| [ Total Views: 990 | Total Replies: 11 | Thread Id: 108443 ] |
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 hulbyw
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| posted on February 23rd, 2015 at 08:17 PM |
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Straight Cut Gears - Question for Engine Builders
It has been suggested to me to use straight cut gears in my 1776. I have Berg HD valve springs, a very mild cam (Wade 149) and 1.25 ratio rockers.
Noise aside, are straight cuts worthwhile with the above specs?
Cheers............Wayne
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bajachris88
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| posted on February 23rd, 2015 at 08:38 PM |
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If u go straight cut ensure u use double thrust cam bearings.
(ô_!_/ô) (ô_!_/ô)
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 Bizarre
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| posted on February 23rd, 2015 at 09:11 PM |
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| Quote: | Originally
posted by hulbywNoise aside, are straight cuts worthwhile with the above specs?
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no - but they do sound cool
Futue te ipsum!!!
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DubbyDo
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| posted on February 23rd, 2015 at 09:18 PM |
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I thought you would have less need for double thrust bearings on straight cuts as you don't have the crank gear trying to drive the cam backwards
/forwards? saying that if you have the case split regardless of what style cam gears you are running double thrust bearings can only be the better way
to go. They aren't that noisy either, definitely nothing like a Holden red 6
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vwo60
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| posted on February 24th, 2015 at 06:37 AM |
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Are you running double valve springs, straight cut gears are only needed if you have high spring pressure, apart from the noise there is no gain as
the cam you will be running is quite mild, be aware of the lack of quality some of the cam gear sets have, standard cam bearings will do the job as
there is no load on the thrust bearing any more. if you are running double valve springs it is a good idea to break the cam in using only the outer
springs and fit the inner after the cam has been broken in.
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hulbyw
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| posted on February 24th, 2015 at 05:15 PM |
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No doubles, only HD Berg singles
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matberry
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| posted on February 24th, 2015 at 06:13 PM |
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| Quote: | Originally
posted by hulbyw
No doubles, only HD Berg singles
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I'd recommend no straight cuts, just double thrust cam bearings which I use in every engine and modify them slightly for improved oiling.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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 vw54
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| posted on February 24th, 2015 at 06:59 PM |
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Straight cut gears give you absolutely no power gain
HOWEVER they do give you a headache listen to the extra noise
if there was a power gain every engine manufacturer in the world would have used them they didn't spend millions on research and design for
nothing
the cam and rockers will give you more power which when added will need the heaver springs you will need extra carburation and a decent exhaust
system as well
what have you planned for that
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matberry
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| posted on February 24th, 2015 at 08:42 PM |
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My biggest concern with straight cuts is getting the cam gear lash right. The stock set up allows a range of gear sizes to choose, gears range from +9
to -9 so 19 different sizes including a zero gear.
You don't get that with straight cuts, one size fits all, or not.
I have seen single thrust bearings very worn on some high mile engines, so I believe paying careful attention to fit, end float and oiling is
important here.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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hulbyw
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| posted on February 24th, 2015 at 09:50 PM |
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Exhaust will be VS and 40dcn ( yes I know I would be better with twins but using that single weber to start with).
The CB straight cuts are actually not too bad noise wise, but given the above advice I will save my money and forget the straight cuts
Thanks all for your comments and help. Much appreciated
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fish26
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| posted on February 24th, 2015 at 11:01 PM |
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I'm no engine builder but I like straight cuts mostly because quality of aftermarket helical gear sux, do you need them in your engine? Not really
but it's up to you to decide. As posted above, dual thrust proper clearance bearings and right combination of size and pitch in gears will work for
you.
bitten by the bug..........several times
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modnrod
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| posted on February 25th, 2015 at 09:39 PM |
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| Quote: | Originally
posted by vw54
Straight cut gears give you absolutely no power gain
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On a Holden six in a 15 sec Torana the straight cuts with no other change at all, nothing, is worth a solid tenth and a half, tested before and after
then back again.
And yes, on a 192 crap they're loud! 
Your experience of doing the same testing was obviously different..........
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