BBC 396 mods

[weq92f]

Bought a 67 C10 with a BBC. It's a later Gen IV block and has the 3/4" NPT threaded pipe fitting just above the oil filter housing. That means it is the higher performance 4-bolt main which should be making 375hp.

It has no vacuum advance on the dist and I think has standard mechanical sprint/arm advance. It's fuel injected with MSD unit which is not currently controlling the timing. Out back is 700r4 and 3.73 posi. The tranny is equipped with lockout plumbing and the tv cable mod to the throttle linkage. Dunno anything about the converter.

Don't know which heads are on it nor exactly the details of the engine internals. I'll get the casting number and date code eventually which may reveal more details. I'll pull the valve covers soon to get the casting on the heads too. Sorry I'm short on details, just excited and ready to get going with this thing.


Where would you guys go first with this setup to find more power?


This is a street machine so it needs to have driver manners, but I want mean idle and as much torque as possible! If the dizzy is not one of those fancy electronic timing curve ( e-dist ) models ( I'll be pulling and checking it soon too ), I will either replace it with a vacuum advanced model or add the advance to it.

-klb

[coreyjhen]

It looks to have cast iron exhaust manifolds, so the first thing to do is put on a good set of tube headers and good dual exhaust. Anything else you do will depend on getting that thing breathing.

[wbc409]

It has an MSD ignition box, there is a good chance that they set up the distributor as a trigger for the box.
For street use and stock heads I would look for large oval port heads. Casting #781 I believe.

[weq92f]

Originally Posted by wbc409

It has an MSD ignition box, there is a good chance that they set up the distributor as a trigger for the box.
For street use and stock heads I would look for large oval port heads. Casting #781 I believe.

Thanks,

I really am hoping those are the heads it has on it, those or the #049. If it has the peanut heads or the others with the rectangular ports, I'll be looking for something else.

I suspect you're right about the ignition box.

-klb

[weq92f]

Originally Posted by coreyjhen

It looks to have cast iron exhaust manifolds, so the first thing to do is put on a good set of tube headers and good dual exhaust. Anything else you do will depend on getting that thing breathing.

Yep, those need to go. It has dual all the way out the back. Nice big pipes too.

BTW, I got this truck from your city. Drove it 8 and a half hours to get it home.


Thanks,

-klb

[kwmech]

I there something wrong with the engine? How about driving it and enjoying it? just a thought

[weq92f]

Originally Posted by kwmech

I there something wrong with the engine?

It starts and runs. There are no physical indications of any issues. The thing just needs more grunt. Drive and enjoy is the reason this truck sits in my garage.

-klb

[un4gvn!]

My 69'CST396 had the 325 horse 2 bolt mains. I took it apart and sent it out to the machine shop. I had him put a 454 Eagle crank, .060 over Wiseco forged pistons, Lunati bracket master cam, and I ported the heads myself. The machine shop hogged out the heads to fit 2.19 stainless steel valves and 5 angle seats. Like a lot of members on here, I used the 2 inch Chevelle Hooker headers. All said and done the motor had 440 cubic inches and 10.9 compression and well over 500 HP. I had 3:73 gears with a Hughes 400 trans because this engine destroyed the original 400 trans. This set-up hauled a 3800 pound long bed truck in the low twelve's all day at the track. Street and strip is the way to go.

[coreyjhen]

Originally Posted by weq92f

Yep, those need to go. It has dual all the way out the back. Nice big pipes too.

BTW, I got this truck from your city. Drove it 8 and a half hours to get it home.


Thanks,

-klb

8½ hours and how many tank trucks full of gas?

[weq92f]

Originally Posted by coreyjhen

8½ hours and how many tank trucks full of gas?

Can't really be sure. Every time the indicator got down to half a tank, I stopped at the next station and filled it up. For sure didn't want to get stranded on account of fuel! I remember stopping about 5 times each time it was around 8 or 9 gallons. Give or take 10 gallons, that's roughly 45 gallons.

I was not driving slow either. Had the speedo pegged at between 80 and 100 indicated the whole way home. It's about 10mph indicated too fast, so I was driving 70 to 90 ( confirmed by my gps ).

It was a risk, especially at night, but saved a ton of money for shipping the thing.

-klb

[weq92f]

The heads have these markings:

C 25 9

GM 3 T

3931063 --

One Net source reveals...
OVAL PORT - Valve size 2.06 intake, 1.72 exhaust
Years CID Chamber CC HP/RPO/Comments
1969-70 396/427 Closed 109cc 325, 350 335, 385, 390, 400L-34/L-35


Looks like the date code means this head was cast March 25, 1969 ( just over a month before I was born! )? Dang.

