Best Carb suggestions?
Pro
Joined: May 2003
Posts: 593
Likes: 0
From: London England
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
The good gas mileage was on a trip from San Diego to Dallas in 1975 using the 6210. One thing about my 1970 Corvette, you know how many gallons of gas was used because you can visually see when the gas at the top of the tank. 70 Corvettes have sealed gas caps, so no worry about getting it to full. My turbo 400 and 3:08 geared 1970 Corvette has always had pretty good mileage on trips.
The mileage with the current ZZ crate engine using a Holley 4777 650CFM square bore type double pumper is about 17 MPG using the air conditioner on the last long interstate/highway trip I took driving it. Don't put a lot of intersate miles on the 70 anymore since I perfer the 96 LT4 for interstate/highway trips.
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
I got it in, and it really does run well. It cruises along nicely and the idle quality is about the same as the qjet. I did notice that the Holley seems to start faster, since I think the gas was syphoning back out of the qjet. So a nice side benefit.
What I really like is the mechanical secondaries. Much better response, and a whole lot easier to chirp the tires. It feels like it runs out of breath earlier, say around 4500rpm, but the response is worth it. Much quicker.
The only other downside is missing the qjet secondaries sound. I do like the sound when those kick in, and the Holley sounds different, though not bad.
The generic bracket from O'Reilly's worked fine. I had to bend up the tang on the front (see in front of the bolt) and the designed location for the cable was too close, so I flipped over one of the kick-down cable brackets. Works great and I now have an adjustable throttle cable (not that I need it).
Bottom line is I would recommend doing the swap for the mechanical secondaries.
What I really like is the mechanical secondaries. Much better response, and a whole lot easier to chirp the tires. It feels like it runs out of breath earlier, say around 4500rpm, but the response is worth it. Much quicker.
The only other downside is missing the qjet secondaries sound. I do like the sound when those kick in, and the Holley sounds different, though not bad.
The generic bracket from O'Reilly's worked fine. I had to bend up the tang on the front (see in front of the bolt) and the designed location for the cable was too close, so I flipped over one of the kick-down cable brackets. Works great and I now have an adjustable throttle cable (not that I need it).
Bottom line is I would recommend doing the swap for the mechanical secondaries.
shouldn't flatten out at 4500. U R positive it fully opens?
if u can tape a vacuum gauge to the windshield, read vacuum at 4500-5000 WOT in 2nd. If it is over 2-3", keep your eyes out for a 4165-6211 used. the 6211 is 800 cfm. not available new. I just found it in the old catalog, or i would of mentioned it before.
.
I agree w/golden's EFI pick. 8 throttles is an awesome system.
.
70ZZ1
thanks for clearing that up! the 4165 is still on top. 22 mpg is about the best i've read about w/th400. That is a strong, but gas sucking trans.
.
my 1st 4165 did NOT bolt on. i had to buy a qjet manifold and change the manifold. What u guys would like is an "installation kit"
so i think u r real lucky that it bolts right on. There are scores of square bore manifolds that can't use this great carb. An adapter is a bad idea, no room, and can reduce torque & mpg.
Last edited by Matt Gruber; Dec 18, 2009 at 09:53 AM.
Racer
Joined: Jan 2006
Posts: 323
Likes: 4
From: McKinney Texas
[QUOTE=Matt Gruber;1572464416]
shouldn't flatten out at 4500. U R positive it fully opens?
if u can tape a vacuum gauge to the windshield, read vacuum at 4500-5000 WOT in 2nd. If it is over 2-3", keep your eyes out for a 4165-6211 used. the 6211 is 800 cfm. not available new. I just found it in the old catalog, or i would of mentioned it before.
QUOTE]
It fully opens, no question. And it gets up to 4500rpm in a hurry. Had a blast driving it around today. It will chirp the tires in 1st and 2nd, even with the tall M21 and 3.36 rear.
I will check the vacuum as I have a hose long enough for a passenger to watch the gauge. The reality is I spend almost no time over 4500rpm, so it is not much of an issue with me.
However, I will keep an eye out for a reasonably priced 6211 if my vacuum shows high at WOT. I assume it has mechanical secondaries as well? I do not see ever going back to vacuum secondaries.
shouldn't flatten out at 4500. U R positive it fully opens?
if u can tape a vacuum gauge to the windshield, read vacuum at 4500-5000 WOT in 2nd. If it is over 2-3", keep your eyes out for a 4165-6211 used. the 6211 is 800 cfm. not available new. I just found it in the old catalog, or i would of mentioned it before.
QUOTE]
It fully opens, no question. And it gets up to 4500rpm in a hurry. Had a blast driving it around today. It will chirp the tires in 1st and 2nd, even with the tall M21 and 3.36 rear.
I will check the vacuum as I have a hose long enough for a passenger to watch the gauge. The reality is I spend almost no time over 4500rpm, so it is not much of an issue with me.
However, I will keep an eye out for a reasonably priced 6211 if my vacuum shows high at WOT. I assume it has mechanical secondaries as well? I do not see ever going back to vacuum secondaries.
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
the 6210-1 uses 2 power valves
6210-2, 6210-3 use 1 PV
if yours has 2, the rear pv will close at high rpm and lean it out for max mpg. this is because it was designed for 327 350 402.
The 454 size makes it think u have let up on the gas
and it goes into economy mode
the solution is to install a plug in just the rear PV, and use .089 max jets.
.
solution #2
the rear venturi is 1 23/32 on the 6211
but only 1 3/8 on the 6210
if u have a dremel grinder i'd go halfway between the 2, enlarge the rear venturi by 0.170" this would give u 725 cfm and should cure it. Larger may cause problems unless a carb porter does it and may hurt throttle response. I'd pick up a spare carb to experiment as there is some risk, but the cores are cheap.
