Ok Guys.(and gals) I'm at your technical mercy. I need help and I'm man enough to admit it.lol. Got my 55 g***er style build on the road, stops,turns, and steers ok w/straight axle. Even mad it out to the strip. Car has .060 454 low compression bigblock peanut head motor. turbo400. Went 14.40 into a 30 mph head wind all night. w/ a speed of 90 mph. Felt like 150 mph.lol. First trip down the strip in 40 years. felt great. Anyway I was told I need a motor to match the bad *** looks of the car. Soooooooo, I tore the motor down in the car, install new APR rod bolts in anticipation of future fun, Installed a comp cam with kit. Something like 500 lift 2230-240 duration.( don't quote me on the cam specs My eyes just glaze over when I hear these things. Has a real mean rumpty rump.) Also old school LS-6 closed chamber heads that are supposed to bump up compression to like 10-1 on my set up. The the crem dela creme. An old school Weiand tunnel ram with (2) 660 holley center squirters. Pertronic ing. 130 gph fuel pump with Holley fuel regulator. Carbs have been cleaned and new kits installed. Anyway got the thing to idle decent or as decent its gonna get with cam in it. Had real bad hesitations off idle backfiring through carbs. And such. I've been trying different things,50cc(2) accelerator pumps. Helped. adj float levels,Adj accelerator pump linkage. Jet sizes were 64 pri and 74 secondary. I bumped up the primary's to 66 and secondary's to 78's Thought I'd do a big swing on the secondaries cause when wide open it would back fire also at times. seemed to help but just when you think you got it licked. bang. Did compression check for kicks and all looked real good 155 lbs plus. I noticed that at some point someone had drilled two small holes in each of the primary throttle plates so it would idle and cover the transition slots and force the idel circuit to stay engaged. Actually the idle aint bad. About 1000 Rpm in neutral.I've also tried running it with and without power valves.(plugged) I have like 7 inches of vacuum at idle. (Holleys you tube video says formula for power valve selection is eng vac divided my 1/2 and I purchased (2) 3.5 inch of vac power valves) I believe my gauge is ok. Old school craftsman. Fuel pressure was a lot different than the jegs gauge in regulator. Sears gauge said 9 pounds and jegs said like 6 1/2 #. I adj to sears gauge. Rigged it up and drove around town and a blast up on the freeway on ramp and stayed steady at 61/2#. Anyway I know someone on this site has run one of these set ups at some time and might be able to give me some hints as how to dial these things in . When the stars line up and I feather the throttle through the pops and bangs it screams and my eyes bleed.lol. So I know it has a lot of potential. Sounds so bad *** when it's not backfiring/lol/ Also I've been told I need a higher stall on my torque converter, I was thinking like @2500 rpm range. Thank you all so much YRUHOT.Doug
You haven't mentioned anything about the timing specs your running... The bigger cam will be hard pressed to give you any kind of decent vac*** readings...
I have some experience with this setup on a small block...same intake as yours and carbs. Briefly, my motor is a 350, 12.6:1, dart heads (alum) with a large flat tappet solid cam. My 660's are modified with different bowls to make them dual feed. You will have to play with the jetting but when I started out i had driveability problems. I ended up square jetting them with 74's. Remember on these carbs you're opening up all 4 barrels at the same time and I believe they're symetrical...all the same size ****erflies. Make sure you have squirter action as soon as you move the throttle. Also you mentione dthat you had power valves. I don't think these carbs were set up with power valves, I know mine don't have them. These carbs were designed for a tunnel ram application. I didn't mess with squirter size...there is only one size available from holley...if you want to increase them you have to drill but I doubt you'd need to. My small block runs crisp and responsive, but only after it gets good and warm. I do have a little bit of a bog off the line but I feel that is due to a relatively tight convertor. This manifold seems to need some RPM. Even with all of that CFM my plugs look perfect and the thing really screams. I feel strongly that you are going in the wrong direction with your jetting. The 66's do not function like a normal Holley where you have a progressive action between primary and secondary. Since everything is the same size and everythign opens simultaneously, you treat them equally...so jet the same. I'd start with a 74-76 jet in all 8 holes and go from there. Good luck! Dialed in right they are really impressive. -scott
Not to be an ***, but look on the cam card and give is actual numbers not about numbers. Also a cam number would not hurt to have so someone can look up the lobe center lines and etc. Those Holleys can be a little tricky to tune, you have to bear in mind that all four ****erflys open at once. The are not a progressive 4 bbl as in you don't have primaries and secondaries. depending on your linkage there may be a little stagger between the front 2 bbls and the rears but not much. Are you running the carbs linked or are you running the carbs progressive, this will also effect your tuning. What are you using for carb covers and are the horns milled or are the carbs as they come from the factory with air horns? Tell me and I'll snap a picture if this is confusing. ( I have 3 on the shelf as we speek, two tweeked and one still original).
