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Author Topic:   help possible carb problem what do you think?
pbrcowboy2
Dirt Freak

Total posts: 380
posted March 13, 2005 09:36 PM  
Dad and i last sunday fired our new motor up motor ran fine all night got the temp up to 180 then shut it down went back tonite to actually break it in and this time when i fired the motor up it ran fine, but i couldnt get the tach to read 3000 im actually tryin t finish breakin this motor in so i can time it.

Now at low idle 1250-1500rpm, the car runs fine but when i up it to say 2000rpm it bogs down then just acts like it runs out of fuel. But then right before it dies i give it gas and it comes back alive but sounds like it running on 7 cylinders then when it reachs idle it sounds great!!

IM gonna time this at 35* at 3500rpm the valve lash is 26 hot and cold and its a mwms #2 cam

help any comments.......ask away guys!!!!

engine combo is 355 flatop with the cam, stock rods, great set of heads "882", 4412 carb, stock crank, stock hei setup

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted March 13, 2005 11:10 PM  
It's because you don't have the motor timed and the first time you start the motor it should be timed right away and never let idle under 2000, or shouldn't even idle, should be reved just a touch here and there for about 15-20 minutes. More then likely you'll be ok but if you start dropping lobes off that cam you'll know what did it. You'll also want around 38 degree's of timing

TEAMPCR
Dirt Freak

Total posts: 238
posted March 14, 2005 06:36 AM  
Check the fuel filter. Had the same problem last year, the guy who plumbed the fuel lines used too much sealant on the threaded fittings and it all wound up in the filter. Dave

pbrcowboy2
Dirt Freak

Total posts: 380
posted March 14, 2005 07:20 AM  
there is a bit of fine rust looking sediment in the fuel cell!!! fuel filter needs cleaned im sure...also when we had the motor running we didnt have our timing light with us we set it by ear.

we get good fuel pumpage out of the squirter!! so i dont think its the carb actually.

when we had the motor running we were revving it up and it never seen 1500-2000rpms it ran near 2500 to 3500rpms sounded awesome and great but we only had it runnin fer about 20 minutes.

i was told that we should only go 35 degrees at 3500rpm yall think 38 will be just fine?

battery is junk wont hold a charge at all corrosion is coverin top of battery so that might hamper it!! we are replacing that!!

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted March 14, 2005 08:16 AM  
when you time it you need to r un it up around 5000 maybe more and time it at 38

waltonjr1
Dirt Forum Champ
Total posts: 516
posted March 14, 2005 08:53 AM  
5000! without a load, I woulden't do that. If your distributor is locked out you can set it at idle, if its stock with the advance hooked up 3000 is plenty.


pbrcowboy2
Dirt Freak

Total posts: 380
posted March 14, 2005 09:27 AM  
what i did last year was distributor was locked out held motor steady at 3500rpm and timed it at 35 worked great for us!!!

everything is basic stock components in this thing too!!!

sbc350
Dirt Full Roller

Total posts: 59
posted March 14, 2005 09:36 AM  
Snapping the throttle and bringing the RPM's up to 5000 would be ok, just don't leave it there. You need to get the RPM up when setting the timing because your cam will twist a little from the stress of the valvetrain. You're measuring the timing off the balancer (front of the crank & cam)and the spark is coming from the distributor which is running off the back of the camshaft. Set your timing at idle and them bring up the rpm, you will see the timing retard a couple of degrees.

Speedracer92
Dirt Full Roller

Total posts: 70
posted March 14, 2005 10:19 AM  
35 or 36 degrees at 3000 is what we have always used.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 14, 2005 11:15 AM  
There will also be play in the gear at the camshaft and distributor. revving it up helps take the slack out of it. A lot of cams woudl benefit by using a oversize distirbutor gear to hold the timing better.

Revving and holding it wont hurt it. I wouldnt wing it wide open and hold it there, but opening the throttle and holding it to 4-5000 long enough to check timing is fine.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted March 14, 2005 11:29 AM  
Also remember we don't race at 3000 rpm. Holding at 5000 would indeed start messing your internals up, but thats after a long time. It won't ever hurt the motor to hold it at 5000 for 10 seconds to get a good solid reading of your timing, just don't goose the thing. Buddy, the only thing that will dictate how much timing you can run will be your pistons, beings that you are running 360 sport mod, I would still run 38 degree's of timing. We ran upwards of 40 a few times last year.

