396 BBC To Keep Or Not?

[Chevymaniac]

A friend gave me a 71 GMC 3/4 ton 4x4 for free. The truck came with a 396 BBC, TH350 mated to a NP205. Motor run on propane. Dana 44 and 14 bolt rear, 4" lift and 33" mudders. Cab and front clip were trashed. I have since gotten rid of them and now have the motor/tranny/transfercase on blocks in my shop. I have been doing some research and need to know if the motor is worth keeping or not. Plan was to throw it into my 72 chevy shortbox stepside that i'am converting to 4x4. I need some advice in which route to go with motor. From what i found in regards to motor is it came out of a 69 car. The numbers found on block did not specify what car though. It is a L35 with @ least 325 HP. Motor is in excellant condition. Thanks in advance for any advice.

[coops714x4]

well I really don't know your intentions, daily driver, off road play toy ?? depending on gearing and tires your looking at about 9 or 10 mpg. here is the way I see it, if you want a big block use it, its FREE . Coop

[Chevymaniac]

The truck will be a daily driver. I'll be running a 4" lift and 33" mudders. Gearing will be 3.73's if i go with the 1 tons i have, but i also have 2 sets of 3/4 ton axles with 4.10 or 4.56's. I do want a big block. Maybe my question is alittle unclear. What i want to know is the 396 BBC a good motor or should i sell/trade for a 454 BBC? Taking into consideration pricing for buying aftermarket parts. Does motor have any flaws compared to 454?

[d-666]

a 396 is a stout motor and you have a 69' wich is good and they are getting hard to find these days..as for parts its about the same cost as a 454. 396 rev a little more and have a little less low end torque but a fine tuned one can kick ass all day long. i've seen 396's beat hemi's, 440+6, bbf, etc. at the track often.a friend of mine have one in blazer on 46`' bogger and this thing really moves.so a well prep 396 is as good as a 454 for me but if you want to have more low end torque go with a 454 and make sure it's in good running order and try to get a good year..73-74+ 454 are considered as boat anchors but they are easy to ''wake up'' for a daily driver i'd keep the 396 it will be as reliable as the 454

[Chevymaniac]

Originally Posted by d-666

a 396 is a stout motor and you have a 69' wich is good and they are getting hard to find these days..as for parts its about the same cost as a 454. 396 rev a little more and have a little less low end torque but a fine tuned one can kick ass all day long. i've seen 396's beat hemi's, 440+6, bbf, etc. at the track often.a friend of mine have one in blazer on 46`' bogger and this thing really moves.so a well prep 396 is as good as a 454 for me but if you want to have more low end torque go with a 454 and make sure it's in good running order and try to get a good year..73-74+ 454 are considered as boat anchors but they are easy to ''wake up'' for a daily driver i'd keep the 396 it will be as reliable as the 454

What could i do to motor to match torque of 454? I was thinking alum. intake, new carb (because the motor is going from propane back to gas), headers. Anything else which would help? Thanks for your advice.

[coops714x4]

Bump up the compression a little, put in a RV cam and port the heads.

[andrewmp6]

A daily driver big block 4x4 will be a gas hog i would use a small block or a cummins and change it to a overdrive trans trying to get the most mileage you can out of it.

[d-666]

Originally Posted by coops714x4

Bump up the compression a little, put in a RV cam and port the heads.

x2

[Chevymaniac]

Originally Posted by andrewmp6

A daily driver big block 4x4 will be a gas hog i would use a small block or a cummins and change it to a overdrive trans trying to get the most mileage you can out of it.

I have two smallblocks, but since my friend gave me the big block for free, i thought i would try it out. Cummins swap is too costly, plus where i live diesel is 10 cents more a litre than gas. Parts for diesel is more than parts for gas motor. So for me a cummins is not worth it. I will be running a 700R4 behind the big block motor.

[Zane M]

You may want to rethink running the 700R4 behind a big block unless you are pre-planning on running a built/modified unit. There is a reason Chevy didn't offer them behind the big block motors.

[argonaut]

The torque of the big block is sweet. But be prepared for 10mpg.
I like mine

[Chevymaniac]

Originally Posted by Zane M

You may want to rethink running the 700R4 behind a big block unless you are pre-planning on running a built/modified unit. There is a reason Chevy didn't offer them behind the big block motors.

What the 700R4 can't handle the torque from the big block?

[54chevytruck]

it is my understanding that a stock 700r4 tranny cant take much more than 250hp max

plus, i think it is similar to a 4L80E in that it should have a lock up torque converter, which requires a separate electronic controller if you put it in anything older...