How much stall speed does the torque converter have? What rearend gears are you running? You need to set up the drivetrain to work with the cam. And the tunnel ram only makes it worse....
Sounds like a lean mixture pop... You say those are center squirter (List-4224) carbs??? I'd go with # 70's on the primary metering blocks for starters... Plus the engine angle is not helping any... your probably uncovering the jets on take off which could cause the lean back fire.... Try raising the floats some more...
Looks like everyone else has this pretty well covered, but I'll throw my .02 in. Two centersquirters that have all 4 bbls opening at the same time, big cam (lumpy), and stock convertor is not a real good combo. Kinda hard to say without having more info, but I'd probably try a bigger convertor than a 2500. 3000/3500 convertor will take care of a lot of problems and is still pretty drivable. Larry T
After you have tried all the logical stuff, try a few other things. Try playing with valve adjustment. Adjust the valves .005 looser to take a little duration out of the cam and see how the engine reacts. Adjusting multiple carb setups should be done with one thing in mind. Since the engine does not know where the air is coming from, you must adjust each carb half of what you would do with a single carb. Each carb must be adjusted exactly the same as the other.
Set your carbs as stated above. A big cam + big intake needs a loose converter and lots of gear. For a street and strip car that weighs in around 3500 pounds figure 3500 rpm stall and a 4.11 gear. This should get you started.
These are all good comments above. I would also suggest you do a search here for threads with "tunnel ram", "tunnelram", "cross ram" and "crossram" in the ***le. There is a TON of info already on the boards regarding making these big plenum dual carb engines work on the street. You will have plenty of guys say "you get what you get", and "it can't really be done properly". Only listen to the guys that have actual experience and tell you about their success, because it CAN be done it you make the combo as matched as possible and tune it for it's purpose (street driving). It takes effort and dedication, but you can get there. The carbs are important and you are getting a lot of info to try here. Here are some thoughts from me... 1. 4.11 or better gear ratio is REQUIRED (I run 4.88.) 2. A manual trans will help, otherwise MINIMUM 3000-3500 rpm stall converter. 3. Use good gasoline (you will be amazed at what a 50% load of race fuel will do). 4. You need a good distributor with proper advance setup. My sbc dual carb cross ram engine requires 20 initial and 38 full in timing (as opposed to stock 14/36). 5. Good plug wires. Not just new ones. Good quality race wires. 6. A decent HEI, Coil setup, MSD 6AL, whatever... but you need some FIRE). 7. Fresh plugs at proper heat range (Experiment hotter and colder and watch for a powdery tan plug, not white (lean) or black (rich). Best way to check this is to run the car wide open through the gears, shut off the engine, roll to a stop and pull a plug. 8. On a previous tunnel ram engine I had, I used to run blocked off power valves in my Holleys. Just one backfire through the carbs is enough to blow one and totally screw up the driveability. 9. Also on the previous tunnel ram engine, I fought a pair of used/rebuilt Holley carbs for a LONG time before just buying a new pair of carbs and tuning them properly. THAT finally ended my problems on that engine. The previous carbs had been through a lot of "backyard" engineering from a previous race "expert" and may have been suitable for 7,000 rpm runs, but ran like **** on the street. Consider where your carbs have been.
Get two 600 vaccuum secondary carbs and sell the center squirters to some one with a manual ****** or auto with a big converter, these carbs are not street car friendly. Look at ignition timing for the back firing. You need initial at 18-25 degress and 38-42 total if the dizzy has an advance mechanism, or you can lock it out and run 36+ all the time (what ever your gas and compression ratio can stand)
I'm running a similar setup, but with a SBC 327 and dual 450 cfm Holleys. Ran into the same issues, but mine weren't as extreme a far as backfiring. Just a small pop or bog when hammering the throttle. Did pretty much the same things you did a far as going to larger 50cc pumps, which helped a lot, but still not perfect. Changed the jets out to larger jets, and bought the 34-2 adapter kits from Quick Fuel to allow for secondary jetting, which the 450's and 660's don't have. The mechanical secondaries without a secondary accelerator pump create some issues with a tunnel ram, so being able to jet the secondaries will help a lot. Here's the kit I used: http://www.summitracing.com/parts/QFT-34-2/ Changing to a vacuum secondary type carb, or adding a secondary pump to make it a double pumper will help, but it's not neccessary to overcome the issues you are having. I'm running a 2500 stall converter with 3.73 gears, but my car weighs less than 2500 lbs. If it was heavier I'd go to a 3,000 stall and at least 3.73 or 4.11 gears.
If you are running a va***e or centrifical anvance your timing could be falling back at lower rpm's . You might want to lock out your timing .
