Gasser HotRod Forums banner
1 - 20 of 27 Posts

·
Registered
Joined
·
37 Posts
Discussion Starter · #1 ·
Wondering if anybody has had any experience with a Edelbrock TR2 (3pc) tunnel ram on a big block chev??? I Originally started off with a set of Holley 660s and I couldn't get the motor to idle ... It had crappy throttle response and would die as soon as engine rpm came down... I figured there might be a problem with the carbs so I picked up a set of 750s and tried to fire it up today.... It's slightly better but will not idle, you have to hold the butterflies open about 1/4 throttle to keep it running... I've checked for vacuum leaks, I've ran the air/fuel screws out from 1 1/2 turns to 3 turns.. I'm wondering if the large plenum is affecting the signal for the idle circuits ???? Any help would be appreciated, I'm pulling my hair out :boy::gun:
 

·
Registered
Joined
·
157 Posts
What are the specs on the cam? What is the timing set at on the motor? Have you put a vacuum gauge on a manifold port? What is it reading? Was the reading steady? Of course these last items are dependent on the engine running, but the specs on the cam and timing are a good place to start.
 

·
Registered
Joined
·
3,593 Posts
check to see if the cam is timed right, more than once I have seen a motor put together with the chain or gears being off 1 or 2 teeth, did you use a degree wheel to make sure it was set to specs, usually on a large cam
with lots of duration.... also have you adjusted the float levels yet, also you need to check the jet sizes and power valves just cause there new and you specified what they where going on doesnt mean there jetted right or have the correct metering blocks, and last make sure you have a fuel pump and lines that can keep up, what brand and model # are the carbs, hate to say it but a dyno with oxygen senors and correct exhaust sensing gauges will solve most problems and get the max power out of your engine
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #5 ·
Thanks guys.. I installed the cam using a degree wheel and double checked my numbers so I feel this is correct.. When the engine rpms are up it runs clean and responds good.. Engine timing is at 34 deg and I'm using a Hunt magneto... Fuel supply is a Holley 110 pump with a -8 supply from the pump to the fuel log and -6's to the carbs. Fuel psi is 6lbs and I set the floats like normal and even tried setting them on the high side to see if it would help.. I'm thinking since the carbs aren't 4corner idle circuits it's just starving it for fuel ..
 

Attachments

·
Registered
Joined
·
157 Posts
I don't think it has anything to do with your problem, but why are the primary squirters routed all the way over to the secondaries? And why no squirters on the secondaries at all?

You can try and adjust the secondary throttle blades to be more open at idle without needing a four corner idle system. Is it leaking fuel into the plenum? Almost sounds like it is getting too much fuel and not enough air. Is the fuel pressure gauge prior to the carb, or after along a return line? Does it have a power valve in it, what opening point? Do you know what the duration and lift are on the cam? What is the lowest rpm you can get on it? Where are the throttle plates in relation to the idle transfer slots?

I know it seems like we have more questions than answers right now, but hopefully we can get to the root cause here.
 

·
Registered
Joined
·
3,593 Posts
Its hard to tell from the pic, can you post a pic of the bottom of the carb, these kind of look like a spread bore type carb, witch would KIND of explain the secondary squitter, and no primary, Also what are you expecting to get for an Idle speed..... some cams will not get down below 1200 rpms at idle, one thing you can do is try choking one of the carbs...NOT with your hand as you try and idle it down, if it gets better it is to lean if it gets worse its to rich, and last where are the rear throttle plate stop screws set at, and as Timberline says you really need to put a vacuum gauge to the manifold
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #8 ·
Thanks for the input guys... The fuel psi gauge is mounted on the outlet side of the regulators going to the carbs.. 1 gauge per regulator... I did try til hold my hand over the choke towers and it did make it better which led me to believe it was lean.. I can't get any kind of idle speed because the motor just flat out dies once the butterflies are closed, you have to hold it at least 1/4 throttle just to keep it running and it acts like a lean flutter/ poor throttle response until you really hit the throttle and get a shot of fuel from all 4 corners..... The carbs are old 780cfm that had a conversion kit to make them double pumpers, the kit came with the long squirter nozzles to go from the primary side to secondary side and gears to connect the 2 throttle shafts together.... The price was right and I thought they were kinda cool and nostalgic so I figured I'd try them, turns out the belong in the garbage... I'm gonna barrow a set of good carbs off a friends motor and give them a shot and re evaluate from there.. thanks
 

·
Registered
Joined
·
3,593 Posts
Ok the conversion explains alot, so it is putting fuel in all four corners, if it is getting better choking it you just have a lean condition, in the idle and low speed circuits, I think you would be better off doing the research on redoing the 660 hollys, correct metering blocks, jets and power valves 1320 cfm is enough for that motor, do you have the holly numbers for the 660's and can you post them I may be able to help as far as what works for your displacement, what is your displacment
 

