At least I have this, if needed. secondaries out in the sunshine. doesn't look as restricted as that 450. Couldn't get the calipers in there accurately.
While your at it pull the accelerator pumps out, they can get hard and still work a little but not like they should.
I did pull the rear one, there are indications something's leaking in the area. Check the left side pic in the first post. It was nice and soft, didn't see any tears. I will check for flatness too. I'll be going thru them a bit more, cleaning and checking things. Since they are coming apart nicely, I'm not concerned with having to buy a bunch of gaskets just to look. I hope the tech lines can ID these. EDIT out with useless info.
Maybe you'll find this helpful https://www.jalopyjournal.com/forum/threads/do-vac-secondary-carbs-work-on-tunnelram.1044776/ .
Holley does have close limit jets in a #62-3 size... The 3 means the jets flow within 3 percent of each other.... Those Holley carbs were used on the '83.5-'85 Mustang GT with 5-speed transmission cars....
@swade41 thanks, I did a quick scan and will read it carefully. Actual experience from others helps. @Deuces Thanks, I don't think the jetting needs major work, it will cruise along with ease at all speeds I've done so far. The typical range of jets runs out at the low 60s. Having 4 barrels and 4 jets feeding means that a small change as you mention will be seen, but it seems close now. I'll want to revisit that once it's really ready for a long steady cruise, but so far it's been cold fire up followed by fairly short run time in town. Not the best for reading plugs and the exhaust doesn't lend itself to modern sensors! Of the 7 circuits of carbs, the enrichment part is the big issue. I have dealt with this before. A big cam will cause a vacuum 'curve' where at low RPM it has low vacuum (weak signal). Bring up the RPM and the signal gets stronger (more vacuum). A tunnel ram doesn't help here. The power valve isn't able to operate the same at 1500 and 2500 because the signal from steady load to increased load aren't the same. So the accel set up is even more critical. The squirt has got to cover every tip in, light to heavy, at all RPMs.
For what it's worth on my Henry J with the tunnel ram and 450 mechanical secondary carbs while tuning at the track it ran the fastest with different jets front/rear. I stumbled onto this changing jets in between rounds and only had enough time to drop a number in the front carb. The carbs were inline so to change jets in rear carb the front carb had to be removed. Every engine and altitude is different but with my combination my best results were only 3-4 numbers over stock, but as I mentioned I also put the 50 cc pumps on and increased shooter.
Since you have 65s in it now, you could try 68 or 69 and see if it makes a noticeable difference. If not, then jet changes probably won't do much.
Swade, I read through the hamb post you linked. Sounds like Blue or Green , like I guessed after you posted that chart. From the descriptions, I'm leaning toward Green. "The green is a good compromise, it gives 10cc more total volume than the blue, and about .010 faster for the same degree of throttle opening than the blue through the first 20 degrees of throttle rotation." That's where I'm at on this, that initial crack of the throttle, when low RPM and low vacuum conspire to weaken the signal. When hitting the throttle at say 2500, it's not nearly the issue but still there. I'll probably pull the choke plates if they aren't staked, at least until I have the squirters dialed in. Jim, it doesn't show any noticeable problems just cruising (main jets). Going with bigger jets might cover some of the bog during accel and I'm not checking MPG on this toy, but my feeling is still going with a more aggressive pump cam along with a squirter that meters the shot out over a bit longer time (smaller). So I just checked and the 25 is the smallest listed. https://www.summitracing.com/search...ine/holley-accelerator-pump-discharge-nozzles so I hope the cam will do the job. also found this which has the chart Swade posted. https://www.enginelabs.com/engine-t...celerator-pump-tuning-for-holley-carburetors/ So the current plan is to clean and inspect everything carefully, then reassemble without spacers and try it again. I'll check the local store to see if they can get individual cams. I'll also mention that I have already tried moving the cams from #1 to #2 hole and there was an improvement. just dialed holley tech. est. 35 minutes wait, 37 ahead of me.