I think we really need to know more about the cam here. A 230-240 duration .500" lift cam in a 467" big block is really a pretty wimpy cam. From Comp on a 224° .510 lift - Hydraulic-Good for daily driven street machine, works with stock converter, likes headers. Sounds like you may need a bunch more cam to make any power with that tunnel ram. I am also suspect of your compression ratio. If you had a low compression Peanut port 454, most of those (depending on what it came out of) were around 7.8 or 8:1. So changing from the 120cc heads to LS6 Closed Chamber which are 109cc would only net you an increase of about .75 to 1 point depending on head gaskets, if no other changes (ie pistons) were changed, so you'd only have about 8.5 to maybe 9:1 Sounds like a bad combo for a tunnel ram to me. Not that you can't make it run decent, it just isn't going to make much power, and will probably make more with a single carb on a good single plane manifold
I agree with hotroddon. I also want to warn you that if those are the stock pistons they are not going to like sharing space with those rectangle port valves. Going from a 2.06 to a stock big head 2.19 or 2.25 is a recipe for disaster with stock pistons.
3500 converter min 4.11 gear set what is your total timing? vac advance on a ported circut?? is the cam advanced ? start fat then lean it out
Probably a good thing he doesn't have much cam in it. Whole deal just seems like a weird combo to me. Just sayin. What gear again? Lippy
Ok many cover most of it . First off a .500 lift cam in a BB is nothing . Try a cam in the .600 lift for a BB . Torque converter should be at least 3500 to 4000 stall for a good BB . Rear gears should be a 4.30 to 4.88 . As for the tunnel ran , sell it and get a single 4 bbl intake . Tea they look kool but they are nothing but headaches when you have no idea how to set them up . With 2-600 cfm carbs , that is way too much carb for a 10 to 1 compression engine with a mild cam ! That's 1200 cfms of fuel on a engine with a .500 lift ! Way too much fuel ! I would use a 750 Holley and Vic Jr intake with the cam you have . You need better rear gears and a better stall . If you can give us the information we need , that will be much easier to figure out your problem but I would really take that tunnel ram off for now ! That a big problem right there . Can you tell use the EXACT cam specs from the cam card , rear gears , heads you are using with valve sizes & rocker arm ratio , exact compression , what ignition system you are using and the size stall you are using now . Then we can all help you much better ! I love g***ers but looking kool and running good are 2 different things all together ! I am also going to be building a 50 Ford g***er this winter . I am using a 1970 Ford 429 with a bigger cam in the .600+ lift size, haven't choose the cam yet , reworked heads with 2.25 intakes , Vic Jr intake with 750 dp , 4 speed close ratio trans and 4.88 rear and will drive on the street . Will take to rake also but just a toy ! Retro Jim
sounds like timing issues to me, one thing i didnt see mentioned, what distributor are u using.. ? ***** ok, just noticed Pertronix,,,***** Here is something i learned about pertronix,,, play with the air gap a little,,might be too big of a gap, measure what u have and close it up and try it,, sometimes it needs less,, had the same issue on a diff engine. also... r u using vac advance or just mechanical? if using vac adv can, check the vacuum can for vacuum advance,, make sure the diaphragm isnt ruptured, use some suction on the vacuum line and make sure the arm is moving that goes into the distributor.. if not replace the vacuum can,, post back with results,,,
I run a tunnel ram with a rat motor, they can be OK however the suggestion to get vac secondary units is valid as well as getting the total timing up, rats like a lot of lead. Too bad you don't have a 4 speed, life would be much easier.
I just re read your post and missed some things . I thought you had 600 Holley's and I see they are 660 ! Still way too much carb . You should think about upgrading the ignition system from a Pertronix for a drag engine . A good MSD and ignition box will be much better for the engine . I would honestly pay someone to set the carbs up for you if you have to have a tunnel ram . While you have the engine torn down , I would really consider a bigger cam than the one you have right now . It's really a small cam for a BB engine . Also can you tell us more about the internal parts you are using like pistons ? What year is the engine you have ? Unless the engine is a pre 1972 then the pistons might be dished for the lower compression . If so you will need better pistons than those . Better torque converter and 4.30 gears will really help that launch from the lights . Just don't be disappointed ! If you start over with the rebuild we all can help you with a much better running car when done . Fast drag cars cost $$$$$$$ ! Retro Jim
I agree with Retro Jim, especially about The $$$ part,, an old racer once said: "SPEED COST MONEY BOY,, HOW FAST YOU WANNA GO,,,"?
Timing and did you check for vacuum leaks ? If I were you I wouldn't go rebuilding the engine again as suggested, get yourself a pair of 600 cfm 1850 carbs. You can get them cheap, hell I got three or four out in the garage now, put those on and go from there. You can get it to work, you don't have to have an all out race engine for the tunnel ram to work.
