excessive backfire and flames! also rocker arm knock - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-17-2010, 09:19 PM
chevykid90's Avatar
454, what turns your crank?
 

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excessive backfire and flames! also rocker arm knock

so i adjusted my valves again today, using the method of losening valve until noise is heard then tighten 1/4 turn. now the even (passenger side) was really easy. but when i tried to do the odd (driver) side there was a lot of noise i even tried tightening all the valves simultaneously but i could not get the noise to go away. the noise i am talking about is the ticking heard from the valves. before i adjusted them i had a slight backfire but nothing too big and not very often. now i have a backfire that happens a lot, and sometimes i cant even get up to speed because of it. and also there is an exhaust rocker arm for piston #5 that is hitting on the valve cover. but it only happens sometimes. doesnt happen when idling out of gear but happens when idling in gear. it will do it with slight throttle but not with full throttle. and i seemed to have noticed that when it starts ticking is when i have the backfire. i am starting to go kind of insane with this build. i just want the car to run right. btw, its a 454, with flat top pistons, performer RPM cam.

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Old 08-18-2010, 03:11 AM
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are you starting with #1 and working around u should be using a guage intake .oo10-.0037 exchaust .0010 - .0047 ok this what i get from my book bring #1 up to tdc then do these vavles exhaust 1,3,4,8 intake 1, 2 5 ,7 rotate the crank one full revolution untill the timing pointer is on O with the crank shaft.... in #6th cylinder firing psition. then do these valves exhaust 2,5,6,7 intake 3,4,6,8
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Old 08-18-2010, 05:20 AM
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Are the pushrods oiling the same on both sides of the engine?

There are two passages located in an annular groove in the rear cam bearing journal that feed oil up to the lifters. If the one side is occluded, it can cause a lack of oil to that side.



But in any event, the valves still do not sound to be correctly adjusted. A vacuum gage will show a rapidly bouncing needle if a valve is off it's seat. But don't continue to drive like this- an open valve can overheat if the cylinder is firing- it needs "seat time" to cool itself.

You can also do the lifter adjustment w/o needing to hear anything. You can easily FEEL the shock coming up through the valve train when there's clearance between the rocker and pushrod. If you place a thumb on the rocker arm over the p-rod cup, you'll feel what I'm talking about.

Using both feel and listening for the tell tale clacking of a loose lifter/rocker will surely tell you when there is and isn't clearance.
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Old 08-18-2010, 10:09 AM
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454, what turns your crank?
 

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the oiling seems to be prity much even, except it seem like the back half of the motor gets a little more oil than the front. i am thinking its just because the motor sitting at an angle, or just the design of the oiling system

thats also were i am really confused at, m vacuum gauge sits very steady. there maybe a little jump of about 1-2lb's but that just because of my cam. but i can see right away when i take a valve too far that needle starts going everywhere.

anyone think of reason why a rocker would be hitting the valve cover?
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Old 08-18-2010, 10:22 AM
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Stock rocker arms, or aftermarket?? Roller tip?? Full needle bearing roller rockers??
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Old 08-18-2010, 10:35 AM
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454, what turns your crank?
 

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i guess i could have stated what they were lol. they are just stock rocker arms, 1.7:1.
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Old 08-18-2010, 10:41 AM
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454, what turns your crank?
 

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it has been hitting for awhile because when i pulled the valve cover off i could see the indent but i could never hear it so i didnt know. but now you can definitely hear it. its at the back of rocker, like the pushrod is pushing it too far up.
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Old 08-18-2010, 11:05 AM
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Stock or aftermarket valvecovers??
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Old 08-18-2010, 03:55 PM
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Was the valve train geometry/push rod length ever checked and verified to be correct?

I'd be measuring the offending valve's pushrod to see that it's the same length as the others- and that they ALL were the correct length for correct geometry.
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Old 08-18-2010, 11:45 PM
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454, what turns your crank?
 

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they are aftermarket valve covers but they are just the stock height.

and it was a budget build so i just used the same rockers and p-rods that i got when i bought the motor. just inspected to make sure they were not bent or warped.
the only thing i did was make sure the block was still good, put in new bearings, rings, and valve springs to fit the new cam. i should have checked but i assumed they were good since it was a running motor before i bought it.
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Old 08-19-2010, 03:46 AM
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Quote:
Originally Posted by chevykid90
they are aftermarket valve covers but they are just the stock height.

and it was a budget build so i just used the same rockers and p-rods that i got when i bought the motor. just inspected to make sure they were not bent or warped.
the only thing i did was make sure the block was still good, put in new bearings, rings, and valve springs to fit the new cam. i should have checked but i assumed they were good since it was a running motor before i bought it.
OK, "good" doesn't necessarily mean "correct".

By that, I mean that, because the pushrod length is what sets the relationship of the rocker arm tip to the valve tip, they need to be the correct length. So a "good" p-rod can still not be the "correct" one.

I hope you see what I'm trying to say here- this is not a negative reflection on your work- a lot of guys do exactly as you did when doing a budget rebuild. But when there's problems, then you need to dig deeper.

If you do a search for valve train geometry, you will find the details of what's involved.

COMP CAMS has a page on the subject. It's as good of a place as any to start.

Good luck.
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Old 08-19-2010, 10:44 AM
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454, what turns your crank?
 

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i completely understand what you are talking about. its just that it never hit the valve cover before like that. and its the only one that does it. i was going to spring and buy new p-rods anyway here soon, so this can be my excuse to do it early. any recommendations??
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Old 08-19-2010, 11:00 AM
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Quote:
Originally Posted by chevykid90
i completely understand what you are talking about. its just that it never hit the valve cover before like that. and its the only one that does it. i was going to spring and buy new p-rods anyway here soon, so this can be my excuse to do it early. any recommendations??
I would use a p-rod w/a thicker wall- something like the SUMMIT brand, 3/8 OD w/a 0.080 wall. A set is about $85. These are stock length though. If you find you need a custom length you'll have to go w/a different maker like Howards or Manley.

Comp and I believe Manley have adjustable p-rods (or you can make your own from an old pair of p-rods) to check for the correct length. Comp also has a tool that is used instead of a rocker arm for checking for the proper length. I've never used one, so I cannot say how it works.

Last edited by cobalt327; 08-19-2010 at 11:05 AM.
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Old 08-19-2010, 10:02 PM
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454, what turns your crank?
 

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ok, i will look more into it.

but wouldn't have given me problems when i first starting running the motor? it only started hitting after i adjusted the valves.

going to buy a new set when i get new rocker arms.
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Old 08-20-2010, 08:35 AM
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Quote:
Originally Posted by chevykid90
ok, i will look more into it.

but wouldn't have given me problems when i first starting running the motor? it only started hitting after i adjusted the valves.

going to buy a new set when i get new rocker arms.
It was probably real close or just touching before the valve adjustment. Then after the adjustment, the rocker may have been set a tad higher, add that to retightening the v-covers down on the gaskets a couple more times- compressing them- and there you go.

Be sure the stud's not loose. The readjusting of the valves should have put the rocker back lower if it was- but SOMETHING is causing it.
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