I'm running a 396-375horse big block in my 69 chevelle. It has the original closed chamber 108cc square port heads, and the original 69 four bolt main block. Here are a few other parts on the engine.

-steel crank
-stock dimpled GM rods
-Lunati cam 234-236 and .500-.510lift(can't find card)Bad info. on cam selection for this motor.
-comp hyd. lifters
-comp 7/16" push rods
-roller rockers
-RPM Air Gap Intake(1500-6500)
-Holley 750 double pumper
-MSD Pro Billet dist.
-GM Perf. wires
-6AL box
The motor makes pretty good power but its nothing to brag about. I have considered more cubes but, would really like to keep my original engine. does anyone out there have any 396 combinations that may help? All input appreciated.

That's a very popular discussion here lately. If you use the search feature at the top of the page you'll find a ton of useful stuff on 396's and 402's.

What are your performance goals? Do you know what it runs now? What do have for a tranny? Rear gear? The motor is only part of the equation,and the easiest IMHO and experience.

I'm running a M-20 muncie (because I wanted the lower 1st gear)and a 3.31 rear gear with a Eaton posi and moser axles. With the addition of more power I have plans for a Tremec TKO. With my factory bench seat 4-speed car the conversion should go smoothly. (I HOPE) Any ideas for power?

i think the motor part of it is ok, decent combination of parts, i think. IMO, the best bang for your buck would be lower rear gears, say like a 3.73 or a 4.10.

I thought about the lower rear gear but I like to DRIVE my car to different shows around, and some are pretty good drives. The tremec I plan to use has a 3.27 1st, combine this with the 3.31 rear I should have plenty of gear. And with the .68 overdrive, highway driving should be about 2000rpm(give or take a few) at about 70mph.

this is just my opinion, but when you have an OD that's all the more reason to run lower rear gears. back in the 60's those factory 375hp 396's needed 4.56 gears and a hard launch to get them to run. the lower first gear in that Tremec should help alot, but what are the ratios in the other gears? you don't want it to fall off between gears or you'll lose alot of what you gained with the lower first gear.

Tremec gear ratios are asw follows:
1st=3.27 2nd=1.98 3rd=1.34 4th=1.0 5th=.68(with an optional.83) Whats your recomendation for a rear gear? http://www.noneckschevelle.com/images/carpics/Will1969Chevelless396

How about leaving the motor alone and just changing the tranny? The increase of gear (especially 1st) should give you all that you need performance wise IMHO
The 3.31's would be perfect..or even a Richmond 5 speed would work instead of the TKO..just keep the 3.31's

the cam will only allow me to turn the engine to about 5500rpm. What is a good cam for this engine? This engine should be able to turn more rpm's than 5500.

if you keep the 3.31 gears, i wouldn't change the cam. with rec port heads and 236@.050 duration camshaft i would think that it should easily turn 6000-6200rpms. what size exhaust do you have? how is the cam installed? advanced? how much total timing? what fuel pump are you running? i assume you have headers, right?

I'm running Hooker comps. ceramic coated w/ 2" primaries and 3" collectors. I'm running about 36 degrees total. I'm using the light springs in my MSD dist. with about 10 degrees of initial and all of my advance is coming in at about 2500 (Been awhile since I've thought about this don't hold me to it)

Sorry about that don't know what happened!
After the headers i have 2 1/4" Flowmaster exhaust and the cam is installed straight up.
The fuel pump is a stock pump for a 375hp engine.

It's in the sig...I've got a mis-matched cam in my combo, but still putting 350 to the ground. If I could do it over again...and listen to those that know, I'd run the Lunati(UDHarold) 288/296 hydraulic.

Do you think that cam would have worked well with the 3.31's out back? 350 to the ground is pretty good! Looked at your pics, nice car!!!!!!!!!!

396-375,

You may not like what I have to say, but here goes anyway.

Your cam is probably one of the older design "lazy" hydraulics. 234 @.050 dur to yield .500 lift is too conservative. GM heads, especially the rec ports need at least 10 degrees additional exhaust duration in order to rpm. The 2-1/4" exahust system is too restrictive - at least consider changing the head pipes to 2-1/2", the 2-1/4" tails will probably work ok. The mufflers also will probably be usable. You have a huge mismatch in the flow - 1-7/8" primaries down to 2-1/4" pipes just won't cut it.

