03-25-2013, 12:23 PM | #1 |
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Engine help please!!!
So I have a 1986 chevy c10 and I just put a 350 crate motor in. I put a comp thumper cam in with quiet gear drive and new valve springs. On top I have an edelbrock performer intake with and quick fuel 600 double pumper carb. I have a jegs hei distributor with vacuum advance. So I can start the truck and it runs good in idle but when I shift into gear it dies. Also for some reason I'm having trouble finding my timing mark. I had to advance my light to 40 just to see the mark on the timing tab. If anyone could help I would really appreciate it.
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03-25-2013, 07:03 PM | #2 |
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Re: Engine help please!!!
could be a few reasons for it to die when it's put into gear, do you have the vac. advance hooked up? if so try putting it on the timed port.if it's hooked to full vacuum and you switch it you will need to re-adjust timing. do you have a stall converter? if not the rpm that seems fine in park will drop out in gear. what is you're idle rpm set at? now about the timing mark-did the crate motor come with the balencer and the timing tab? i'm assuming this is an all new setup.
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03-25-2013, 08:42 PM | #3 |
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Re: Engine help please!!!
I had the same problem. Turned out to be a combination of timing and idle setting.
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03-25-2013, 11:49 PM | #4 |
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Re: Engine help please!!!
I don't know what the specs are on your cam and what the stall speed is on your torque converter but when running an automatic with a tight converter and a big cam it is common to have the motor die when shifted into gear.
Most guys will keep adjusting there idle speed up hoping that will fix the problem.The problem with that is once you get over 1100 rpm at idle you get past the idle circuit.The carb thinks you are driving slowly down the road and your not your trying to idle. I am not familiar with your carb but if it has 4 corner idle circuits plus the secondary butterfly adjustment a combination of the two will usually get you a decent idle.By opening up the secondaries a little bit you are giving the motor some more air allowing it to idle without the primaries being opened to far and essentially removing your idle circuit.Do you get dribbling from the primaries? An old racers trick is to pull the carb off and drill a 1/8 inch hole in each of the two front butterflies next to the idle slot.This allows more air into the carb while keeping the butterflies more closed.The newer race Holleys come out of the box with the holes already drilled to solve this common problem Does your motor idle for about a minute then start to fade out then die? If yes and you don't have the four corner idle circuits drill the two holes and re-adjust the butterflies. |
03-26-2013, 12:30 AM | #5 | |
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Re: Engine help please!!!
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When I'm off work I will help you with your setup but its to much to type on phone. But I can get you fixed up Posted via Mobile Device
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03-26-2013, 02:43 AM | #6 | |
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Re: Engine help please!!!
this is a sloppy mess of a combo
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third im pretty sure your torque coverter is stock BAD but it can work JUST BARELY fourth your going to learn alot about ignition and timing soon THIS IS WHY THE THUMPR CAM GETS BAD REP lets start with issue one this cam needs initial timing LOTS all high overlap cams do an msd streetfire distributor has the stuff you need for the proper tuning we need but we can make do without but again this would make your life easier you need to get it idling at about 750 rpm out of ger for what we need to do so first lets set base timing started at 14* initial timing with no vac advance yet. then you need your curve you need to change the hei springs to get all timing in at 3500 rpm or sooner but no sooner than 2800rpm at the lowest to test this you need a dial back timing light and a buddy or visable tach rev it till the timing does not advance any more change the springs till you hit your goal now plug vac advance back in to FULL manifold vacuum. you also need to LIMIT total timing to under 42* total not including vac timing many ways to do this but im not going to type a page heres good info http://www.73-87.com/7387garage/drivetrain/hei.htm ok now we have gotten a base to work off of for the engine and it will respond for us at this point after reading all this take the time to think wether you have the couple of days to deal with this and fine tune it to work otherwise take out the cam and get a 268 cam next thing that will help tremendously GET a 2000 stall minumum converter and install it. otherwise our job is going to be hard cause we will be splitting hairs ok now the carb...mama mia please get something bigger you need to now take off the carb and this is where all our hair pulling begins set carb upside down there are these slots at the edge of the butterflys on the carb you can prob see them really good right now cause im sure your throttle is