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Old 11-05-2005, 01:17 AM
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350 pop noise (new cam, heads, ect)

I just did my first engine build, and now it is starting to take more time than i expected. My problem is that it now pops through the exhaust at any rpm but will more or less just sound like a miss at idle. It seemed to shoot flames out the pass side more when i had open headers. Engine specs--( 350 gm replacement motor with stock pistons and 15-20 thou miles on it, stock dished pistons, xe 268h-10 cam, tfs 195 cnc cc heads 202 160, comp 1.6 rockers, (STOCK PUSHRODS), rpm intake with air gap, and a 4 year old elderbrock 600. I have ruled out plugs, wires, electrical, timing, and rockers. Could it be that the pushrods are wrong, flat cam, or lifters. I originally had three cyl too tight and it missed bad, but I have fixed that problem. It seems to just pop out the exhaust now and a little out the carb.

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Old 11-05-2005, 01:22 AM
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I also used a .015 head gasket.
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Old 11-05-2005, 01:25 AM
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I would pull the covers and watch the rocker travel for a wiped lobe.
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Old 11-05-2005, 01:33 AM
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All seem to be fine just by looking and not measuring. I also almost know for sure that i used the right key slot on my new double roller and everything is in line. I also tried 1.5 rockers and it is still bad.
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Old 11-05-2005, 03:28 AM
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Quote:
Originally Posted by David03
I also almost know for sure that i used the right key slot on my new double roller and everything is in line.
Did you turn the motor over and watch at what point #1 exhaust valve closes and intake valve starts to open? The valves on #1 cylinder should be at that point when the crankshaft is at top-dead-center on compression stroke on #6 cylinder {every 2nd revolution of the crankshaft since it's a 4 stroke motor}.

Did you install new lifters?

brand new lifters will "push in easily" when they are not "primed", or don't have any oil in them. when you adjust the rocker arms on a new set of lifters, they do the same thing, "push in easy". therefore, you set them dry, and wind up with the lifter inner piston bottomed out. if you set them at the bottom of the travel, then they have no room to adjust if you get them too close, causing a miss from valve sealing leakage. what i usually do is set the rocker arm adjustment at the point where the clearance is just barely being taken up by your adjustment , and then back off the rocker adjustment about a 1/4 turn in order to let the lifter piston run at fully extended position on start-up. this will let the cylinder of the lifter fully load with oil from the pump. it may clatter like h$ll on the initial start up, but after the lifters have had a chance to fully prime, then you can adjust them as you normally would to get rid of the clatter.
also

if you want to make sure the lash is set with the lifter all the way 180 degrees opposite of the cam lobe, bring #1 piston up to top-dead-center on exhaust stoke. this will be where the exhaust valve closes and the intake is just beginning to open. at this point #6 clinder will be at top dead center on power stroke.adjust the rockers on #6 intake and exhaust.
just follow the firing order. turn the crankshaft 1/4 turn. #8 will now be closing the exhaust and opening the intake valve. at this point adjust the rockers on #5 cylinder intake and exhaust.
another 1/4 turn on the crank adjust #7 I and E.
another 1/4 turn on the crank adjust #2 I and E.

the next 1/4 turn will put the crankshaft back on the timing mark but this will be #1 TDC on power stroke. #6 rockers will be closing on exhaust and opening on intake so you will adjust the rockers on #1 cylinder.
another 1/4 turn on the crank adjust #8 I and E.
another 1/4 turn on the crank adjust #4 I and E.
another 1/4 turn on the crank adjust #3 I and E.

that's the way i do it. takes a little longer but it always works for me.

Last edited by mike 96 ws6; 11-05-2005 at 03:33 AM.
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Old 11-05-2005, 08:22 PM
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Yes i used new comp lifter that came with the cam. I have set my rockers several times. Cant remember how i did it the first time, but it was going by what comp cam recommended. This resulted in # 2,4,3 cyl not working when i first started it up. I turned them back 1 to 1.5 rev and they started to work. I do not now how they got so tight since i had only presoaked the lifter and pushrods the first time. Later i reset the valves by the book doing 4 ex and 4 int valves at a time and turning it one revolution to #6 tdc then adjusting the others. I left it so the up and down movement was gone and then .25 turn. I did this twice and had neg results. After this i did it the messy way and had poor results. I know a guy that talked to an engine builder and he said that popping could come from to short a pushrod, or the keyway being off, or bad cam. I was tolled to watch the number one cyl valves. They should be closed at tdc and should be right together at 180 degrees more from that when turning the crank. Is this what you were saying. I appreciate the answers guys.
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Old 11-05-2005, 08:30 PM
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My pushrods are 7.750. Cam lift with 1.5 rockers .477 int .480 exh. With 1.6 rockers .506 int and .512 exh. Tfs recommends 7.900 inch pushrods with .039 head gasket as a starting point. This is going off of a piece of paper though. I used a .015 head gasket and never measured push rod length.
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Old 11-07-2005, 09:01 AM
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Quote:
Originally Posted by David03
I was tolled to watch the number one cyl valves. They should be closed at tdc and should be right together at 180 degrees more from that when turning the crank. Is this what you were saying.
Nope. The #1 rockers will both be closed all the way from ~bottom dead center after the intake stroke, until ~bottom dead center after the power stroke. So you can't tell much by knowing when they are closed {or "right togther} since they are in that position most of the time.
You need to know exactly when they rock open and closed.

The #1 rockers will be rocking {exhaust closing / intake opening} at top dead center, {but not on compression / power stroke}, which will be when the timing mark on the crankshaft is at the TDC mark.
The #6 piston will also be at TDC at this same point, although the #6 piston will be at TDC on the top end of the compression stroke / starting power stroke.
This is the position that you need to set the rockers on #6 cylinder since it is at fire position and both lifters are at the bottom of the cam lobes.

