Thinking of getting a Holley
August 29th, 2015, 07:59 PM
#1
Registered User
Thread Starter
Join Date: May 2013
Location: Richardson, Texas
Posts: 223
Thinking of getting a Holley
I am thinking of putting a Holley 670 Street Avenger on my recently rebuilt SBO350. I've had the q-jet adjusted by a very knowledgeable q-jet/olds afficienado but it still idles poorly -
my question is my intake is spread bore and I will need to use an adapter (e-brock manifold) - are they problematic? Also, how much trouble getting the throttle linkage modified for the Holley?
my question is my intake is spread bore and I will need to use an adapter (e-brock manifold) - are they problematic? Also, how much trouble getting the throttle linkage modified for the Holley?
August 29th, 2015, 08:29 PM
#2
Administrator
Join Date: Oct 2009
Location: Poteau, Ok
Posts: 41,081
If your going to change carbs change the manifold too. In all seriousness the Quad is the way to go for your mild build. I'd see if you can get it squared away. There should be no major mods to your linkage by changing the carb. You may have to adapt the way it connects to the carb and make sure it goes to WOT.
August 30th, 2015, 07:21 AM
#9
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
What are the specs on your 350? You should be able to run the Street Demon 625 or 750, which is a 3 barrel based off the Thermoquad that fits square and spreadbore flanges. The Quick fuel carbs are more refined versions of the classic Holley carb. The Holley spreadbore has a base that looks like it came off a Qjet, so it will bolt right on. Anything other than Qjet will require fuel line mods.
August 30th, 2015, 07:31 AM
#10
Registered User
Join Date: Sep 2013
Posts: 3,612
I run demon carbs and not a fan of the 625. The 750 is a different story.I know of three other guys using demons with no problems besides myself. I have two demons.One is a 750 street demon the other a 850 mighty demon.My next carb will be a quick fuel.
August 30th, 2015, 07:47 AM
#11
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
The confusion comes because Demon makes mostly Holley style carbs, but the Street Demon is totally different. It is basically a Thermoquad with a bunch of improvements and new 3 barrel castings. I was very close to buying the 750 but figured after buying the carb and geometry corrector for my 2004R, a custom tuned Qjet was actually cheaper since I had a good 78 800 cfm core.
August 30th, 2015, 08:23 AM
#12
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 48,277
It idled fine from the factory, so maybe you should figure out what's wrong before swapping carbs. You may very well have a problem not related to the carb and end up spending money on a new carb that doesn't fix the problem. Unless you have too much money, try free troubleshooting FIRST.
August 30th, 2015, 07:56 PM
#13
Registered User
Join Date: Sep 2013
Posts: 3,612
The confusion comes because Demon makes mostly Holley style carbs, but the Street Demon is totally different. It is basically a Thermoquad with a bunch of improvements and new 3 barrel castings. I was very close to buying the 750 but figured after buying the carb and geometry corrector for my 2004R, a custom tuned Qjet was actually cheaper since I had a good 78 800 cfm core.
September 1st, 2015, 06:43 AM
#14
What does "idle poorly" mean. What kind of vacuum is it getting, what idle rpm does it like the best? Is it getting hot? Smoking?
-I had a quadrajet on my 307 for 10 years that quit when the sh*t gas ate away the needle/seat- great carb.
-When it died I panicked and let somebody talk me into an edlebrock 1406 - Worst carb I've ever had. Bog, erratic fast idle..just don't get an edlebrock.
-I'm still in the process of tuning my quick fuel but it's a real dream to work with- float adjustments, air bleed access/ single screw secondary adjustments- readily available parts...find me a 750 cfm carb with an electric choke near $300.00 that can match it.
-I had a quadrajet on my 307 for 10 years that quit when the sh*t gas ate away the needle/seat- great carb.
-When it died I panicked and let somebody talk me into an edlebrock 1406 - Worst carb I've ever had. Bog, erratic fast idle..just don't get an edlebrock.
-I'm still in the process of tuning my quick fuel but it's a real dream to work with- float adjustments, air bleed access/ single screw secondary adjustments- readily available parts...find me a 750 cfm carb with an electric choke near $300.00 that can match it.