open a bunch just to idle. you need to make that slot look like a square very small http://www.chevyhiperformance.com/ho...8/viewall.html yes we are going to have to drill to get it to idle with the throttle blades in the right position so we can tune the mixture with some response when all is said and done you have two scenarios either you have a high stall converter and you can put it in gear and it will just barley keep going till you tune it in gear(against a wall or planet sized object with parking brake on) or you havent and you proceed to kill the engine IN WHICH CASE kill yourself no seriously your going to end up drilling big holes and your idle will be at like 1500rpm and it will drop to about 550 in gear you can see why that converter can either help you or break your back in a nutshell you threw a big cam in a setup that is not built for making use of it, you NEED stall+gearing+headers and a proper intake setup hell this cam takes stock camel hump heads and works them to their outer limit, vortec heads are better suited to give this cam what it needs to shine plus a high flow intake YOU JUST PUT A 450+hp cam in a crate motor that has possibly 380hp at its upper limits (not talking about what it can handle just produce). a smaller throttle blade carb will require more throttle blade angle than say a 650 or 750 carb and that makes it harder on us too a small carb wont save more gas at all same hogwash as a quadrajet with small primaries vs any other carb. way more involved than that and guys i will be more than happy to explain in another thread theres more but lets start with this and question time
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03-26-2013, 03:10 AM | #7 | |
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Re: Engine help please!!!
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You might like to talk to these guys about what you need, they have a quality product and stand behind their converters. Also important, find that timing mark and set the engine properly. Make sure that you are trying to time it without vacuum connected to the distributor. Look to see if you can set the timing at a total advance around 35 degrees and then try to drive the truck.
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03-26-2013, 03:18 AM | #8 | |
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Re: Engine help please!!!
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You might like to talk to these guys about what you need, they have a quality product and stand behind their converters. Also important, find that timing mark and set the engine properly. Make sure that you are trying to time it without vacuum connected to the distributor. Look to see if you can set the timing at a total advance around 35 degrees and then try to drive the truck. The carb can be smaller but you will learn that it will run out of air at RPMs over 3500 to 4000. If you go too big, then you overload with a lot of eul while driving city streets. YOu have a 4000 pound truck and that takes a carb that has a higher velocity of airflow to make it work efficiently, if you go too big on the carb, then it loads up and lays garbage onto your valves under low load conditions. Your engine will perform a lot different if it was ina Camaro, but you are putting it into a heavier frame, so buildi it to work in that frame. I am running a 385 Stroker engine in a 4000 pound 84 GMC with a 700 R4 tranny and a 2400 stall converter, along with 3.73 rear end gears. I have a Comp Cam roller setup and Dart II heads on the truck. I had the same issues as you are until I figured out the timing and the stall issues and now it drives well and can actually idle reasonably at a stop light. WIth the setup that I have it will light up the tires on request and run as ahrd as any pony car. WOW, how did this end up with two answers to this question????
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03-26-2013, 01:24 PM | #9 | |
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Re: Engine help please!!!
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Allen86 Drilling two 1/8 inch holes in the front butterflies isn't doodling up the carb.If you buy a Holley HP series carb they come with the two holes already in them and Holley knows more about carbs than everyone posting here combined.You can call them at 270 781-9741 and verify that. I just looked up your carb and it has 4 corner idle mixture screws.You want to screw them all the way in and then back them out 1.5 turns each.You want to adjust them all evenly not individually.Make sure and throttle up the motor between each change to clean it out or you'll likely go to far. If you have already adjusted the primary and secondary butterflies back them off completely and start over. Put a 1/2 turn on the secondaries once you see it start to move and leave it alone.You can now adjust the primaries.If you have to run the idle past 1100 rpm stop and give them a call at Phone: (270) 793-0900. If you get it set-up properly and it still stalls on you now is the time to spend $300 on a torque convertor and pull the driveshaft and exhaust and do all of that work. I tend to try and fix things as cheaply as possible before resorting to pulling the radiator cap and replacing everything under it. |
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03-26-2013, 02:22 PM | #10 | |
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Re: Engine help please!!!
