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

Thread: Fresh 383 compression Reply to Thread
Title:
  
Message:
Trackback:
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:
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.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
06-30-2012 01:19 PM
painted jester What kind of rings are you running and what were the gaps set at ? Im just a little interested, are you running forged or cast pistons, what was the piston to cylinder wall clearance at their tightest points If you have no knowledge of this forget I asked! I was interested because 10 years ago it was bored honed and piston clearance was checked and ring gap set for 30 over and the type of rings and pistons installed! and now its been re honed besides 10 years of ware so those cylinders have been opened a little more! there's a formula for setting ring gaps for every inch of bore and different pistons & rings. For instance the Hastings rings I installed last: set at .0045" top ring for every inch of bore, second ring .005" for every inch of bore.
You cant pick up a repair manual and look up ring gaps and set them to those settings once you have strayed away from factory blue prints! If your bores are a little wore from being true (say .002") in some areas, cast rings are more forgiving in bores with a little ware then steal molly, and others! So I was Just a little interested in what you did during your freshening or who did it for you? Did you use .030 over file gap rings say .005 or .010 to make up for the ware and hone or just install .030 over rings?

Jester
06-30-2012 05:39 AM
CNC BLOCKS NE
Quote:
Originally Posted by Michael 9111 View Post
It was bored years ago. Has two sleeves in the block. Haven't had it checked for straightness since bored. It has a Lanati voodoo cam. 600 lift 110 love separation. Can't remember duration off top my head. My compression test I ran is all over the board. Goes from lowest cylinder being 110 and the highest being 145 and the rest inbetween. From what I hear there shouldn't b that much of a difference. And I checked my blow by. When I first crank it up it has no blow by. After it warms up it's has a little at idle but if raise the rpm to say 1500-2000 rpm there is no blow by. Im stumped. Maybe bad rings. Maybe worped cylinder. Idk. Besides it blowing the intake gasket it runs great in my opinion.
Seeing your blocks has been sleeved and it has not been plate honed there is a good chance ring seal is your problem, You need to do a leak down test at TDC which will tell you what going on.

Blocks that have sleeves the cylinders next to the sleeves will not be round more so once the heads are torqued on.

Plate honing is a must for good ring seal.

Here is a link on plate honing.

Values Of Torque Plate Honing - Team Camaro Tech
06-29-2012 04:17 PM
BigChevyFTW your not suppost to put anything on the rubber seals that go in the front or back they will blow out everytime.

i throw them in the garbage where they belong and use a thick and i mean thick bead of silicon and torque it down a.s.a.p! never had an issue and ive done it at least 50 times.

the 2 times i tried the seals leaked both times!

if you think there is a serious rise in pressure put a cheap gauge on a vac port and see if its excessive
06-28-2012 08:07 PM
painted jester Warm engine is better especially with forged pistons! rings and pistons expand as they warm up increasing ring tension and decreasing piston to cylinder clearance and ring gaps decrease! but cold is ok if you have burn issues If you dry test and compressions down and you add oil to the cylinder (wet check) and compression comes up you have bad rings if compression stays the same wet or dry you have bad valves or seats! A leak-down test is how long the cylinder holds compression pressures and only tells you it leaks it doesn't pin point where it could be, head gasket ,rings, valves or seats, a crack etc, etc,

Chris
06-27-2012 09:44 PM
Michael 9111 I'll try to get the wet test done tomorrow and I'll let y'all know how it goes. Thanks for all the advice and pointers. Learning something new everyday.
06-27-2012 09:39 PM
68NovaSS The ring tension is what it is, so probably not a big deal. Besides cylinder pressure you're looking for variation between cylinders, the wet/dry is to see if there's any difference. That will point you to rings or valves depending on the values you see or changes after the wet test.
06-27-2012 08:46 PM
Michael 9111 This may be a dumb question but from researching does the motor need to b warm to perform a compressiontest???I've only done the compression test when my motor hasn't been running all day. I have custom exhaust bc I have this motor in a mustang and there's no way of running a compression test on my motor while hot unless I burn my wrists to blisters????FORD TOUGH WITH CHEVY STUFF
06-27-2012 08:38 PM
68NovaSS The wet test is squirting a couple shots of oil into the cylinder and take the test. I give a test 5 compression strokes, or until the needle stops climbing.

The throttle has to be at WOT for an accurate compression test.
06-27-2012 08:06 PM
Michael 9111 And the motor only has little blow by at idle none after I rev it up. And when I plug my PVC valve back in and leave my other hole in valve cover opened the PVC sucks it all up and I don't see any then. So I'm thinking if it's got enough blow by to push a gasket out then it should b pouring out the breather hole
06-27-2012 08:03 PM
Michael 9111 I've done the compression test both ways throttle opened and closed and came up with the same numbers. How do u do a wet compression test?? Never done that b4. But one of my buds just brought me a leak down tester. Should I do the leak down or wet test?? Which is better
06-27-2012 06:32 PM
68NovaSS You're doing the compression test with the throttle blocked open, right? Just had to ask, it's about the only thing that hasn't been mentioned.
06-27-2012 04:06 PM
painted jester
Quote:
Originally Posted by Michael 9111
383 keeps blowing back intake gasket out. Ran compression test and all cylinders had from 120 to 145 of compression. I hear that's low but this motor always has had around that much. I didn't degree in the cam just lined up the dots. But it's still blowing intake gasket out. Any thoughts on any of this or opinions?? Any help is greatly appreciated.

120 to 145 is a big differance on a freshened eng a 20 percent difference isn't except able take a wet compression check and see if pressures increase and level out, my guess is your rings are shot. And the blow by is pushing your gasket out!

Jester
06-27-2012 02:53 PM
dromero5
The Right Stuff

The best trick i have for sealing the front and rear of the intake manifold is to use a spring loaded punch and punch about 100 or so holes throughout the length of the front and rear walls then use the Right Stuff (1/4" bead) and that seems to seal up the best and prevents blowouts. Good luck that is a weird issue.
06-27-2012 01:00 PM
Michael 9111 I used permatex the last time and let it set for a day and a half. But I'm going to pull it apart again and see what happens. Yes I have bolts with washers. Wish me luck.
06-27-2012 12:46 PM
cdminter59
manifold gasket

Clean everything again and set the intake manifold in place with no gasket. Check the gap in the front and back. The gap should be smaller than the thickness of the gaskets. Like I said I tried glue with the rubber gaskets and they would always slip back out. I would throw them away and use Permatex. Are you torquing the bolts in sequence? Do the bolts have flat washers installed with them? Also after warm up re-torque bolts again.
This thread has more than 15 replies. Click here to review the whole thread.

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 02:42 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.