6210-2, 6210-3 use 1 PV
if yours has 2, the rear pv will close at high rpm and lean it out for max mpg. this is because it was designed for 327 350 402.
The 454 size makes it think u have let up on the gas
and it goes into economy mode
the solution is to install a plug in just the rear PV, and use .089 max jets.
.
solution #2
the rear venturi is 1 23/32 on the 6211
but only 1 3/8 on the 6210
if u have a dremel grinder i'd go halfway between the 2, enlarge the rear venturi by 0.170" this would give u 725 cfm and should cure it. Larger may cause problems unless a carb porter does it and may hurt throttle response. I'd pick up a spare carb to experiment as there is some risk, but the cores are cheap.
Racer
Joined: Jan 2006
Posts: 323
Likes: 4
From: McKinney Texas
Thanks Matt.
I have the 6210-3. I went with the -3 because the different pictures on ebay showed the -3 with the shorter linkage to the secondaries. Not sure it is any better, I just figured shorter would have less play.
So one power valve.
Solution #2 is beyond my comfort level. I like to bolt parts on, and if it is not an improvement I can usually recoup my spend by reselling on ebay.
I am going to start another thread to see how other '74 454 rev. Is it really that free of a reving engine? I think my experience is more of a function of the 6210 already having the secondaries wide open by 4500rpm where the qjet top plates are just starting to open the rest of the way up.
I have the 6210-3. I went with the -3 because the different pictures on ebay showed the -3 with the shorter linkage to the secondaries. Not sure it is any better, I just figured shorter would have less play.
So one power valve.
Solution #2 is beyond my comfort level. I like to bolt parts on, and if it is not an improvement I can usually recoup my spend by reselling on ebay.
I am going to start another thread to see how other '74 454 rev. Is it really that free of a reving engine? I think my experience is more of a function of the 6210 already having the secondaries wide open by 4500rpm where the qjet top plates are just starting to open the rest of the way up.
Racer
Joined: Jan 2006
Posts: 323
Likes: 4
From: McKinney Texas
Matt, thanks for all your help on this. I know you are following in the other post, but wanted to add the test results to this thread as well.
I ran the vacuum test today. The results were:
Gear RPM Vacuum Speed RPM/MPH
N 800 18 0 0
1 2000 19 20 100
2 2500 19 40 63
2 3000 20 50 60
2 5000 1 80 63
4 1800 16 45 40
4 2700 19 70 39
4 4000 23 100 40
There were several other WOT runs, and the vacuum always went to 0-1 or close. So I am thinking the 6210 is good for the car. Sure gives it a lot of snap.
The car gets to 70 (about 4500rpm in 2nd) in a hurry but I had to be pretty deliverate to run it to 5600rpm. What roscobbc wrote regarding his experience with his L36 seems to be on the money with what I am experiencing.
Bottom line is I am happy with my combination, and I would recommend the 6210.
Thanks for everyones input.
I ran the vacuum test today. The results were:
Gear RPM Vacuum Speed RPM/MPH
N 800 18 0 0
1 2000 19 20 100
2 2500 19 40 63
2 3000 20 50 60
2 5000 1 80 63
4 1800 16 45 40
4 2700 19 70 39
4 4000 23 100 40
There were several other WOT runs, and the vacuum always went to 0-1 or close. So I am thinking the 6210 is good for the car. Sure gives it a lot of snap.
The car gets to 70 (about 4500rpm in 2nd) in a hurry but I had to be pretty deliverate to run it to 5600rpm. What roscobbc wrote regarding his experience with his L36 seems to be on the money with what I am experiencing.
Bottom line is I am happy with my combination, and I would recommend the 6210.
Thanks for everyones input.
Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
Paul,
If you are still having "My Q-Jet has an off-idle stumble that all the Lars papers in the world (and I) cannot seem to resolve.", check that the centrifugal weights in the dist. are moving freely.
If you are still having "My Q-Jet has an off-idle stumble that all the Lars papers in the world (and I) cannot seem to resolve.", check that the centrifugal weights in the dist. are moving freely.
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Race Director
Joined: Jun 2000
Posts: 10,046
Likes: 675
From: FL
90% of "carb" problems are actually ignition issues.
Race Director
Joined: Jun 2000
Posts: 10,046
Likes: 675
From: FL
Still amazes me that people forget that there is a perfectly good 750 cfm mechnical secondary carb out there that is known to deliver 20 mpg. It is called a Quadrajet. Q-Jets are not vacuum secondary, they have mechanical secondaries with a demand actuated air valve.
Advanced
Joined: Dec 2009
Posts: 90
Likes: 0
From: sebastian florida
carb
Hi Matt....I need a carb for my 69 350/350 ...spread bore...do you have a spare you could sell me...?? Rick in sebastian 772 643 5283 are you going to old town for the ncrs meet ? thanks
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
yes but the number of people out there that can fix, service, repair, or rebuild these things are going down so fast that if yours is broke then its not going to get fixed easily.
Thread Starter
Burning Brakes
Joined: Jan 2009
Posts: 1,224
Likes: 1
From: Clarksville Indiana
Thread Starter
Burning Brakes
Joined: Jan 2009
Posts: 1,224
Likes: 1
From: Clarksville Indiana
Le Mans Master
Joined: Dec 2006
Posts: 5,557
Likes: 9
From: Oquirrh Mountains
St. Jude Donor '09
http://store.edelbrock.com/1901edelb...1966-73-1.aspx