Also you are cammed wrong for the class and motor your running

NJantz
Dirt Forum Champ
Total posts: 755
posted March 14, 2005 01:44 PM  
I've always ran mine up to about 5000 just long enough to get a timing reading when the distributor wasn't locked out.

waltonjr1
Dirt Forum Champ
Total posts: 516
posted March 14, 2005 03:34 PM  
You may get away with it, but theres no sense in it. 3,000 is plenty enough to get a good timing reading. I ran the same motor for 4 years without changing a ring or bearing. The little things pay off in the long run.


dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 14, 2005 03:59 PM  
5000 is 5000 whether on the track or in the shop. I assume your turning more than that on the track arent you? Plus on the track its under a load whereas in the shop it isnt. If you are turning 7000 on the track your motor is spending way more time at 5000 or above during 1 lap than the time it takes to check the timing. If you are worried about revving it to check timing then I would be scared to death to put it on the track.
Some stock distributors may not fully advance until well into the 4000 range depending on the weight setup. The only way to check it is to rev the car until it quits advancing then you know it is fully advanced. 3000 may not cut it on some distributors, and you'll end up with more timing than you want at 5000 up.

Locking the dist is the best thing you can do. Then you set the timing and thats what it is no matter what speed you check it at. You dont have to worry about whether the advance mechanism sticks not allowing enough timing or somehow allows more timing or jsut flies apart all together. Most performance distributors have the advance in by 3000-3500 or so and I would venture to say that you never get that low on the track so it doesnt matter, theoretically if your advance is working correctly you are fully advanced all the time while you are racing anyway.

[This message has been edited by dirtbuster (edited March 14, 2005).]

waltonjr1
Dirt Forum Champ
Total posts: 516
posted March 14, 2005 05:08 PM  
To each his own but you will not make me beleive that reving your motor that high without a load on it is not bad for your motor. Hold your engine at 7 grand in the driveway and see how long it last.


Blackgold
Dirt Full Roller

Total posts: 71
posted March 14, 2005 07:06 PM  
Have any of you had a fan blade go past your ear or thru your hood when playing with the throttle? I've seen it happen twice. Both times the guys were lucky. I'm always careful to stay out of line with the fan when rapping the engine or timing at the higher rpms. I think that the important thing with the timing is to be sure that the advance is maxed out or locked. I use 34-36 on 355s and no more than 34 on my 406.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted March 14, 2005 08:24 PM  
Black gold good point...
Walton we are not holding the car at 7 grand, and yes, if you did it will spit something, if you hold it there. your at 5000 for maybe 10 seconds while your timing it, not 7000 goosing it.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 15, 2005 07:35 AM  
black gold,
To answer your question, no i havent had that happen, in fact I havent seen a fan fly apart ever.
What kind of fans are they? Stock fans or aftermarket, plastic, aluminum etc? I could see it happeneing with plastic or aluminum from stress or having the rivets break on a stock one. The fan we use is a 4 blade fan basically 2 pieces of steel overlapping ea other and then bolted through ea to the water pump. The only way the fan will come off is if the water pump does.

walton
Like posted above, your not holding it at 5 grand for 5 minutes. How long does it take to get a ttiming reading 3-4 seconds or so.


waltonjr1
Dirt Forum Champ
Total posts: 516
posted March 15, 2005 07:55 AM  
You stated that 5 grand is 5 grand in the shop or on the track. This is not true. I agree that it probally wont hurt the engine to hold it there for 5 seconds but it is overboard and not neccesary.


Xtreme12x
Dirt Forum Champ
Total posts: 874
posted March 15, 2005 08:27 AM  
Walton, 5 grand is 5 grand no matter where it is. A load on the engine will not change the timing at all. If you've got a powerglide bolted up it gives it a little bit of a load in park. To get an accurate timing reading you need to get the rpm up to 5000 and then run it up a little more just to be safe. I've seen distributors start to mess up past 5500 rpm and gain or lose timing, or even jump around. Remember we don't race at an idle so you wouldn't want to time it or judge how it runs at an idle on how it'll run on the track.

waltonjr1
Dirt Forum Champ
Total posts: 516
posted March 15, 2005 10:43 AM  
Im saying that reving a motor that high without a load is bad and pointless especially with a locked distributor. I know the timing will be the same on the track or off at 5 grand. Lets just agree to disagree. You set your timing at 5 grand and I will continue to set mine at 3


Blackgold
Dirt Full Roller

Total posts: 71
posted March 15, 2005 12:50 PM  
The fans that I saw come apart had single blades come loose or break. One was a flex fan and the other was a stock steel fan on a camaro. The flex fan was'nt rated for the high rpms. I think it was rated for 7000 or something like that and by the time you overdrive it with stock pulleys it was probably turning considerably more than that. This probably isn't a common happening, but something to be aware of.

sixwillwin
Dirt Freak

Total posts: 493
posted March 15, 2005 01:35 PM  
this post is getting stupid.......everybody do whatever they want as far as timing, I'm with waltonjr1, I'll keep doing mine at 2500-3000 no matter what anyone else says.