·
Administrator
Joined
·
13,427 Posts
I think your problem is the carbs. I'm running twin 600cfm 1850's on my .040" over 454, and it idles just fine, and has excellent low end response. Those modified squirters your carbs have were designed strictly for wide open throttle response, and not for operating off the primaries. You're throttle is opening and giving the secondaries a shot, but primaries are the only thing open until the throttle gets farther open. If those are 780 double pumpers, then both primary and secondaries have accelerator pumps, and the secondary not having a nozzle on it, is creating a huge flood of gas into the secondaries from the open passage, and the primaries dumping into the secondaries also. I'm not surprised it wont stay idling, or have good low end response.
You never answered the question about your engine specs, so I have no idea what would be best without knowing cubic inches, head specs, cam, compression ratio, etc. It could run on anything from a pair of 500 cfm carbs, to a pair of 800 cfm carbs. Just need more info to determine the issue.
I will add one other thing though. Those old Edlebrocks tunnel rams run well, but can be a big disaster if they ever have issues with carbs flooding, or timing being off. The bread box is hollow in the base, and runners stick up into the base a 1" or more. If gas puddles in the base, it has nowhere to go, and they've been known to catch fire, blow up, and cause all sorts of issues, if the gas puddles. The guys I know who run them for looks, fill the base with epoxy to ensure the gas can't puddle and create scary problems.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #11 ·
Sorry for the slow response ...
?The carbs have 1 squirter and 1 accelerator pump ... The squirter has a set of holes in normal position that feed the primary's and then it has the upper tubes that feed the secondary side as well (they were free and cool looking so I figured I'd run them)
?the motor is a 468 , 10.8:1compression, 990 rectangle port heads, the cam is a comp 638 ? Lift solid flat tappet, the intake is the 3pc design... It does not have the runners that stick up like you are speaking of, The middle plate is flat inside and tapers into the lower runner/ base so fuel cannot puddle..
I figured I could atleast get it to idle with any carb but I'm missing the boat somewhere... I have not checked it with a vacume gauge yet, I'm kinda disgusted with the entire project at this point, dealing with carbs and the body shop
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #13 ·
You can see here the secondaries are gear driven off the primary shaft.. They work just like a normal double pumper other than the fuel is delivered through the tubes to the secondary side and the primary's are fed out the bottom of the squirter like normal.... I understand this isn't the most latest greatest carb technology but they seemed nostalgic and different but they should work and at least idle..
 

Attachments

·
Administrator
Joined
·
13,427 Posts
Yes, they should idle, regardless, IF there's no issues with the idle circuit on them, or other issues. I wouldn't expect much vacuum with the duration and LSA of 108 on your cam. Mine is very similar, but less lift, and running Edelbrock aluminum heads. I can't get much over 11" of vacuum, and I'd expect to see the same with yours if it could idle down. I'd guess your tunnel ram has been reworked if it's no longer got the hollow base and raised runners that they originally had.
I'd begin by spraying some starting fluid or carb cleaner around the carb base, and intake, as it's running, to see if the rpm's go up. That's a sure sign of a leak. Hopefully the intake doesn't have issues sealing the halves, or sealing at the carb bases. I've got a hunch that your issue is the intake somewhere, since you tried two different sets of carbs, and neither wanted to idle. I wonder if it's been reworked, and some problem created during that process? Hopefully it's got a good seal to the heads, and to the two halves, plus carb seal.
Those carbs still puzzle me, just because of the single accelerator pump, and mechanical connection. I'd guess it must use a 50cc pump, instead of a 30cc to provide enough shot to overcome both primary and secondary plates to open simultaneously with a single shot of gas to both.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #15 ·
One thing that makes me think it's a intake issue is 2 sets of carbs do the same thing.. I have sprayed carb cleaner and even tried propane all around it and it doesn't affect it, I've sprayed from top to bottom ... I'm stumped... The intake has not been modified to be 3 pcs, it came that way from Edelbrock... The carbs use a 50cc accelerator pump...
 

·
Administrator
Joined
·
13,427 Posts
No, I didn't mean it was modified to be 3 pieces. I meant the bottom might be modified to eliminate the raised runners. I haven't seen the old "bread box" style tunnel ram that didn't have raised runners in the bottom half. I also think the issue is the intake, but if you've checked for leaks, I'm not sure what else to look for.
 

·
Registered
Joined
·
157 Posts
In the picture down the carb, it looks like there is no squirter on the primary side and if so, it could be spilling gas down the venturis?

Also, with those cam specs, I'd say you'd be hard pressed to idle below 1000 rpm. Especially with a tunnel ram.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #20 ·
@timberline 65.... I wish it would idle at 12-1500 lol If you have the engine rpm up around 2500 - 3000 and you release the throttle and the butterflies close the engine just dies off, doesn't even try to idle.. If you try and open the butterflies slowly to keep it running you'll end up around 1/4 throttle before it revs back up.. It's just no responding to anything down low, I'm in the process of locating a manifold to try right now
 
1 - 20 of 27 Posts
Top