Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic -- 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> 383 engine vibrations????
User Name
lost password?   |   register now

Thread: 383 engine vibrations???? Reply to Thread
Send Trackbacks to (Separate multiple URLs with spaces) :

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:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


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.

Additional Options
Miscellaneous Options

Topic Review (Newest First)
09-04-2011 10:59 AM
swp1983 well i figured it out. After hours of research i finally dropped my trans to check for correct flexplate install. Sure enough, the flexplate was a couple holes off. The scat crank did not have a dowel pin and i just slapped on the flexplate. So, I learned, on a externally balanced 383 the counter weights on the flexplate and harmonic balancer need to be aligned properly. If not, you WILL get a vibration.
Live and learn, my next engine will be evan better. This is the first engine I have built, still cant believe it runs lol
08-10-2011 04:40 PM
swp1983 The Scat assembly was externally balanced and included the 9000 crank, rods, pistons, rings, 400 weighted flexplate and weighted harmon balancer. It included a balance sheet with weights of all parts. I tried my old balancer which was a 400 weighted piece from my old 383 to rule out a bad balancer. I put the new one back on though. If it was a balance issue, shouldnt the vibration get worse as rpm's increase?
08-10-2011 12:49 PM
Originally Posted by lmsport
Was it a balanced assembly?
Scat rough balances all their cranks but the assembly must be balanced to the rod-piston-flywheel at some point.
X2 ^^

Are you sure it's externally balanced? Assuming the crank, rods and pistons weren't balanced as an assembly? A 350 would be internally balanced OEM. You say you put on the old balancer, which should have been non-weighted for an internally balanced motor if it was stock, for an external balance you would have used a 400 balancer with the balancing weight adjustment "lump" cast into it. I'm assuming the flexplate or flywheel is externally balanced, has weights? Just curious if the sum of all the parts are compatible, and properly externally balanced. Odd that it's only vibrating within a 300 rpm range.
08-10-2011 11:32 AM
lmsport Was it a balanced assembly?
Scat rough balances all their cranks but the assembly must be balanced to the rod-piston-flywheel at some point.
08-10-2011 11:11 AM
383 engine vibrations????

New engine installed and still chasing a vibration. It is present in and out of gear and starts at 2900 rpm and smooths out at 3200 rpm. I have double checked all drivetrain bolts, timing, ignition, rocker adjustment, new plugs ( non foul), disconnected belts and pulleys, put on the old balancer, and checked the compression. Now im wondering if the flexplate / torque converter was installed correctly. Any pointers? Here are the specs:
1969 C10: 383 with scat rotating parts externally balanced, isky 280 cam, dart heads, turbo 350 with 3000 stall.

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

All times are GMT -6. The time now is 02:37 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.