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Holden six cam database

Started by _oldjohnno_ , Aug 23 2013 10:47 AM

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#26 _oldjohnno_

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Posted 20 October 2013 - 08:47 PM

Here's another one courtesy of Warren (thanks!). It's a Camtech 641B, 292 adv and 262@50, one of the bigger .842" cams we've seen so far. I've put it with a Camtech 624A for comparison. They have nearly identical accelleration rates, in fact they are almost perfect scaled copies. Lift rates are comparable to some of the US grinds and the area under the curve would indicate good performance - and the cars times would back this up. That's one of the things about running an engine like the little six with limited breathing, as you keep throwing more cam at them they keep making more power.

Here it is again, this time showing a 1.5 rocker compared to a 1.6 rocker. Again, because of the limited breathing you'd expect these engines to respond well to more rocker.

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#27 _oldjohnno_

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Posted 21 October 2013 - 06:38 AM

Something else worth noting with these grinds; they are very noticeably assymetrical with a gentle closing ramp. Should be good for high rpms without bounce.

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#28 warrenm

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Posted 21 October 2013 - 07:02 AM

Is 7000 rpm enough revs?

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#29 _oldjohnno_

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Posted 21 October 2013 - 06:26 PM

I'd expect it to handle 7 - 7500 easily

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#30 _Bomber Watson_

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Posted 21 October 2013 - 07:26 PM

Im staying quiet but paying attention, i assume the 641B is about the best we have seen thus far for a 200cfm 12 port with 2" SU's, suitable comp ratio for the fuel and a bottom end that can keep up?

Cheers.

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#31 _oldjohnno_

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Posted 21 October 2013 - 07:44 PM

Im staying quiet but paying attention, i assume the 641B is about the best we have seen thus far for a 200cfm 12 port with 2" SU's, suitable comp ratio for the fuel and a bottom end that can keep up?

Cheers.

Yeah, even if only because everything else we've seen so far has been smaller. And remember all we've looked at so far has been 0.842" stuff, I'm really looking forward to graphing some 875 or bigger flat tappets and comparing them to roller lobes. But yes, it does look good, quick off the seat, gentle closing and a useful amount of lift.

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#32 _Bomber Watson_

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Posted 21 October 2013 - 07:48 PM

And looks nice and streetable to

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#33 _oldjohnno_

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Posted 21 October 2013 - 08:13 PM

And looks nice and streetable to

I guess you're half-joking, but.... that's the thing about these cams with limited seat timing yet much more area under the curve where it counts - you really could run something like this in a street car without too much trouble, and still make a ton of power.

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#34 greens nice

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Posted 21 October 2013 - 09:07 PM

:ph34r:
Data is on its way!

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#35 _Bomber Watson_

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Posted 21 October 2013 - 09:46 PM

I guess you're half-joking, but.... that's the thing about these cams with limited seat timing yet much more area under the curve where it counts - you really could run something like this in a street car without too much trouble, and still make a ton of power.

Bingo. Like i said i have been paying attention but keeping my trap shut.

*edit* and learned a farking lot of brain info to i must say old chap

Im talking sunday arvy quick cruise "nice and streetable" not "daily it just like you would a stock VF commy" streetable. Maybe cruise it to work for shits and giggles if you woke up early enough to spend and extra 10 minnutes on your commute time due to not being game to go near the speed limit and being arrested.

Basically it would be possible to operate a clutch with such a combo, providing you had 3.9 or shorter diff gears lol.

Cheers.

Edited by Bomber Watson, 21 October 2013 - 09:49 PM.

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#36 warrenm

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Posted 21 October 2013 - 11:16 PM

I'd expect it to handle 7 - 7500 easily

At this stage 7000 is it, I think the head is holding it up now.

Bingo. Like i said i have been paying attention but keeping my trap shut.

*edit* and learned a farking lot of brain info to i must say old chap

Im talking sunday arvy quick cruise "nice and streetable" not "daily it just like you would a stock VF commy" streetable. Maybe cruise it to work for shits and giggles if you woke up early enough to spend and extra 10 minnutes on your commute time due to not being game to go near the speed limit and being arrested.

Basically it would be possible to operate a clutch with such a combo, providing you had 3.9 or shorter diff gears lol.

Cheers.

It drives on the road Ok with 26" tyres & 4.1 diff. It would be a lot easier to drive if it had a rag clutch instead of a metal one.

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#37 _oldjohnno_

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Posted 22 October 2013 - 06:17 AM

Back in the day we wouldn't think twice about running 310 or so seat to seat on the street, so these newer cams should be no problem at all. What you would have to keep in mind though is the durability aspect - the newer, more aggressive profiles are harder on the entire valvetrain, and if you're running enough spring for 7500 or so then I wouldn't expect it to last forever. I'd limit idling as much as possible.

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#38 _oldjohnno_

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Posted 24 October 2013 - 07:36 PM

Heres another one (thanks Kev!), a Comp 6267 XTQ series. It's shown with the closest other lobe we have seen, the Camtech 641B. They are much closer than I expected them to be with very very similar acceleration and deceleration rates. Performance wise I'd say there'd be nothing in it apart from the difference in duration.

