Cam help

Ray

If the intake opened at 1.5* ATDC then the duration would be (44-1.5) + 180 = 222.5

222.5/2 = 111.25 + 1.5 = 112.75

In either case the cam is retarded and you need to advance it. Try using the +8 on the bottom gear.

If you don't mind would you do another set of 4 pictures after the cam is advanced?

 

Ok here is 6+
That's intake

 

Ray

Nice pictures and a lot easier than a verbal description.

This shows the intake lobe center at 110* ATDC and the exhaust lobe center at 115* BTDC

What is consistent with this set of pics and previous pics is the cam lobe separation angle is clearly just over 112* not the 110* that the cam card specifies.
That being the case means 4* advanced puts the intake lobe center at 108* instead of the 106* being specified.

If you set the bottom gear at +8 that should put the cam where it needs to be.

The nice part of a 112* LSA is it has 4* less overlap and the idle quality and fuel mileage will be better than with the original cam profile.

Your measurements show the intake duration at 226* and the exhaust duration at 232 degrees. Close enough.

On the next set of measurements we are also going to have you do the max lift method where you measure .050" down both sides from the top of the lobe.
This will be the double check for the method you are doing now.
If both methods agree then you can feel sure about the cam timing.

Will call

Paul

 

I run the numbers again at +6 and come out the same as above pic, so here are the+8 intake pic
4.5 ATDC
40.5

 

Exhaust 52.5+ 1.5

 

I also checked the + 8 on the #6 piston and it was about the same 4+41.5 intake and 52+1 EX.

 

Have you tried max lift yet?

 

Not yet ,I had to come in and get ready for dinner.

 

Using these readings

Intake duration = 225*
ICL = 108*

Exhaust duration = 230.5*
ECL = 116.75*

LSA = 112*

If the max lift method of measuring the intake and exhaust lobe center lines gets close to the same then you are done.

Hoping for 108* intake and close to 116 exhaust. The intake center line is the more important point.

Paul

 

I did max lift last night and on the +8 and I`m right where I need to be IN.61+155=216/2=108 and the EX.67.5+ 165.5=233/2=116.5.
Thank you Paul and Rob for your help and your time.

 

Awesome! Nice job!

 

So the cam is ground to the proper specs then?


Derek

 

Not exactly

The .050" intake duration is 225* instead of 223* and the LSA is 112* instead of 110*
So the ICL was set to 108* instead of 106*

The exhaust duration is correct at 230* and the lift measures .291"

Paul

 

Thanks Paul.

Do you think these specs are better than the ones on the card or will performance suffer slightly even though its close but no cigar?

Derek

 

I think Ray is going to like it.

The engine is a 400 so the decrease in overlap will help the idle quality and fuel mileage.

Should have a nice strong midrange which is what he is looking for.

Don't care about upper rpm power so the relatively shorter exhaust duration is just fine.

This is one of those accidental custom cams that fits the requirements.

Paul

 

Cool!

So in your opinion is this cam close enough to the card specs to not worry about?


Derek

 

Kinda.

The smaller displacement engines are more sensitive to overlap.
Since this is a 400, not a 455, the wider LSA will help idle quailty and low rpm smoothness.

Paul

 

Paul what you think I should run for a Torque converter?

 

Larry I don't have one at all. I have 3.64`s