stacey honn
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Posts:28
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| 03/08/2008 7:28 AM |
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I'm on a role with ?'s this morning. 2nd cup of coffee ya know.
My engine is new, been bored and stroked to 492, merlin heads, hooker headers, roller rockers, edelbrock intake and I just put a 800 edebrock carb on it. Aso have the gear vender OD. Runs unbelievable and I'm now pulling 13 at highway speed on vacuum instead of 10 with the old quad jet. I tried rebuilding the quad but just couldn't get the take off stumble out or the fall on it's face four barrel from opening up. Anyhow, love the new carb but wondering if it's on the large side. Stacey |
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Balrgn
Moderator
Expert
Posts:805
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Southern NH
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| 03/08/2008 1:02 PM |
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| Sounds like alot of motor! NICE |
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1977 Argosy 20
454 V8 Gas
Southern NH
Maintenance Analyst
www.balrgn.com |
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new-to-rving
Not a Newbie
Posts:26
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| 03/09/2008 10:11 AM |
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I would say maybe on the bigg side, but not by much. adjustments can be made, with the overdrive you want low end torque,and not really top end cubic feet per min. of flow. but that thing must get up and jump when stumped on! check out summit racing or jegs and check out oxygen sensor in stall kits and thet would help with checking for performance and gas mileage, with this info. you can adjust jetting and advance if needed |
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Gon Mad
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Posts:18
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| 03/09/2008 9:39 PM |
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| If you use this formu;a You wll be switching to a 650 thunder series.
cubic inches x max RPM=total divided by 3456 (a constant) equals total CFM at whatever rpm you choose as a cutoff point.
example 454x4500=2214000 divided by 3456=640.62 CFM.
If you figure that the overdrive generally keeps the engine under 3000 & usually cruising at or close to 2600 the need for a carb that size would satisfy my 10 second street car. And if you wish to go a step further try knocking off 10 or 15 0/0 for parisitic losses the CFM drop even further.
The carb you have is a very good one & try resrtting the secondary thighter to slow down the back barrels opening too soon. |
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Jim Elliott
Camper
Posts:63
Registered Users
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| 03/10/2008 10:12 AM |
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Posted By Gon Mad on 03/09/2008 9:39 PM
If you use this formu;a You wll be switching to a 650 thunder series. cubic inches x max RPM=total divided by 3456 (a constant) equals total CFM at whatever rpm you choose as a cutoff point. example 454x4500=2214000 divided by 3456=640.62 CFM. If you figure that the overdrive generally keeps the engine under 3000 & usually cruising at or close to 2600 the need for a carb that size would satisfy my 10 second street car. And if you wish to go a step further try knocking off 10 or 15 0/0 for parisitic losses the CFM drop even further. The carb you have is a very good one & try resrtting the secondary thighter to slow down the back barrels opening too soon.
V/E on that formula is missing....Usually everyone considers their engine at 100% V/E but thats not so.....If we reach 85% that is/would be a strech.
Jim |
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Gon Mad
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Posts:18
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| 03/10/2008 6:36 PM |
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| My Bad . I meant That!? Even 85 percent relates to mostly race engines.
Thanks; Steve |
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stacey honn
Not a Newbie
Posts:28
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| 03/10/2008 7:21 PM |
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I kinda thought I was over carbed. This tranny is govned to shift really early and we all know the MH's aren't race cars, they're torch monsters. I have a friend that has a wide band o2 senser that I can barrow and use the laptop to dial in a good jetting but think a smaller carb is the best route.
Shifting gears here.... What about high altitude. Planning on a trip to the Rockies this summer. How to jet for the mile high? Stacey |
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Gon Mad
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Posts:18
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| 03/10/2008 9:42 PM |
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| Try installing a RED stripe adjustable vacuum modulator. I have mine turned to shift at a higher rpm.
Jetting for high elevation is not my forte. Try googleing for the info & dont be hesitant to refine your search a couple of ways to get what you can be happy with. Been a sea level dweller most of my life, I like an A/F ratio around 14.8. ( I like it not quite frying the valves & not killing pulling power).
I personally like lots of carbureters on my engines like TWO Predators on a tunnel ram on my street car but its for a little extra if needed. In reality only one more than adequate.
Keep up what your doing & enjoy the results C YA Strve |
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Jim Elliott
Camper
Posts:63
Registered Users
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| 03/10/2008 10:56 PM |
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Posted By stacey honn on 03/10/2008 7:21 PM
I kinda thought I was over carbed. This tranny is govned to shift really early and we all know the MH's aren't race cars, they're torch monsters. I have a friend that has a wide band o2 senser that I can barrow and use the laptop to dial in a good jetting but think a smaller carb is the best route.
Shifting gears here.... What about high altitude. Planning on a trip to the Rockies this summer. How to jet for the mile high? Stacey
Stacey, The carbs are a pita to dial in most of the time......My Quadrajet is now with 73 jets and the idle jet circuit is leaned out....
When I get back home I'll produce the "Chevy high performance" carb site that shows the idle circuit remains in play up to and around 2500 RPM then the mains really kick in, I dont mind a 15.2 lean burn but when the throttle is pushed up against the wall I want a 12.8 climbing those hills........
I started a "Ignition section" with NO follow up as of yet but IMHO that where the greatest gains are and once set and locked down then it's on to the carbs and fuel injection.......Gon Mad is correct about the V/E 85% being a dab high but my GUESS with the small heads (even the L-29 heads) the numbers are about 80% at best.
Jim
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Gon Mad
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Posts:18
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| 03/11/2008 7:17 AM |
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| Very good on the fuel ratios, I'm concidering an Edelbrock Diirect port RAIL system. I saw one closley at a car show here in Ft. Myers & the owner couldn't speak more highly about it. Kinda pricey though.
Tignition is the most misunderstood part of an engine. I was fortunate to work with & knew very well Dr. Chris Jacobs of JACOBS Electronics when it was located in LA I got firts hand Knowledge of how important & how difficult proprer timing curve & initial timing are. I use nothing but Jacobs equipment on everything I own. Also Jacobs sells the best book on ignitions I've ever read. Not only does it explain electricity, it gives a better understanding about ignitions. Chris (at the time) has 9 phds. in electronics engineerring a really super guy. Pick up a copy & be delighted with the info it provides. C YA! Steve |
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