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What I am saying is the smaller throttle blades in fact do not bleed as much air as a bigger throttle plate carb IE 650-750 and will have to have more throttle blade angle as a result to flow enough air and that will expose the transfer slots way to much and give garbage low end and unresponsive mixture screws. It will never idle like that. Drilling holes and getting the transfers correct will be the way we need to go but even a stock gm crate can take advantage of more carb Posted via Mobile Device
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03-26-2013, 09:37 PM | #11 |
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Re: Engine help please!!!
For those who were asking the motor is a good wrench crate 350 with 260hp. The cam is a thumper with .479/465 lift.
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03-26-2013, 09:40 PM | #12 |
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Re: Engine help please!!!
Also the trans is re built 700r4 that was done about a year and a half ago. The torque converter is most likely a stock style
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03-26-2013, 09:44 PM | #13 |
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Re: Engine help please!!!
i have a thumpr in my dually with a stock converter and it surges in gear at idle, im putting a 268 in it
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03-26-2013, 09:46 PM | #14 | |
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Re: Engine help please!!!
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If you want the sound of a lopey idle and none of the heavy burdens of a ludicrous camshaft I would suggest a a voodoo 268 cam and thinner head gaskets Posted via Mobile Device
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03-26-2013, 09:55 PM | #15 |
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Re: Engine help please!!!
Would this cause the motor to stall when shifting into gear but not at idle?
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03-26-2013, 10:17 PM | #16 |
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Re: Engine help please!!!
Allen86
I posted the phone number for your carb above.Give them a call and tell them what you have.That cam isn't very big. |
03-26-2013, 10:37 PM | #17 | |
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Re: Engine help please!!!
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03-26-2013, 11:10 PM | #18 | |
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Re: Engine help please!!!
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Never had an engine slough and bog around the streets with whatever size carb I put on it. Other than a....quadrabog.... Da da daaa lol Either way a boggy carb can be 10000 other issue other than its size. Btw crap getting on the back of your valves is what happens when air and fuel seperate when the valve opens. The fuel being heavier continuous a straight path splashes on the back side of the hot valve. This is from poor mixture. Posted via Mobile Device
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03-27-2013, 04:20 AM | #19 | |
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Re: Engine help please!!!
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the cams specs on this are pretty wild, duration is the cause of it. these cams have high duration, can run 10.1:1 static comp ratio, and still not pre-detonate because of low Dynamic compression ratios because of the duration, and are flexible to any application. thats why there rep is so bad, usually if there very versible, they get thrown in to any motor in any setup-combo car or truck and here we are. but not many know things like this. They get lucky. timing has to alot with it to. and i believe you hit the nail on the head with the vortecs insidious. vortecs Have the popular heart shaped chambers, and can handle up against the wall type comp ratios. id say 9.0:1 will do with this cam and these stock heads. The cam you chose will need that comp ratio to work effectively and broaden your lower end torque range to over power the wieght of the converter. too much air and fuels are for lighter vehicles. you have wholesome truck. i say you dumb down the carb and see what happens. if it runs to rich at say idle, then this can be a problem, cause that cam is demanding it, holding valves open alot longer than a stock cam. this could richen the mixture to were it just chokes in gear. since you have no vacuum controlled secondaries?
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03-27-2013, 09:27 AM | #20 |
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Re: Engine help please!!!
