205 lbs. compression?

[ekvh]

What did I miss? The 1100 cam and the 1200 cam, how does that fit in this post?

 

[dan filipi]

What did I miss? The 1100 cam and the 1200 cam, how does that fit in this post?

I was experimenting running cams from a 1000 and the set I have in it now from a 1200.
The 1200 has no fuel pump or tach drive like the 1000 or 1100.
That's the reason for this mod.

 

[mike in idaho]

Advancing the valve timing will increase cylinder pressure at cranking speeds. You might try retarding the camshaft by one tooth on that side to see if it helps to even out the compression numbers.

 

[dan filipi]

Old thread update:

While looking at the options to drive an ignition housing from the cam on this 1200 and comparing the cams with steve83, it became obvious when standing the cams on end with the pulley keyways lined up and looking down at them, I could easily see the lobe profiles were different from left to right head. Enough different to make this compression oddity happen I guess.
This may seem an obvious check by most but........I missed the obvious

 

[slabghost]

I did mention they might be different.

 

[dan filipi]

It never occurred to me the cams would be side specific but of course they would be because the cam ramp has to be opposite.... I think that's right.

 

[scdmarx]

dan filipi » Sat Mar 22, 2014 7:25 am[/url]":bpajic52]
It never occurred to me the cams would be side specific but of course they would be because the cam ramp has to be opposite.... I think that's right.

Maybe just my combination of meds, but I'm not connecting the dots.

I just looked at the manuals and the firing order (1-3-2-4)
In my mind, ramping would be the same - side to side, and both shafts turn in the same direction. I could see them being keyed different for correct timing, but to be ramped opposite wouldn't they have to rotate in opposite directions?

:headscratch:

Anyways.... can you get 205lbs from both sides with the right combo?

 

[dan filipi]

This is still confusing.
Maybe it's because other side has to have keyway 180 out to use the same gear flipped around.
I'll try to look at this more later.

 

[dan filipi]

It looks to me (by looking down the cams standing side by side) the difference in position of lobes would retard the cam timing a small amount, I'm guessing less than a degree.
How this comes into play to bump compression is beyond what I understand about cam timing.

 

[mike in idaho]

The 1200 motor uses somewhat shorter(milder) valve timing than the earlier motors. The intake valve closes sooner on the compression stroke, than with the older cams, so the pressure built up at cranking speed should be higher.

 

[ekvh]

Digging up a three year old post. With what is now confirmed from backlander about 1200 cams I can see two possibilities for this anomaly. (I confess, I didn't reread every post to see if it has been mentioned here already, seven pages and I jumped to the end)

One, joe's right, you could put a 1200 left cam in the right side and visa versa. The question is whether or not the cams are symmetrical on each side of the peak, probably not. I'm not sure if the cams are marked left and right or have different numbers. You would think they were if they were different. If the ramps were set up to ease up when closing the valve so seat doesn't slam and bounce, then reversing it could change the filling events.

Two, could Dan have had an 84-85 cam on one side and an 86-87 cam on the other side?? They had totally different overlaps (+10 degrees)and LSA or lobe centrelines, I admit I'm confused on the differences of LSA and centreline. One cam with ten degrees more overlap would give different static compression readings for sure. More overlap should give less compression on that side.

Three, and totally separate from the above issues, and apologies in advance to all who will now have to read through 13 pages of conjecture--lol--- I also was digging details here from msgt's related posts to the cams. She said the 1200 cams had a larger base circle. To me, getting a set of 84-85 cams with ten more degrees overlap, but a mm less lift, makes it a great candidate to regrind. Taking a mm off the base circle would give you 75-77 lift, to go with higher compression. The negative to grinding down 75-77 cams like webcamshafts.com does is that they do it by reducing the base circle and reducing the base circle increases unbalance to the bumpstick. Using 1200 cams would diminish this allowing them to handle the extra rpm better than 75-83 cams. This would increase overlap and duration of the 1200 cams. Sounds like a great way for me to piss a little more money down my leg, right?

Im going to check in with some machine shops here in the Philippines to see if they could do this. My brother-in-law regrinds crankshafts here for 30+ years. He is now up to $390 a day in pay. Sound good? That's not quite $8 US per day. The cost might be considerably less here. Yesterday, I sat my a$s on a chair as my car was hand washed, wiping out door channels, trunk and hood channels, vacuumed out, mats washed for $3.

Go Patriots!

 

[slabghost]

Could he regrind 1500 cams to 75 cam specs if he had a 75 cam to compare?

 

[ekvh]

Not sure, I'll ask. The interesting part in my reading is the growing body of engines using cams with bigger base circles. Seems like quite a few of the newer engines are going that way. They consume a little acceleration energy, but allow smoother lobes for followers.

 

[ekvh]

They don't do camshafts.

 

[slabghost]

Bummer. But hey thanks for checking!

 

[ekvh]

I'm going to look around while here. I'll let you know if I have luck.

 

[slabghost]

I bought a spare pair of 1500 cams to be reground.

 

[ekvh]

I'm pretty sure they'd be good candidates as well, but the want a lot of money for it in. The little reading I've done show it is labor intensive and takes a big dollar machine.