engine problem • The Dodge Challenger Message Board

by **Wojpi** » 16 Jun 2007 17:23

I have redone 318 engine. It has :

Keith Balck dome pistons
Compression ratio 10,5:1
360 heads, with big valves and porting done,
MSD 6 A ignition ,MSD distributor (non vacum type), MSD wires and coil
EDELBROCK performer RPM intake
SPEED DEMON 650 carb (stock specs) vacum secondaries
TTI exhaust system with Dynomax mufflers
Hughes engines camshaft 223/228

The engine is going nicely, i have the vacum at the idle 850 rpm around 15 inches, in the drive it is 11-12. What is my concern is that at low rpm when i start to drive it is like not to good, but when the rpm increases lets say more than 4000 rpm it starts to pull like hell. It revs up to 6000 Lets say from the start to around 60-70 km/h at first gear it is not to good but suddenly it starts to pull like hell, and what is strange when i change the gear to higher one it is not droping power but continue to pull.

When i stop and start again it is the same. \
What do you think can be the problem.

Thanks in advance for any suggestions.

by **Eddie** » 16 Jun 2007 23:54

What spring or bushing do you have in your dizzy? My 360 is 12 initial with 24 centifugal for 36 total at 2400 RPM no vacum advance either, I use a complete MSD6 as well with their billet dizzy. A good baseline is to use the biggest bushing and the two light springs with the advance kit. This usually covers most street/strip applications. Also put a dial back timing light on it and "see" what your total advance is a whatever rpm you have it set up for. Your vacuum is good, and the cam isnt too big, actually I would have used a 245@.050 cam with that compression and those big valve heads, but your's is a nice street cam and should pull hard to 5000RPM at least. Also what primary and secondary jets do you have in that 650? I could never get my Barry Grant to run consistently so I bought a Holley!! :biggrin:

And the "big" question is what rear gear do you run?

by **Wojpi** » 17 Jun 2007 6:32

The jets are 70 / 78 PV is 6,5 Distributor is set to around 18 centifugal advance and around 12-14 so total is 30. The rear end is 3.23

by **dave-r** » 17 Jun 2007 11:59

You want at least 34 degrees total. Any more over that depends on the quality of fuel you use. Just keep increasing it until you start to hear "pinking" from the engine when pushing hard up a hill. Then back off two degrees.

Set your initial timing higher as well.
Those Demon carbs very sensitive to initial timing.

You will probably need to have at least 16 degrees initial timing. The best way to do it is to advance the initial timing and try to start the car (when hot). It it starts OK advance it some more and try starting it again.

As soon as the engine kicks back on the starter, or sounds "not right" when trying to start, back it off two degrees and that will be the best initial advance for that Demon.

You should NEVER use a Demon carb straight out of the box. Suppliers like FBO and their agents will check it over first (for a small fee) and jet it to your requirements based on the information you give them about your car. They will also advise you over the telephone.

by **Wojpi** » 18 Jun 2007 7:57

Does anybody have any experience with jeting the Demons ? I have also speed Demon 750 that i can use, another jets i have is 80 and 86

by **dave-r** » 18 Jun 2007 8:21

I tell you what.

Get in touch with this guy I know called Neil Willett.
http://www.usaimports.co.uk/

Tell him I sent you if you like. He will probably help you out even if you didn't buy the carb from him. He know how to get these carbs running right.
But the first thing he will tell you is to do a starter kickback test. So do that first.