Regardless of what else you do - trans, rear, etc. Change the cam and exhaust first. My personal experience with 400 CI engines is an intake duration of 230 @ .050 or less will get the motor into the 6k + range for a hydraulic. Or you could (and should) consider a stout solid cam for this motor like it was designed to run. Those duration numbers in a solid with upwards of .550 - .600 lift when combined with more exhaust capacity will be like night and day. If you are really after some power and like hydraulics, do what I did and go to a hydraulic roller. My 408CI has a 228/238 @ .050, .580/.580 lift. Tremendous area under the curve with one of these cams. The duration at .300 - .400 lift is close to 30 degress longer than a low lift flat tappet like you are running. Yet with the shorter .050 and seat timing, the idle quality is a lot better. I had mine ground on a 112 LSA to improve the idle quality even more so I could run the A/C. Most guys do the same thing - overcam with too much duration, but not enough lift and the motors never make the power we expect.

Later if you throw in the 5 or 6 speed it will run even better.

Good luck.

Thanks for the tips!!!! My mistake, the primaries on my hooker comps is 2". I had 1 7/8" on some old Dynomax headers before the restoration. What kind of power are you putting to the ground with your 408 and the cam you have chose?

Don't know yet. Other than starting it to move around the driveway or in/out of the garage it hasn't been driven yet. Just finishing a frame off overhaul. But I would expect mid 400's at the crank. With the 2" primaries, maybe the first thing you should do is upsize the exhaust and see what that yields. You may really be choking that motor more than you think.

The 396-375 will like a lot more cam but believe it or not the exhaust won't hurt this motor too much. If you throw this size exhaust on a 454 it dies,(80-100) horsepower. I suppose a good mandrel bent 2 1/2" might be better but the cam is the main downer. The 375 is a RPM loving engine and the tighter you wind it the faster they run. Throw that hydraulic cam as far as possible. A good solid lifter cam in that motor will fly. My last cam was the factory ZL-1 grind and would go off the end of the tach. Be careful to always keep good valve springs on these with plenty of seat pressure (I used Isky 8005-A's) shimed a little. This prevents pulling the tops of the valves off. The newer solid lifters with the EDM oiling holes should allow a good lifespan and you won't believe the power. All hydraulics require a lot of valve spring pressure and still have trouble going past 6200 RPM and the large ports need high rpm or you might as well use oval ports as they are more responsive to lower revs.

Harold Sutton,
What are the specs of the ZL-1 cam you mentioned? Can any of you guys explain to me how cam duration and lift effect a engine. I've got a pretty good idea, but maybe you can teach me a thing or two!!!!!!!!!!! Thanks again for all your help guys!!!!!!!!!!!

Well heres my old 396 combo,it was a 325 horse version with L-78 replacement pistons a strip dominator intake, 850 DP,herbert roller 657 lift 246 @50 dur. on a 108 center,rec. port closed chamber heads,10 inch 3800 stall,4.88 gear and 28X10 slicks.The car was a total pig to get going(best 60 ft. 1.80)at almost 4000 pounds it ran a best of 11.98 @ 113.It was a bad performance combo but it was a great bracket race combo out of the 6 rounds of racing I did I had 3 over and unders of .000 to bad my reaction times stunk.

I'll take a 1.8 60ft. any time if the end result is a 11.98 through the 1/4!!!!!!!!!!!

Originally posted by 396-375:
I'll take a 1.8 60ft. any time if the end result is a 11.98 through the 1/4!!!!!!!!!!! ..and it go along well cruising with 4.88's :eek:

sub the 4.88's with a overdrive 5-speed, and rear gear to give you the same gear multiplication out back as a 4.88. am I crazy or on the right track?

A Tremec with a 3.27 1st and a 3.31 out back equals (I think) about a 4.56. Could be wrong! If anyone has any calculations on how to figure this out please respond. Thanks

An M21 has a 1st gear of 2.20 X 4.56=10.03 overall 1st gear
A 3.27 1st gear with 3.31's=10.8 overall 1st


my 2.73's and TH400 has an overall 1st gear of 6.77 :D but it still ET's well graemlins/thumbsup.gif

Whats your secret? Just a good engine combination????????

Originally posted by 396-375:
Whats your secret? Just a good engine combination???????? yes..lots of compression (10.59 to 1) and a cam that builds a lot of cylinder pressure,which equals alot of torque,which is needed to get a 4000 lb. car going with no gear.

Tell me what you think about this ! Today I aquired a 454 bored .60 over and 4-bolt mains to boot!!!! this block with my 396 crank should give me about 440 cubic inches (give or take a few). With my 108cc, closed chamber, square ports, and about 11 to 1 comp. what cam spec would you recommend? And would this work in your high cylinder pressure theory? Also you are running nearly 11 to 1 comp, does this do ok on 93 octane??????

My motor runs fine on 93 octane pump gas..no booster ever.I think the Lunati/ old Ultradyne 288/296 flat tappet hydraulic cam would be great if you want hydraulic..specs are 231/239 @ .050 .550/.575 110 LSA powerband is 2500-6500
I just bought one myself for a another project I have going..

Thanks for the info, I'm going to research the cam.