Find My Cam Degreeing-In Error!

[92 GSR-4]

I'm trying to degree-in a set of BC280's in my 1G. I've been referencing this walkthru: 4G63 Camshaft Degreeing

Please read through my procedure and see if you can find what I'm doing wrong!

I'm using the summit degree wheel:

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I am also using BLE solid lash adjusters, adjusted to zero-lash per their instructions.

A couple conditions that have caused me to modify this procedure:

- Engine is in the car, making me have to peep through a sight hole in the driver's wheel well to see the degree wheel and my pointer. It's accurate, but this means I can't adjust the pointer to TDC once I find my "True TDC", meaning I'm taking raw measurements on the degree wheel and then doing the math to find out what the actual degree readings are.

- Summit Degree wheel is a POS and doesn't fit the stock DSM crank pulley. I mocked it up perfect on another motor and drilled four new bolt holes. Unfortunately I can't adjust this wheel at all.

Okay, Here's the step-by-step actions I have taken:

Finding True TDC

I put the T-belt on the car with all marks perfectly lined up. This was verified by rotating the crankshaft 6 rotations and re-checking.

I installed the degree wheel and put the pointer where I could see it, which was at 53* ATDC. I installed the piston stop and measured the following degree readings: 76* ATDC and 36.5 ATDC. 76 + 36.5 = 112.5/2 = 56.25* ATDC "True TDC".

At this point, most would rotate the crankshaft until the pointer points at 56.25* and then move the pointer over to the TDC mark on the degree wheel. Because I need to be able to see the pointer and the degree wheel through the peep hole in the wheel well, I am leaving the pointer as-is and doing the math to adjust my upcoming measurements.

Measuring the Intake Cam Valve Events

I mounted the dial indicator with a plate I fabbed up on the cyl head. Here are the measurements and math I did (This is going to get complicated and confusing):

Intake Open (.050"): 45* ATDC (RAW NUMBER, not a true measurement)
Intake Open Adjustment: 56.25(My "True TDC") - 45 = 11.25* BTDC

Intake Closed (.050"): 96* ABDC
- With this reading, the 96* ABDC was the "big" number on the degree wheel, and since I was using the "small" numbers meant to be used with valve timing this number converted to 84* ABDC. For the sake of doing the math, I used the 96* and will covert it over to the cam degreeing in a moment.

Intake Closed adjustment: 56.25 + 96 = 152.25 Converted to 27.75* ABDC

The BC Specs for this cam are:
Intake Open: 7* BTDC, meaning my measurement was 4.25* Advanced
Intake Closed: 31* ABDC, meaning my measurement was 3.75* Advanced

- I verified both of these measurements, but I'm sure there had to be some variance and .5* isn't bad. So I'm going to call the intake cam an even 4* advanced from what the BC specs are.

Exhaust Cam Valve Events

This is where it gets confusing to me. The BC specs are inconsistent with what I have on my degree wheel. Read below.

Exhaust open (.050"): 173.25* ABDC (RAW NUMBER)
Exhaust Open Adjustment: 56.25*+173.25 = 229.75 degrees from the TDC on the degree wheel. I'm going to subtract 180* from this figure so I can start counting from BDC, so 229.75 - 180 = 49.5* BBDC

Exhaust Closed (.050"): 46.5* ATDC
Exhaust Closed Adjustment: 56.25 -46.5 = 9.75* BTDC

BC Exhaust Cam Specs:
Exhaust Cam Open: -2* BTDC, while I have 49.5* BBDC. I have no clue what to make of this..
Exhaust Cam Closed: 38* BBDC while I have 9.75* BTDC. Again, I'm way off.

I completely started over on the exhaust cam and got the same results. I hope someone can follow my steps and see what I'm doing wrong. All help is appreciated, thanks!

 

[92 GSR-4]

Okay,

I can see there is a bunch of math in my first post and nobody wants to read through it and try to follow along... I wouldn't either.


Can somebody please explain to me the BC280 exhaust cam specs? According to their cam card it is:

http://www.briancrower.com/dl/06cat.pdf

Valve Opening: -2* BTDC
Valve Close: 38* BBDC


Am I reading this right? How can you have -2* BTDC? How can I find it on the degree wheel, or is there some sort of conversion that takes place? I'm very Korn-fused right now

Here's the degree wheel again (stole the image)

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[sawnuoff]

instead of putting the degree wheel on there with the zero up try mounting it upside down where you can see it better. In the car is a pita, done mine.
For mounting it I had found a old wrist pin, I cut down, and a old bearing race to space it out from the engine and a longer bolt for the crank.
Your pointer doesn't have to be on the engine you can put it on anything solid and just bend it over accordingly.

 

[brisvr4]

You also have the exhaust figures mixed up. It opens at 38 and closes at -2.
It would seem that you are approx 11 crank deg out on it.
I'm going to be doing my BC280's soon in the car and will be using the degree wheel mounted upside down as suggested by the OP.
Good luck with it!

 

[boosting_laser]

To help make things easier for try this. It allows you to re-zero your wheel after finding ttdc. No more funky math.

Fyi: Size is M14 x 1.5 pitch

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[delta448]

Am I reading this right? How can you have -2* BTDC? How can I find it on the degree wheel, or is there some sort of conversion that takes place?

