Help deciding on 400 or 440 powered

[polara66hardtop]

My 400 with the thermoquad gets 11-12 in town. It might get better if it didn't have the 9 1/4 with 3:23 ratio limited slip. It pulls really well up to 100, though. it is running 3000 rpm at 70. about the same as my 67' 440 hp. It gets 11-12 in town as well.. I think I could put in a 68' 440 hp and get the same mileage. In the end it is still a lot of fun combined with a nice luxury car!

 

[Mr C]

Eventually, I'm going to do a performance rebuild on 400 in the NYB. I'm going to use the 1971 pistons and it'll raise the compression to almost 10:1. Add a .484 lift cam. I'm undecided about heads.

I want to get rid of that exhaust manifold with the tube, I'm wondering if the 76 or 77 exhaust manifold has that tube?

I just checked on my 77 T&C, the proviso for the tube is there, but my car (Canadian emissions spec) came with the block off plate bolted on to cover the hole.

 

[1978 NYB]

Thanks.... Scratch 1977 manifolds.

I made a block off plate for mine.....the dang thing is leaking.

 

[1978 NYB]

Stan, does your 1976 NYB have a tube coming from the rear of the right exhaust manifold and goes to the air cleaner assembly?

 

[moper]

If it's mileage you need, you need to do a couple things.. First is replace the Lean Burn controller and distributer with an adjustable aftermarket ignition (or earlier stock if you can tune really well). Thne you need to tune it. For the Thermoquad that may mean modifying the parts as nothing is available for them. The fuels out today have very little in common with what was in the tanks in the 70s. And the parts themselves are not calibrated, not are "user friendly" enough to simply adjust for it. Not to mention if a component isn't functioning perfectly after 30 years... Years ago I did that with the '81 slant 6 in my then-wife's father's truck. By simply adding adjustability, and then tuning it properly to maximize the new stuff, it gained about 8mpg and he was getting close to 26 in mixed driving in a 1/2 ton truck. It also was a lot more peppy.