Are all Cams Equal?????

[SpecOps13]

I don't mean lift or duration. I mean adjustment or clearance wise. I ran a compression check on my 89 several months ago. The cylinders measured 220-230 (My 94 was 150-160) with basically no leak down from that. Then I did all the wiring upgrades on the 89 to have a better hot start. That didn't improve a great deal. Bike still struggles to get the first revolution when hot. It usually starts easily from there. The engine sounds like a box of rocks at idle, so I'm wanting to adjust the valves and see if it quiets down. Are the clearances for various cams the same as the factory shim settings. I might FU a good thing going after a valve adjustment if they're not the same and I have some weird cams...

BTW: running octane booster quiets the rocks some...:rofl_200:

 

[AtlasMax]

Could it be that the tight valves are the cause of the compression difference? A delay in valve opening/closing should cause dynamic compression to increase, as normally cam timing bleeds off a certain amount of compression during the stroke.

Just a thought. I have never heard of different stock Vmax cams through the years, but I am no expert and that is certain!

 

[joelyons50023]

What type of cams do you have and what's the static comp. Of it also. And does the noise come from the left side more or can u hear it directly from the cam area

 

[bazwell]

Without knowing what has been done to your motor, I can only give a few guesses.

To answer your question, it is possible that a reground cam has different clearances required.
You could just check the clearances and report what you find. You won't FU a good thing if you don't change the shims!
If you consider a cam lobe is a circle with a bump added on, you could measure the size of the circle (across the base) and maybe compare that to a known standard cam to see if it has been re-profiled. Or compare the casting marks to a known standard cam. I don't know what aftermarket cams are available. Someone else might know.

Joelyons suggestion holds water. See if the noise is on the left side. It may not be cams making the noise.

The comment about octane boost could mean something else. Any history on what has been done to the engine would help a lot.

 

[SpecOps13]

bazwell

I thought this thead had died. I PM'd joelyons50023 with this: That's the big problem. I don't know what the PO may have done to this 89's motor. It puts my 94 in the dirt. Both are similarly modded. Except for the unkonwns in the 89's motor. I really have no idea what the cams are or the Static Compression Ratio. Just wondering if the valve clearance is the same or different for different cams in the VMax... So I know if I can do a straight forward valve adjust or if I need to dig deaper into this engine first...

Thanks for any input...

Dave

 

[Rusty McNeil]

When and if I ever get home I'll look at the set of megacycle .380 lift cams I have new in the box and see what the clearance spec sheet call for....

 

[one2dmax]

Actually calls for a tighter spec on the exhaust side if I remember correctly. They may have figured the exhaust valve doesn't grow as much as the OEM thought it does. It's not the different cam that determines the spec. It's the change in valve length when heated up.

Intakes don't get as hot so they don't "grow" as much. Exhausts get much hotter and need more clearance to account for the length change they made as they heat up.

Too little clearance will result in valves not fully seating (which can cause power loss and erosion of the seat). Too much clearance and you could spit a shim out or damage the cam lobe.
Sean

 

[SpecOps13]

Even setting at 220-230 lbs pressure in the cylinder, there was no bleed down on any of the cylinders. I was concerned about blowing a head gasket setting like that but pressure didn't budge at all...:confused2:Thanx for the inputs. I have all the wiring mods possible done to the stock wiring. I haven't doubled any cables. The engine always starts but it's slow to turn over the first compression hot or cold... My Odyssey reads 12.9 after setting for a week...:ummm:


Ouch, Corrected the 13.9 to 12.9.... Thanx for catching me on that joelyons50023 and Garrett... See next 2 posts... My Bad...:bang head:

 

[joelyons50023]

If your battery reads that then its toast anything over 12.8 is cause for concern. Get the battery load tested to tell for sure

 

[SpecOps13]

It's an Odyssey so 12.9 is normal in both bikes...
8-12 year service life battery for Extreme Sports
like SeaDoo's and Snow Mobiles.... Load Test's good
At Auto Zone BTW....:confused2:

 

[gamorg02]

It's an Odyssey so 12.9 is normal in both bikes...
8-12 year service life battery for Extreme Sports
like SeaDoo's and Snow Mobiles.... Load Test's good
At Auto Zone BTW....:confused2:

you said 13.9 in your previous post, did u mean 12.9?

 

[SpecOps13]

I corrected it and noted the reason, I can be a Dumb Ass some Fridays.:bang head::rofl_200:

 

[bazwell]

Dude,

Sounds like you got an interesting bike! If the engine might have had something done to it, and no-one knows what, then you could have anything. I would like to know how many miles you've done on it. If you've had it for ages and done like 20 000 miles on it, I'll shut my mouth right now. Otherwise, heres my 2 cents.

As far as cams go, you can reprofile any camshaft with any almost cam grind.
Theres no reason why someone who works in an engine shop can't put an F40 grind or a Cosworth BDG grind on a v-max cam. Not common, but possible.