Redline toys has it all together.... My sentiments exactly. I have tuned a lot of combos like this and now will not do it without an AF ratio gauge. Sure they may cost three hundred dollars and you will need to weld a bung into your collector or exhaust system. The info on your air fuel ratio at tip in, idle and WOT is priceless. You will save fuel, aggravation and possibly keep your engine out of detonation and lean conditions. Once you tune like this you will never go back to the seat of the pants method. This gauge will pay for itself in fuel economy.... People won't have watery eyes following you and you will zero in on razor sharp tip in and not worry about leaning it out. The gauge will also show you when a jet or air bleed is plugged. Having said all that....put a single four barrell on it and enjoy the simplicity....if you like constantly ****ing with linkage and the possibility of twice the fuel leaks then stick with the duals!
i'm working on a customers car it's running a small block tunnel ram 2 600 holleys .600 lift cam 9.2 compression powerglide 5.28 gears 32 tall MT sportsman tires magneto with lock advance timed at 38* he reduced the plenum size for better throttle response as it would hesitate he filled the center with hard wood blocks until he was satisfied you have to warm it up before taking off or it will stall by the way he's been running this for 10yrs.
Wow, you guys are awesome. thanks so much for all the info. I'm going to scan the cam card that came with the cam and maybe it'll make more sense to you all. And will add some details that you have requested. It's funny how if I drive slowly through all the hiccups by feathering the throttle etc and the stars line up this think really gets it and leaves me shaking.lol. I know there is alot of potential in there I just have to get the set up a little better. Let me go to battle with the scanner.lol.Thanks YRUHOT.Doug
I got 2 #1850's for a 289/302 tunnel ram and added the stiffest springs in the vacuum secondary pods... I should be able to dail it in from there... Can't wait to get that "roller" motor going..
OK guys I'm back and I've scanned cam card data and will attach. I will tryand answer the questions that I've read about on my set up. OK Installed the cam at straight up timing marks as recommended by the comp answer guys. they say that the cam is already set up for a 5 degree advance already built in to it. Did that. INstalled timing tape on harmonic balancer and am running like 10 deg. advance at idle, and about 40 degrees by 3000 rpm's. It hard to watch the timing and the tach inside the car at the same time. No vac advance it being used at this time. Checked valve clearance with the modeling clay and lots of valve clearance. Yes dished pistons in cylinders. Gone are peanut heads. According to casting numbers they are 1970 closed chamber LS6 heads that came off a mid 10 second drag truck with what looks like some mild porting job. Rect port. I believe the Harland Shapr roller rockers are 1.5 ratio. Bought used and seem ok. Funny how you close you guys were to the car weight. it weighs 3580 with me in it and I weigh in right at 200 lbs but I don't think that is really the trouble here.lol. Interior is gutted.Guys looked at me funny when I rolled it across the weight scale at the recycle yard.lol.and then split. I have got ford nine inch in rear with 4:56 gears. Has plenty of r's running around town. I run a 29.5x10.5x15 Et slicks on it. Carbs are mechanical secondaries and they are slightly progressive. Primarys open like1/4 I believe and the every on comes open after that. I do know she don't like any shanigans until she is up to 180 degrees on the water temp. lm running a tight stock convertor right now. I know it would kill me down low but once it gets rolling things start happening pretty quick. I know I will have to step up on that issue. Like you say its all a matter of how much money you got to go fast and converters aren't too much these days from what I'v seen. I liked that attachment on the edelbroc instruction about the idle circuit mods. I don't seem to have hardly any idle screw adjustments. Set the fuel pressure at about 6# according to the jegs fuel gauge on the regulator and fir kicks I hooked up my old reliable craftsman fuel and vac gauge and right off the bat it said the I was running at 9# fuel pressure. Dropped pressure down to 6.5 according to craftsman gauge and drove around a bit and a blast up on the freeway on ramp and it did seem to improve a bit I think. Now I need a third gauge to verify my readings and average them out and see whose lying to me.lol. Seems I read on here that these small gauges at notorious for wrong readings.Just repeating what I've read.I like the comment on these are different tuning then other holley carbs in that everything should be jetted same all around. Never looked at it that way. And he stated what these came with in stock form. It thats so I got a long way to go to get back to square one. Bought these use and God knows what has been done in the past. Probably had guys like me working on them,lol, I hope I've covered most questions about my set up and will read through all of them again and post some more answers as I can and keep you all posted. I have thought about a single four barrel carb. Actually the car was a lot easier to drive with the q-jet that came on the engine out of the surburban.lol. life was simple then,lol. But how exciting was that.Happy Easter to everyone. Yruhot.........Doug
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