September 1st, 2015, 12:22 PM
#15
Registered User
Thread Starter
Join Date: May 2013
Location: Richardson, Texas
Posts: 223
it is a rough idle, thready - the 350 has a 262 cam in it and while I don't have the numbers, my olds buddy in Plano TX has torn this down and replaced parts, made sure all was working properly and the vacuum was fine - he's a long time q-jet expert who is a member here. my el camino, with a cam, also did the same thing with 2 different e-brock carbs and a q-jet..... switched to Holley and all issues went away 2 years ago and not adjusted since
September 2nd, 2015, 06:42 AM
#17
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
The idle circuits will need enlarged and probably also needs more bypass air. Unless the internal circuits are modified, new parts won't do squat. What is the duration on that cam?
September 2nd, 2015, 07:07 AM
#18
Registered User
Join Date: Sep 2013
Posts: 3,612
The confusion comes because Demon makes mostly Holley style carbs, but the Street Demon is totally different. It is basically a Thermoquad with a bunch of improvements and new 3 barrel castings. I was very close to buying the 750 but figured after buying the carb and geometry corrector for my 2004R, a custom tuned Qjet was actually cheaper since I had a good 78 800 cfm core.
September 2nd, 2015, 09:24 PM
#19
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
Why not? The reviews for the new Street Demon have been great. They fixed a lot of the Thermoquads short comings, mickey mouse choke, leaking O rings that caused flooding were eliminated, Aerospace grade polymer vs Bakelite, optional aluminum body and spread or square bore 3 barrel configuration. The Thermoquad and Qjet both got a bad rap running ultra lean calibrations on terribly anemic engines. Holley's just couldn't pass emissions and were only aftermarket in the ugly 70's. They were also tempermental junk for street use. It sounds like refined carbs like Quickfuel's version are very daily driveable.
September 3rd, 2015, 06:19 AM
#20
Registered User
Join Date: Sep 2013
Posts: 3,612
Why not? The reviews for the new Street Demon have been great. They fixed a lot of the Thermoquads short comings, mickey mouse choke, leaking O rings that caused flooding were eliminated, Aerospace grade polymer vs Bakelite, optional aluminum body and spread or square bore 3 barrel configuration. The Thermoquad and Qjet both got a bad rap running ultra lean calibrations on terribly anemic engines. Holley's just couldn't pass emissions and were only aftermarket in the ugly 70's. They were also tempermental junk for street use. It sounds like refined carbs like Quickfuel's version are very daily driveable.
Last edited by wr1970; September 3rd, 2015 at 06:21 AM.
September 5th, 2015, 06:22 AM
#22
Registered User
Join Date: Dec 2012
Posts: 162
UMM i will tell you why not.Because it is fugly looking.The street demon i have that is now called a mighty demon is much better looking in style and never had a problem i use mine on the street and at the track.You should be a salesman for Holly.In my case knowing the difference in street demons it would be a no sale.
Here's a street demon, you can get the basic 625 on sale at advance auto web site for $270 shipped.
September 5th, 2015, 06:45 AM
#23
Registered User
Join Date: Sep 2013
Posts: 3,612
Better yet go and type in mighty demon 750 and you will see what my carb looks like.It looks similar like my other demon carb and it is a 850 mighty demon.A few years ago before holly bought out Barry Grant there was no street demon that looked like a thermoquad.
September 5th, 2015, 07:41 AM
#25
Registered User
Join Date: Sep 2013
Posts: 3,612
I know what you talking about.Google 750 might demon then 750 street demon.The new street demon is plain ugly compared to what i have which is what holly now call a 750 mighty demon. When i bought mine new a few years back the 750 street demon looks just like the new 750 mighty demon. Neither carb looks like that hunk of junk that Holly is saying is a street demon 750. Just bear this in mind i bought my carb when Barry Grant owned his business.Now Holly owns the brand a put their spin on things.
Last edited by wr1970; September 5th, 2015 at 07:44 AM.
September 5th, 2015, 09:03 AM
#27
Registered User
Join Date: Sep 2013
Posts: 3,612
September 5th, 2015, 07:42 PM
#29
Registered User
Join Date: Sep 2013
Posts: 3,612
September 5th, 2015, 07:53 PM
#30
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
Problem is Barry Grant was big time hit and miss, one would work great, the next was full of filings. The Demon line has great features and maybe now has the consistency it needs. Most go to Quickfuel for Holley style carbs, tough to beat them dollar for dollar. The Qjet is great, IF you get an properly built one. The Edelbrock line of AFB and AVS have given people a lot of issues. The Street Demon, I have seen one, yes one, negative review.
