Need help . Ive got a 78 400 - Moparchat

Bret · #1 06-25-2002, 12:01 AM

In a 3/4 pickup up . The first step towards righteousness was taken by the previous owner with a new holley and eldebrock . There is a problem , first with me . I cant tell what size the holley is , duh , any help there . And second it wont idle down to a nice slow glub glub glub like i want my big blocks to do . The idle screw is not touching anything . You will hear and see more of this ride in the future. Dont forget your Motruckin brothers in arms

dave571 · #2 06-25-2002, 12:13 AM

The high idle is most likely caused by a vacuum leak. Not much of a stretch since the intake and carb have been changed.

Spray some carb cleaner around the base of the carb, and where the manifold bolts to the head. If the running sputters, then you've found the leak, and know what you have to do to fix your idle fault.

As for id'ing the carb, I would get a number off of it, and try to match trhe number at holley.com

rumblefish360 · #3 06-25-2002, 10:56 AM

The number is on the airhorn. (Right?)

Bret · #4 06-25-2002, 07:44 PM

Thanks for the tip . hows that 400 do for horse power set up the way you have it .

dave571 · #5 06-25-2002, 11:23 PM

It's not bad!

The only references I have, are G-tech readings.

I replaced a 1974 360. It was stock, except for a mild cam, dual exhaust, an mp performance intake, and an edlebrock 600 cfm carb.

On the G-tech it made 154 wheel horse power. Not a bad driver, but not much of match for anything except other small block trucks, and ricers

My highest reading since the swap is 224. Big change. It's fun to drive now. Surprises the sh*t out of people. The smarter ones recognize the healthy sound of it, at idle.

What has surprised me, is the torque it makes. The 360 has a longer stroke then a 400(or any other B engine) does, and with the cam(490 lift/ 272 duration, not too crazy but meant to breath a bit) I though it would be a bit of a dog out of the hole. But the opposite is true. I would race anyone up to 100ft. I used to have a 69 dart 340, and it certainly pulls as hard as it did(for about a hundred feet) The stock "motorhome" manifolds seem to be holding me back above 4000rpm, so I'm saving my money for headers.

If you want to see some pics of the motor, in the van, they're under the heading"yellow big block". Presently on page 8 of this forum.

Bret · #6 06-26-2002, 12:12 AM

Ive had several 400,s and a 383 mag including a 400 hp as well . I have allways been amazed at the power these machines made . There is just something right about the whole set up of these blocks . This is the first one i will build beyond stock though . I have a 78 motorhome with a great 440 in it and have considered doing a swap for my 400 but i think ill stay with the 400 and have a little fun . My goal is 400 hp . It shouldnt be too hard and it should still be relatively streetable . Are there any other truck builders out there . Tell me your stories.