Hi There,

I am pretty new to the world of carbs but wanted to ask the general opinion with regards to selecting a carb for my 383 3rd gen camaro.

The engine has been mildy modded with comp cams, keith black forged pistons, edelbrock performer intake... will be upgrading air cleaner as its way too small and restrictive...

As the holley carb I have is years old and not responding too well to adjustment I was going to consider an edelbrock performer 750 vac sec with electric choke, but then I have been offered a speed demon 750 for a lil bit more.

I have checked the net but wanted some indication from fellow users of both carbs or from those who have used both carbs. Does anyone have any experience that they can share to help me decide between the two please? I have read the manufucturing literature but wanted real life experiences from runners.

Thanks for your time

Regards

Derek

 

Edelbrock is not vacuum secondary. I would say most people on here are going to tell you to use the demon.

 

Thanks for reply...

I will check the spec of the edelbrock in that case.

I did actually buy a 750 vac sec speed demon when I was in the US earlier this month but TSA or AMerican Airlines security consficated it and *allegedly* destroyed it (more like took it|) before I could get it back to send via UPS to the UK.

What are the speed demon's like to tune?

 

You're half right, most people here will tell you to run the Speed Demon. But you're wrong, Edelbrock's 750 Performer carb is a vacuum secondary carb. You didn't mention much about your setup, specifically cam specs, manual or auto, and converter stall speed if auto. The biggest thing you negelected was to advise your intended use. Is this a daily driver, street cruiser, a weekend warrior, or a track car? Either carb can be setup to deliver good performance, spending the time tuning is the key. I know little about Speed Demon tuning, but the Edelbrock is pretty easy to get setup and start tweaking. You've gotta take it apart to change main jets for the primaries or secondaries, but rod and spring changes are nice and quick with the carb still on the motor.

 

Thanks for response again.

The car is a 4 speed auto and has stall conv up to 2500 (I believe). The comp cams in there are high energy ones but unfortunately I don't have specific timing/setup info for these to hand.

With regards to usage, its driven mainly weekends, cruising with the frequent heavy right foot driving when with pals with TVRs and such like.

The car does seem pretty sluggish off the mark needs the revs to be high before it really comes alive, but I understand that this could be due to the cam setup (it is pretty lumpy at idle and there are signs of wear on the cams so it is something I need to look at in the future). ALso the air cleaner is restrictive at the mo. (PLus I need to confirm rear axle ratio)

Apart from the obvious price difference with the carbs, I wondered if there were any features and characteristics which favour one unit to the other...

Thanks again for help.

 

Is the Speed Demon you're looking at a vacuum secondary, or mechanical secondary. If you've got a relatively low stall, you might want to stay with a vacuum secondary carb, mechanical secondary carbs don't always play nice with auto's w/ low stalls. If you've got cam wear, you should figure that out before doing mods. Sluggish off the mark sounds just like a long duration cam with too low off a stall speed, that would even tougher with a mechanical secondary carb.

 

i never had a edelbrock but i do have a speeddemon. i had two different carbs on my set up and i would take the demon carb for performance any day but that is my own opinion.as far as tuning goes i was going crazy because of it being so rich.i got tired of buying new plugs so i pulled it off and checked to see where the butterflies were set.they were open over double the recomended twenty thousands.i set the four screws out three quarters turn and it never ran so good.they tell you to start with one and a half turns out but with 400 horse i was surprized at how much i had to turn them in in order not to run rich.good luck on your choice.

 

i'd go with a holley 750 double pumper over a speed demon. Mechanical secondaries will always outperform the vacuum secondary on the strip. So if max HP is your goal then that's what I would go with over edelbrock which IMO is junk.

 

I second the Holley 750dp!!

 

If you go Demon, get a good used older model. Not too old, just the ones before the Idle EZ stuff. I had good luck with my old Speed Demon, crap luck with a brand new Mighty Demon and good luck with my current Mighty Demon I got off ebay used. All I did was clean it up and put it back to it's stock settings then went from there.

 

Thanks for the comments and tuning tips there; interesting to read peoples views.

The Speed demon is a 750 Vacuum sec, I currently have a holley 750 vac sec but its in pretty bad shape (due to age) hence the change. The max HP is not ultimate goal but taken on board about performance differences between mech and vacuum secs. I think I need to go do some more reading about them

Just to elaborate; the cam wear was minor when I talked to the guys who rebuilt block but something to keep in mind I was advised.

I was thinking of dp at one point too but would like to be able to cruise for more than 100 miles b4 having to fill up A pal has a 650 dp holley he thinks its great for strip but round town it just runs way too rich and drinks unfeasibly too much.

I may bite the bullet and plump for the Speed demon for the price its being offered in that case after doing a bit more reading about this. Is it also recommended to get a carb sapcer the same time?

Thanks for info, any more tips/experiences about the types will be greatly apprecated.

Thanks again,

Derek

 

proper jetting and fuel mileage won't be an issue with the double pumper, i don't know where this myth came from. Stay out of the secondaries and you're fine. I jetted a buddies carb to 15.5:1 cruise A/F ratio and his car runs mint and gets great gas mileage with a double pumper.

 

My pal has offered his 650 dp so may try this for a week or so see how it fairs.

I have external o2 sensor so I shud be able to monitor my AFRs.

Which dp you been using?

 

That might impact how much aircleaner to hood clearance you'll have. I know I have carb heat soak issues in the summer months, and I'd love a carb spacer, but I have no underhood clearence for one. May be something worth considering.

 

Ummmm no, I am 100% right...lol! Edelbrocks are a mechanical secondary carb. The have a mechanical secondary air velocity valve the sences air flow according to air flow demand.

 

No, it's not. It's an air-valve secondary, similar to a Quadrajet, but with a primitive counterweighted air door instead of spring-loaded.

 

Let's try to straighten this out. . .

Edelbrock Performers, like the q-jet, falls into the general category of "demand-based" (which is also true of vacuum secondary carbs). For the Performer and q-jet, the throttle butterfly is mechanically operated, but air flow is controlled by an air valve above it - spring loaded on the q-jet, weighted on the Performer. Making them demand-based, not mechanical.

Vacuum secondary Holley and Demon carbs have the secondaries opened by a vacuum created in the primary venturis - there is no mechanical link from the throttle to the secondary butterflies on the VS carb. They are also demand-based.

Extra credit if you know why they go through all this trouble, rather than just mechanically linking the secondaries to the throttle and leaving it at that.

 

Oh I know...so you can have a smoother transition when going from primaries to secondaries.

Do I win a free oil change or something...lol!

 

Nope. Wrong answer.

(At the very least, incomplete.)

 

Cheers for the comments guys and the information. I may as well try the speed demon to see how I get on.. Its got to be an improvement on the old holley I have on it now.

I will try for the carb spacer also as the cowl induction hood is there ready for install I believe. I need to look at the depth tho and I think it may still be close. Again any prefs from anyone to consider?

Thanks again for your time and input.