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Engine bogs when floored

Rochester uses a plunger type pump with two or three holes to place the linkage on the lever. The lever placement is the only external adjustment. The accelerator pumps are prone to failure if they dry out or deteriorate. Ethanol is not friendly to them. There is a check valve, ball with a spring under the squirters and they are prone to damage, corrosion, especially when ethanol is involved. The ethanol is also detrimental to the foam floats. I would disassemble and check the primary carb, replace all floats in all carbs with brass if they are foam. Mikes carbs is a good source for parts. Also, make sure the float level is correct. I had issues on my boat recently related to float, accelerator pump, and check valve stuck due to corrosion from ethanol and it was a fresh carb that sat over the winter. Don't feel stupid for asking questions, we who have answers have had question also. Some of us have had experience with different things, that's what makes a site like this valuable, imho. One observation I have related to the hi rise manifold, that's a high rpm setup. It will not likely perform well at low rpm or off idle situations. You will have to make concessions. Look up the power range for the manifold as well as the other components. That is your target performance area. You should match the components used in a build to perform in the range that you intend the vehicle to be used in. Just my .02. Tune it to where it is designed to run, if that's not where you want it to make power, you may need to make some changes to get the rpm up, or the power band down. From your description, it sounds like you have a fuel level, accelerator pump issue as well as some tuning issues. Fix the carb first, or eliminate that question. Silly question, what type choke setup are you running? I presume none on the secondaries, but is it electric on the primary? If so, a quick test would be to enrich it and un plug it, do a test run. If there is a significant improvement, you have a lean fuel issue, i.e., a low fuel level, etc...
 
Any chance the air filters are causing a rich condition at speed ? maybe they seem fine just in the shop working the throttle but maybe at speed they might have some sort of turbulence or air flow problem.
Just shooting out possibilities.
 
fletcherson said:
One observation I have related to the hi rise manifold, that's a high rpm setup. It will not likely perform well at low rpm or off idle situations. You will have to make concessions. Look up the power range for the manifold as well as the other components. That is your target performance area. You should match the components used in a build to perform in the range that you intend the vehicle to be used in. Just my .02. Tune it to where it is designed to run, if that's not where you want it to make power, you may need to make some changes to get the rpm up, or the power band down.
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Just an observation about tunnel rams: several street-driven buckets in the St Louis Chapter of NTBA use tunnel rams, and the owners say that as long as you use small enough carbs and set them up properly, they will run like gang busters on the street!
 
Who told you that :rolleyes: ??? Please check out coloradohotrods.com for their take on tunnel rams. Also a Edelbrock Street Tunnel Ram with smallish Hollys (600 cfm w/vac secondarys) or 600 or 500 Edelbrock carbs, Weiands set up like Edelbrocks, same carbs, wonder how 500 cfm Holly two barrels (a pair) would work on a Street T.R. ?

John
 
Spanky said:
Just an observation about tunnel rams: several street-driven buckets in the St Louis Chapter of NTBA use tunnel rams, and the owners say that as long as you use small enough carbs and set them up properly, they will run like gang busters on the street!
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I'm just speaking in generalities based on my experience. I don't even know for sure what exact intake, etc, we are dealing with in this situation. I'm sure there are ways to make them work, the new engines are basically hi rise, but they are injected at the port, so the atomization issue is no longer an issue. I, too, am running a tunnel, or will be once it's back on the road. I am gearing the car to get the rpms up into the power band of the cam and intake. I like the look and the nostalgic era parts or I would not choose it for street application based on what I know about them. It's a toy, not transportation, so enjoy! I would choose a dual plane whatever, multicarbs are fine if sized and syncrhonized correctly, but it's hard to negate the difference between a single or dual plane manifold. They are designed for different rpm ranges and that is what creates the velocity needed to atomize the fuel. I am by no means trying to be negative of anyone's machine or understanding, nor do I profess to be a wizard or the like. Just offering my experience. I've been through this with tri power setups and tunnel rams, just not at the same time. I've also played with and built cars since the late '70's, if any of my experience helps, that's my only intent.
As for running a small carb with a tunnel, I guess if that's what it took to make it driveable and still retain the look, but I would think that overall performance at top end would be off. It may not be an issue in a light street car, idk. Interesting idea though. I would be interested to see actual numbers or feel how it works, not to be argumentive, just to know. In this case, he is running a small carb on a tunnel with two dump carbs. I would think that if the center carb was right, and the overall tune was right, it should work well and run great. The wild card is getting the secondaries to open when the engine can use them either by staging them via the linkage or the right foot, and jetting them correctly.
 
