[GMC boogie]

SBC hydraulic roller. Valve events at .050 listed on cam card:

IO 8º BTDC
IC 40º ABDC
EO 48º BBDC
EC 0º ATDC

As found:
IO 7º BTDC
IC 46º ABDC
EO 47º BBDC
EC 6º ATDC

Another thing, This is suppose to be a 228/228 duration at .050 cam. It measures 233 on both the intake and exhaust. What is the deal with that?

Specs on cam is 228/228 at .050 280/280 at .006 110LSA 4º advance. install intake lobe to 106º centerline.

7+180+46=233 intake
47+180+6=233 exhaust

Also done the Intake centerline method and got 109º which tells me I need to advance the cam 3º to put it at 106

I am very confident I have found true TDC. I am using a fixture that fits in the lifter bore with indicator that reads directly off the lobe for the degreeing process.

[hcompton]

Originally Posted by GMC boogie

SBC hydraulic roller. Valve events at .050 listed on cam card:

IO 8º BTDC
IC 40º ABDC
EO 48º BBDC
EC 0º ATDC

As found:
IO 7º BTDC
IC 46º ABDC
EO 47º BBDC
EC 6º ATDC

Another thing, This is suppose to be a 228/228 duration at .050 cam. It measures 233 on both the intake and exhaust. What is the deal with that?

Specs on cam is 228/228 at .050 280/280 at .006 110LSA 4º advance. install intake lobe to 106º centerline.

7+180+46=233 intake
47+180+6=233 exhaust

Also done the Intake centerline method and got 109º which tells me I need to advance the cam 3º to put it at 106

I am very confident I have found true TDC. I am using a fixture that fits in the lifter bore with indicator that reads directly off the lobe for the degreeing process.

Sounds about right? Who makes the cam. It is not uncommon for cams to be way out of spec. I like to map out the cams to be sure i got what i purchased. One wrong stamping and your cam might not even be the one you purchased.

Some manufactures are really bad with cam grinds. A lot of ppl like isky but never mapped on myself so cant tell either way. If the cam is ground in house or a regrind it may not be done on equipment that can make those types of cuts. Sometimes cam mfr. Dont let stuff like that get in the way of the sales pitch.

[GMC boogie]

It is a custom grind. I am not going to say the company.

Someone told me the fixture I am using for degreeing off the lobe is not accurate as it has a different radius.

Going to redegree using an actual lifter.

[hcompton]

Originally Posted by GMC boogie

It is a custom grind. I am not going to say the company.

Someone told me the fixture I am using for degreeing off the lobe is not accurate as it has a different radius.

Going to redegree using an actual lifter.

Not sure on that one but probably pretty close either way. You can get a very cheap and accurate dail indicator from the net with magnetic base and arms to allow it to clear the valve. Its point should be put right on to the retainer.

This works pretty well remeber to use a little preload cause the first few thousands are not accurate off any indicator like this or even the lifter style indicators.

Standard Magnetic Base 1" Dial Indicator All New Tools | eBay

I use these on my mill in case i want to use the dail while the mill is cutting. I used these cheap ones in case they get trashed or filled with chips or oil.

[hcompton]

Originally Posted by GMC boogie

It is a custom grind. I am not going to say the company.

Someone told me the fixture I am using for degreeing off the lobe is not accurate as it has a different radius.

Going to redegree using an actual lifter.

Are all the lobes the same? Did you check any of the other lobes. Its one thing to be ground outside of spec its another to be off from lobe to lobe. One will still make power the other will not.

Is it a big company? If so let us know. None of them are dead on the cam card. One look at the way they are made its easy to see why. Looks very accurate but really it seems pretty easy for it to get screwed up. When cutting hard metals things just dont always go to plan. Actully it never does go well its always a fight to get it down to the .0001 range and not go over. So the cams are sometimes left a little large. I would be suprised if you saidit was dead on and want to buy all my cams from that guy. But the biggest machines make the closest grinds to the specs.

