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Old 09-22-2019, 02:31 AM   #1
sliding
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Default Why the NR Racing torque cam has so much tappet noise.

I have run the NR racing torque cam in my GX270 clone and was unhappy with the amount of valve train noise. I tried different valve clearances and even set them at zero when cold.

I ended up removing the torque cam and going back to the GX390 camshaft I had previously run as the noise was unacceptable and made my cart sound like a diesel.

I had the torque cams specifications checked on a cam doctor. This machine gives readout of all the camshafts specifications. It turns out that the torque cam uses a grind more suited to an engine with hydraulic lifters not solid lifters like in our engines.

The article below explains it well.

CLEARANCE RAMPS: The portion of the cam lobe just up off the base circle which lifts at a
slower speed than the flank. Its purpose is to dampen or ease the initial lifter motion, rather than
opening and closing suddenly. Ramps on hydraulic lifter engines are very small, maybe only as
high as .003” and only serve as noise reduction devices because the dampening effect is mostly
catered for by the hydraulic lifter. Ramps on solid lifter camshafts are much higher, anywhere from
.006” to .020” (ramp height multiplied by your rocker ratio equals your maximum valve clearance).
Ramp designs have a tremendous effect on power output and valve-train reliability.

That's why these cams are so noisy in our engines.
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Old 09-22-2019, 08:48 AM   #2
BIKERMIKEYBLACK
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Default Re: Why the NR Racing torque cam has so much tappet noise.

Very interesting I have one of these cams I was going to use but after hearing this and the other posts about lobes failures I Kind of Leary about it
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Old 09-22-2019, 09:22 AM   #3
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Default Re: Why the NR Racing torque cam has so much tappet noise.

The torque cam started out as a "cheater cam" for racing. The cheater cams have the same lift as the stocker but add duration. I have been running one in my VC 460 since 2014 with the added lift if the 1.3 ratio rockers without any issues.
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Old 09-22-2019, 09:55 AM   #4
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Default Re: Why the NR Racing torque cam has so much tappet noise.

I used the Isky racing cam in my VC440/460 and the noise was terrible. You could hear the tapping from quite a long distance. I disassembled it and found the tappets are wearing terribly and there are defect on the cam lobes. This is the main reason I pulled the engine and parked it. I will likely put the stock cam back in and sell the engine. I don't think the factory tappets and the racing cams go together too well. If a clone engine is to be built for power and rpm the valvetrain must be addressed with roller parts etc. Does anyone even make hydraulic tappets? Or roller tappets?
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Old 09-22-2019, 11:22 AM   #5
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Default Re: Why the NR Racing torque cam has so much tappet noise.

I have 2 460's and out of the box they were very noisy on the top end. The OP didn't say what he gained or lost changing the cam back to the original. I can say without a doubt that the little tin rocker arms - guide plate - valve cover amplify that engines noise level. VC did a great job building the 460 for the amount of money spent. They couldn't have added any more to the basic engine without making it cost prohibitive.
Knowing from the beginning that the valve train in this style engine is there weakest point, I changed over to roller rocker arms. I run Gage 1.3 to 1 rockers in my truck and NR rockers in my second engine.
A combination of aluminum "Gage" rockers and cast aluminum valve "Aussie Speed" cover deaden the sound. I do run tighter tolerances valve settings because of this, .002 intake and .004 exhaust. With added air shrouds on the head it cools better so less expansion. Amazing what a piece of tin and a bolt can do.

All said, mine runs very very quiet compared to the first time it ran.
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Old 09-22-2019, 01:10 PM   #6
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Default Re: Why the NR Racing torque cam has so much tappet noise.

