM7 from Scoggin Dickey costs about $3,000. But, when I compare specs on both engines (stock) I get
LM7: horsepower is 285-295 hp and torque is 325-330 ft.lbs,
sbc 400: horsepower is 180 hp and torque is ?.
The numbers make the 400 seems amemic.

If I run the 400 with a 700R4 though a 3.55 rear end (what I've got) to a 29" tire, I get a little over 2000rpm in overdrive. That seem pretty good but I don't know where that fits on the torque curve for the 400. Does anyone know where I can get torque specs for the 400? I realize they will change after the engine is warmed over. I also like the idea of an aftermarket EFI, I hadn't considered that. Any other suggestions in addition to the Holley Pro-Jection?

[PatM]

The shape of the torque curve will rely largely on the profile of the camshaft and the ability of the cylinder heads to feed it. But remember, at 2000 RPM, when you press the go button, and the tranny downshifts and disengages the lockup, you'll be at a little over 3000 RPM (with the lockout out, your 700R4 will be at about 1:1 in 3rd gear). Most street motors are doing pretty well at 3000 RPM. The couple that I have built seem to peak at about 4000, but are really coming up on the torque curve even at 2500-2800.

Pat