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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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 Posted: Fri Oct 21, 2016 8:50 am Post subject: Re: Chromoly push rods |
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| MConstable wrote: |
Ray, I thought I had saved a link on adjusting lash this way, but I can't find it...could you post a link to it?
Thanks |
I will see what I can find. There are several versions of it depending on how it is approached and explained.....but in general its a version of "rotate until Intake closes and exhaust just starts to close"....or vica-versa ....or similar.
Really what you are looking for is the exact BDC...meaning somewhere on the base circle.
You do have to be careful though. Depending on the profile of your cam lobe that "0" base circle area before you start hitting the ramp...can be very narrow or quite wide.
Its funny...a lot water cooled and V-8 guys I have spoken to over the years look at ACVW guys with a funky glance when I tell them the factory lash setting....and the most commonly used method of setting it...which is starting at TDC on the crank pulley mark on #1....both valves closed...and setting to .006"...then rotating the engine backwards so you can proceed in 1, 2, 3, 4 order. They almost always ask...."is that TDC point on the base circle?"
It was that pointed look and question I got....many years ago...that made me start looking at how I adjusted my valves.
Bearing in mind....virtually everything I work with is D-jet injected....so what I am about to say will not apply to everyone....BUT....D-jet is VERY sensitive to proper valve adjustment.
The tighter/leaner your fuel mixture is (within safe reason)...the better this injection system runs and tunes....and.... the more sensitive the system is to EXACT and EVEN valve adjustment.
Its a vacuum signature and injection timing issue.
So I started checking my valve lash hot just to see how EVEN the valve lash was. I started finding a consistent variation on one or more valves of between .002" and .004" depending on level of warmed up.
In general I found....a .006" valve lash set at exact crank TDC...works out on the stock type 4...to .003" nominal to .002" minimum valve lash hot.
It was during this testing that ...I found the extra lash that is ACTUALLY in the valve train...from not being on exact base circle during normal valve lash adjustments.
In this long train of tinkering and measuring events I also swapped pushrods around to see if one was expanding differently. I found that they were quite uniform (these were stock PR's).
It was not until a couple of years later when re building the heads...that I had the opportunity to do another test with the valve out of the heads. Put them on a cookie sheet and put them in the oven.
Check the temp with a laser thermometer to make sure they were all equally hot. I burned a few fingers even with gloves and tongs making snap micrometer measurements...cooling off in between....and found the .001"-.003" differences were actually in the valves. This is not uncommon. Most valves with hardened stems are actually two piece with the heads spin welded on. No two valves will have the EXACT expansion characteristics.
While some would say the .001"-.003" is fairly insignificant....I say it is significant. If its not...then our advertised valve lash would not say .006". It would .0045" to .0075"...because .003" is not significant 
So I changed two things:
1. After numerous tests and driving measurements I started setting my initial lash at TDC cold...and adjusting it evenly when hot....to make sure the lash was even for all valves. This actually made a tuning difference for D-jet. An improvement.
2. Later....I started doing the method where I would use crank position to get me to general TDC...then rotate the crank until maximum lash opening was achieved at the adjusting screw...meaning I had hit base circle. I now adjust valve lash there.
HOWEVER....adjusting to .006" with the base circle method....results in a measured lash using the old crank indicated TDC method ...of about .002"....cold. When hot...that lash closes to nearly exact "0" when checked.
I found for safety that setting the lash on the exhaust valves needs an extra .001-.002". Ray |
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neil68
Samba Member
Joined: March 17, 2007
Posts: 3440
Location: Calgary, Canada
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| Posted: Fri Oct 21, 2016 10:14 am Post subject: Re: Chromoly push rods |
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| raygreenwood wrote: |
| neil68 wrote: |
I've run Manton chromoly pushrods for several years, both the 0.035" and 0.058" wall thickness. They have to be set at zero cold lash and will start getting noisy when the engine warms up. I've checked the warm lash many times and it's usually 0.010-0.014"...not ideal.
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Are you sure you do not have a decimal point error in your post?
Ray |
0.010-0.014" is indeed what I've measured with feeler gauges on a hot engine at the track. I've had others tell me similar numbers and that is probably what creates the telltale clatter sound. In street driving it's not as bad, but still routinely gets up to 0.006-0.008". I'll be sticking with the aluminum tapered pushrods from now on.
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Neil.
Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Fri Oct 21, 2016 11:29 am Post subject: Re: Chromoly push rods |
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| neil68 wrote: |
| raygreenwood wrote: |
| neil68 wrote: |
I've run Manton chromoly pushrods for several years, both the 0.035" and 0.058" wall thickness. They have to be set at zero cold lash and will start getting noisy when the engine warms up. I've checked the warm lash many times and it's usually 0.010-0.014"...not ideal.
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Are you sure you do not have a decimal point error in your post?
Ray |
0.010-0.014" is indeed what I've measured with feeler gauges on a hot engine at the track. I've had others tell me similar numbers and that is probably what creates the telltale clatter sound. In street driving it's not as bad, but still routinely gets up to 0.006-0.008". I'll be sticking with the aluminum tapered pushrods from now on. |
Is that measured at normal valve adjusting points...or with the base circle method I was getting at above? I would expect those measurements if you are on the base circle. Ray |
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maui
Samba Member
Joined: May 16, 2004
Posts: 438
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| Posted: Sat Oct 22, 2016 2:09 pm Post subject: Re: Chromoly push rods |
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| I bin running aluminum hd for a few years and bent 2 straights so far. I say cuz I go 8000 often so now I get dual tapered and that should get rid of that problem. Big diff in revs with alum PRs and light lifters and ti valve retainers and only scat racing dual vw springs. Super combo to me. Aloha |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26789
Location: Colorado Springs
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| Posted: Sat Oct 22, 2016 3:10 pm Post subject: Re: Chromoly push rods |
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engle cams the lash ramp ends at about .010 or a hair less lift
Web cams the lash ramp ends more like .012, .013
It's hard to measure exactly so those are just ROUGH estimates, but certainly a web cam will like .002 at least looser lash, and you might notice that engle you may need more like "TIGHT zero" to make it right with steel pushrods.
My valves are quieter at .006 than .004, aluminum pushrods and WEB cam  |
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