Here's the same lobe with 1.5, 1.6 and 1.65 rockers.

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#39 _Bomber Watson_

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Posted 24 October 2013 - 07:49 PM

Ooooo that ones slightly bigger....

Forgot to ask earlyer, why do you say you would limit idling with these largish profiles?

In my tiny and ill informed brayne idling would be seen to put the least stress on the valve train...Or is it for some different dark sacred scarcely shared reason?

By limiting idling do you mean "i personally wouldnt sit at traffic lights with the car running" or "dont let it idle for four hours"?

Cheers.

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#40 Litre8

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Posted 24 October 2013 - 07:59 PM

I'll take a guess and say if its a flat tappet cam then idling provides minimum cam lobe lubrication so bad news if it has high spring pressure.

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#41 _Bomber Watson_

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Posted 24 October 2013 - 08:03 PM

AHA.

Could be the ticket......

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#42 Litre8

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Posted 24 October 2013 - 08:04 PM

Let's wait for someone who knows what they are talking about to provide the real answer..

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#43 _oldjohnno_

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Posted 24 October 2013 - 08:08 PM

Think about the pressure on the nose of the lobe. If the revs are high enough that the valves are just starting to float then the pressure on the nose is zero. As you decrease the rpms the pressure over the nose increases until it hits its maximum at a slow idle. On the other hand the pressure on the opening flank is just the opposite and increases with rpms. Somewhere in between - maybe 4000 or so - is probably going to be the most gentle speed overall, plus it'll be getting some oil and the lifters will be turning.

Personally I wouldn't drive a car with a big cam and springs anywhere that involved a lot of time at traffic lights. If I had to sit still for more than a minute or so I'd shut it off.

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#44 _Bomber Watson_

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Posted 24 October 2013 - 08:10 PM

Im in the middle of nowhere, if im at traffic lights for more than a minute im out of the car abusing people.

Big cams for me

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#45 Litre8

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Posted 24 October 2013 - 08:23 PM

Just go with a roller Bomber.!

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#46 _Bomber Watson_

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Posted 24 October 2013 - 08:26 PM

Theres a lot of people telling me that....

Not sure if i believe the whole "some lad picked up 25hp going to roller" jive but reliability.....

Im going back to being quiet and paying attention.

Cheers.

Edited by Bomber Watson, 24 October 2013 - 08:27 PM.

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#47 rodomo

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Posted 24 October 2013 - 08:30 PM

My cam is that lumpy the inlets are always open and the exhausts never close. :3gears:

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#48 _oldjohnno_

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Posted 25 October 2013 - 06:00 AM

My cam is that lumpy the inlets are always open and the exhausts never close.

Wow, that's gotta be at least a Stage 7...

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#49 _oldjohnno_

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Posted 25 October 2013 - 06:27 AM

At the risk of boring people to death over the idling issue.....

There's another reason to avoid idling big cams and springs that's related to lubrication. One of the hardest things to properly oil is a pair of rubbing surfaces that have a very low relative speed - there just isn't enough speed there to build up a hydrodynamic wedge. An engine like a 202 idling at say 1000 rpm spins the cam at only 500 rpm, and the lobes have an effective diameter of something like only 1-1/4". There just isn't enough speed to form good oil separation so much of the time you'll be relying on last-line-of-defence tools (like zddp) to avoid eating the lobes. This will be the case at very low speeds no matter how much oil you throw at the cam.

If there was no way that I could avoid idling I'd have to consider sacrificing some hp by using a higher-than-ideal oil viscosity, which would help with the low speed oiling.

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#50 _Ned Loh_

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Posted 25 October 2013 - 09:53 AM

At the risk of boring people to death over the idling issue.....

There's another reason to avoid idling big cams and springs that's related to lubrication. One of the hardest things to properly oil is a pair of rubbing surfaces that have a very low relative speed - there just isn't enough speed there to build up a hydrodynamic wedge. An engine like a 202 idling at say 1000 rpm spins the cam at only 500 rpm, and the lobes have an effective diameter of something like only 1-1/4". There just isn't enough speed to form good oil separation so much of the time you'll be relying on last-line-of-defence tools (like zddp) to avoid eating the lobes. This will be the case at very low speeds no matter how much oil you throw at the cam.

If there was no way that I could avoid idling I'd have to consider sacrificing some hp by using a higher-than-ideal oil viscosity, which would help with the low speed oiling.

certainly not boring, in fact I'd say the best engine/202 thread for a long while.

By the way, speaking of cam lobes, the engine I grooved the lifter bores on (pic is in another thread somewhere) a few months ago is now together. Yet to be used in real anger, but at normal road use type temps (70 odd c) is holding good pressure and doesn't seem to have bled too much flow away from the rest of the system. 'Shakedown' tomorrow...

Back on the cams, gee I would have guessed an XTQ lobe to be a least a little steeper. Nice suprise though as what we are really finding out is that we don't need to go offshore. I'm not sure the camtech closing ramps need to be as gentle as they are though (?)

After I get this shakedown out of the way tomorrow, next week I should be able to get an old skool lobe done that has similar adv duarion to the ones just posted.