383 VS. 400

[troy.70R/T]

Well I recently purchased a 68 Charger R/T With no motor or trans. I have a 75 400 2 barrel motor and trans that runs good. I see that in 72 (that is as far as my book goes) it would have been rated at 190 HP with 8.2 compression. I might be able to trade some Coronet parts to a guy for a running 67 383 2 barrel. I see the 67 383 2 barrel is rated at 270 HP with 9.2 compression.  Well my question is this I am going to put a 4 barrel on which ever one I use.  but will the 75/ 400 have hardened valve seats? I am sure the 67/ 383 will not. Are hardened valve seats really that big a deal? I had a 69 GMC truck that didn't have them and it ran for years with no problem. I also have a brand new cam that I bought for a 440 years ago but never used it because it was designed to be used with an automatic but I put a 4-speed in the car instead. The cam was probably stock or a step above for a 70 440 HP motor. If I put this cam in the 383 and a 750 Holley four barrel on it will I get close to the 335 Hp that a 70 383 with 9.5 compression was getting in 1970 (according to the rating in my book anyway). I also plan to install a set of headers and 2-1/2 inch exhaust. Will the car run ok on pump gas With 9.2 compression. I know these a lot of questions in on shot but just wanted to see what you all thought and wanted to tell you everything that I had planned for the motor. Thanks

[tricky lugnuts]

Not an engine expert by any means, but I'd guess hardened seats were installed on most Chrysler cylinder heads by 1975. You can run an engine without them on regular gasoline, it's just that the seats are softer and over time without the continuous build up of lead deposits in leaded gasoline (or some additive) your valve seats will eventually deteriorate.

I don't think a cam will affect the compression ratio of an engine - if you use the 400 with the 440 cam you'd still be at 8.2 unless you mill the heads or deck the block also. I'm not sure about using the 440 cam in the 383 and I also would not want to guess on the HP estimate.

As far as I know, engines with a 9.2 compression ratio will run OK on regular pump gas, though you might want to run something better than just regular unleaded. I think my 1971 non-HP 440 engine is about 9.1 compression and I can run it all day long on 87 octane so long as I don't advance the timing too much.

FYI: Some of those 400 blocks are supposed to work great for stroker builds, but I'm not sure off the top which years or casting numbers are the most sought after.

[Nacho-RT74]

KB240 pistons, HP camshaft and voila, will have allmost a 383 with more displacement, so should get kinda same or more power.

and I say allmost JUST because the cast crank instead forged

( beside that, get a basic 451 stroke from a 400 with an stock 440 crank making some jobs on it )

[bull]

The 906 heads did not have hardened seats but the next generation 452 heads did. Looks at the casting numbers on the heads and read the last three digits. If stock the 67 should have 906 and the 75 (probably) has 452. I don't know when they stopped producing the 452 heads for sure. In my case I have 906 heads with hardened seats because they were rebuilt that way.

Be that as it may, I wouldn't buy either of those engines for an R/T because they came with 440s or 426 Hemis.

[Nacho-RT74]

Be that as it may, I wouldn't buy either of those engines for an R/T because they came with 440s or 426 Hemis.

[troy.70R/T]

Well I am not looking for a long term motor for the car I am looking for Cheap right now. I just want to drive the car until I can get a good 68 HP motor to rebuild. I already have the 400 and like I said I could trade some 66 Coronet parts that I will never use for the 67 383. If I have trouble wiht the 906 heads will the 514 heads fit the 383?

[b5blue]

If your looking for a driver motor the 400 will be fine, it may have 346 heads and they are induction hardened seats and flow better on exhaust then stock 906's. all the B/RB heads will inter-change, just remember intakes, valley pans and pushrods are 383-400-440 specific. 9.2 compression would let you run 89 Oct. gas maybe even 87. I would go through the Mopar B/RB book and review cam/intake choices and look at axle ratios and such. You should be able to put a great running all round package together pretty cheap, you have the basic stuff you don't need the 383. Good Luck!! 

[Nacho-RT74]

just remember intakes, valley pans and pushrods are 383-400-440 specific.

383/400 are the same, except olders 383 with adjustable rockers on mechanical tappets, using ball/cup pushrods, but still rest is the same

[troy.70R/T]

are 67 383 mechanical lifters?  I was just wondering about the 383 over the 400 cause it has 80 more HP. I want some power in the daily driver. I was hoping that I could get close to the 325 HP that it says a 67 383 4 barrel motor has. That is why I was wondering about  putting the new stock HP cam that I had for a 440 HP  that I never used in the 383 along with  a Holley 750 and a set of headers. Just sounds like I would have more fun with an extra 135 more horses than I would the 190 HP of a 2 barrel 400. Since the 383 is also basically free. I guess that I am just looking for as much power as I can get for now until I can get a 68 440 HP motor to rebuild. so any other inexpensive tricks and tips to get more power out of a motoer would be welcome.

[RD]

67 and 72 numbers are different based on how they rated the HP.. dont use those as markers to distinguish the two.

a 383 is a 400.. the difference, 400 has more displacement.  383 = 4.25" bore; 400 = 4.34" bore.  everything else is the same.  400's are given a bad rap because they came in when the smog / insurance stuff was hitting hard.

remember, their aint no replacement for displacement.

personally, i would just find a 440 and build that.  it roughly costs the same to build one of those as it does a 383/400.

[bull]

personally, i would just find a 440 and build that.  it roughly costs the same to build one of those as it does a 383/400.

Exactly. Why do this twice? Not to mention 440 internal parts are a lot easier to find. I got very frustrated trying to locate the kind of 383 pistons I wanted for my original engine build; took six months to get it all together. Meanwhile the 440 guys were doing burnouts.

[Nacho-RT74]

the diff on Horsepower is because lower pistons. Replace pistons and voila!!!. But I'm agree built a 440 is about same cost and will match the R/T

make the spend once

[b5blue]

I thought he was just going to ring bearing and cam a motor he has? (Cheap $$ I can relate, times are tuff) 

[Nacho-RT74]

well he really din't mention what kind of job on engine is thinking about. We are talking more that we know , talking about options.

[b5blue]

Yea, he has the 400 and they are really good engines. 

[Cooter]

Wish he was closer, I got a nice '72 440 "HP" engine that needs a good home(Apart).....Even have a fresh 727 rebuilt and upgraded that goes with it...

[Ghoste]

And as a side note-no the 67 383 is NOT a mechanical lifter engine.

[pettybird]

And as a side note-no the 67 383 is NOT a mechanical lifter engine.

...and they have 715 heads, not 906...


if this is a temporary situation why put another motor you don't want in the car?  run the 400, find a swap meet intake and buy a $100 cam kit from Summit or PAW or something.  don't run an H pipe as you'll have to cut it apart for the wider 440 when you get one.