It's just the conventional nomenclature that accompanies cam card specs. Exhaust valve closing is usually expressed as a BTDC value. A negative BTDC value is the same as a positive ATDC value.

Your card specs are:

IO: 7 BTDC
IC: 31 ABDC

EO: 38 BBDC
EC: -2 BTDC or 2 ATDC

From what I can gather of the mess of numbers you first posted you may have a very slight non-zero lash condition, because your numbers indicate 220 I duration and 218 E duration. That can play into the accuracy of your degree wheel measurements a bit.

I also suggest using one of the degree wheel holders posted above and mounting the wheel upside down. When you can easily see and re-zero the wheel, the specs will be much easier to make sense of.

 

[92 GSR-4]

Thanks to everyone for the responses. Today was productive, in that I set the degree wheel up the way sawnuoff suggested and I think it worked well. Thanks to him for that!
Unfortunately, there had to be something wrong with the way I set up the dial indicator because I kept getting inconsistent opening/closing results, meaning the # of degrees the cam was advanced/retarded on opening/closing of the valve was inconsistent, so I was unable to determine definitively what the exact advance/retard of the camshaft was. It confused the hell out of me, but tomorrow I'm going to try setting it up a little different and see what happens.

You also have the exhaust figures mixed up. It opens at 38 and closes at -2.
It would seem that you are approx 11 crank deg out on it.
I'm going to be doing my BC280's soon in the car and will be using the degree wheel mounted upside down as suggested by the OP.
Good luck with it!

That's great, thanks for pointing out my mistake! I can't believe these cams were 11 deg / 4 deg out when installed straight up. Today's measurements were too inconsistent and I had to take a step back so I swapped out my intake manifold so I could say I accomplished something, haha.

It's just the conventional nomenclature that accompanies cam card specs. Exhaust valve closing is usually expressed as a BTDC value. A negative BTDC value is the same as a positive ATDC value.

Your card specs are:

IO: 7 BTDC
IC: 31 ABDC

EO: 38 BBDC
EC: -2 BTDC or 2 ATDC

This is odd. The intake open/close events are in order when I rotate the engine clockwise, while the exhaust specs are backards. But my readings are in the ballpark so I can use them!

From what I can gather of the mess of numbers you first posted you may have a very slight non-zero lash condition, because your numbers indicate 220 I duration and 218 E duration. That can play into the accuracy of your degree wheel measurements a bit.

I also suggest using one of the degree wheel holders posted above and mounting the wheel upside down. When you can easily see and re-zero the wheel, the specs will be much easier to make sense of.

When I originally set up the BLE solid lash adjusters, I set them up the way BLE indicated in their instructions, by using a .0015" feeler gauge in between the rocker and the cam lobe. Today, I readjusted the lash without using the feeler gauge at all, taking any sort of play out of it. I'm sure I screwed up the mounting of my dial indicator, or the cam lobes are asymmetrical (not). Tomorrow I'll see if I can get some concrete results.

 

[92 GSR-4]

Success!

Tonight I took my sweet time, and with a friend (who has an incredible 10sec Evo8) were able to get the camshafts dialed in perfect.

It wasn't easy and I learned a lot along the way. Mostly, you have to have the dial indicator set up perfectly and parallel with the angle the valve stem is at. I know my problem, among other mistakes, has been the dial indicator moving around on the retainer. You have to take it very slow, make sure everything is perfect, and ensure nothing shifts while rotating the motor.

For now, I set the cams for exact mechanical baseline, though I plan to advance the exhaust and retard the intake. Now I can button up the engine and get her back on the road!

Many thanks to all the above, I appreciate the assistance!

 

[sawnuoff]

We all like to see when it finally works out.

 

[brisvr4]

So what settings did you end at on the cam gears?

 

[92 GSR-4]

Bottom line up front, the cam gears read 3* Retard on Intake, 2* Retard on Exhaust.

However, in my experience using these cam gears, each mark on the cam gear really represents about 3 degrees on the crank. So my best guess is that the cams were really 4/3 retarded when I installed them straight-up.

I can't stress how important it is to do this procedure absolutely perfect. My initial measurements were garbage. My second attempt was complete garbage. I had to take a step back, work on something else, and then start from scratch after a few days with the help of a friend. The friend was great at helping mock everything up perfect, and then watch the dial indicator setup to make absolutely sure it doesn't budge. Which reminds me...why the hell does nobody make a cam-degreeing kit for us? First off, you have to fab a bracket just to set the dial indicator on, and then the POS magnetic dial indicator moves too easy and is hard to adjust without moving everything out of whack. A special tool that threads into the head is needed. I'm thinking about making one. Anyway, the friend is good to have.

This time I did every single measurement 3 times. I verified my mechanical TDC 3 times. Then I measured the valve events 3 times before making an adjustment. Then I re-measured 3 times to verify the adjustment that took place. After three adjustments (one VERY minor) I am confident that the cams are spot-on.

I'm waiting for a couple water fittings and then my street fighter will be back on the road with its new cams, turbo setup and extrude-honed intake manifold. Wish me luck!

 

[miliman13]

Sorry for thread jacking. But I have bc272s and I zeroed them and I believe that is why I'm losing compression. I need to dial them in, but can't find a kit or products or anything really I can buy to get this done, supposedly theres a "cam degree dial kit". Thanks