Will not run at operating temp - 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 04-25-2012, 04:56 PM
Registered User
 
Join Date: Apr 2012
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Will not run at operating temp

Hello all,
Sorry for the long post!
Just found this forum and looks like there's some good advice here! I have a nagging problem that is baffling me. I have a 70 Chevy impala that my grandfather purchased new which I recently obtained. It has 54k original miles (i know for a fact) and was completely stock. It has the L48 350 4 barrel engine. The car sat in the garage for the past 10 years with no use. Once I got it home and went over it good and got it back to running condition. As time and money have permitted I have been upgrading and renewing the engine. It's a 4 door sedan so I'm not concerned with keeping it completely stock but I am saving all original parts. Currently these are the mods that have been done.
New distributor cap, points, condenser, wires, spark plugs, fuel pump, coil, battery, Holley 600, Weiand street warrior polished intake. My goal is to chrome out the engine.
The problem,
Before I installed the intake, I was running the Holley on the stock intake using an adapter plate. Everything was running great and all the above items were already in place except the fuel pump. That was added later after the problem began. The last time I drove it, it ran fine until I got close to home and it started trying to die. Well instead of fixing the problem first, I decided to add the polished intake. I know, bad mistake! I have not driven it sense then because once it warms up it dies unless I keep giving it gas. The thing I've noticed is the throttle linkage on the carb gets real hot! As in too hot to touch. I have a clear fuel filter housing and sometimes the fuel almost all disappears from it when it's hot. I've added a 1" plastic spacer plate below the carb thinking the intake may be conducting too much heat and that has helped but it still dies. The timing stays steady until it heats up and then it takes a plunge with the vac line off and plugged. I then replaced the fuel pump thinking it may be worn out but that hasn't helped. The engine seems to only run when the timing is advanced almost off the scale. Could this be why the intake and carb are getting so hot? May be hot exhaust gases are transferring into the intake manifold? The vac advance on the dist doesn't seem to make any difference.
Any ideas would be great! Thanks!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-25-2012, 06:23 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,095
Wiki Edits: 0

Thanks: 4
Thanked 541 Times in 457 Posts
Quote:
Originally Posted by Ablissit
Hello all,
Sorry for the long post!
Just found this forum and looks like there's some good advice here! I have a nagging problem that is baffling me. I have a 70 Chevy impala that my grandfather purchased new which I recently obtained. It has 54k original miles (i know for a fact) and was completely stock. It has the L48 350 4 barrel engine. The car sat in the garage for the past 10 years with no use. Once I got it home and went over it good and got it back to running condition. As time and money have permitted I have been upgrading and renewing the engine. It's a 4 door sedan so I'm not concerned with keeping it completely stock but I am saving all original parts. Currently these are the mods that have been done.
New distributor cap, points, condenser, wires, spark plugs, fuel pump, coil, battery, Holley 600, Weiand street warrior polished intake. My goal is to chrome out the engine.
The problem,
Before I installed the intake, I was running the Holley on the stock intake using an adapter plate. Everything was running great and all the above items were already in place except the fuel pump. That was added later after the problem began. The last time I drove it, it ran fine until I got close to home and it started trying to die. Well instead of fixing the problem first, I decided to add the polished intake. I know, bad mistake! I have not driven it sense then because once it warms up it dies unless I keep giving it gas. The thing I've noticed is the throttle linkage on the carb gets real hot! As in too hot to touch. I have a clear fuel filter housing and sometimes the fuel almost all disappears from it when it's hot. I've added a 1" plastic spacer plate below the carb thinking the intake may be conducting too much heat and that has helped but it still dies. The timing stays steady until it heats up and then it takes a plunge with the vac line off and plugged. I then replaced the fuel pump thinking it may be worn out but that hasn't helped. The engine seems to only run when the timing is advanced almost off the scale. Could this be why the intake and carb are getting so hot? May be hot exhaust gases are transferring into the intake manifold? The vac advance on the dist doesn't seem to make any difference.
Any ideas would be great! Thanks!
Having to crank up the advance and running hot can have a number of possibilities, but being an old car one of the first places I'd look for problems is the cam timing. When engines age the timing gears wear and the chain stretches, this typically allows the cam to fall retarded to the crankshaft position. This is seen at the distributor as constantly having to add advance to keep it running. The engine gets hot, especially the exhaust because the cam events are late which has the pressure peak late and fuel still combusting when the exhaust valve opens this has combustion occurring in the exhaust manifold with little energy having been transferred to the piston which removes heat from the exhaust gasses so everything in the exhaust manifold is hotter than usual. If the hot spot that is in the bottom of the intake's plenum still works the late hot exhaust passing through this will really heat up the intake manifold.

To test for this is a tight range of degrees is somewhat complex requiring a degree wheel and dial indicator to measure crankshaft degrees of rotation against valve motion. A quick and dirty test is to use a timing light on the marks, rev the engine up a couple, three thousand RPMs and slam the throttle shut. You should see the base setting and the variables come in on the up throttle. The variables should come back to the base setting when the throttle is closed maybe with a small wiggle of the timing marks if the timing chain and gears are good. If they are worn out it's likely that the timing will fall below the base setting and oscillate back up several to quite a few degrees and back again perhaps more than once.

If the timing gears are original the cam gear is most likely an aluminum hub with nylon teeth. When the plastic gets old it becomes quite brittle and breaks up in addition to the wear the metal chain does on the plastic teeth. You do not want to push this, if the teeth fail the cam will fall very far out of synchronization with the crankshaft and itís very possible that valves will still be hanging open when the piston arrives in the same space. This makes for a most costly repair as certainly valves will be damaged beyond repair, rockers, push rods, and possibly the lifters and cam lobes involved will be ruined as well. Sometimes even the piston gets busted. So you want to identify if this is the problem and if it is get it fixed NOW!

Sorry for the long answer.

Bogie
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-25-2012, 06:47 PM
Registered User
 
Join Date: Apr 2012
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for the prompt reply

The timing gear has been something on my suspect list. I know it is original and after 42 years I started falling apart too! I've been debating pulling the engine soon to detail engine and compartment and it may be a good time to do it? Gotta get the honey do's caught up first and then I'll dig in. Thanks for the reply! I'll post some pictures soon.
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:
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
1965 Impala - operating temp JohnBoySS Engine 25 06-29-2010 10:57 AM
tbi dies at operating temp big mudder Engine 3 11-03-2006 09:51 PM
engine surging until operating temp hellrzr Engine 2 09-21-2004 03:34 PM
Miss on 383 @ operating temp. blown81 Engine 3 08-26-2004 05:48 PM
302 operating temp? 79fairmont Engine 18 01-06-2004 10:44 PM


All times are GMT -6. The time now is 11:25 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.