Whatdyathink?

-klb

[Ironangel]

Really need those casting numbers to have an idea of what your options are. Can you get any info from the PO on what mods such as what cam and what pistons are in it? That appears to be a well thought out engine package. I have a 1969 396 that came out of an SS El Camino in one of my 72 C/10's. That SS motor is a two bolt block that was bored out .060" over. It has Forged TRW/Speedpro 22cc domed pistons, 3964290 closed chamber oval port heads with hard seats and Comp Cam springs matched to a Comp Cam 268H hydraulic lifter cam. Weiand intake, hand built Quadrajet for that motor. I went with the MSD Pro Billet 8360 distributor and is worth every penny, I love that thing! They dont need the box, they have a built in rev limiter, and are fully adjustable mechanical and vacuum advance. I ceramic coated a set of Hedman 69110's and ran 3" pipes through a set of Thrush Welded Turbo mufflers and dumped them in front the Sticky Mickey's Sport Pro's. Havent dyno'd the motor but seat of the pants feels like 400+ pony's...The 396 is the BBC motor that thinks it's a small block. They're limited in bore and stroke and unless you throw a set of heads, a cam, and at least a set of flat top pistons in them, they are overweight baby big blocks starving for air. So with all that said, we need to know what's inside of your motor as well as what heads are on it? The 396 responds well to boosting the compression and making them breathe, that's what the General did with the 350hp L34 and the 375hp L78, "L" standing for "Legendary"...~Ghostrider~

[weq92f]

On the rear of the block I find these markings:

3969854 -- Cast number
GM8
A 7 70 -- Date stamp the 7 in the middle is questionable

The second digit of the casting number (9) could also be an 8, which would put it as having been cast in the mid 60's. That is obviously not true given the date code so it must be a 9!

So this is a 396/402 rated at 375hp? No head info just yet, but getting there.

Anybody know more details for this engine?

thanks,

-klb

[68bowtie]

you have the casting right. same block i have. it's 2-bolt.

[RustyBucket]

Look down in front of the pass. side cyl. head where it meets the block deck. If the block hasn't been decked the suffix code will usually identify the engine's original application. Should be 2 or 3 letters after a series of numbers stamped into the block deck.

[weq92f]

That casting included 2 and 4 bolt blocks I think. Does your 2 bolt have the 3/4" NPT threaded port there above the oil filter housing? Just curious. Getting the other code off the passenger side head could be problematic, but I'll give it a shot. Thanks!

-klb

[67 chevelle]

396 is a powerfull engine , better than most of the 454s out there , 70 was one of the best years ,take a valve cover off , post the head casting number , that tells the whole story , I dont believe penut port [low performance] heads were stock on any 396s , doubt you have the 375 horse motor , they were solid cam motors , with rectangle ports a pretty rare , something must be off with your motor , maybe tune , for you to be looking for more power , most 396s are anything but "slugish" , they rev fast and pull hard to high rpm

[weq92f]

Originally Posted by 67 chevelle

396 is a powerfull engine...

Agreed. I'll be attempting to tune it better when I get the time, but there is definitely something not right. The rotor has some corrosion so the whole ignition system is probably in need of a tune up/once over.

Regarding the 375hp version of the 396/402: My reading suggests that only 2 bolt blocks were the lower horespower 325 and 350 versions where the 4 bolts were the higher performance versions. Now I haven't seen for sure whether this block I have is a 4 bolt, but the consensus is that if the threaded 3/4" oil port is there rather than the smaller, non-threaded oil port, it is a 4 bolt.

I'll get the valve cover off tonight and get the casting for the heads. That should answer whether it's the 375 or not. My understanding was that those rectangular port heads did nothing for low end torque. That they were meant more for 3000-3500+ RPM range power. We'll see...

Thanks,

-klb

[geezer#99]

It's not a holley, it's one of these.
http://www.tdotperformance.ca/msd-29...FRUlgQodXL4EDw

Did you get the motor suffix code from the pad in front of the pass side head?

[weq92f]

Even so, the truck is pushing a lot more air and is much lighter in the rear. Good point that many a Chevelle rolled out with this same engine and blazed down the track with it -- time after time for years and years!

This truck does go very nicely. It pulls hard at launch ( WOT going straight ), just hard enough to induce but not maintain wheel spin then shifts pretty good into second around 5300 indicated and continues to pull but with a bit less vigor up to 3rd around the same rpm. By the time the shift to 3rd finishes, 5-7MPH have vanished along with those RPMs and forward momentum. Fourth gear is a very low OD and I love it!!!!!!!

The timing at idle on the crank is ~12 degrees BTDC and I see it advance as RPM increases.

Compression test is next.

-klb