[cobalt327]

Originally Posted by GMC boogie

It is a custom grind. I am not going to say the company.

Someone told me the fixture I am using for degreeing off the lobe is not accurate as it has a different radius.

Going to redegree using an actual lifter.

If you were using a roller radius indicator on the flat tappet lobe (or vise versa), you'd see an error, but it would be larger than what you're seeing, and it wouldn't add duration to just the closing side. Even a slightly different radius from the lifter your cam uses would not indicate what you're seeing, so it's not the tooling, per se.

This sounds like a mistake by the manufacturer, or they have pulled a cam off the shelf that's close to what you wanted- but even w/that, it's more cam than you bargained for.

I'd be on the horn to these guys...

BTW, if you use a hydraulic lifter to recheck it you should make it solid to remove the lifter piston travel from skewing the measurements. Stack it full of small washers or fill w/grease.

[GMC boogie]

The motor is in short block form on the engine stand. It is a hydraulic roller cam and the fixture I have that fits in the lifter bore has a plunger for a roller camshaft.

I checked amount of degrees from .050 on the opening side to .050 on the closing side just to verify and it is 233 degrees. What a bummer, not that much bigger but bigger than I want.

[hcompton]

Originally Posted by GMC boogie

The motor is in short block form on the engine stand. It is a hydraulic roller cam and the fixture I have that fits in the lifter bore has a plunger for a roller camshaft.

I checked amount of degrees from .050 on the opening side to .050 on the closing side just to verify and it is 233 degrees. What a bummer, not that much bigger but bigger than I want.

What really sucks is the 233/233 is a common cam avilable in many standard grinds. So you could have went off the shelf and saved a few bucks.

[GMC boogie]

I degreed again(several times) using the actual lifter/mag base/ indicator and got:

IO 4 BTDC
IC 44 ABDC
EO 44 BBDC
EC 4 ATDC

4+180+44=228 What it is suppose to be.

228/2 = 114 -4 = 110 intake centerline.

Now if I advance the cam 4º, my timing events at .050 should be as the card states,correct?

[cobalt327]

Your previous measuring set up must not have been parallel to the lifter/pushrod and/or the radius was way off. Still doesn't make much sense that it was off only on the closing sides...

In any event usually the advance will be correct when the cam is installed straight up. Can you show the cam card?

[GMC boogie]

I was using this fixture:

http://www.jegs.com/images/photos/2494925.jpg


When I degreed using the traditional method of off the lifter, my results were correct other than needing to advance the cam 4º.

Someone told me using the fixture I used the first time would skew the numbers due to the different radius and so it did.

I listed the cam card specs in a previous post,they are posted correct.

110 LSA 106 ICL 228/228 280/280

[cobalt327]

Originally Posted by GMC boogie

I listed the cam card specs in a previous post,they are posted correct.

110 LSA 106 ICL 228/228 280/280

The cam card will often say what position it's to be installed in to get the amount of advance correct. Example:


Otherwise if it's ground on a 110 degree LSA, move it to 106 degrees if you want it 4 degrees advanced.

[GMC boogie]

Yeah, I need to move it to 106. Timing set is not adjustable. What about using a 4º offset key?

[cobalt327]

Originally Posted by GMC boogie

Yeah, I need to move it to 106. Timing set is not adjustable. What about using a 4º offset key?

Well, it's that or a bushing in the cam gear. The offset woodruff would be the easier of the two, and could be said to be a better choice because the three bolt holes holding the cam gear on don't need to be elongated.

[hcompton]

Originally Posted by GMC boogie

Yeah, I need to move it to 106. Timing set is not adjustable. What about using a 4º offset key?

Isnt the timing set adjustable in 3 degree increments. So only need a 1 degree offset key.

I would run it at 3 and be done with it. Dont want to take any chances with the offset key failing.