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Discussion Starter #1
I have a 1970 455HO all original w/ the motor rebuilt about 300 mls on it. Over a year ago I did a sprint on the hwy and took it up to about 100 mph. After I got it home I heard a slight tapping or knocking and thought it was in the valvetrain. Put a stethescope all over it and cant locate it. Felt it was a lifter and wanted to put in a Ram Air 4 cam anyway which I did. Lifters, cam, and timing set from Comp Cams. Still there. Never gets louder and I can't really hear it when I rev it. I have had rod knocks before and this isn't like that at all. And a rod gets louder when hot and worse over time. So I put STP honey and 20w/50 on an oil change which I figured would quiet it down if I was wrong and it was a rod and it is exactly the same cold and hot. No change. Well I had it on my new lift running and had the stethescope all over it again and the sound seemed to strongest at the fuel pump. So I figured I would change it out only $31.00. No luck. The essentric on the timing gear for the fuel pump seemed fine when I did the cam. Are there more than one size and mabey it's smacking the fuel pump arm when it rides around? This is now driving me insane. Any ideas or known issues? Help!!!!!!!
 

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Discussion Starter #3
No forged pistons. I know they knock a bit especially cold. Wrist pin?? When I put the stethescope all over the motor in doesn't seem to be louder along either side high or low.
 

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A good test to see if it`s a wrist pin or a connecting rod knocking, rev and hold the motor to about 2,000rpm (you should be hearing the knocking) then stab the throttle hard and then let off quick and pay attention to the knock when it revs up. If the knocking gets worse when it`s rev`ing up, it`s a connecting rod, if the noise goes away as it`s rev`ing, then it most likely is a wrist pin. Theory being if it`s a wrist pin, when the motor revs it puts the wrist pin under a load and the noise goes away. I would also try to run it just a bit with the fuel pump off just to eliminate that as the culprit too.
 

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Discussion Starter #5
I'll giveit a try tomorrow, starting to sound like it may be a wrist pin but of course i'll be pulling th efuel pump first. Will it run w/o pressure in the fuel line just being fed fuel?
 

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Discussion Starter #6
Well it was blue printed and built by a pretty good shop, the wrist pins are pressed in do you really think it's slopping around that soon w/ so little mileage. Seems like that would be a high mileage condition> The rod I agree could pop up any time if it wasn't right.
 

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Yes it will run without the fuel pump, at least until the carb runs out of gas anyway. Should be long enough to tell if the pump is making the noise.
And it won`t be the actual wrist pin that fails, but the piston around the pin. The wrist pin hole in the piston gets ob-longed so the pin moves up and down within the piston hole. That problem is more with cast pistons then with forged ones and it can crop up at any time, usually after a high speed run. I`ve also herd motors with noisy wrist pins run for thousands of miles making the noise too.
 

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I have a 1970 455HO all original w/ the motor rebuilt about 300 mls on it. Over a year ago I did a sprint on the hwy and took it up to about 100 mph. After I got it home I heard a slight tapping or knocking and thought it was in the valvetrain. Put a stethescope all over it and cant locate it. Felt it was a lifter and wanted to put in a Ram Air 4 cam anyway which I did. Lifters, cam, and timing set from Comp Cams. Still there. Never gets louder and I can't really hear it when I rev it. I have had rod knocks before and this isn't like that at all. And a rod gets louder when hot and worse over time. So I put STP honey and 20w/50 on an oil change which I figured would quiet it down if I was wrong and it was a rod and it is exactly the same cold and hot. No change. Well I had it on my new lift running and had the stethescope all over it again and the sound seemed to strongest at the fuel pump. So I figured I would change it out only $31.00. No luck. The essentric on the timing gear for the fuel pump seemed fine when I did the cam. Are there more than one size and mabey it's smacking the fuel pump arm when it rides around? This is now driving me insane. Any ideas or known issues? Help!!!!!!!
I have a 1967 GTO with a 400 and it developed a tapping sound after I had the oil changed shortly after I purchased the car in January 2008. In the most recent edition of "The Legend," there was an article authored by "Mr. Goatwrench" that discussed the additive ZDDP, which used to be part of motor oil manufactured prior to Jan. 1, 2008. I contacted a company in Chicago that sells ZDDP as an oil additive and added a bottle to my engine. Once the engine reached operating temperature (around 160 degrees), voila, no more tapping noise. You may want to give this a try. A caveat -- I'm not a mechanic and Rukee has much more engine knowledge that I ever hope to have. Anyway, that's my "tapping" story. Let me know if this works for you.
 

