Slight rattle from engine when revving up (SBC 305) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sethv · 11-15-2015, 05:58 PM

Hey guys. Recently I had 0 PSI oil pressure on idle, so I revved it a little bit to see if the pressure would go up (And it did) and then it sounded like a slight bottom end wrap around 1800 rpm or so (Just in park...) Changed the oil and there are zero metal shavings and the oil was smooth. Had a JUNK Fram filter on it and replaced it with an ACDelco one. Cold PSI went from 15 with the Fram to a little more than 30 with the ACDelco. Still has that slight wrap but it's not down on power and the oil level is fine. I can't hear anything under acceleration, it's just doing it from idling in park or neutral. And it's holding pressure now. I'm not sure what the problem could be, since the last time I had a bottom end noise with my 350, there were metal shavings everywhere. This 305 is clean and only has 60k on it. Can't take a video right now though. What do you guys think it could be?

homemade87 · 11-16-2015, 08:43 AM

Take the alternator belt off and start it. See if it goes away . Could be alt bearing . I have had a couple sound like it was rattling .

Also in my opinion never use anything but ac delco filters . There may be some better but they have seemed to be consistent in quality and perform well over the years for my daily drivers and my hp engines . I also had a off brand filter fail .

sethv · 11-16-2015, 10:33 PM

I'll give it a shot in the morning, thank you! Never even thought of the alternator...

Rich84 · 11-17-2015, 12:03 PM

Also, check the bolts on the flywheel..They could be lose or the flywheel could be cracked.

Dead Parrot · 11-17-2015, 01:39 PM

Hydraulic lifters can be noisy if they don't get enough oil.

While doing your belt test, might as well run it briefly without any belts. Had a PS pump sound similar to a bad lower end bearing. That PS pump caused a bit of panic since I had just installed a new crate motor two week previous. If your noise continues with no accessories turning, engine related. Otherwise you can try various belt combinations until you locate the noisy accessory.

11-15-2015, 05:58 PM	#1
sethv Registered User Join Date: May 2011 Location: Bradford, PA Posts: 395	Slight rattle from engine when revving up (SBC 305) Hey guys. Recently I had 0 PSI oil pressure on idle, so I revved it a little bit to see if the pressure would go up (And it did) and then it sounded like a slight bottom end wrap around 1800 rpm or so (Just in park...) Changed the oil and there are zero metal shavings and the oil was smooth. Had a JUNK Fram filter on it and replaced it with an ACDelco one. Cold PSI went from 15 with the Fram to a little more than 30 with the ACDelco. Still has that slight wrap but it's not down on power and the oil level is fine. I can't hear anything under acceleration, it's just doing it from idling in park or neutral. And it's holding pressure now. I'm not sure what the problem could be, since the last time I had a bottom end noise with my 350, there were metal shavings everywhere. This 305 is clean and only has 60k on it. Can't take a video right now though. What do you guys think it could be? __________________ 1981 K10 Scottsdale 305 ci \| TH350 \| NP208 \| 60k miles

11-16-2015, 08:43 AM	#2
homemade87 Registered User Join Date: Apr 2010 Location: Guntersville Alabama Posts: 1,073	Re: Slight rattle from engine when revving up (SBC 305) Take the alternator belt off and start it. See if it goes away . Could be alt bearing . I have had a couple sound like it was rattling . Also in my opinion never use anything but ac delco filters . There may be some better but they have seemed to be consistent in quality and perform well over the years for my daily drivers and my hp engines . I also had a off brand filter fail .

11-16-2015, 10:33 PM	#3
sethv Registered User Join Date: May 2011 Location: Bradford, PA Posts: 395	Re: Slight rattle from engine when revving up (SBC 305) I'll give it a shot in the morning, thank you! Never even thought of the alternator... __________________ 1981 K10 Scottsdale 305 ci \| TH350 \| NP208 \| 60k miles

11-17-2015, 12:03 PM	#4
Rich84 Registered User Join Date: Mar 2012 Location: Woodbury, Ct. Posts: 1,692	Re: Slight rattle from engine when revving up (SBC 305) Also, check the bolts on the flywheel..They could be lose or the flywheel could be cracked.

11-17-2015, 01:39 PM	#5
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,611	Re: Slight rattle from engine when revving up (SBC 305) Hydraulic lifters can be noisy if they don't get enough oil. While doing your belt test, might as well run it briefly without any belts. Had a PS pump sound similar to a bad lower end bearing. That PS pump caused a bit of panic since I had just installed a new crate motor two week previous. If your noise continues with no accessories turning, engine related. Otherwise you can try various belt combinations until you locate the noisy accessory.



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