Jason at Holley was very helpful and understood what my situation is, but was unable to find the list #s anywhere. He did provide the QFT (not Holley) cam assortment as 41-100QFT which will help. Holley and others have it for 33-35 https://www.holley.com/products/fue..._parts/accelerator_pump_parts/parts/41-100QFT This also points out that while the parts are on the same architecture, they may not be exact. The holley kit uses different colors (different ramps?). He found that the tunnel ram 450 CFM carbs they have use 59 mains and a 65 power valve, so same pv, smaller jets. EDIT: 56 <59, so I have smaller jets, same PV. https://www.holley.com/products/fuel_systems/carburetors/street/parts/VK060100 QFT home page has "New" 450 CFM carbs, but bigger throttle bores and no List #s. Bottom of this page. https://www.quickfueltechnology.com.au/ He wasn't able to pinpoint when Holley bought QFT, and it probably won't help but just found this. Holley Acquires Quick Fuel Technology On April 10, 2013 So the plan is the same. Clean, inspect, put it together with less internal volume (spacers) and get the cam kit to try. Probably get a pair of the accel diaphragms, too. https://www.oreillyauto.com/detail/c/holley/holley-accelerator-pump-diaphragm/hly0/13510
Apart Bottom screws were tight, so I'll take another crack at them soon. Going to try less obnoxious liquid than carb cleaner, hoping to save the labels.
Have you thought about the 50cc accelerator pump ? Plus the squirter and cam color change . Its worked for me . It’ll cover up a lot of “too much cam , low vacuum “ . Its not a cure all but can improve the off idle bog usually associated with large volume intakes with large cams . Good luck
If I had the stuff in hand, I'd still want to take this a step at a time. Having to buy the stuff makes me even less ready to make big changes. It IS under consideration, but I'll try little stuff first. I'm running out of driving weather here quick, so I'd rather put funds toward stuff I can get done over the winter like Body & paint. Also wheels & tires which are also not needed ASAP, but gotta have the money if some good used deal pops up. I will say I'm impressed with these carbs. They came apart nicer than any Holleys I've dealt with. It's like they studied all the issues and made changes to fix things. I didn't see QFT pumps, here's Holley That 150 might get a pair of rear wheels or convert the rear axles to Ford pattern so I could use the wheels I've got. https://www.holley.com/products/fue...ster_parts/accelerator_pump_parts/parts/20-11
You can get by with just the pump and housing . I’ve done it many many times . You can also increase the pump volume by cutting the pump part out of 2 old pumps and just use the gaskets as spacers . You don’t get the volume of the 50 but you do increase the volume using all stock parts plus some old pump s .
I too started with jets, then shooters, then float levels, none of it removed the bog but it did slightly help, when I put the 50cc pump kits in then the bog was history. We all have a certain amount of pride and determination to do it ourselves but compare prices of jets, shooters, power valves to the bigger pumps. I know the bog is more of an annoyance for you rather than something that keeps you from driving the car but just consider the advice. Like I mentioned before I don't have a huge experience with performance tuning a pair of vacuum secondary carbs but have you considered a lighter spring in the vacuum canister and tieing the two canisters together so the secondaries operate as one ? These are the pumps I bought off of ebay a few yrs ago for another pair of 450's that I plan on using on a crossram. I don't just buy the cheapest priced stuff but I do a lot of research and comparisons and these were a good quality set from a name brand manufacturer, not generic junk.
Thanks for that! You guys keep working that 50cc! Those would be close to the cam kit! It looks like they use a different cam (of course, more stroke), are there a bunch of cams to tune them? Also, without the spacers, I'll have to check clearance between the pumps and intake. It's fairly close with the 30cc pumps. I tried those quick secondary spring kits on the old car. I found them to be kind of fussy, but quicker than the remove take apart, change deal. The QFT has something similar to an idle mixture screw restricting the ported vacuum signal to the vacuum pots. The tech gentleman also mentioned the tops that have a port to connect both together which they have stock on the TR carbs. Part of the setup on that old car was restricting the air bleeds to increase signal along with the accel cams. These have replaceable air bleed jets. I am hoping that this will be the secret to getting a better signal to the circuits. Larry Hofer guided me and helped. If you don't know the name, he DID write the book on SBM engines, and has been doing resto to wild stuff on Corvettes for decades. Hie current project is the BB C8, fully integrated with the car's computers. BTW, the main body casting does have SL 450 cast in behind the secondary plate too. I didn't post that picture, so here it is. There are also some felt marker writing on the plate and the body. I'd guess they are factory marks. I'll try to get legible shots today. The jets back there don't seem to have legible numbers. Ther whole secondary side is a later problem. First, get the primary side happy! 2 450s will be better to tune than 2 600s, even if the secondaries are blocked off.
