72delta88

after 2 months and 2500 miles of driving my 72 delta 88 350 4 barrel i feel like i can safely and honestly write this review.
Its a great carb for a mostly stock 350 ( msd ignition offy 360 ) i set the secondaries a little tight and it runs great i get 14-17 in town and 16 - 24 on the highway depending on my foot i set the idle and the choke and it runs great even in - 7 degree weather ( illinois winter ) if you want a good out of the box carb for a stock 350 or 455 its great

the bad
the choke was to tight i had to grind the edges down a bit so it wouldnt rub and its jetted a little rich.

overall i would buy one again

76olds

Thank-you very much for the Street demon Carb review. I have heard that they are a good carb. Christian (olds 307 and 403) speaks highly of them.
If I hadn't bought 2 Edelbrock 1406 - 600 cfm carbs I would have tried it.
How would you rate the throttle response through the RPM range now that the choke is working properly? A little rich is OK.
Do you feel any bog at all?
Much appreciated 72delta88
Cheers
Eric

olds 307 and 403

Cool, these carbs get very good reviews. It is a good alternative to Qjet and Holley style carbs.

72delta88

no bog after i goit the seondaries set itll spin the tires through second gear with the throttle response of efi

76olds

Like EFI, Impressive!
Thanks again, I'm sure many will be throwing their e-brocks in the scrap metal bin soon. I have 1- 1406 E-brock 600 currently on my 350 and 1 new in the box as a spare that will end up in my metal bin soon haha.
Put-r-ther!
Eric

72delta88

mail em to me i could use spares

76olds

I really can't complain. I've had good luck with the e-brock after I put a 1" spacer under the carb.

72delta88

i run a 2 inch spacer under my carbs i boiled a holley last suimmer

JohnTN

I have had good results from switching from a reman QJet to the Street Demon 625. My car has a 1971 Olds 350, internally stock except for a RV cam. Transmission is a 2004R with 3.42 posi rear gear and 28 inch tall tires.

Initially my gas mileage was poor, 14-15 mpg vs an average of 18 mpg with the QJet. I talked to the tech help line and they said the carb was setup for high performance SB. Mine does not fit that mold with 8.5:1 compression and RV cam. But tech didn't suggest what changes to make.

I experimented with leaner primary rods and jets and settled on one size larger primary rod and 1 size smaller jet. This equates to about 20% reduction in fuel flow. My gas mileage increased to about 18 mpg average and 21 mpg on the interstate at about 60 mph.

Performance is better than the QJet, but QJet might not have been calibrated to match my car. I can lay a 12 foot strip of rubber from a standing start which I couldn't do with the QJet.

My only complaint is that the secondary throttle plate tended to stick in the bore and it took extra pressure on the gas pedal to push through that. I have sanded on the edge of the plate and also loosened the 4 screws that position the plate on the throttle shaft to reposition and eliminate the contact. It is usually free now but occasionally binds when pushing accelerator to the floor to set choke on cold engine.

So I agree it seem to be a good carb for street useage. I have had it on for 2.5 years and about 5,000 miles.

John

AZ520

I have one as well, I went from edelbrock 600, boils fuel too easy even with thermo spacer. I have a quadrajet as well same issue and jets are a pain, but its better than the edelbrock. I got the black coated composite bowl street demon and its much better all around.

I currently have it on a smogger stock low compression 350 and I had to go with 76 primary jets with .064x.056 rod , but I had to die grind away the .064 upper section to get it a little richer at cruising, green spring, 78 secondary jets. Tuning with a wideband A/F guage gets about 15mpg. Runs very well, crisp throttle response like the Q-jet. I just wish you could get at the jets without removing the carb.

JohnTN

Similar to AZ my leaner tune was 76 primary jets and 62/54 rods. I tried even leaner 64/56 rods but I got some lean surging at constant interstate speeds, but 22 mpg.

Stock was 78 rods, 60/52 jets.

On secondary I went down two steps on jets from 80 to 76, a 10% leaner jet.

I don't have AF sensor, just had to go by the plugs and how it runs. I get no pinging or surging with the final combo.