September 5th, 2015, 08:08 PM
#31
Registered User
Join Date: Sep 2013
Posts: 3,612
Problem is Barry Grant was big time hit and miss, one would work great, the next was full of filings. The Demon line has great features and maybe now has the consistency it needs. Most go to Quickfuel for Holley style carbs, tough to beat them dollar for dollar. The Qjet is great, IF you get an properly built one. The Edelbrock line of AFB and AVS have given people a lot of issues. The Street Demon, I have seen one, yes one, negative review.
September 6th, 2015, 04:47 AM
#32
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 9,145
Whatever, I have drove many Qjet cars and my family owned them too, much better carbs for the street than Ford or Dodge ever had. Th Street Demon fixes many of the Thermoquad's issues. Have you ever used a Thermoquad? I have. Many, many problems with Demons on quality control, gee why did Barry go bankrupt? Done here, you are a strange guy.
September 6th, 2015, 05:35 AM
#33
Registered User
Join Date: Sep 2013
Posts: 3,612
Whatever, I have drove many Qjet cars and my family owned them too, much better carbs for the street than Ford or Dodge ever had. Th Street Demon fixes many of the Thermoquad's issues. Have you ever used a Thermoquad? I have. Many, many problems with Demons on quality control, gee why did Barry go bankrupt? Done here, you are a strange guy.
September 8th, 2015, 07:10 AM
#34
Registered User
Join Date: Sep 2011
Location: Plano, TX
Posts: 1,900
I'm the lucky guy that worked on the carb. John, sorry it didn't settle down nicely for you. In my experience idle is hit or miss - some carbs it'll work out great, others just seem to be cursed.
For the group, this is a shop bought reman, I forget the number offhand but it's a 7042XXX for big block manual transmission (7042953???). It was actually in really good shape without the normal rebuilder shortcuts (hot idle air was there, piston stem wasn't cut, etc). The idle bypass air was blocked off - I opened to 0.070" and there are no holes in the primary blades. Opened idle tubes to 0.037".
Ignition is an HEI with base at 15 degrees. I switched vacuum to manifold instead of ported which seemed to help quite a bit.
With all that I was able to get the blades nearly fully closed. IIRC, vacuum was low - 12" or so - with a rough idle at 700 in gear. I didn't replace the power piston spring and didn't check to make sure the piston was seated. It wasn't leaking fuel out the venturis. It responded well to being slightly choked, which tells me it wants more fuel. Idle screw holes were enlarged a bit, screws were out 4 turns or so.
The idle tubes that were in there were 0.042"!
I'm no expert, but I try to figure these things out. John, just let me know when you want to swing around again.
For the group, this is a shop bought reman, I forget the number offhand but it's a 7042XXX for big block manual transmission (7042953???). It was actually in really good shape without the normal rebuilder shortcuts (hot idle air was there, piston stem wasn't cut, etc). The idle bypass air was blocked off - I opened to 0.070" and there are no holes in the primary blades. Opened idle tubes to 0.037".
Ignition is an HEI with base at 15 degrees. I switched vacuum to manifold instead of ported which seemed to help quite a bit.
With all that I was able to get the blades nearly fully closed. IIRC, vacuum was low - 12" or so - with a rough idle at 700 in gear. I didn't replace the power piston spring and didn't check to make sure the piston was seated. It wasn't leaking fuel out the venturis. It responded well to being slightly choked, which tells me it wants more fuel. Idle screw holes were enlarged a bit, screws were out 4 turns or so.
The idle tubes that were in there were 0.042"!
I'm no expert, but I try to figure these things out. John, just let me know when you want to swing around again.
September 9th, 2015, 03:51 PM
#38
Registered User
Thread Starter
Join Date: May 2013
Location: Richardson, Texas
Posts: 223
hi Jason, yes it is better but only when warmed up now... it stalls when cold and now stumbles a little more off the line. I thought about maybe trying the other q-jet that I have - who knows? Maybe it's just cursed
September 10th, 2015, 06:07 AM
#40
Registered User
Join Date: Sep 2013
Posts: 3,612
