very tight new bbc- HELP - 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 02-25-2004, 07:14 AM
New Member
 
Last photo:
Join Date: May 2003
Location: Leeds - England - UK
Posts: 24
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
very tight new bbc- HELP

I have recently rebuilt a bbc, 454, 76 motor with new just about everything but have a slight problem I have never experianced before. When rotaitng the motor by hand (huge bar on crank or in blower drive) the engine rotates evenly and freely. If you leave the engine stood then rotate it, it gets very tight - very tight, to the point where it stops rotating and I would normally asume there is a major mechanical defect. If you continue never the less (not my normal practice) it will free off and if you keep it rotating be free and even.

A few notes, on the problem -if there is one.

so tight it seems to be locked up and bar requires good heave but only on the initial rotation -1st valve spring compression.
had the lifters and rockers backed off and rotates freely
checked valves and chambers for seal after tight spot to see if valves bent - all ok and no issues there, clearances where all ok anyway.
rotates freely when moving
every time stood initial tight spot seems to be on valve spring compression but not in the same place. Dependes where stops and tightens up ridiculously on first spring compression phase of rotation.
also creaking heard on the tight spot -like a spring creak, but only on this first initial rotation.
valve springs are new and comp cams units matched to cam not particulaly high pressure - just above stock
never had an engine this tight, had some realy tight ones but this seems very unusual as the problem goes away on further rotation.

I have had the sugestion that this is newness, especialy of the valve springs, as all the clearances are correct and the problem is resolved on rotation I would be inclined to agree but realy don,t know and that,s the bit that bothers me, the not knowing bit.

any body any experiance to pass on, I have pulled this bloody thing apart on the top end twice now but will do it again if needed - thanks in advance and best wishes from the UK.

Simon
Attached Thumbnails
Click image for larger version

Name:	mvc-002s.jpg
Views:	127
Size:	39.0 KB
ID:	1296  

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-25-2004, 08:07 AM
deuce_454's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Copenhagen, Denmark
Age: 39
Posts: 1,000
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
woaahhh nice engine... it sounds like the oil runs out of all the barings and you have a lot of initial friction. i think you should prime your oil pump, and rotate to unstick everything before attempting to start it.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-25-2004, 08:21 AM
Wrencher's Avatar
Member
 
Last photo:
Join Date: Aug 2003
Location: cincinnati
Age: 56
Posts: 607
Wiki Edits: 0

Thanks: 5
Thanked 0 Times in 0 Posts
Maybe the thrust bearing isn't seated good, sometimes a couple smacks frt and back w/ a rubber mallet helps? Did you check crank endplay?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-25-2004, 06:57 PM
4 Jaw Chuck's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Mar 2002
Location: Manitoba, Canada
Age: 46
Posts: 4,898
Wiki Edits: 0

Thanks: 0
Thanked 72 Times in 60 Posts
Does it do it without the blower attached?
__________________
Outlawed tunes from outlawed pipes
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-25-2004, 10:03 PM
LilSmoke's Avatar
Member
 
Last photo:
Join Date: Aug 2003
Location: kansas
Age: 63
Posts: 300
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hpefully u did lube the pistons real gd and the rings,because it sounds like dry rings much like when u shut off an alcohol or nitro motor because of the non lubricating qualitys of the fuel there is always both squeak and initial tightness when u go to run the valves even with the plugs out. Try and squirt some oil in the cylinders and then try it .
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 02-26-2004, 02:12 AM
New Member
 
Last photo:
Join Date: May 2003
Location: Leeds - England - UK
Posts: 24
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks Guys for the info, I have checked all the clearances and the motor was the same before the blower was on and as stated turns freely once rotating, the cam is gear driven and I have watched the cam movement on rotation and it appears to be stationary, no walk forward or backward that is noticeable.
The crank end play on the thrust also seemed fine when the rotating assembly was installed and this rotated perfectly at the time and does so if you remove the rockers and push rods, the problem disappears completely.
I have oiled the bores though these where oiled up before and the whole motor is well lubed up anyhow.
The bores are fresh honed however with moly rings, 25 tho gap for street blower application.
The problem however still persists, it is absolutely fine on rotation but stop rotating and leave a while and its always there on that initial rotation then goes and is never in the same spot.

Will keep looking

Thanks again Simon
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 02-26-2004, 05:19 AM
deuce_454's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Copenhagen, Denmark
Age: 39
Posts: 1,000
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
i still think its the lifters pushing the oilfilm out from underneath, and sticking, metal to metal after a while
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 03-06-2004, 08:05 PM
racerkvn's Avatar
Registered User
 
Join Date: Mar 2004
Location: Alabama
Age: 39
Posts: 7
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I had a 454 do me that way once and I thought it would be ok since I could move it once you got it going, but I was wrong, we started it up to break in the cam and it locked up tight after about 5 minutes of running at over 3500 rpms. The problem on mine was the crank wasn't polished. I had it turned .010 under but the machine shop that turned it didn't polish it. Since then every motor I've built I've had the crank polished, and I have never had anymore problems. We also have our brand new cranks for our Pro Mod motors polished before we ever put it together. Our Pro Mod blown alcohol motors turn freely by hand via 3 foot long bar on the blower pulley. Hope this helps.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 03-07-2004, 01:05 AM
Magikal's Avatar
How can it go faster?
 

Last journal entry: Been a long Winter
Last photo:
Join Date: Jan 2004
Location: North Idaho
Age: 37
Posts: 240
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I am no professional mechanic but a hobbyist. I would check lifter bore maybe. I once put a 4 cylinder together w/ the timing chain wrong. my cam lobe was coordinated with crankshaft stroke in such a way that my piston was at TDC at the same time the valves were opening up. They basically were crashing into each other. I had the same effect though. It would turn over but got real tight. I used a big bar to see just how tight it would go and it eventually would turn over ( after it bent the valve, that was what gave) anyways, just a thought. Good luck
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 03-07-2004, 08:25 PM
more coffee's Avatar
Registered User
 
Join Date: Mar 2004
Location: wisconsin
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
the first engine I put together, I needed to use a weight lifting bar to turn the thing over also, I torqued the crank shaft in from front to back instead of looking at a book and doing it the right way. This still make's me feel stupid 35 year's later..............
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 08:14 AM.


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.