Could I get away with using a Mighty Demon 650cfm on a stock 383?

[Zanx]

Finger is hovering over the eBay Buy it Now button. From what I can make out, the only difference is that the Mighty Demon has no choke facility.

Hell yeah! or Heck NO! ?

[Zanx]

Too late now.

Well, it's got to be better than the Eddy.

[dave571]

The 650 mighty will work, depending on your combo of course

The upper series of carbs are calibrated to be more sensitive to the erratic vacuum signals made by more radical cams.

It is easy to go to more tame combo with the better carb. Harder to go the other way (ie use a road demon where a mighty should go)

[Zanx]

Dave, I'm planning on a mild cam and TTI headers in the future, that's about it really. Maybe a freshen up and mild post of the heads if they ever come off.

[dave571]

I find the throttle response of the mighty demon to be very good.

It may cause you a problem if your car is heavy, or you don't have enough stall, or gear.

Something to keep in mind when planning the car

[Zanx]

Originally Posted by dave571

I find the throttle response of the mighty demon to be very good.

It may cause you a problem if your car is heavy, or you don't have enough stall, or gear.

Something to keep in mind when planning the car

Only one way to find out. It's been used for one hour and has saved me £200 so even if it's lame, I can put it back on eBay

[Zanx]

Bit of an update on this. To get it all running I needed to mod the linkages that were on the Eddy and bolt them to the Demon, no big shakes, just a couple of enlarged holes. With that done I offered the Demon up to the Edelbrock Performer manifold only to find that the secondary accelerator pump linkage fouled the part of the manifold where the mechanical choke would have been. This was duly removed with a grinder and it all dropped on perfectly. Bolted everything down, re-located the coils slightly to accomodate the very non standard shaped Demon, plugged in the gas and tentatively bumped the fuel pump bit by bit (as shown in the cheesy but informative CD)......


R..R..RR..RRRR....RRRR........VROOOOOOOOOOOOOOOOOO OOOOOOM!!!!

Perfect tickover, started from freezing cold (about 5c) and this carb has no choke on it, couple of squirts of the accelerator pump and it was running like a watch. Tweaked the idle mixture a quarter turn at a time till it ran smoothly without loading up. Lovely

Still not road tested it yet, it might be undrivable still but I need to secure all the linkage nuts and bolt with Plastex before going out on the road.

Generally speaking, pretty damned happy with it. Song might change later though It's a Mighty Demon 650cfm BTW.

[pishta]

Im still game on my previous offer, good to hear you got a good Demon. I had to tweak a linkage piece on my Demon to get it to fit too.

[ehostler]

I used the Holley to MOPAR adapter with a small modification. It all bolted right up.

Glad to hear that she is rumbling well. Hopefuly she'll drive as well as she idles.

[Zanx]

Weeeeel, I took her out today and everything is looking pretty good, still pinks a bit when I floor it in second gear despite having only 8 degrees of advance, but the stumble has gone and I'm having trouble keeping traction in the wet if I hit the gas hard from a standstill

Anyway, it works better than the old Carter and ALOT better than the Eddy, happy bunny

[Tarrbabe]

many stock HP 383's came with Holley 650 carbs as the performance option. Yes you can use one that small but performance would be better with a 750. The old 3310 - 780 cfm was great on those engines.

[rumblefish360]

Tarrebabes right about that. The OE Carters were small unless it was a HP version of the engine. The Demon he has will do just simple great on top the 383.

[dave571]

Originally Posted by Zanx

Weeeeel, I took her out today and everything is looking pretty good, still pinks a bit when I floor it in second gear despite having only 8 degrees of advance, but the stumble has gone and I'm having trouble keeping traction in the wet if I hit the gas hard from a standstill

Anyway, it works better than the old Carter and ALOT better than the Eddy, happy bunny

Glad it's working out.
The 650 demon is almost the perfect size for a 383.

As I mentioned earlier, the carb is calibrated for a more radical cam, but usinge the better carb on a milder combo is easily done.

I ran a 650 speed demon on my 400 and it gave me the best results of about 5 carbs I tried.

[Zanx]

Dave, you might be able to help me with the pinking here then, I'd need to up the jets on the primaries if it's pinking under heavy acceleration right? It's not foor to the floor stuff, I don't want to screw up the pistons, about 3/4 of the way I reckon. Are the Demon jets that same as the jets on any other carbs?

I'd watch the setup CD again but a guy can only take so much cheese in one lifetime

[dave571]

If you are pinging, the problem is more than likely timing related.

8 degrees of advance? Is that with the vacuum disconnected or not?
8 base, and how fast does it come in? do you have the light mp springs in? If you do, that brings the timing in really fast. Can easily cause a ping depending on your build.

Obviously other things can cause a ping too. Poor fuel, carbon in the cylinders, etc.

The mix could be off, but the other areas need to be adressed.

Put a new plug in one whole, and take it for a rip. Pull the plug and see what it's like.

The jets work the same as a holley, but flow very marginally more. maybe .5 of a jet size. Holley jets will fit it. You will now the jets are holley, because they have an H next to the number.

Pull off a float bowl and see what jets are in it now. Since the carb is used, it could be anything.

You can email me for info, or don at FBO is a demon guru. bigdaddy@4secondsflat.com