396/375 or 396/350 - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 14th, 17, 09:24 AM Thread Starter
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Tommy
 
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396/375 or 396/350

hello im new here i have a 69ss looking to go from sbc to bbc i have both motors 396/375 and 396/350 to chose from both all done to factory specs both all origanal some say the 375hp motors are very temperamental and run hot and dont like pump gas and not good for just weekend driving im 56 and thats all i do the 350hp motor is more for me i like the 375 myself but not if i am going to have problems can you give me the good and bad of both motors thank you
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post #2 of 13 (permalink) Old Mar 14th, 17, 09:37 AM
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kevin
 
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Re: 396/375 or 396/350

my 68 came with a 396/375 that I bought in 72 and I never had any problems other than keeping it together
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post #3 of 13 (permalink) Old Mar 14th, 17, 09:48 AM
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Dave
 
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Re: 396/375 or 396/350

Gas will be the first thing that will be an issue. 375's are 11:1 engines and will require race gas or at least a mix of race gas and premium to keep from detonating.

There are things you can do to reduce this (cam timing through a cam change) but then it isn't a stock 375 anymore.

The 350 at 10.25:1 compression would be much better for today's gas (still premium).

Dave
1970 Code 48 10 Z28 4 speed with Z87
Got it in 1978..first car i ever bought!
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post #4 of 13 (permalink) Old Mar 14th, 17, 09:57 AM
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Dave
 
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Re: 396/375 or 396/350

The 375 horse uses the huge 320 cc rectangular intake ports that are incredibly lazy on the street. The engine was designed back in 1961 to win at NASCAR racing which is stand on it and turn left. It is the stand on it that gets you in trouble quickly on the street.

To use those heads with any expectation of throttle response you need a 540 cube motor. A 396 will not begin to respond with those big heads unless you are above 4,800 RPM. Racers from the seventies quickly dropped the High Performance heads in favor of the oval port (230 cc ) Passenger car heads as they offered better throttle response and performance over all. Especially on the 396 that had issues with the small bore obstructing the heads air flow at low lift.

The BBC adds 230 pounds of extra cast iron over the nose of the front end. This can be left on the starting line by instead using a SBC 400. This engine is more efficient lighter, and cheaper to build than a big block of the same size. The smallest big block I would even consider is a 496 which looks just like a 396 when you put that decal on the air cleaner. Like I said a 540 is a good starting point for a big block, and I tend to go even bigger as you are hard pressed to obtain even one horse per cube on pump gas.

Speaking of pump gas a cast iron headed 375 will not even run on pump gas the static compression is too high. Dropping compression drops horsepower and the big block was designed initially as a high compression engine and suffers greatly when it is reduced.

Big Dave
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post #5 of 13 (permalink) Old Mar 14th, 17, 01:19 PM
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Chick
 
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Re: 396/375 or 396/350

X2 Big Dave! Street driving the L34 does better than the L78. I purchased a L78 (69 Nova) new and my just sold off 65 L79 Chevelle would have spanked the L78. The 350 hp L34 works much better with the round port smaller heads Dave aforementioned.
Our 69 Nova (survivor) we purchased new as it looks today.

Chick
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post #6 of 13 (permalink) Old Mar 14th, 17, 01:42 PM
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Mark
 
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Re: 396/375 or 396/350

I fell over from oxygen trying to read through that without one period. Really?
Go with the 375 hp or sell it.

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post #7 of 13 (permalink) Old Mar 14th, 17, 03:00 PM Thread Starter
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Tommy
 
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Re: 396/375 or 396/350

no periods oh sorry professor what are you a english teacher
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post #8 of 13 (permalink) Old Mar 14th, 17, 05:20 PM
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Mark
 
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Thumbs down Re: 396/375 or 396/350

Sorry, expected from a new-be, SA.

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post #9 of 13 (permalink) Old Mar 14th, 17, 07:38 PM
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Re: 396/375 or 396/350

Quote:
Originally Posted by COPO View Post
I fell over from oxygen trying to read through that without one period. Really?
Go with the 375 hp or sell it.
You fell over from oxygen? Really?
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Chick
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post #10 of 13 (permalink) Old Mar 14th, 17, 09:43 PM
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frank
 
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Re: 396/375 or 396/350

Having had an L78 Chevelle back in the day I can say it was no problem at all driving on the street. Don't get turned off by some jargan that the heads had too large of runners which made the engine lazy. I had to laugh, the L78 certainly was not lazy and I am sure you would enjoy that engine in your car. As for the fuel thing,I run a born with 302 in the 69 Camaro on 94 octane pump gas with no problems.

wot
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post #11 of 13 (permalink) Old Mar 15th, 17, 06:34 AM
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Re: 396/375 or 396/350

Quote:
Originally Posted by frankk View Post
Having had an L78 Chevelle back in the day I can say it was no problem at all driving on the street. Don't get turned off by some jargan that the heads had too large of runners which made the engine lazy. I had to laugh, the L78 certainly was not lazy and I am sure you would enjoy that engine in your car. As for the fuel thing,I run a born with 302 in the 69 Camaro on 94 octane pump gas with no problems.
Frank, you are surely correct that the L78 is not lazy and our L78 runs on 93 octane and its internals are the way it came from the factory (32K miles) but for sure the large runners do impact lower engine rpm performance. Would I want to change ours to a L34, no! But the L34 works very well and between heads and compression it fits pretty darn good. On the street when I picked up our L78 with 3.55 gears it was a dog compared to other lower HP machines but 4.10 gears and some tune up work picked her up.
Another really key question to the op is transmission to be used as the automatic with a L78 creates more to make it work to its efficiency.

Chick
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post #12 of 13 (permalink) Old Mar 15th, 17, 06:59 AM
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Michael
 
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Re: 396/375 or 396/350

All you have to do is start a cold L78 and listen to the engine warm up to make your decision. If you have a soul, the staccato exhaust and solid lifters will speak to it.

The comments from the Chevelle owner are accurate and bear in mind that the Camaro is the lighter car.

I owned a L78 equipped 67 and they work pretty well, even as a daily driver (which mine was). Use premium fuel and give serious consideration to upgrading the brake system (not just to a sliding caliper design, but 4 piston).

As for the weight, get a big front sway bar, good gas pressure front shocks, Hotchkiss BB front lowering springs, consider making the car an L89 (I did) and decent modern tires.
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post #13 of 13 (permalink) Old Mar 15th, 17, 10:29 AM
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Re: 396/375 or 396/350

I think you should listen to the LARGE ONE that's solid advice the 350 horse will be a lot easier for you less maintenance and more fun . retired automotive machinist. Alex
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