Further notes on valve train. I started with a very early 5/2014 which came with a stock clone cam and the silver asian HD valve springs.Being Ray I changed to the then sold by VC billet stud mounted 1.3 rocker arms. That really quieted the ting ting valve train noise. VC then posted that the silver hd springs had issues with coil bind on anything but stock lift cams and recommended going to the gold comp cams version. But I continued to run the silver spring set up for about 200 hours until my 2016 tear down. This was to change to the torque cam and replace the cast rod with the VC produced billet rod. The only issue I seen was the guide plate for the push rods was sort of ovaled out from wear. Sho 305 was doing his 420 lifan near this time so I advised him to look at his guide plate. It showed a similar issue. We both switched to the NRracing shaft mounted roller rockers and torque cams at this time.That was 3 years + now and whenever I check valve lash it is basically unchanged showing no wear anywhere in this upgraded valve train.The 2014 lifters are still in the engine since they showed no wear on the tear down.They now have 330 hors + on them.
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Old 09-22-2019, 01:34 PM   #7
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Default Re: Why the NR Racing torque cam has so much tappet noise.

Good info
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Old 09-22-2019, 02:14 PM   #8
raydhd
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Default Re: Why the NR Racing torque cam has so much tappet noise.

The real thing to note here is whether you are using the $20 VC, $120 NR,$180 Gage shaft rockers the guide plate is no longer needed along with the limitations of the stud mounted rocker system. As Shepard noted this change along with either the Billet or cast aluminum valve covers really quiets valve train noise AND those pesky valve covers oil leaks.
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Old 09-22-2019, 05:45 PM   #9
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Default Re: Why the NR Racing torque cam has so much tappet noise.

I had a 420 lifan from home depot. I ran it, later put the stamped 1.3 rockers on from VC. They are for some other engine and don't work perfect. I put them on with the old HD springs from VC. This setup with stock cam worked ok, gave some new power on top end. This had a cut and ported head, header, at some point a larger 32mm carb. All this time it made about the same valve noise as the stock G9 engine did, it was not loud IMO but could hear it some. It lost a little power and I found the head gasket was blown, but before the 94c clutch it would spark knock some. Then I put in the NR shaft billet rockers and big pushrods and VC rod and cheater cam, still running stock valves and caps on both. I had to shim the shaft rockers higher (1.3 ratio also). It is still roughly the same to me maybe a little quieter. It always would get louder if the lash was big. The old stamped 1.3 rockers did wear into the guide plate on an angle, I read the geometry was not quite right. Just put a 30mm slider carb on and it runs nice but have to make a custom cable hookup for it, can't ride with a hand pulling the cable lol.

Now reason I can get away with this is the cheater cam is stock lift, so it does little in way of changing the action of the valves just open longer. 1.3 rockers give me lift about like a real cam would, and the HD springs (the new model VC springs) seem to work fine it can hit rpm well over 5K that I don't really want to run it to and only have in speed run tests up to 42mph gps with 22s and stock gears in a G9. It was over 5K rpm at 38gps with the stock cam. It does have more power everywhere, and it does have a 94c clutch that shifts about 4100 rpm now. It engages a little higher than stock clutch did because it would spark knock at low rpm, still around 2K or something so its fairly drivable for utility use yet, and has pedal start still.

I don't have a lot of hours on it this build yet, I hope the cam is working ok in there. It did have a lot of slop and should have been shimmed. Sometimes hear it knock a little at low idle speeds. I had a lot of metal in the one hour oil change, I figured it was from the hone job but not sure, it was very fine likely alum. Its still running great so not sure, not going to inspect maybe will this winter if time but I never have time.
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Old 09-22-2019, 06:01 PM   #10
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Default Re: Why the NR Racing torque cam has so much tappet noise.

Quote:
Originally Posted by slonomo View Post
If a clone engine is to be built for power and rpm the valvetrain must be addressed with roller parts etc. Does anyone even make hydraulic tappets? Or roller tappets?
With only splash oiling hydraulic tappets are not possible, you would need pressurized oiling. The lifter bores would also need to be much larger.

I think that there just isn't enough space above the cam to design an effective roller, you also would need to devise a method to prevent a roller lifter from rotating in it's bore, that eats up more space. There just isn't enough room there to use a roller and get acceptable lift.
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