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Spanky said:
Just an observation about tunnel rams: several street-driven buckets in the St Louis Chapter of NTBA use tunnel rams, and the owners say that as long as you use small enough carbs and set them up properly, they will run like gang busters on the street!
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Spanky, after thinking about the small carb, big intake idea, do you know what they are doing with jetting? I know that a smaller than needed carb can actually create a rich condition, or so I've been told, because there is not enough air flow, and the added velocity creates a rich mixture. I wonder if this is an advantage in this situation. Perhaps the low rpm velocity is increased by basically choking the carb via small cfm. I can see how this would help with low end power, sort of like closing the choke, but I still think that high rpm, top end performance would suffer due to the cfm. Interesting thought, either way! Sorry if we derailed the post. Maybe this should be a separate topic. There are many guys who are or would like to run tunnels.
Let's get this hi rise tri power running right, then we can examine the theory behind the science...
 
Yes, I messed up on the name but I'm glad that you say thru it. Interesting way to cut down on the plenum area. For a long time they wouldn't show the plenums and I kept saying to myself "Self, they are not showing everything!". My only question is how many cubic inches and how big a cam can you run? They really emphasize street and more street for usage. And how many pounds do each of the separate plenums weigh? Even though they are aluminum (I think) they must be pretty heavy.
If you would, share your opinions about installation, carbs, etc. Might get a conversion from Rubicon.
I believe $1500.00 for the whole set up seems to be a deal, especially compared to that other deal at $2500.00.

John
 
From what I've read these colorado systems work fine....they're a kind of hybrid between a TR & an IR [indidual runner] & that's where my problem w/them arises , we all know that no 2 cylinders pull the same , w/o the balance of a full plenum , I would think exact tunig would be difficult ,.....or maybe just run rich ???
 
The separate plenums weigh between one and two pounds each if I remember correctly. My only complaint was the casting (aluminum) is too rough for easy polishing. I gave mine a skim coat of body filler and painted them with the same paint that I used on the body and engine. As far as installation, it is just bolt and go. I was having problems with off idle stumble using two 500 cfm Edelbrock AVS carbs on an Edelbrock tunnel ram, but this system with two QuickFuel carbs fixed all of that and more. I am very pleased. As to 2o2f's comment, I'm sure he is correct about exact tuning, but my question would be how "exact" do you want (or need) to be? The answer is probably different for each of us. If "get in and hang on" performance is good enough, then again I am pleased.
 
First off, I want to thank everyone for their input. Its nice to have all this knowledge at my finger tips. When I started ordering parts for the car I did so by what I liked. I love this triple deuce set-up, so I had the engine builder discuss it with the carb guy to build me an engine that would work with this set up. That's how I ended up with what I have. Cost was not an issue, I've been saving for this a long time. So far, the build has been great fun. Even more so with you guys giving me help when needed. The opinions expressed here are done so to help me out. Thank you. Sometimes the thread gets headed in a different direction but, I don't believe it was deliberate, it just happens. When it does, a lot of the time I learn something new, we hit a bump and it goes back on track. Right now I took the air horn off the center carb and pulled the accelerator pump. The cup on the pump was not round and the cup spring was missing. I do not know if the cup spring is an up grade to an old design or they always had one. Ordered new pumps and gaskets. Getting the old gaskets off is not easy. Any suggestions? I will check the carbs over 100% after I clean off the gaskets. I only have one month before I go up hunting, so my time to work on this is running out. Still working on new baffle to cut down on the loud exhaust. Hope to be able to test it before I leave. The last two I build did not work. Maybe three will be a charm. Thanks again for all the input.
 
I replaced the accelerator pump and that seemed to solve the issue I had. Pump on left is the old one. The new pump on right has a spring in the boot to keep outward pressure on the boot. I was able to get my tires to break loose for the first time. I will replace the pumps in the outer two carbs this winter. Thanks to everyone who gave me advice to help solve my problem.
 

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Man..... I am soooo glad you figured it out. Nothing sucks more, than not having a set up at it's true and full potential.
 
Don't leave any ethanol in it this winter. Run it out... just my advice. I've had many issues with fuel recently. It's frustrating and exhausting to keep having to deal with. Glad you figured it out!
 
fletcherson said:
Don't leave any ethanol in it this winter. Run it out... just my advice. I've had many issues with fuel recently. It's frustrating and exhausting to keep having to deal with. Glad you figured it out!
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I'm doing the body work this winter so the last fill up will be Ethanol free gas. Then I will run the tank down to almost nothing and drain the rest so I can lift the tank out. If this is a bad idea please let me know and why. Thanks
 
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