So this is the least expensive kit I saw from the USA. $45 each. I'll call this one Basic. https://www.ebay.com/itm/194017830687 @gary macdonald and @swade41 I have a couple of dumb questions, since I haven't gone this way before. 1. What I'm seeing is the more expensive or Deluxe 50cc kits have 2 cams, Brown and kind of Yellow. The Basic kit only has the Brown and that seems to be the one most single part sellers have. Were you guys using the Brown cam? Here's a Deluxe kit with both cams and the arm for the next question. https://www.ebay.com/itm/285018444578 2. Both kits come with a new arm, which I understand, but the Basic one has an exposed spring like a 30cc arm, where the Deluxe one and other 50cc carbs I've seen have a tube, as shown. I'd assume that will work for my app, but is this okay? Looks like it's stronger, too. If I need the Deluxe kit, I would rather buy once, cry once. The kits swade posted are like the Basic one. 3. When looking for the Yellow 50cc cam separately which seems to be not listed, I came across this, a wide Brown cam. From all the pics, the arm is only so wide and should ride on the 'narrow' cam just fine. Is it just for the tube arm, for edge cases? https://www.ebay.com/itm/170478745767 From a review on this item Do you have an application that requires a 50cc accelerator pump? If so, pick up one of these pump cams. It is slightly different from the standard 336 brown pump cam and has pre-drilled holes for both the #1 and #2 positions. It also has a wide top surface for better geometry with the pump arm. The cam profile will give a relatively mild shot for low throttle angles, and it gets progressively more aggressive with increasing throttle rotation (hole #2), or a little bit more aggressive early shot (hole #1). Only use it if you need it and have already tried all of the standard pump cams. Probably NOT needed for most typical double pumper applications (dual 30cc pumps - 60cc total). Good for a lightweight car with a manual transmission and shorter rear end gearing. I know this sounds very timid, but I'm watching the budget hard on this build.
You don’t want to open the secondary faster , if anything you need to retard its opening . The idea is to keep the velocity mixture up so fuel doesn’t drop out of suspension and lay on the floor . Do anything to keep the velocities up . Thats what a small plenum does . I’ve gone so far as to , well lets say I experiment alot and a brick didn’t work . the pump cams are interchangeable
I'm long winded already. Let's just say that the passages for the secondary vacuum won't be opened up until the primary is sorted. For Holley's I'd disconnect the arm. Yeah. Just paying attention to an Offy TR from the early 70s to a holley street ram from the 90s gives you a pretty good idea! all 30cc group and all 50cc group, right? Or is it the arm ratio that's different and everything can be swapped? More info https://www.holley.com/blog/post/accelerator_pump_tuning_for_holley_carburetors/ This doesn't list different cams for the 50cc, so I may have answered my own question.
Past foolishness. I'd tried the ones that were advertised at that time as tunnel ram carbs. 390 CFM 4160s with mechanical secondary but no double pump and no chokes. Horrid lil boogers, worked best with the secondaries disconnected, but as you can imagine, limited top end. This is a pair of 600s that I got used, pulled apart, matched up in parts and installed. They were so Much better, responded to adjustments and with Larry's help were without hesitation, started well, didn't foul plugs, and ran at all speeds well. I'm positive the secondaries didn't open much, but the 340 didn't need all the airflow they could provide. Plenum volume was bigger than the current one.
