Any ideas to improve stock 400 engine on Newport?

[moper]

Got any ideas besides raising the compression ratio? Would going to dual exhausts be worthwhile? I would not be opposed to going to headers, either. Would a later transmission that locked up in 3rd gear be worthwhile?
I don't think I ever got over 14mpg on this heavy car.

In terms of economy and power there are some things that will always pay solid returns for minimum investment. Here's what I'd suggest:
1. Make sure tires are inflated to maximum (printed on the sidewall)
2. Make sure the front end parts, alignment, and rear drum brakes are good and ropy adjusted.
3. Update the ignition. If you do not have lean burn - install a performance centrifugal advance curve and make sure the ignition components are good. If you have lean burn, invest in a modern distributor with integral multi-spark setup. I like MSD but there are others that all will be better than what you have. Whicever you ce, make sure it has vacuum advance on it, or settings in it. Base timing settings I'd want are 16* initial, 20* centrifugal all in by 3Krpm, and as much vacuum advance as you can get.
4. Install a performance air fliter assembly. It will sound cooler, you'll get power and mileage.
5. Install true dual exhaust system. I like loud *** mufflers but that's me. There are plenty of sound bytes to help you choose. You only need a 2 1/4" pipe, but 2 1/2 is fine too.
6. Rebuild and super tune the carb. Make sure the floats are right, air bleeds are clean, etc etc. You can slightly richen the jets by drilling, and rods by sanding. Adjust the rod hanger and air door.
7. Learn to drive more steady. A lot of gas is wasted by driving habits.

 

[Turboomni]

this is why id rather have a 9-1 comp 383 than a 8-1 comp 440.

I would tend to agree but how about a 9-1 440 or a 9-1 383?
Asking cause my 440 does well for her age but is low compression I think and I have always wondered if it had higher compression what it would be like. I have never heard of a way to check compression ratio without pulling it apart. But I am assuming it is low compression but have no proof.

 

[BeatersRus]

you can buy yourself a decent comp gauge off evilbay cheap w free shipping.
do a comp test and post the results
write down each cylinder as you do it,keep the carb wide open gas off and spark off.

just for example,my 76 440 smogger has 130lbs compression in all 8.
this seems to work out to around a 8.2-1 motor/piston setup.

now a 9-1 or even a 9-5 383 or 440 is a sweet piece.
i personally like the 383 because you can build them up and run them high rpm.
those strokers for the 383 arent bad either,and the 400 stroker kits,yeah.
nice stuff.

 

[Turboomni]

I got a compression gauge. I always thought there would be a wide range because of camshaft type.
So basically a 440 is a 383 with a longer stroke and a bit more piston diameter? Different blocks of course.

 

[Henrius]

I got a compression gauge. I always thought there would be a wide range because of camshaft type.
So basically a 440 is a 383 with a longer stroke and a bit more piston diameter? Different blocks of course.

At some point all both valves are closed in a cylinder and compression is what is is, regardless of cam.

The 440 is the RB engine, which stands for Raised Block- Taller than B block with longer stroke. But I thought the heads were the same on both.

Never had an engine with compression so uniform in all cylinders as Beaterbus!

 

[Turboomni]

What I meant is it really isn't possible to deduce the actual compression ratio of the engine with a compression check alone ,or can you?

 

[Henrius]

Not to my knowledge, because you never know how much of the lower compressions readings is due to leakage past rings due to wear.

 

[Turboomni]

Depending on the cam of course too.

 

[Henrius]

So in a 2.73 ratio, the driveshaft turns 2.73 times for every rotation of the tire? Or is it the reverse?

So to have more economy, you want to slow the driveshaft (and thus driveshaft revolutions) down? And if you want more torque, you raise it higher?

Pardon me, but I am just a rank amateur compared to most of you.

 

[Turboomni]

So in a 2.73 ratio, the driveshaft turns 2.73 times for every rotation of the tire? Or is it the reverse?

Correct the drive shaft turns 2.73 for one revolution of the tire.

 

[Turboomni]

To make it easier you could chalk a line on the drive shaft and a line on the tire and if you can see the drive shaft you can figure it out. Just dont get run over lol.

 

[pomonamissel]

those 400's are very low c/r . so put a turbo on it , and open up the exhaust to a big single , like 3 or 3 1/2 out the rear . it would help any fuel mileage . but the power with be there . won't feel heavy when that turbo kicks in , lol .

 

[marty koirtyohann]

Got a 1972 Newport with a 400 engine. By this time, they had detuned the engine and lowered the compression ratio to meet solution standards.

I want the car a good street driver, but with more power and more fuel efficiency if possible- but still maintaining a good idle.

Got any ideas besides raising the compression ratio? Would going to dual exhausts be worthwhile? I would not be opposed to going to headers, either. Would a later transmission that locked up in 3rd gear be worthwhile?

I don't think I ever got over 14mpg on this heavy car.

 

[marty koirtyohann]

i get 15 out of my 72 new yorker it has a 440 with 2.71 gears in the rear .if u want to make her better put early heads 90 cc is want i have on mine i also put a 71 magnum cam

 

[moper]

While there might be references to a higher static compression for the performance versions of big blocks, after '71 there isn;t any physical difference that would give one more static over another. Plus, Mopar machining sucks, so the factory compression ratings are wishful thinking. Most 400s are in the 7.7- 7.9 range when actual measurements are taken.
Regardless, adding static compression will not do much in and of itself. The cheapest way is milling the heads and replacing the head gaskets. But then you have to think about push rods, and milling the intake too if you go aways. Which all means a lot more cash than reward.

PS- you cannot use cylinder pressure readings on any engine to determine static compression ratio.