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Comp cams

Started by _Bluejinx202_ , Oct 19 2012 04:01 AM

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114 replies to this topic

#51 _Inj gtr202_

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Posted 18 November 2012 - 09:04 AM

Great post Johnno.
The only difference in method to the one I used (I've only done it once) is that I used a second dial indicator to measure top dead center as I found that I kept getting slightly different readings with my positive stop. Most likely is was not a very positive stop :blink2:

.

Also make sure you are measuring the intake valve, not the exhaust valve, I won't say how long I was dong it wrong and getting more and more confused.
Hehe.. one more, make sure you turn the crank clockwise :dohdoh:

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#52 _Bomber Watson_

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Posted 18 November 2012 - 09:42 AM

I've done the whole exhaust valve thing to......

Its not so bad when you do it on your own, but when your around at a mates place dialing his cam in and do it its rather embarrassing.

Cheers.

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#53 _oldjohnno_

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Posted 18 November 2012 - 10:10 AM

I've done the whole exhaust valve thing to......

Its not so bad when you do it on your own, but when your around at a mates place dialing his cam in and do it its rather embarrassing.

Cheers.

The likelihood of doing something dumb is in direct proportion to the number of witnesses present.

I've proven this law enough times to vouch for its truthiness....

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#54 _Bomber Watson_

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Posted 18 November 2012 - 10:51 AM

Bahahaha.

Im going to steal that one.

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#55 _oldjohnno_

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Posted 18 November 2012 - 11:36 AM

There's more to it. If the likelihood of a mishap is related to the number of onlookers, the severity of the mishap is related to how badly you want to impress those onlookers.

Lets say you are starting a newly built engine for the first time. If you are alone it will start first go and won't leak a drop. If there is one or two mates present you'll have to pull the dissy and put it in the right way, then it'll run fine.

But lets say you are trying to start it in front of a group of hot, nubile young women. The engine will start first go. Then as you blip the throttle it will stick open. As you frantically jiggle the linkage (with the engine idling at a steady 8000rpm) the little nylon tube to the oil pressure gauge will melt on the exhaust and spray both you and the floor with hot oil before starting a fire. As you scramble for the extinguisher you slip face down on the oily floor, whereupon the dog decides to jump on your back and start humping you.

Next time, you think to yourself, I'll do this when there's no-one around.

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#56 _Bomber Watson_

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Posted 18 November 2012 - 11:48 AM

PMSL!!!.

Aaaahhhh, wise words indeed.

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#57 _stretchlc_

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Posted 18 November 2012 - 12:08 PM

Hahahaha...never a truer word spoken.....I'd love a dollar for every time shit like this has happened to me

Your explanation of cam timing is beautifully explained John...thanks

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#58 _Inj gtr202_

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Posted 19 November 2012 - 08:05 AM

The likelihood of doing something dumb is in direct proportion to the number of witnesses present.

I've proven this law enough times to vouch for its truthiness....

Next time the line stops at work and I gotta go fix, the managers and observers are gonna cop that quote. Love it

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#59 _nicko61_

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Posted 19 November 2012 - 08:31 AM

changing your prop is the same as changing diff ratio's,have you tried a couple of other props before changing what sounds to be a well made strong motor

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#60 _Ned Loh_

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Posted 30 November 2012 - 07:50 AM

I have not tried but it appears that you may be able to get them through JEGS & Summit.

http://www.summitrac...s/CCA-81-000-5/

http://www.jegs.com/...parentProductId=

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#61 N/A-PWR

CABIN ENGINE CONTROLS GALORE

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9,595 posts

Name:Dave I
Location:Wooroloo, 65km's East of Perth
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Joined: 08-December 12

Posted 10 December 2012 - 02:36 AM

Great Discussions here,
Another cause of performance loss/ gain is the same Cam in different Motors ( Blocks ) act differently.
saying the said XCam in a 186 pulls at 4500rpm and the same XCam in a 202 pulls at 3100.
Both Motors have exactly the same added components. Dave I

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#62 _Bomber Watson_

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Posted 10 December 2012 - 07:59 PM

Thats because of capacity......

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#63 _Ned Loh_

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Posted 19 December 2012 - 08:36 AM

Hi Oldjohnno,

Do you know what RPM peak HP was with this cam? I am curious how the greater area under the lift curve effects peak hp rpm compared to a more traditional grind (with wide LSA, although I note this cam was only 108).

Cheers.

Edited by Ned Loh, 19 December 2012 - 08:38 AM.

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#64 _oldjohnno_

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Posted 21 December 2012 - 10:58 AM

Do you know what RPM peak HP was with this cam? I am curious how the greater area under the lift curve effects peak hp rpm compared to a more traditional grind (with wide LSA, although I note this cam was only 108).

Cheers.