------------------
The Joy of Six website

Speedracer92
Dirt Full Roller

Total posts: 70
posted March 15, 2005 02:43 PM  
I agree! I'm going to set my timing at 500 rpm and then i'm going to run it up to 9,000 and if it blows i won't even worry about the timing anymore.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 15, 2005 03:32 PM  
waltonjr,
I agree that with a locked distributor you only need to raise the rpm enough so that you can get a steady reading.
My point of revving the motor was that with a functioning advance mechanism you may have to rev it pretty high to check to make sure it is fully advanced. Again I think the safest way is to lock the advance and forget about it.



Istock66
unregistered Total posts: 2007
posted March 15, 2005 05:38 PM           send a private message to dirtbuster   Edit/Delete Message   Reply w/QuoteBBBBBB
you all are better than me if you can see the tack while setting the timeing..

I accelerate my motor by hand until it stops advancing bump the dist to where I want it, then shut it down and tighten the dist, and restart and recheck it.


stew6371
Dirt Full Roller

Total posts: 38
posted March 15, 2005 10:22 PM  
3000 should be plenty for setting timing. i always set my timing or advance to be all in by 3000 rpm.

ARR
Dirt Full Roller

Total posts: 68
posted March 17, 2005 07:04 PM  
Sorry to interupt your timing, but I have the same problem. When I hit the starter it fired right up, took it to 2000 rpms, set the timming at that rpm and ran it for 20 min. The rocker arms seemed kind of loose as they were just loud enough to here them and about half way through the breakin the sound of the engine changed, something I never experienced before when breaking in an engine. I reset the valves after the 20 min when the engine was up to temp and run it again. It idled good but when I reved it up it was bogging down. Any more ideas? Some one told me it's possible to bend push rods on a breakin?

One more thing, tonight I turned the engine over and watched the rocker arms. All of them are moving up and down the same distance. Don't seem to have flat lobes.

[This message has been edited by ARR (edited March 17, 2005).]

[This message has been edited by ARR (edited March 17, 2005).]

pbrcowboy2
Dirt Freak

Total posts: 380
posted March 18, 2005 08:22 AM  
extreme i went and put my cam from last year back in my motor put on my ported and polished heads on now im not sure if they have been milled but now get this......my heads that i had on were stock "882"'s with .600 springs now i put on these "882"'s that have been ported and polished and now we cant get the valve s set at all the polylocks are at their there very ends we can get no more adjustment in them we got some of the valves set but then some of the others we cant get set at cold!!

we think the pushrods might be the wrong length but if you mill yer heads i would assume u have to run shorter pushrods

[This message has been edited by pbrcowboy2 (edited March 18, 2005).]

[This message has been edited by True Blue (edited March 18, 2005).]

ryan
Dirt Forum Champ
Total posts: 776
posted March 18, 2005 04:16 PM  
You really need to get an adjustable pushrod and check your geometry

Blackgold
Dirt Full Roller

Total posts: 71
posted March 18, 2005 06:42 PM  
Pbrcowboy, I'm not sure I understand whether you can't get the rockers far enough down to get the right settings or if they are too tight before the polylocks catch threads. We had a set of skrew-in studs installed and the machinist didn't machine deep enough to allow for the guide plates that we used and when I put the rocker arms on and tried to set them it was like the studs were too tall. Had to take heads back off and have them machined down the thickness of the guide plates. This could possibly be your problem. Ed

Istock66
unregistered Total posts: 71
posted March 18, 2005 07:18 PM           send a private message to Blackgold   Edit/Delete Message   Reply w/QuoteBBBBBB
buddy,

I have a pushrod length checker you can come borrow it.

I also have .050 .100 .150 .200 and stock length pushrods here so you can see what length you need.

Studs come in diff lengths for screw in studs depending on whether you have roller rockers or not. Its possible your studs arent deep enough or are a diff length.

Ive also got some lock nuts with the allen lock in the end that are diff lengths than some others I have so that could be your problem, they do come in diff lengths also apparently.

Either way call me if you want to come by and borrow some stuff to get it right. Ill be in beatrice saturday all day, but home sunday.

In all the motors Ive ever built, I have only ever had one that used stock length pushrods. Last count Ive put together really close to 20 motors.

dirtdoc
Dirt Roller

Total posts: 8
posted March 22, 2005 07:57 AM  
if you are running a bone stock hei, it makes no difference 3000 or 5ooo they counter weights will be fully open anywhere above 3400 and anything more is useless let alone senseless

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