John

72delta88

dont you have videos of your car on youtube ?

part of my mpg issue is a lead foot an th400 with 3.31 out back

olds 307 and 403

The primary metering rods are adjustable, aren't they? They were on the aftermarket Thermoquads. I can see that secondary issue being one large plate. Those mileage numbers are amazing. I got 19 mpg imperial with my 800 cfm Qjet with the APT turned down a good 2 turns, takes 2 minutes. I might have eeked out 20+ mpg going another 1/2 to full turn but it would have been gutless. It barely spun the tires compared laying rubber hard. This was non ethanol 91, mild 214/214 cam, 2004R locked up with 2.78 gears along with 25" tall tires and 3 people on a warm day with no A/C on my 70S. Just shows how incredible the mileage is from that carb. I would like to try the 750 cfm version and I may do a back to back at the track between it and my custom 800 cfm Qjet eventually.

OLDSter Ralph

So, if I read your post correctly, the Qjet is a fairly good carb ? It does sound as though you tuned the Qjet ? What difference does the spacer have on power and fuel economy ?
Ralph

oldsmobiledave

Up to 24 mpg from a 1972 Delta 88? Respectfully I find that optimistic.

Thanks for the feedback on the carb.

JohnTN

72Delta, yes I hae a YouTube video, Street Demon 625 Cold Start, I think is the name. In retospect watching an engine idle for 5 minutes isn't very exciting.

John

olds 307 and 403

The spacer on the SBO Performer provides side to side plenum sharing. Think of notching the center divider on the RPM which I also did which I also did, I just did the switch. My Qjet was custom tuned and rebuilt by Everday Performance. I added a thread on plug and notched the APT adjustment so a flat screw driver removes the plug and adjusts the APT metering rod stop. It makes complete tuning simple. Every run with a consistent launch at the track went faster from where Ken set the carb 1 turn richer at a time. But MPG went down a good amount. I agree that 24 MPG especially US MPG sounds very high.

AZ520

You can get at the rods and springs on the Demon, but to get at the main well jets you need remove the carb, stupid design on their part I think.

JohnTN

The primary metering rods are not adjustable except you can change the spring that raises the rods up during low vacuum, I stayed with the stock spring since my vacuum is about 18 in. Hg. As was stated they are easy to swap out, both rod and spring, from the top of the carb.

There are no secondary rods. Both primary and secondary jets are only accessible from the bottom of the carb. I think the secondary jets are same as Holley jets.

There is a tuning kit available from Demon for $50-70, don't remember for sure. But a pair of rods is $10 and a pair of jets is only $5 so if you have an idea of what you might need you don't need the whole kit. At one time I found an EBay site that sold a set of multiple jet sizes for $12.

The carb was on sale at Summit for 10% off ($280) before Christmas. Don't know if it still is. Reviews are heavily positive.

John

70sgeek

ok, I'm throwing my curiosity into the ring.


Does the factory Olds 350 throttle cable mount up to the carb the same way as on a Qjet without modifications or length issues?


Any special suggestions as to how to fab a carb-to-pump fuel line for it ?


I was thinking about replacing my current Qjet with a 750 demon 1905
https://www.summitracing.com/parts/dem-1905/overview/


but wasn't sure what it would require for install.

76olds

The reviews are good with the demon carb however some had issues running them out of the box. I also read about the carbs flooding easily.
I seen some of Cutlassefi posts and he seems to think the quick fuel carbs are the best bang for the buck.
The 350 engine will be coming out of my 76 in the next couple months and I'm pretty sure a quick fuel carb will be on it.
Maybe someone could start a quick fuel carb thread if they do the swap.

Firewalker

On tuning the primaries changing jets is probably not needed, just change the rods, but holley demon rods and jets, for it, are not the only ones that can be used. The carter afb and thermoquad, plus the edelbrocks should all be the same rods, and they came in many sizes (diameters), and anything to large in diameter can be ground or sanded down to a desired diameter. Plating the too small a rods, with some liquid solder and then sanded to size also has been done.

