The 400 was a suggestion for better performance. I approached it this way:
Assume you have a healthy 250 straight 6. You add a Clifford 4 bbl intake, headers, new exhaust, new carb, hot cam & valvetrain, you'll have about 200 HP or so max.
This setup can easily exceed 400-700 dollars to install, once you add the cost of brackets, throttle linkage, gaskets, new aircleaner, hoses and all the other nick-nacks that come with a manifold/cam swap.
I used a similar Clifford setup on my 235, and was very happy with it. But I was still only getting about 165 HP. Look at some other cam manufacturers also, cuz the Clifford cam gave up too much low-end torque on my 235.
200 HP in a light car like that would be fun for cruising around town. The straight 6 would also have the cool split-6 sound.
This assumes the I-6 is in very good shape. Adding speed parts to a worn engine will just hasten its demise. You'll want to run it harder, and the worn parts will hinder the performance.
If your straight 6 would need to be rebuilt, then I'd ditch it. If you add the cost of the rebuild and the Clifford parts, It could easily come to 2500-3,000 bucks. And you'd still only have about 220 HP max.
The Pontiac 400 was made from '67-'78. It was the performance option on a '68 Firebird. It was available with either a TH400 automatic or a 4 speed standard. All the brackets & stuff you'd need are available from aftermarket or internet. You'd have to change out the motor mounts, the tranny, the tranny mounts, shifter linkage, and the driveshaft to go back to the drivetrain that is supposed to be there. But all the mounting holes on the car are there unless they've been cut/welded.
The 400/TH400 swap would cost about 3,500-4,500 bucks. This would include the DIY cost of engine/tranny rebuild, and the other stuff mentioned.
Why spend that much? Cuz the extra grand would be worth the power. How much power? How about 425-475 HP and 500 Ft-lb of torque on pump gas. And the extra 1,00-1,500 bucks spent at the outset would increase the value of the car by more than 2 grand. Look into the resale values! Not to mention that you'd be the only GM guy at a car show with a non-chebbie engine.
A friend of mine had a '67 Firebird with the 400/TH400 setup. It was stupid fast! It would shred both back tires like cheddar on a cheezegrater. One day we were doing a steady 30 MPH in Hattiesburg MS. He stomped it, and the whole car went sideways. Car did need some suspension work.....
That not enough power? Find a '67-69 Pontiac 428. 375 HP bone stock. Not enough? Find a Pontiac 455 and a set of Nunzi motor mounts. (455 was '70-77, m mounts are different) Hows 550 streetable HP on pump gas sound? You can afford the race gas? How about 700 HP, no NO2.
We breaking axles yet?
*bwooohahaha* Evil laughter
And some guys here apologize for a post that isn't 1/2 as long as this one....
Chip
Neighborhood Poncho Nut
