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excessive backfire and flames! also rocker arm knock

8K views 53 replies 8 participants last post by  chevykid90 
#1 ·
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.
 
#2 ·
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
 
#3 ·
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.
 
#4 ·
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?
 
#10 ·
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.
 
#11 ·
chevykid90 said:
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.
 
#12 ·
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??
 
#13 · (Edited)
chevykid90 said:
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.
 
#15 ·
chevykid90 said:
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.
 
#16 ·
ok so now that i have adjusted the valves there is a really loud "pop" coming from the odd side. i cant pinpoint what piston it. its fine if i hold it steady but when i let off it does it. i think it could just be a back fire and in my shop it sounds like its coming from the front with the echo. its not like metal on metal, its hard to try to explain. maybe my timing is off now?? oh, btw there is now backfire through the carb anymore.
 
#17 ·
just checked the vacuum and its holding steady at 15-16. drops normal to 0 when i open the throttle and when i let off it goes up to about 25 then drops back down to 15 and sits there.

took it for a test drive and it almost sounds like something tumbling around. or something spinning and hitting something else. i know i didnt drop anything down into the motor. and its coming from the top end.
 
#19 ·
I'd be checking the stud length also. If it was lifting before the build as could be indicated by the track marks on the inside of the valve cover. Of course I am assuming this cover has not been dented, could prove that by swapping the drive/pass.

Then you put a cam in that had a higher lift . Did not say if you replaced the springs, none the less, if the stud was pulling up with the old cam and old springs, then a new cam with a higher lift will further lift the stud up and cause your rocker to hammer louder and more often. Sounds like you got the adjustments handled.

Need to figure out one thing at a time, fix one problem and go to the next. Jumping all over will just confuse the issue. Go after that rocker hitting the cover, that is not right plain and simple.
 
#20 ·
i did swap out the springs to handle the lift of the new cam, and also because i didnt know what kind of condition they were in either.

so then how would i go about fixing the stud lifting? buy new studs?

i am new to the whole building engines, as this being my first build on my own.
 
#21 ·
so i just pulled the valve cover off and i now have another rocker hitting the top and and one that is rubbing up against the vent housing. (not sure of the technical name, but its a rectangular box on the inside of the valve cover. baffle maybe??)
and now with my homemade valve cover (one i cut the top half off so i dont get oil everywhere when adjusting valves) the metal "pinging" isnt there.

so now what??
 
#22 ·
Sounds like your chrome valvecovers are just like a lot of typical cheap chrome jobs, made in China or Taiwan, they never fit right and either leak or distort and rub after being installed a couple times. The fact that your stock cover clears and the noise is gone confirms this.

Big block studs are threaded studs, not pressed-in studs like small blocks are, it is just about inpossible for them to pull out. You will definately know it if one did strip the threads out of the head, it and the rocker would just be laying there in a pile when you pulled the cover.
 
#23 ·
yup these covers were made in Tawian. and after fijiting with them i figured out why i always heard ticking when i tried to adjust the valves. the rockers were hitting, so i could never tighten them enough to get the ticking to go away, (hence the valves being to tight and backfireing) now that i have taken out the "baffle" no more ticking, and after messing with my homemade one again taking out the "baffle" there is no more ticking and i can hear when the valve is too lose.

what a relief this is, i thought something major was going on. turns out just cheap valve covers. (wont make that mistake again)
 
#24 ·
screw in studs answers that. Lets refresh, the valve noise is gone the adjustment took care of that?

After market valve covers could be undersized, the fact that another rocker is now hitting sure sounds like that be the case. Why you may ask did that that happen, pulling the valve covers on and off you have changed the thickness a bit, compressed the gasket. You can get thicker valve cover gaskets . Look here :http://www.summitracing.com/search/...e/CHEVROLET/Engine-Size/7-0L-427/?Ns=Rank|Asc
there are a load of them and click on the MORE link and find the thickest set for the money you want to spend, I run roller rockers under stock hight valve covers and had to get a thicker gasket set. Not an uncommon part to find, however the parts boxes AZ, Oreally types might not have them .

You are getting there it just takes some time and persistence for sure. Keep us posted.

Without the oil baffle it will throw oil out the breather and the pvc will suck oil also, you need that.
 
#25 ·
yes, valve noise is completely gone. and so is the backfiring (atleast idling anyway) have not taken it for a test drive since the adjustment. but i think it will still backfire since my shooters are too big. and yes they are the cheap chines imitation crap, i will be investing in some thicker gaskets.
 
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