You're way over thinking it, you might not even notice the difference in cams, once the bog is gone it might just blow the tires off. As far as that tube on the accelerator pump arm, it may be stronger but there's not many carbs with them. If you notice on my higher end blower carbs they don't use them. Not on my tunnel ram either
If you do plan on going with 50cc pump and arm, plan on adding a minimum of a 1/4" spacer under the carb(s) for clearance.....
@swade41 thanks for the sanity check. Pretty pictures too! BTW, ya got me. I saw the top of the pic and the carbs were covered! Had to scroll down. EDIT: Just saw your T bucket video over in the garage driveway paint thread. NICE! Spent an hour or two wiping parts down. Not quite half way done. Used detail spray, lots on hand and mild. The base isn't tumble polished like the rest, but things are much improved. Still can't read any secondary jet numbers, but did see the secondary air bleed numbers. Did get the main body and throttle plate separated on one. Just needed the bigger grip and right tip with the impact. Didn't hit it, just twist. Right tool for the job and all. The blades were just right, barely uncovering the transfer slots. It blew the tires off the other day in the rain. Considering the rear suspension extends on acceleration (pushes tires down = good), it usually grips pretty well. I haven't got on it really hard (WOT) yet.
I would work on increasing the squirter size before changing the pump size, get the pump travel right and put bigger squirters on. If you have some extra's you can drill those out. I don't remember the break but after about a 32 you will need hollow screws to go with the bigger nozzles.
Got everything cleaned up, wiped down and both arms adjusted. One did have a bit of play but doubt it changed things much. Still need to buy studs to install, and either the cams or the 50cc pumps. If I get the pumps, I'd expect to use the included Brown cams, so won't buy both. Still researching sellers, since I don't do paypal or amazon. Jegs and summit want 11 bucks for regular shipping unless I buy more stuff. Wondering if I should just wait for sales in a couple weeks and try it as-is. Not much driving weather left.
I like ordering my Holley carburetor stuff from these guys - ordered many times and always had a good experience. Talked to them on the phone once and they answered my question right away. They have pretty much anything you can think of for a Holley 4bbl. https://allcarbs.com/product/polished-50cc-conversion-kit/
@Tim_with_a_T thanks, but that will only work if they will take a card over the phone. I will give it a try tomorrow. They are the first place the Holley tech guy mentioned to find out about the List #s on these. I didn't bother after pulling them down and seeing the casting inside. ALLSTATE CARBURETOR & FUEL INJECTION 143 Brightside Avenue Central Islip, NY 11722 Phone: 631 234-8327 Hours of Operation: Mon-Fri 8:30am-4:30pm est Closed Sat. and Sun. Paypal lost me as a customer back in the oughts.
Just got off the phone. He was able to provide the stock jetting from the list numbers. They are 450 CFM (as cast). 55 main primary, 60 main secondary (mine has 56 main primary, can't read anything on sec) 65 power valve (matches) Idle air bleeds - primary 70 secondary 39 (haven't confirmed yet) High speed air bleeds - primary 35 secondary 33 (matches) 25 squirter and Pink cam (matches) I described the bog and asked his opinion. He said that he would change the idle feed restrictions in the metering block from 29 to 31. He also said that he might go up on the squirters from 25 to 28. He felt that the 50cc pump wasn't needed. I didn't ask about cams, Doh! Called again and got an assortment ordered, but he said the Pink cams usually work fine. I bought both the bleeds and the squirters along with the cam assortment. We will see. I know sometimes drilling is the only way and is quick and cheap, but I'd rather avoid if possible and swap to the right part. I also asked him if he could give an idea of when they were made, since Holley couldn't give me info. He said from around 2010 to about 2019. Very impressed with his knowledge, understanding, and tech help. Really hope this will get me going and help others. It seems foolish to buy a quarter pound of parts from across the country, but the support beats anything else I've dealt with for a while. It seems like the carbs were bolted on out of the box with one step up on the primary mains, and his suggestions are that it should be pretty close, just a bit more squirter and a little less idle feed restriction. A delicate touch. Will have to pull the primaries apart again, but no big deal. Still need to get the shorter mounting studs.
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