I have a 390 w/C-6 and also a '70 429 that's .030 over and ready to assemble and the C-6 that goes with it.
I would like more HP and Torque than I have, which would be the best to build?
The 390 has the stock 360 heads and 1 3/4" full length headers and a performer intake with a 600 edelbrock carb. and it looks as the best way to pump it up is cam, heads, intake, carb or about $2000.
the 429, by adding an intake, carb, headers,and the mounts, oil pan and changing the C-6 tail shaft housing, although is more work would be less than $1500.
just wondering if I missed something or if the 385 series is just the best choice??????
which ever way I go the other one goes in the Cobra kit...........

 

putting the parts on the 390 is going to be alot easier than swaping in the 460, i'd go with the 390. and you'll have about the same HP and Torque maybe more. A 385 series isn't the best choice every single time the option comes up, neither is any engine.

 

I prefer the 385 series engines over the FE's, but new frame mounts and such will be needed to swap over. Also the accessories may need modifications to work if the 429 isn't out of a truck.

 

Tough call... Both motors can be made to do big numbers. The FE is limited to large gains by the heads (nothing another $1200-$1500 can't cure though). Considering your "not used" motor will go to the Cobra, an original looking FE would be cool in there, as well as weighing about 100lbs less then the 429. What are you putting the motor into, truck wise, and what did it originally have. The thinking is the driveline may need swap as well depending on your choice...

--Mike

 

the truck is a 76 F-250 highboy with a 390/C6 (the 390 was the original 360 and has the same heads, just bored .030 over and changed the crank)added a performer (not RPM, wasn't made yet) intake and a 600 edelbrock carb and full length headers
I do have the complete 429/C6 from a '70 LTD that is bored .030 and has hardened seats in the stock heads, which uses the rail rockers, that will be changed to rollers/guideplates/new studs, and it has dished pistons to put the compression @ 9:1...........all that I need is the cam and intake to complete the engine.........if it goes in the truck it will need an oil pan kit and mounts and of course headers
just looks like the 429 is about $500 cheaper to use than the FE.........

 

The 360 and 390 heads are the exact same thing! You best bet on the heads is to port them out or leave them alone. Edelbrock makes rpm heads but they cost $1300 and will not start making power till 3000. They are overkill on a 4x4 truck.

If you have a 2wd truck and wanted to go fast i would use: rpm intake, rpm heads, crane 343801 cam, and aftermarket ignition, a stall and 750cfm holley or so. I have tested brandnew 600 edelbrock against a brandnew 670 holley street avanger and i will tell the the holley is better for power. The problem is people **** around with the old junk holleys too much while some of the new ones have quick change secondary springs, clear site plugs, million mile power valve warranty.

Anyway with a 4x4 truck i would use ported heads with the rpm intake or police interceptor intake. I like the 343901 crane camshaft. and like i said the holley makes more power but the edelbrock might have more "manners".
And i would reuse your headers.

Does that 1970 429 have dove heads? That is a very popular cylinder head. I am not current on 429/460 performance parts but i guarantee the 429 will make more power than a 390 will dollar for dollar.

And have have to remember or know the C6 is the biggest power robbing transmission, and it tends to shift early on normal cruising, but it is very dependable. I consider a c6 4x4 combination to rob 30-33% rwhp and the 2wd combination is about 25-28% rwhp loss. And a 300 horsepower 390 makes that figure at about 4500rpm not thru the entire rpm band. At 1000rpm theres around 45-55 hp when you try a burnout! not 300hp.

 

To be honest, it sounds like both motors will come out or are headed in the same direction. The 390 already has the goodies for the vehicle, stick with it. Find out what grind your cam in there now has and go from there, a good dual pattern works wonders for the 4x4's. The RPM manifold will let it breath better in the upper rpm range, you may want to consider sticking with the performer for low rpm grunt. Spend a few extra on getting the stock heads masaged, go with the CJ size valves and a little polishing and call it good. The 429 only has 9.0:1 compression, your 390 is probably 9.5:1 or so, i think you would be dissapointed after the work involved that you really didn't gain much of anything.

JMHO, --Mike

 

the heads for the 429 are DOVE-C and the compression can move up or down depending on the pistons, the ones that are on the rods now are about 9-9.5:1, haven't really checked, just wanted to run pump gas
the 390 is about 9.5:1 as I spark-knock with the timming where it is supposed to be when under load (like with a heavy trailer), so it is backed off some (the heads were shaved about .010 to get them flat when I rebuilt it about 10 years ago but there is only about 10-12,000 miles since then
I don't have the specs on the cam, it was a TRW replacement from the engine shop