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A way to isolate the cylinder making noise is to pull the plug wire off of each plug, one at a time, with the engine running, and see if the noise goes away or changes pitch. Rukee may have something: it sounds like a wristpin to me. Also, it COULD BE a wristpin if you're not running ZDDP additive. ZDDP was removed from most oils in 2006 to protect worn out, oil burning cars with CAT converters from fouling the converters. ZDDP is needed to prevent galling and wear in all flat-tappet engines. It is a metal based zinc and lithium product that coats moving parts, like wristpins! I run Delo 400 or Shell Rotella Diesel spec oil with an additive.
 

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Discussion Starter #11 (Edited)
Well had to move the cars around today and it was actually louder when I first started it. It's almost like a rattle and definetly goes up and down w/ the rpm's. It got quieter as it warmed up but just alittle and never goes away. I did the 2000 rpm thing held it at 2000 then floored it and it does seem to go away at higher revs but returns as it winds down to idle. But there is alot more engine and muffler noise at 4000 rpm's but I don't hear it. I hear it at the top of the motor but it can't be located to either side. And when you put the stethescope all over the valve covers and manifolds all you hear is ticking nothing unusual. It could be deep in the motor but doesn't sound like any rod knock I've ever come across. I heard about that zddp from a Jay Leno video but the damage may be done, whatever it is. Would a cam bearing rattle or knock, never spun one? I forgot about that pull the plug wire trick, thanks, I'll be trying that tomorrow. Thanks for the help and suggestions guys, this is really fustrating.
 

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Discussion Starter #12
Pulled each plug wire while running and no change in the noise. going for the fuel pump next. Starting to sound like a wrist pin... Damn thats more work than I want to do. Anyone in the market for a 1970 GTO 455 HO all #'s matching pwr win,seats,A/C, 8track, all steel never rotted w/ a bad wrist pin on a 300 ml motor????? Da mn!!!
 

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Discussion Starter #14
I'm in the market,:willy:

Have you checked for a loose pushrod?
Yep that was my first thought and swapped to polylocks to make sure of the adjustment. I went as far as replacing the cam, lifters, and timing chain from comp cams, did the Ram air IV cam. I thought it may have been a sticking or collapsed lifter. It's not super loud it's almost like a marble is in there. Like a rattle. I'm going to pull the fuel pump just to make sure and then loosen the fan belts on the water pump and alternator to see iff it's one of those. I'm just in denial w/ so little miles and having been professionally rebuilt and blueprinted. Although I don't doubt the great info I have gotten here. I'm sure we will get to the bottom of this soon. If your serious shoot me a PM w/ an email. I have alot of cars and a couple of projects so something is gonna have to go. Jim
 

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Discussion Starter #16
Can you take it to the guy who built the motor and let him listen to it??
If removing the fuel pump and belts don`t make it stop that is.
And I`ll raise my hand if the price isn`t out of sight.
No that's not an option. I was living in NY when the work was done, it ran beautiful ,broke it in a bit, changed the oil and continued w/ other stuff never using or finishing the car. Then this issue popped up as described. Since then I'm divorced, remarried w/ kids, sold the house , bought the house , retired, and moved to Florida. There is 6-7 years in between starting this and today and 1400 mls!!! LOL I held on to her because there aren't many like her. As far as selling her I threw that out impulsively and I should probably have her appraised as she sits to be fair. It is a collectable w/ #'s matching, all steel, high option, 1 of something like 1671 I believe. send me a PM w/ your thoughts and email I'll send some pics Jim
 
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