Help w/ 78 c3 engine
Thread Starter
5th Gear
Joined: Jun 2020
Posts: 3
Likes: 0
Help w/ 78 c3 engine
Hello all, I am new to the forum so let me apologize in advance if I am in the wrong area to post this. I have a 78 c3 with a 350 and 700r4. I was told the engine was rebuilt by the previous owner but I cant find any numbers anywhere. I am looking to build another 350 to drop in so that I can don't have alot of downtime rebuilding the current motor. I have been looking to find a rebuildable core but am under the impression that vette motors are different than others with location of alternator, ac, etc. Is this the case or will any 350 block work? Thanks in advance for any help. Any numbers I should be looking for in particular. Looking to try and get 400 to 450hp but don't want to go with LS swap.
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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Cruise-In VIII Veteran
Any Gen 1 small block will fit. just reuse all your accessories and brackets. Also note Corvette uses specific water pump.
But a 350 block is a 350 block. 400 HP shouldn't be to difficult with the right combination of parts.
Good luck
But a 350 block is a 350 block. 400 HP shouldn't be to difficult with the right combination of parts.
Good luck
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
flat pad right in front of the right cylinder head. clean it up and get the numbers off it. post a pic of the pad. that will tell you if it is the original engine or not. it is not that big a deal with 75 and up cars but still nice to know if numbers-matching or not. and if not, that engine is no more deserving of a rebuild than any other small block chebby you find.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
A much later model sbc Is better. 5.7L / 350 from '96 thru 2002 GM truck, suv, van whose VIN's Eighth character is "R" has L31 iron head & block Vortec. Best ever production sbc heads and has OE roller cam/lifters. 400 hp is a walk in the park. L31 bolts in frame & to trans same as OE vette.
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
For me...the more interesting question is how did a 700R4 get into your 78. 78's had 3 speed TH350's.
Your L-48 is a 2 bolt main block. Trying to attain 400+ HP out of a 2 bolt main is 'iffy'.
Go find a 4 bolt '69 BASE' or any L-82 for your build. At least with the L-82 you'll get the 'big valves' for free as well as the 4 bolt main..
Good luck.
Unkahal
Your L-48 is a 2 bolt main block. Trying to attain 400+ HP out of a 2 bolt main is 'iffy'.
Go find a 4 bolt '69 BASE' or any L-82 for your build. At least with the L-82 you'll get the 'big valves' for free as well as the 4 bolt main..
Good luck.
Unkahal
Thread Starter
5th Gear
Joined: Jun 2020
Posts: 3
Likes: 0
Thx for the replies. As to how the 700r4 got there. It was there when I bought the car. The previous owner did alot of bubbafying as I am slowly finding out piece by piece. That's why I am unsure of what shape the motor is in. All I know is it is a dog. I can beat it off the line with my lawnmower...lol. I looked for the numbers on the block but can't find them...it looks like the plate may have been ground down at some point. I would be willing to bet the car is not numbers matching.
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
Actually the 700R4 is a big upgrade. The 700R4 has a very steep 1st gear (gets off the line SMARTLY!) and a .70:1 super overdrive top gear....super gas milage and relaxed cruising at hi-way speeds.
Your problem is two-fold. (DOGGINESS)
The L-48 'tain't no rocket'
You need to find out what rear gears you have...look up the code on the pumpkin....3.08's were available and that is a bit 'doggy'.
Keep the TRANNY!
I have one and love it! 109 mph is 3000 RPM 1000 RPM = 36 MPH.
Unkahal
Your problem is two-fold. (DOGGINESS)
The L-48 'tain't no rocket'
You need to find out what rear gears you have...look up the code on the pumpkin....3.08's were available and that is a bit 'doggy'.
Keep the TRANNY!
I have one and love it! 109 mph is 3000 RPM 1000 RPM = 36 MPH.
Unkahal
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