Can't find the knocking source! - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-26-2004, 09:28 PM
Member
 
Last photo:
Join Date: Apr 2003
Location: québec,canada
Posts: 164
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Can't find the knocking source!

I took the pan off the 383 stroker to check out a knocking noise that appeared on it after having had the heads checked over and the valve seals and bronze exhaust guides replaced. Since it sounded like a rod noise I took out the bearings from number 3 5 7 and 8 and they looked normal..I've plastiguaged number 8 and 5 and came out with .002 and .00175 inches...I took off the rear main cap and it looked normal. This is a fresh rebuilt with 1500 miles on it and it didn't have that knocking noise when I stored the car last fall for winter time.

Oil pressure is at about 65/70 (high volume pump) idling at start-up and would stay there. Hydraulic cam/lifters no bent pushrods and oil coming up through all pushrods/rockers. Engine starts easy and idle good....but there is that knock..should I plastiguage every one bearings?? Not an easy job laying and crawling under the car...!

New bronze guide valves could be trouble??

This engine was showing 210 pounds per cylinder last summer and it has a 10.25 compression ratio with aluminium heads.

I remember having had one or two lifters out their holes just to have a look at them and putting them back into their holes...is there something I could have disturbed doing so and wich could cause the actual knocking?

Hey I'd like to get that thing on the road now its time of the year to do so here up north...but I first have to find out what's the problem...any help appreciated!

thanks, Ronald.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-26-2004, 09:40 PM
gpeak's Avatar
Member
 
Last photo:
Join Date: Oct 2003
Location: Kansas
Age: 42
Posts: 384
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Since this just started i don't know. But, i had the problem with what i thought was a rod bearing in my 383 a couple years ago. Turned out i needed a different oil pan. Crank was tapping the pan slightly.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-26-2004, 10:24 PM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,654
Wiki Edits: 0

Thanks: 15
Thanked 58 Times in 55 Posts
when we built a 383 years ago it developed a knock in the bottom end, but all the bearings were fine when we stripped it down the next season, the knock wouldn`t appear until the engine got hot. have you checked the torque converter bolts? have you inspected the flexplate? if the plate is cracked or the bolts loose both of these sound Identical to rod knock. we also had one sbc that we had just rebuilt, it had new TRW forged pistons, it ran great and after 2000 miles it started knocking, we couldn`t find the source of the knock and it never got worse, so finally we pulled it and stripped it down, when I removed the number 6 piston the skirt on the valley side fell off. it was jammed in place so it couldn`t fall out but it knocked like hel*, we were lucky it didn`t do any bore damage. one trick we learned when inspecting for broken skirts are to adjust the valves with the engine running, and real slowly, adjust the exhaust valve to the point that it just stays open, if the knock stops for a moment it`s a good sign it`s a skirt or a collapsed piston. don`t give up and you`ll find it, just remember not to overlook the small stuff, good luck.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-27-2004, 04:03 AM
blazer74's Avatar
Registered User
 
Join Date: Jan 2004
Location: Tn
Age: 50
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Just a thought, I had a 350 that had a very mild thump/knock shortly after a rebuild. Believe it or not the belows in the fuel pump was making the noise. I didn't find it until the pump started leaking. replaced it and no more noise. If you have a block mounted fuel pump and can't find anything else, try another pump.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-27-2004, 05:28 AM
Member
 
Last photo:
Join Date: Apr 2003
Location: québec,canada
Posts: 164
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks to all for the ideas...This is a doug nash 5 speed car so flexplate cannot be the cause,the pan is the same one as before it started knocking,and its an electric pump rig wich wasn't knocking before the heads work. As far broken pistons well they are KB hyper with less than 500 miles and from what I can see of them from underneath they look fine altoough I understand they could be dammaged and not showing evidence of it with the limited visual access I have actually. But this engine was not having any knocking last fall when I stored it but right at start up,after heads work this winter,it started knocking...this makes me thinking I should concentrate on what I removed and my reassembly work involved then....

One extra tought: there is a windage tray and many rod bolts (new at rebuilt 1500 miles ago) show some bright shinny spots at their ends like if they were rubbing on something....but no signs of contact on the tray neither with the block internal surface and again here why this would be now and not before?? I had the pan of when reassembling to recuperate a small dried out piece of RTV (wich I got) but didn't moved the tray from its original position then.

I will keep looking but fear that I'll be inclined to put the pan back on soon to find out the same noise will be still there and hence the darn engine will be in need of total tear down and this will be a summer without a funny car! Won't even be able to test my newly repaired salisbury differential....

Not totally despaired but getting there

thanks, Ronald.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-27-2004, 04:01 PM
club327's Avatar
Member
 
Last photo:
Join Date: Nov 2003
Location: australia
Age: 49
Posts: 334
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Tvr, I'd seriously get a professional to listen to that noise. No point getting us to diagnose a noise via the net! You've ripped the pan off at least once, and are not sure if the noise is from the valve train either. No offense but you're kind of chasing your tail. Most noises are easily identifiable by an experienced mechanic, and it'd probably cost you nothing for the advise.
My only suggestion from this point for diagnosis is to eliminate the belts as suspects. Belts are responsible for all kinds of noises, with some sounding quite chronic. Usually a spray with wd40 or spray grease to the belts with the engine running stops any noise they're making. Or you could take the belts off and momentarily run the engine. Why don't you also invest in an automotive stethoscope? At least one would point you away from the trouble free areas.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-27-2004, 04:46 PM
79 camaro 454's Avatar
Member
 
Last photo:
Join Date: Jan 2004
Location: norfolk
Posts: 96
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
take out 1 2 4 6 seems to be the only thing left you havent done.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-29-2004, 06:01 PM
Registered User
 
Join Date: May 2004
Location: Brooklyn NY
Age: 52
Posts: 13
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hi: I have experianced a knocking noise that was very hard to find from a damaged keyway slot in the crankshaft hub(balancer).sounded like a lower end knock when engine was idling. Dont know if this will help you tho. Good luck, Harry
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 01:40 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.