The valve clearances in that case are likely to be ones from the cam master, not from the engine you put it into.

I commented on this thread before because I noticed that no-one had answered your original question.
I just want you to know that there are some people who don't always play safe and do things by the book! MAYBE it has had a different grind put on it.

However, on the topic of your motor, this isn't what springs into my mind. The cam grind can be an F1 grind, if it works. That's not a worry.
I'm a bit concerned about your cranking compressions.

When you say it sounds like a box of rocks, one of the things that comes to mind is pinging/detonation. When you say octane boost helps, it rings true. Engines with higher compression ratio's often need higher octane fuel.

The drama you really have is - is the cranking compression so high that you are getting piston detonation? What if that is the cause of the box of rocks noise?
Detonation causes the crown of the piston to get eaten away and turned into a sort of salt like substance. Some of the pictures on this page do pretty good justice to what can happen - http://www.google.com.au/search?q=p...&source=og&sa=N&hl=en&tab=wi&biw=1360&bih=576

I am not a particularly wealthy person, and if my bike engine blew up, I would be gutted.
So my motiviation for writing this is just that I want to tell you to tread carefully with this motor. This might be one of those occasions when you need an expert to look at it, or just bite the bullet and pull it down.

Just my 2 cents. ;-)

 

[Rusty McNeil]

Box of rocks at idle is very likely not due to compressionn....no load equals no detonation even with some really ridiculous C/Ratios....Unless the engine is ridiculously hot on top of that........Detting at idle is pretty rare....Unless it's a mid 70's GM with a 230 degree t-stat, low octane gas etc...they were famous for that....

You cranking comp tho is through the roof....could a stock max could create 220 psi.....????

How many compression cycles are you counting before calling it done....I think my tester says 5 strokes, not sure, the whole thing seems kinda subjective to me since your counting comp strokes and I've seen different testers tell you different ways to do it.....


But I would think unless a very short duration cam was installed most cams would lower the C/ratio due to more duration?????

 

[alorio1]

My guess is PO had a blown head gasket and shaved the head to the max.....

 

[bazwell]

Whilst I agree that detonation at idle is unlikely, jesus, that description rings alarm bells.

Back in the day, when I worked in an engine shop, we would ask people if it sounded like they had an engine full of golf balls.

He's used "box of rocks", stated 220 cranking compression, mentioned octane boost helps, and says the starter has issues getting it moving.

I'd feel like an ass if I didn't warn him about detonation. Really.

Oh, and the penny just dropped! PO is previous owner?

 

[SpecOps13]

I've got about 3k miles on the bike, it has 35k on the clock. I've spent so much time renovating this bike, it's part of me. It has my DNA all over it in the form of Blood, Sweat and even some tears. I've had it about 1 year. Long enough that Kyle's taken it out and I've made one ride with our group.

There's no real indication of any problem at running rpm's. In fact, it runs like A Bat Outta Hell. It doesn't overheat or smoke. It still occasionally drops 1 cylinder for a short time but always clears in a mile or two. Sooner or later, I'll find that intermittent problem...

Compression testing is subjective. all we can expect from it is a comparison between cylinders. I use 5 to 10 revs, equal for all cylinders, with the throttle wide open.

Kyle and I talked about this yesterday. It shows no signs of blowing up and I'm not one to look for troubles when I could create more than might now exist. Eventually, I'll put it on a dyno and get some clue as to whether the motor is more than stock or I'm just full of crap....:ummm::confused2:

 

[Rusty McNeil]

Whilst I agree that detonation at idle is unlikely, jesus, that description rings alarm bells.

Back in the day, when I worked in an engine shop, we would ask people if it sounded like they had an engine full of golf balls.

He's used "box of rocks", stated 220 cranking compression, mentioned octane boost helps, and says the starter has issues getting it moving.

I'd feel like an ass if I didn't warn him about detonation. Really.

Oh, and the penny just dropped! PO is previous owner?

oh, I definetely agree with you brother, your observation was well founded on all the symptoms that would lead any sane gearhead in that direction.......I just took "box of rocks" to mean the noisy ass valve train we have all come to love on these bikes.....:bang head:.Wasn't thinking about your interpetation...

 

[bazwell]

Ha ha Rusty... that made me chuckle. :rofl_200:
Seen this??? --> http://www.vmaxforum.net/showthread.php?t=19564

What if he's got a bike with a fantastic high compression motor, full gearbox rebuilt with undercut gears, crazy hot cams and HD valve springs, and it just rattles?
Maybe theres nothing wrong with it at all...

:whistlin:

 

[06VMAXIMUS]

Could the cylinders being carboned up cause the higher than normal compression reading? Maybe a peek into the cylinders with a scope through the spark plug hole would answer some questions....