At the moment it's zero rpms; it's still in the box :blush:

Theoretically it should have a torque peak around 5600 - 5700 and peak HP at around 6200 - 6300. I know that sounds lowish but the rpm range has as much to do with port and manifold characteristics as it does with the cam, and it is for a mild streeter.
And the cam companies often seem to quote hilariously optimistic rpm ranges that have nothing to do with the real world. Eg cams that have a quoted range of 2800 to 6800 that really only have a useful range of less than 1000rpm. Maybe they are talking about the minimum rpms the engine will run cleanly at and the maximum it will pull with a very light loading????

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#65 _Ned Loh_

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Posted 21 December 2012 - 05:00 PM

At the moment it's zero rpms; it's still in the box
Theoretically it should have a torque peak around 5600 - 5700 and peak HP at around 6200 - 6300. I know that sounds lowish but the rpm range has as much to do with port and manifold characteristics as it does with the cam, and it is for a mild streeter.
And the cam companies often seem to quote hilariously optimistic rpm ranges that have nothing to do with the real world. Eg cams that have a quoted range of 2800 to 6800 that really only have a useful range of less than 1000rpm. Maybe they are talking about the minimum rpms the engine will run cleanly at and the maximum it will pull with a very light loading????

Of course you are correct about the other characteritics effecting peak HP RPM. I would have guessed about the same, but was curious how the greater area under the valve curve would effect it.

Maybe the cam companies measure the RPM range of their cams on an engine test stand? Would perform well for certain.

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#66 _oldjohnno_

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Posted 21 December 2012 - 05:25 PM

I would have guessed about the same, but was curious how the greater area under the valve curve would effect it.

Some of older style cams had similar rpm peaks using anything from 10 to 20 or more degrees of seat duration, so it definitely makes a difference.

I guess it's hard to come up with a "usable rev range" - one blokes definition might be any speed that runs cleanly, another might say it's any speed where the torque is within 25% of the peak (which to me sounds more reasonable). At the end of the day the advertised numbers are meaningless.

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#67 _Bomber Watson_

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Posted 21 December 2012 - 05:41 PM

Bullshit OJ, useable rev range for anyone with half a brain like me is from the lowest you can get the frOcker to idle without stalling untill the valves bounce :tease:

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#68 _oldjohnno_

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Posted 21 December 2012 - 05:49 PM

I stand corrected Bomber, from now on I'll assume it's any speed that the engine can spin under its own power :spoton:

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#69 _Bomber Watson_

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Posted 21 December 2012 - 05:50 PM

Good lad, life is a lot simpler when your a dumbass

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#70 _Ned Loh_

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Posted 21 December 2012 - 05:59 PM

Some of older style cams had similar rpm peaks using anything from 10 to 20 or more degrees of seat duration, so it definitely makes a difference.

Let us know how you go when the cam is installed. I'm sure there are more than a few here interested.

I guess it's hard to come up with a "usable rev range" - one blokes definition might be any speed that runs cleanly, another might say it's any speed where the torque is within 25% of the peak (which to me sounds more reasonable). At the end of the day the advertised numbers are meaningless.

IMHO Usable rev range is easy = Lowest RPM it will 'nicely' take full throttle to 500rpm/1000rpm below the point where it goes bang.

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#71 _Ned Loh_

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Posted 12 February 2013 - 02:19 PM

Oldjohnno / bluejinx,

What lifters did you end up with these cams? Did comp supply lifters to suit?

Within each lifter 'family', Comp only seem to offer one .842" lifter for all applications. Lifter part 800 (ok priced EDM hole lifter) in .842" for example is listed as fitting Caddy/Pontiac/Olds/SB Chev/BB Chev.

Cheers.

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#72 _Bluejinx202_

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Posted 12 February 2013 - 06:28 PM

Oldjohnno / bluejinx,

What lifters did you end up with these cams? Did comp supply lifters to suit?

Within each lifter 'family', Comp only seem to offer one .842" lifter for all applications. Lifter part 800 (ok priced EDM hole lifter) in .842" for example is listed as fitting Caddy/Pontiac/Olds/SB Chev/BB Chev.

Cheers.

Sorry Ned, not sure. Haven't put the cam in yet. I swapped the engine do I could keep racing while I changed cam and re-ringed old motor. I was just going to re-face current solids and wack em back in.

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#73 _Ned Loh_

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Posted 13 February 2013 - 09:59 AM

Ok, cheers. Refacing should be ok, but it'd be nice for certainty of compatibility, to buy lifters from comp.

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#74 _Bluejinx202_

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Posted 05 August 2013 - 07:37 PM

I'm diing this process wrong, or my cam isn't ground correct....

Lobe centre 110

Installed cam gear dot to dot,

112L lift@ TDC
Int 77deg -.020
132deg +.020
= 104.5 CL

EX 126 deg-.020
71deg+.020
= 98.5CL

Shouldn't I have 114.5 on ex for a 110LS Cam?
Also this cam is ground +1.
I'll go +5 if I can work out what's going on here....