383/400 4 barrel intake questions

yorker78

New Member
Joined
Sep 13, 2022
Messages
16
Reaction score
3
Location
saskatchewan, canada
So I've got the carb off my 78 400. It's got the stock 4 barrel EGR intake with block off plate on the EGR. Don't need EGR where I live. I have a 68 383 4 barrel intake just sitting and I'm wondering if there would be any advantage to installing the 68 383 4bbl intake over the stock 4bbl intake on my 400. The 400 is pretty much stock except some rv cam and 383 hp exhaust manifolds. I'd be blocking off the exhaust crossover aswell. Thx for reading.
 

Davea Lux

Old Man with a Hat
FCBO Gold Member
Joined
Mar 27, 2017
Messages
9,073
Reaction score
8,323
Location
Cornelius Or
So I've got the carb off my 78 400. It's got the stock 4 barrel EGR intake with block off plate on the EGR. Don't need EGR where I live. I have a 68 383 4 barrel intake just sitting and I'm wondering if there would be any advantage to installing the 68 383 4bbl intake over the stock 4bbl intake on my 400. The 400 is pretty much stock except some rv cam and 383 hp exhaust manifolds. I'd be blocking off the exhaust crossover aswell. Thx for reading.
Aside from getting rid of the EGR passage so you would not have to worry about the EGR carboning up, you will probably not notice any improvement in performance as the '78 engine is a low compression, smog tuned unit. Unless you you are running an after market electric choke, you should probably keep the crossover open. The '78 400 ran a lean burn system that requires additional sensors, so you would need to junk that carb setup, distributor and the lean burn computer system to get the vehicle to run properly with the older manifold. You might want to consider leaving the system as is and wait until a major rebuild is necessary and then go after performance upgrades like higher compression pistons, a HP cam and a good aftermarket intake and carb setup. EGR block off plates are readily available if getting rid of the EGR is a primary concern.

Dave.
 

yorker78

New Member
Joined
Sep 13, 2022
Messages
16
Reaction score
3
Location
saskatchewan, canada
Aside from getting rid of the EGR passage so you would not have to worry about the EGR carboning up, you will probably not notice any improvement in performance as the '78 engine is a low compression, smog tuned unit. Unless you you are running an after market electric choke, you should probably keep the crossover open. The '78 400 ran a lean burn system that requires additional sensors, so you would need to junk that carb setup, distributor and the lean burn computer system to get the vehicle to run properly with the older manifold. You might want to consider leaving the system as is and wait until a major rebuild is necessary and then go after performance upgrades like higher compression pistons, a HP cam and a good aftermarket intake and carb setup. EGR block off plates are readily available if getting rid of the EGR is a primary concern.

Dave.
I picked it up without lean burn 4150 double pumper carb on it wired the electric choke to a pressure switch on it running standard distributor with vacuum advance been playing with stock ignition and gm modules different ignition setups. Carbs isn't right I know I've got it as close as I can but switching to avs 2. Wasn't worried about lean burn but thank you. Was just wondering about if any performance difference between the two intakes so thank you also for that.
 

yorker78

New Member
Joined
Sep 13, 2022
Messages
16
Reaction score
3
Location
saskatchewan, canada
I picked it up without lean burn 4150 double pumper carb on it wired the electric choke to a pressure switch on it running standard distributor with vacuum advance been playing with stock ignition and gm modules different ignition setups. Carbs isn't right I know I've got it as close as I can but switching to avs 2. Wasn't worried about lean burn but thank you. Was just wondering about if any performance difference between the two intakes so thank you also for that.
I've got a rebuilt 76 400 sitting beside the car here i believe it's 9.8 compression nothing crazy but around 400 horse it's going in when I hit 100,000km with the original engine
which should be like another 2 years at my rate.
 

57fury440

Active Member
Joined
Mar 17, 2019
Messages
343
Reaction score
329
Location
Long Island, New York
The 68 manifold is a better piece than the one on it now. Swapping it would most likely add a few horsepower but not enough to make it worthwhile.
 

yorker78

New Member
Joined
Sep 13, 2022
Messages
16
Reaction score
3
Location
saskatchewan, canada
The 68 manifold is a better piece than the one on it now. Swapping it would most likely add a few horsepower but not enough to make it worthwhile.
I pulled the original one off the 400 to clean it up and put in the gasket with exhaust crossover blocked off. It was leaking pretty good and just ugly aswell as Id like to have the carb a little cooler. I might put the 383 one on since I'm there anyways it should be worth the slight gain
 
Top