Allen86
Is the cam in question the mutha thumpr big mutha thumpr or big bad mutha thumper? I ask because just about all of these posts are not making any sense at all. These are hydraulic cams meant for low compression smog dogs so they have a good sound.They have increased the duration to add a choppy sound but the duration at 0.050 is still quite tame.My blue haired mothers daily driver runs more lift and more intake duration.On your cam they added a bunch of exhaust duration so it sounds nice. The thumpr says straight from comp cams to use the stock converter.The big thumpr and big mutha thumpr say to use 2000 rpm stall and 2500 rpm stall respectively. As to all the carb talk your carb is perfectly fine,I have run Holley 650's on 454's and a 1050 Dominator on a 327.The carbs size sets the amount of air available to the cylinders nothing more nothing less. The smaller carbs give good bottom end and nice driving habits as the airs velocity is at its optimal range at lower rpm,The big carbs allow peak HP at maximum rpm because they allow the cylinders to fill at very high rpm levels that would be restricted or choked off by a smaller sized carb but they are lazy in the lower rpm range.This ain't rocket science were talking about here. And by the way the jets in your carb control the fuel not the carbs cfm rating.Small jets in a big carb means burnt pistons at high rpm.Big jets in a small carb means fouled plugs poor mileage and a lazy motor. The idle screws as the name suggests only control your idle hence the name. What happens is guys tend to twist the idle rpm up and actually go past the idle circuits range as I pointed out earlier.The carb thinks you are driving down the road when your not and with the high idle the convertor locks up thinking your cruising along when your not. The fix is to start over with the carb returned to its baseline settings and to follow the advice from Quick Fuel Technology at (270) 793-0900.Call them from your cell phone and do the work while they talk to you. This is straight from Comp Cams Hydraulic-(Thumpr™) High performance street, stock converter ok, best with 2000+ converter and gears, choppy/thumping idle, They list an operating range of 1900 to 5600 rpm the same as a 290 HP crate motor or any typical hydraulic motor from 1955 to the present. |
03-27-2013, 11:55 AM | #21 |
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Re: Engine help please!!!
He showed the smaller of the three thumpr cams really the issue isn't that the cam is all that big (it isn't except exhaust) its that the lobe separation angle is real small. 107 degrees. THAT'S ALOT of overlap. They say they can be used with the stock converter and that's true. And I'm doing it right now in fact in a 400. But I have a single plane intake a 750 demon but high comp pistons and ported heads. This cam really is a modified circle track cam with some old school design with just some newer ramp profiles
The converter being grabby when stock makes this really hard to pull off since we have to tune it as if its a bracket master cam or such. His carb will work no doubt The two things we are fighting most is compression and converter stall. The low compression is going to make this engine run like a wet noodle the high overlap means we need much more initial than the cams size suggest and a looser converter will help keep it from dying at idle. No matter what we need to make changes to get it to work with the cam or change the cam out Posted via Mobile Device
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03-27-2013, 12:14 PM | #22 | |
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Re: Engine help please!!!
Quote:
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03-27-2013, 12:33 PM | #23 |
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Re: Engine help please!!!
This is just the thumper cam the smaller of the three. Insidious86 the car will run in idle but when shifted into gear it dies. Does anyone know what it sounds like if the torque converter was stalling the motor out?
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03-28-2013, 07:01 PM | #24 |
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Re: Engine help please!!!
really why? i have the advance in my crew run this way because after extensive tuning and trial and error, this was how to make my cammed big block/auto stop dying when put into gear. hooking it to full vaccum adds timing, putting it in gear causes the timing to drop out by reducing vacuum.
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1977 srw cc lb 396/700r/4:11's/6'' bds lift/ 35's. sold 1986 suburban 350/700r/3:73's 31's: parted out. 1980 silverado swb 5.3/700r/ 2'' drop/ daily driver. sold 1985 c10 long bed 5.3/700r/2'' drop/17" wheels/ daily driver. sold 1970 c10 long bed-new project! getting ready for the 6.0 |
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