Those thinking about the 750 have to realize it is still just a small 2bbl, when running on the primaries, and the secondaries is the same as the 625 and that is air flow controlled by the spring adjustment screw, so like the 3 bears it is always just right.

Another benefit is larger needle and seats, for the old carters along with brass floats, that should be the same as these street demons.

An SS/GT Ford Mustang with a thermoquad ran a 9.58.

JohnTN

70sgeek,

My SD package came with a number of different fittings to adapt the throttle cable to the SD throttle bracket. As for the length of the throttle cable, I think I had to change it by an inch or two (from QJet setup).

There are connecting points for GM2004R or 700R4 transmissions, and the geometry is correct.

A couple of things to consider:
1. I have a Edelbrock Performer intake with the EGR boss on the passenger side next to where the carb mounts. The SD throttle linkage wouldn't clear this boss without a 1.5 inch spacer which reduces the clearance above the air cleaner.
2. There is no internal fuel filter so you will have to plumb an in-line filter.

You would have to modify your fuel line and maybe use a short length of rubber fuel line hose for the final connection.

Are you sure you need the larger 750 carb? My 350 engine is mild (maybe 220 hp) and I had to lean the stock SD 625 down for best performance and mileage. There are primary rods and jets to richen it up if you have a high performance 350 that requires more than the stock SD 625 setup.

John

JohnTN

If you look at my photo album you can see the egr boss that is below the SD carb linkage that forced me to use a spacer under the carb. Sorry, boss is on the drivers side.

Macadoo

Thanks for the review. Sounds like a good carb. Also, You're in Pekin? There are three of us Cutlass Owners in the Bloomington area that hook up for shows and such in the summer.

olds 307 and 403

Surprised on not making the metering rods adjustable. I know my later 9000 series aftermarket Thermoquad was similar to what I have done with my Qjet, adjustable with a flat screwdriver. They improved everywhere the Thermoquad was lacking. No special secondary air door tool, better choke, Aerospace polymer instead of bakelite and no failed o rings That was the reason I finally pulled the Thermoquad. The choke was a joke as well. To bad they added screws making the top more difficult to remove. My Thermoquad also didn't clear the EGR boss on the Performer.

72delta88

yup ive got the only 72 olds delta 88 in town

slade69

I also have a 750 SD in my stroker 374 sbo. 9,75cr and 219/228 cam. E-brock heads, headers. Worked decently out of the box. No need to change jets or rods. Adjusted idle speed, idle mixture and choke. Next summer I will see with lambdas if further adjusting is needed. Good street carb!

72delta88

mr gasket throttle cable
demon throttle cable gasket 3/8 rubber line and inline filter

72delta88

im gonna start doing reveiws on carbs the sd was only the 1st quick fuel may be the next one maybe i need to take donations

72delta88

the secondary control spring snapped holley has one on the way to me the next review will be

A edel 1406
B QFT 600 CFM VS
C SUMMIT 600 CFM VS
D PROFORM 570 CFM VS

PLEASE COMMENT WHAT CARB YOU WANT REVIEWED

Firewalker

Which type secondary Holley snapped broke a spring?? Thanks

cutlassefi

Will you be using a wideband to correctly tune any or all of these?

72delta88

its a holley street demon 625 looks like a thermoquad

72delta88

at some point yes but atm i'm doing the reveiw from the stand point of a fix it on saturday go to work monday so im looking at the out of the box value not the tune it to death 1

i'm starting with the summit 600 cfm vs

Firewalker

Interesting, thats the second one that snapped a spring in that carb that I have read about. May or may not be a problem in other Street Demons. Not a worry since you can make them, or get replacement or may borrow one out of a Thermoquad, thats already lasted a thousand years.

72delta88

yea i had to panic order a carb from summit

olds 307 and 403

If you want to get rid of one, I may be interested in a Street Demon. Do the new Edelbrock AVS 2 with different boosters.

72delta88

im doing the summit 600 cfm its the cheapest and im goin t fix the sd and keep it for a spare

olds 307 and 403

If you change your mind, let me know.