Replaced my quadrajet with a Holley 7150 spreadbore w/mechanical secondarys. It made a world of difference on bottom end. Not many miles on it yet but so far I really like it. I didn't have to change a thing as far as fuel line, linkage, nothing.
How about the air filter? Same size? Sounds like initial response off idle is good. How about WOT with the mechanical secondaries? Any lag time or bog? Seems your saying this is a easy "bolt on" improvement. Yes?? By the way, where did you get the carb? I looked at Summit's site and couldn't find it...............Don B
I rode Wags bike last Saturday.....what an improvement over his 750 8)
His 750 always had a "lag" in the response.....Wags damned good at tuning, but never could get that carb to work right.....this Holley is really great. Marv had told me last year that they run a lot of 650cfm carbs on small blocks, gives them a lot better bottom end performance....I gotta tell ya, if I wasn't running NOS I'd make the same change......his bike goes into smoke when you think about twisting the throttle......I lit it up at about 50mph just by getting into the secondaries easy, not wrenching on the throttle 8)
Don...I guess we've got more to talk about than tires. My mecahanic, whom I trust implicitly also recommended the Holley but I do love the kick of the secondaries on the Q-Jet which, I understand is not the same as the Holley. The Holley also sits lower and so air cleaner size is less of an issue. Will it ever end? ...I hope not!...Joe
PS. Which specific PN carb are you speaking about...Joe
According to Wag, it's a Holley 7150 spreadbore with mechanical secondaries. I searched and searched and couldn't find that carb. I'm waiting for Wag to post again.
As for the secondary "kick" on the Q-jet, I don't have the big kick, because I drilled the passage of the vacuum diaphram that opens the air valve on the secondaries. So my air valve opens a bit quicker, lessening the kick of the secondaries opening. Don't get me wrong.....I srtill feel them when they open. It's just a bit more linear. I'm hopiing to hear back from Wag soon, cause I need to spend some more money!! Ha Ha! .......Don
The height from the baseplate to the air cleaner base ring on both the Q-Jet , Hollies, and Demon carbs is 5.25 inches.
The reason the Holly or Demon type carbs give you more bottom end,
lies in the fact of the mechanical linkage controlling the secondaries, vs
the air flap on the Q-Jet. But then again, this depends on how you have the tension adjusted on the secondary air flap spring.
The Holly or Demon type carb will not give you the hit when the secondaries kick in like the Q-Jet, but will provide a more smooth constant
Generally speaking, the Q-Jet will give you better mileage than the Holly
type carb due to the fact the metering system is very percision for a
carb. We have to remember, GM spend a ton of money developing this
carb just prior to going all fuel injection for the EPA.
At the stock ZZ4 and 502 level of performance, both types are great carbs. On a race type engine, the Holly or Demon will usually provide
This Holley is a spreadbore small primaries, large secondarys.
The only thing I really had to change was the accelerator pump cam and discharge nozzle. Got rid of a slight, very slight hesitation when cracking the throttle from idle.
Wag...thanks for the input about the Holley carb. I just love to change **** and see how it works out but I have absolutely NO hesitation anywhere in the acceleration spectrum with the Q-Jet and love the "kick in the ass" feel of WOT as well.
As far as this street rider is concerned...I'm gonna stick with "good" instead of "better" this time. The Q-Jet has performed flawlessly for me and the way I ride. The three things that are essential are the correct idle mixture and speed, the accelerator pump and the spring tension on the secondary opening. Carb Mike could say much more but with these essentials lined up you are going to get good performance...Joe
Quadrajets just have to many little measured adjustments, to many variables but to each his own I procrastinated all winter about working on my quadrajet, sun came out and I slaped on a Holley. With quadrajets, it seems they work or they don't, if they don't you might as well get a different one or get a Holley. Just my 2 cents.
Funny thing about carbs, everyone has a strong opinion about the carb they run. I know of one BIG Boss Hoss dealer and a few owners that say that Holley carbs are the best carb when they run right but they don't run right very long. :roll: These guys say you are always having to mess with them because any little grain of anything will clog them up. The one dealer said you could fill you tank with straw and the quad would still run great.
I'm afraid to mess with my carb for a couple of reasons. First, my bike gets great gas mileage. I have been on rides with other BH guys and if we fill up at a 100 miles they will put in 1 gal. more than me and we all ran the same roads and played the same. For whatever reason my bike gets great gas mileage. I average about 21 mpg and I have never got less than 17 mpg and that was when I had a single speed tranny running 90 to 115 all the way from Atlanta to Daytona. I was over 4000 rpm most of the time. I did a slow run with a group one time with the two speed and got 26 mpg but we never went over 50 mph on that run.
RayO and I just added a choke to my bike and while we were there we did a little work on the secondary flap. It was hanging up just a bit and that is why sometimes I couldn't get the secondaries to kick in and other times it would hit real hard when they cut loose. :shock: Now the bike pulls hard all the way and I don't feel the same kick as I use too but it is kicking in. At first I thought maybe they weren't kicking in but I got to play with it a little yesterday and she's working just fine.
So for me I think I'll just stick with what works for now. 8)
Guess I was just bored and looking for something else to tinker with before the riding season actually started around here in the Northeast. But as of yesterday, 70 degrees, the season has started!!
I will put the Holley info in my "book of knowledge" and leave the Quadrajet on for now, as yesterday the bike was running great. Triple digits in no time :cop2: , smoking the tire at will :twisted:
Life is good!! :capwin: ..........Don B