[1quik70]

I run a 396 in my 70 Nova, and a 454 in my pickup. I daily drive the pickup and have gotten 10 MPG on the road at 55mph. The 454 pushes my SWB 4x4 just fine, that being said my 396 is twice the motor my 454 is. The 396 spins 6800 RPM all day long with no hesitation, and makes gobs of power. It isn't real radical but not practical for daily driving 11 to 1 comp, .600"+ lift solid lift cam, mechanical secondary Demon 750, Ect. I would say run it and enjoy if you don't mind the milage.

Ditch the idea of a overdrive trans behind your big block, its not worth the hassle! The 4l60E won't work without expensive adapters and I beleive moving the crossmember, and a 700R4 will never hold the torque. If you must have overdrive, I would choose a Gearvendors unit or something similar. For the amount of miles I put on, >20 miles a day, I couldn't justify the cost. I just try my best to keep it running as good as possible, maintain tire pressure, and try not to get into the secondaries too often.

[RenoKeene]

A 69 L35 put out 410 ft# of torque with 10.25:1 comp, all in all a pretty stout piece. I'd take it over a late model 454 boat anchor any day.

[1972RedNeck]

Originally Posted by coops714x4

Bump up the compression a little, put in a RV cam and port the heads.

What would you bump it to? 11:1 like the L78?


I had a L35 in a '72 2wd about a year ago. I bought it for a motor swap but didn't use it. I drove it around a little to see how it ran. That thing was a horse! I had to run premium and set the timing at 6* and never lug it down to keep it from pinging. As previously stated the compression is at 10.25:1. I tore it down for the swap and saw that the std. bore/crank was in perfect condition. I also saw one of the piston rings come out in 13 pieces! Evidently the PO didn't know what pinging was. I reassembled it, advertised it and sold it for $1500 (apparently the JG stamped on the front of the block made it worth a little bit).

[Chevymaniac]

Originally Posted by 1quik70

I run a 396 in my 70 Nova, and a 454 in my pickup. I daily drive the pickup and have gotten 10 MPG on the road at 55mph. The 454 pushes my SWB 4x4 just fine, that being said my 396 is twice the motor my 454 is. The 396 spins 6800 RPM all day long with no hesitation, and makes gobs of power. It isn't real radical but not practical for daily driving 11 to 1 comp, .600"+ lift solid lift cam, mechanical secondary Demon 750, Ect. I would say run it and enjoy if you don't mind the milage.

Ditch the idea of a overdrive trans behind your big block, its not worth the hassle! The 4l60E won't work without expensive adapters and I beleive moving the crossmember, and a 700R4 will never hold the torque. If you must have overdrive, I would choose a Gearvendors unit or something similar. For the amount of miles I put on, >20 miles a day, I couldn't justify the cost. I just try my best to keep it running as good as possible, maintain tire pressure, and try not to get into the secondaries too often.

So what do you run for trannies behind your BBC's?

[Chevymaniac]

Originally Posted by 1972RedNeck

What would you bump it to? 11:1 like the L78?


I had a L35 in a '72 2wd about a year ago. I bought it for a motor swap but didn't use it. I drove it around a little to see how it ran. That thing was a horse! I had to run premium and set the timing at 6* and never lug it down to keep it from pinging. As previously stated the compression is at 10.25:1. I tore it down for the swap and saw that the std. bore/crank was in perfect condition. I also saw one of the piston rings come out in 13 pieces! Evidently the PO didn't know what pinging was. I reassembled it, advertised it and sold it for $1500 (apparently the JG stamped on the front of the block made it worth a little bit).

Are you saying i would have to run premium gas? Motor was running off propane the last 10 or 15 years. My intention was to convert it back to gas. Can i run motor on regular unleaded gas?

[1972RedNeck]

Originally Posted by Chevymaniac

Are you saying i would have to run premium gas? Motor was running off propane the last 10 or 15 years. My intention was to convert it back to gas. Can i run motor on regular unleaded gas?

You can run regular if you back the timing off a ways, which would hurt performance.

[Redcap]

Originally Posted by Chevymaniac

What the 700R4 can't handle the torque from the big block?

That is exactly what is being said.

[1972RedNeck]

Originally Posted by 54chevytruck

plus, i think it is similar to a 4L80E in that it should have a lock up torque converter, which requires a separate electronic controller if you put it in anything older...

They can easily be make to hydraulically lock up.

[Chevymaniac]

Originally Posted by 1972RedNeck

You can run regular if you back the timing off a ways, which would hurt performance.

How much performance would i lose going with regalur unleaded?

[1quik70]

I run TH350's behind both my stockish 454, and mildly built 396.
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