DZ302 Backfire - noise from front of engine - Team Camaro Tech
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post #1 of 22 (permalink) Old Nov 27th, 18, 11:41 PM Thread Starter
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Shane Aberdein
 
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Question DZ302 Backfire - noise from front of engine

Hi Everyone - I have a 1969 Z28 with a matching # DZ302 engine. When I went to start today the engine backfired quite badly on initial attempt to start. I the cranked the engine and it started O.K the next time but now there appears to be a light metallic noise coming from the front of the engine near the timing cover area.
I removed the fanbelt but the noise was the same as the noise appears to be a circular motion noise.
Has anyone heard of something similar happening?
Appreciate any feedback.
Cheers Shane
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post #2 of 22 (permalink) Old Nov 28th, 18, 03:14 AM
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kevin
 
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Re: DZ302 Backfire - noise from front of engine

could be timing chain stretch and or teeth missing off the cam gear
have you checked the timing ?
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post #3 of 22 (permalink) Old Nov 28th, 18, 04:41 AM
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Ed
 
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Re: DZ302 Backfire - noise from front of engine

Sounds like it may be time to replace the timing chain. I go with a good double roller setup.
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post #4 of 22 (permalink) Old Nov 28th, 18, 06:29 PM
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Re: DZ302 Backfire - noise from front of engine

pull the valve covers and check the valve springs rockers and push rods

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post #5 of 22 (permalink) Old Nov 28th, 18, 11:30 PM Thread Starter
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Re: DZ302 Backfire - noise from front of engine

Thanks for the feedback guys - I will check the timing, then pull the rocker covers to check the push rods and rockers.
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post #6 of 22 (permalink) Old Nov 29th, 18, 01:06 AM
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Re: DZ302 Backfire - noise from front of engine

I also think timing chain. It is one of those things that never hurts to change anyway. Only way to really check condition is to pull the cover. Hope you find it.

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post #7 of 22 (permalink) Old Nov 29th, 18, 10:27 AM
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Re: DZ302 Backfire - noise from front of engine

Cracked pulley or bad balancer?

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post #8 of 22 (permalink) Old Nov 30th, 18, 06:36 PM Thread Starter
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Re: DZ302 Backfire - noise from front of engine

Hi guys - Have checked the ignition timing and it appears to be O.K. . Also the Harmonic balancer and pulley appear O.K so I guess will need to pull the timing chain cover and check the timing chain and sprockets. Its just weird the noise appeared after a backfire.
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post #9 of 22 (permalink) Old Nov 30th, 18, 07:31 PM
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Mike
 
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Re: DZ302 Backfire - noise from front of engine

Quote:
Originally Posted by MRCOOL_RSSS350 View Post
pull the valve covers and check the valve springs rockers and push rods
I agree with this as a starting point.

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post #10 of 22 (permalink) Old Nov 30th, 18, 07:51 PM
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Re: DZ302 Backfire - noise from front of engine

Quote:
Originally Posted by 69z28302 View Post
I agree with this as a starting point.

X2. Unless you already know there is something wrong with the timing chain, it isn't worth pulling the cover. WAY easier to put valve covers. Besides you KNOW the timing chain has not jumped a tooth or your timing would not have been where it belonged.

One more thing to try even before you start pulling anything apart. Put a stethescope on the fuel pump. When the spring breaks (and they do break from time to time), you will get a light metallic noise from the front of the engine. When you are in the diagnostic stage, always start with the easiest.
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post #11 of 22 (permalink) Old Nov 30th, 18, 09:38 PM
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Re: DZ302 Backfire - noise from front of engine

if the timing is good and hasn't changed or jumping around while you checking it is not the timing chain. I wouldn't be running that engine to much just encase something has dropped down the cylinder like a broken valve or valve guide. take the valve covers off and do a inspection even take the plugs off and see if any are damaged

67 rs/ss 350 original eng,700r4, a/c, tilt, deluxe int,strato bench,Ca.emission,front disk,am/fm,floor clock,17" W/V Ralleys,Toyo T1S 255/40/17, 245/40/17
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post #12 of 22 (permalink) Old Nov 30th, 18, 09:50 PM
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Nick
 
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Re: DZ302 Backfire - noise from front of engine

this happen to my 3 year old truck engine this summer while I was driving. The valve broke and took the cylinder out I din't have time to react to shut it down and it cost me a engine

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67 rs/ss 350 original eng,700r4, a/c, tilt, deluxe int,strato bench,Ca.emission,front disk,am/fm,floor clock,17" W/V Ralleys,Toyo T1S 255/40/17, 245/40/17

Last edited by MRCOOL_RSSS350; Nov 30th, 18 at 10:08 PM.
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post #13 of 22 (permalink) Old Nov 30th, 18, 10:00 PM
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Re: DZ302 Backfire - noise from front of engine

Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

67 rs/ss 350 original eng,700r4, a/c, tilt, deluxe int,strato bench,Ca.emission,front disk,am/fm,floor clock,17" W/V Ralleys,Toyo T1S 255/40/17, 245/40/17
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post #14 of 22 (permalink) Old Dec 1st, 18, 08:31 AM
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Re: DZ302 Backfire - noise from front of engine

Nice carnage. I don't know why, but I always like looking at internal engine damage. I realize this was painful for you, and feel your pain. But, can't help but look at the pics.

A few years ago I filled up my 83 745i (factory turbocharged BMW, gray market car). Started it up and got a horrible loud noise.

Pulled the head and found this on top of a piston. I had built the engine two years prior. An small unaccounted for hose clamp found its way into the intake. It was too large to get past the intake valve, but after two years the screw vibrated all the way out of the clamp and made it past the valve onto the top of the piston. The rest of the clamp was still on the other side of the valve. Was able to save the head.

Sorry for the hijack.
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post #15 of 22 (permalink) Old Dec 2nd, 18, 10:25 PM
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Nick
 
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Re: DZ302 Backfire - noise from front of engine

Quote:
Originally Posted by bilodeaulynn View Post
Nice carnage. I don't know why, but I always like looking at internal engine damage. I realize this was painful for you, and feel your pain. But, can't help but look at the pics.

A few years ago I filled up my 83 745i (factory turbocharged BMW, gray market car). Started it up and got a horrible loud noise.

Pulled the head and found this on top of a piston. I had built the engine two years prior. An small unaccounted for hose clamp found its way into the intake. It was too large to get past the intake valve, but after two years the screw vibrated all the way out of the clamp and made it past the valve onto the top of the piston. The rest of the clamp was still on the other side of the valve. Was able to save the head.

Sorry for the hijack.
you got lucky not so much with me though, I was on the hwy doing 60mph when it happen I knew what it was but I couldn't shut her down having hydraulic brakes and steering, by the time i pulled over it was to late. The valve was a clean fresh break 45 years in the trade never saw another one like it

67 rs/ss 350 original eng,700r4, a/c, tilt, deluxe int,strato bench,Ca.emission,front disk,am/fm,floor clock,17" W/V Ralleys,Toyo T1S 255/40/17, 245/40/17
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