FYI: The crankshaft will need to be turned a full 360 degrees {1-turn} in order to get the #1 piston at TDC in fire position, which is where the rockers rock on this cylinder and which is where your cam gears should be aligned and the distrubutor should be initially installed.
But;
the proceedure I gave above is given in 1/4 turn-of-the-crankshaft increments in order to set initial valve lash for all 8 cylinders without having to turn the motor over more than 2 revolutions of the crankshaft.
Also;
Since you may have already depressed the lifter inner pistons past the setting they need to be at, then I would suggest first running the motor while backing off all adjustment nuts in small increments, {about 1/2 turn at a time} until they each individually start clicking. If they are not at the top of the lifter bore, then the oil will pump the lifter piston up and quieten them within about 5 or so seconds. Then back off some more {1/2 turn} and it will start ticking again. When each rocker gets to the adjustment point when it continues to click, {at the top of the lifter bore} leave that lifter there for now.
After all 8 rockers are clicking continually, shut the motor off and adjust the rockers as I posted in the previous post.
I know that's a lot of stuff, but it is a fail proof way to get them right the first time.
Hope this helps.
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Old 11-07-2005, 09:14 AM
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Quote:
Originally Posted by David03
I know a guy that talked to an engine builder and he said that popping could come from to short a pushrod, or the keyway being off, or bad cam.
I doubt you have too short a pushrod length causing a problem on only select cylinders.
If the comp cam is new, I would not think that is the problem either.
If the keyway is off, then that could certainly cause a popping noise, but again, not necessarily cylinder specific.
The adjustment is a more common problem and should be ruled out first.
JMO
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Old 11-07-2005, 05:25 PM
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How bad is the popping? You could have a crossed spark plug wire. The #5 and 7 cylinders are right next to each other in the firing order and it can be easy to swap the wires by accident.

This may sound like a strange question but I have had it happen to me. How is your exhaust routed? I installed an engine in my Blazer a few years ago and everything ran fine but after I had the exhaust installed I couldnt get rid of the popping sound that sounded like a backfire. I tried everything to find the problem. My dad ended up pointing out that one up the turn downs was aimed right at the rear axle and the exhaust gas was making a "slapping" sound as it exited the pipe and bounced off the axle housing . I relocated the exhaust from the mufflers back and it went away.


As for adjusting the valves. Whenever I set valves I always bring one cylinder to TDC compression and adjust the valves on that cylinder. When a cylinder is in overlap you can adjust the companion cylinder because it will be on TDC compression. Ex. when the #1 cylinder is at TDCC both valves will be closed and the rockers will be loose (I have solid lifters) at the same time the valves on the #6 cylinder will be in overlap. It takes a little longer but doing it that way I know Ive set all of the valves correctly.

Last edited by Blazin72; 11-07-2005 at 05:32 PM.
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Old 11-07-2005, 08:10 PM
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I think i will try it your way mike. I took off my oil filter and found no metal shavings. I will drain the oil and check for metal also.
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Old 11-08-2005, 07:15 AM
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Quote:
Originally Posted by Blazin72
Ex. when the #1 cylinder is at TDCC both valves will be closed and the rockers will be loose (I have solid lifters) at the same time the valves on the #6 cylinder will be in overlap.
Overlap is probably a better word than I used {rocking}.
so if you don't mind I'll use it.

David, I'll list an easier to follow table below, what valves to adjust while which cylinder is at TDC at valve overlap position.

First column is clyinder @ TDC while valves overlapping.
Second column is the cylinder to adjust valves on at that point.

#1 TDC overlap / Adj. #6
#8 TDC overlap / Adj. #5
#4 TDC overlap / Adj. #7
#3 TDC overlap / Adj. #2
#6 TDC overlap / Adj. #1
#5 TDC overlap / Adj #8
#7 TDC overlap / Adj. #4
#2 TDC overlap / Adj. #3

Just follow the firing order for your SBC motor.

Be sure to run the motor while backing off the present adjustments {as described above} in order to get all the lifter inner pistons at the top of the bore. Your motor is going to make lot of rattling when you do this so you may need a piece of rubber hose about 5/16" x 3' or so. You can hold one end of the hose to an ear and the other end close to the contact point between the rocker arm & the valve stem to isolate the ticking for that particular cylinder your adjusting. Kind of like a stethescope.

Last edited by mike 96 ws6; 11-09-2005 at 07:15 AM.
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Old 11-08-2005, 04:56 PM
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You got a leaky spark tube...
 
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Quote:
Originally Posted by mike 96 ws6
First column is clyinder @ TDC while valves overlapping.
Second column is the cylinder to adjust valves on at that point.

#1 TDC overlap / Adj. #6
#8 TDC overlap / Adj. #5
#4 TDC overlap / Adj. #7
#3 TDC overlap / Adj. #2
#6 TDC overlap / Adj. #1
#5 TDC overlap / Adj #8
#7 TDC overlap / Adj. #4
#2 TDC overlap / Adj. #3

Just follow the firing order for your SBC motor.

You explained it better than I did.
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Old 11-09-2005, 08:48 PM
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sorry mike it is still popping out carb and exhaust. What is the next step to take. Maybe check to see how the valve tip is being contacted, new carb or jet. Man i am ready to drive this thing and break it in.

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Old 11-16-2005, 04:54 PM
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Just got through talking to boyds racing engines in oklahoma. They said that stock pushrods did not sound like a problem. I said that i used the springs that came with the trick flow heads. He said that those springs were weaker then what they advertise and might be suffering from coil bind. How do you know if your having this problem and should i use the springs that the comp cam came with.
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