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help from engine builders - straight cut gear problem in 1776 - video

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type3lover in the garage...

796 posts · joined Feb 2005 ·

#752719
Hi all,

I'm building my 1776...again...and will do so until I get it right!
Concerned about the backlash between the steel straight cut gears and also the oil pump drive off the cam.
It is an AS41 german case but it HAS been line bored by hellbug's old machinist 0.5mm undersize on the back of the crank bearings.
It has been running but there is definitely more engine noise than there should be and I think one of these is the culprit. Kinda of a clacky sound when idling but everything else should be fine as it's all new.
Am running aftermarket cam too.
This can't be right!
Gears, cam and hi rev valve springs were bought new from CB performance.
Oil pump is an anodised tooleys 26mm replacement pump.

http://www.youtube.com/watch?v=LxOmulQMWKo

Any ideas from experienced people??
More info needed? Let me know!

Toby
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type3lover in the garage...

796 posts · joined Feb 2005 ·

#752721
Valves set at 4thou inlet and 6 thou exhaust....double thrust on cam bearing.
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hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 ·

#752730
have you vid of the engine noise you are concerned about when it was together and running..........

yeah, back lash is a concern..........pump gear/drive can be "adjusted" to have it engage in the cam better.

send "dangerous" a PM, he will be happy to help you and his answer will be the one you act on............he is sometimes on here later, but religiously each morning before his walk, so i would bet you will have a definative answer tomorrow morning

type3lover in the garage...

796 posts · joined Feb 2005 ·

#752748
Hey mate! Thanks for the reply :-)
I'd love to know what Dave thinks about this too.
Prolly should have bought Berg gears 👍

Here is a link to it running...audio isn't great: http://www.youtube.com/watch?v=aU2rssXq3Iw
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Sides Veteran Volks Folk

2,220 posts · joined May 2007 ·

#752757
Yikes - loud !!!

Am a bit curious Toby... how are you doing the crank signalling now ???
VWDCQ vice pres & web dude - vwdcqinc.org.au
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type3lover in the garage...

796 posts · joined Feb 2005 ·

#752760
Hmmm too loud!
Not sure what i had for crank signalling then...might have been a haltech setup, but now i have 36-1 trigger wheel mounted onto the fan pulley, ford EDIS-4, and a VR sensor from a late model falcon.
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1500S Custom Title Time!

1,418 posts · joined Mar 2005 ·

#752764
type3lover wrote:Hey mate! Thanks for the reply :-)
I'd love to know what Dave thinks about this too.
Prolly should have bought Berg gears 👍

Here is a link to it running...audio isn't great: http://www.youtube.com/watch?v=aU2rssXq3Iw
Toby, can I ask why the use of spur gears rather than helical. I know that they make a hell of a noise but what is the mechanical advantage of their use??

DH

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#752772
Backlash excessive x2
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 ·

#752789
Factory specification for gear backlash is between zero and .002".(.052mm)

The factory used cam-gears with larger pitch circle cam gear, to account for variances in the spacing between
the cam and crank,
but aftermarket gears do not offer this option.

Measure the clearance you have now with a dial indicator,(or trimmed feeler guage).

A swap back to the standard gears will tell you if the problem is case, or gear, related,
but my guess is that it is the actual gear set.

Personally I would allow as much as .004"(0.1mm) backlash on new steel gears,
remembering that larger backlash may induce more noise.

The oil pump tang does sound noisy too, but requires that amount of clearance in the cam slot
to allow unhindered alignment with various tolerance variation of pump body, cam slot and crank case.
but provided the engagement of the tang within the cam-slot is a the correct depth,
and a pre-lube of moly assembly paste is used, the constant load on the gear teeth of the pump should not create noise.

Of worthy note is to check that the oil pump holes,
and the chamfer on the pump body do not allow air to be sucked into the suction port in the crank case.
Most of the pumps I have fitted of late neeed 1mm to be removed from the back gasket surface.
westi wrote:That's mad Alan.

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#752828
^^^ Yep Dave, just what I thought.

The only other thing that needs mentioning, possibly the oil pump may be making that excessive noise if it was set up oirginally without rotating the crank/cam assembly a few rotations during assembly to centralise the pump drive into the cam slot. Pull the drive gear and look at the wear in the cam slot and on the oil pump drive.

That cam backlash almost certainly will rumble. As opposed to too tight that will increase gear noise. mmmmmmmmmm straight cuts 😁
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

type3lover in the garage...

796 posts · joined Feb 2005 ·

#752887
Thank you for the advice!!

DH: I'm using straight cuts instead of the stock helicals for 2 reasons...camshaft thrust is greatly reduced (I'm running HD single springs and a cam with a short ramp) and I love the noise :-)

Dave: Thanks mate for the info...i don't have any precision measuring tools but it "feels" like more than 0.1mm hahaha. Seriously though, i was expecting to see some damage based upon the awful noise but nothing apparent. I have a stock cam and gear set (stock type 3 one from a different case) and will put that in and see how it feels and try to measure the backlash. I know the factory ran -7 to +7 on the cam gear. As my factory one is not marked I assume it is a "0". I also heard that aftermarket sets are all "zero's".


Will also align and spin the pump before tightening as per matberry's advice.

There was obvious wear on the oil pump drive tang where it's been "hitting".

I'll let you all know how I go.

Cheers! Toby 👍
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