Fuel injection rebuild

[Simmy]

Seems like the massaging is working! A bit of both solutions is doing the trick. A little more fussing over the weekend will have it sorted, and hopefully see the cam a little happier and degree'd.

Muchas gracias Tony & Herman!

[Tony Z]

anytime
keep us posted

[retrovan]

Seems like the massaging is working! A bit of both solutions is doing the trick. A little more fussing over the weekend will have it sorted, and hopefully see the cam a little happier and degree'd.

Muchas gracias Tony & Herman!

Herman

[Simmy]

After much umm-ing and aww-ing and a bit of tool making, I think I have figured out this cam degreeing business.

Using the dial indicator method, I found TDC. Looks like it's 0.75deg advanced relative to the marking and split line.

Then measured up the intake and exhaust opening and closure points on the cam at the recommended 0.05" lift point. But now here comes the issue... The profile on all of the lobes opening side is 3.5-4.0° off of the cam card spec. Basically this is what I am finding:

Measured: IO-15.5 IC-11.5 EO-51.0 EC-47.5
Card: IO-19 IC-12 EO-55 EC-48

Doubting myself, I checked both sets of lobes in both directions of rotation and find the same thing. Unless there is some difference in measuring opening Vs closing, it looks like it's out of spec.
From the little I know about cams, this is quite a margin and I certainly can't fix it myself. So from the folks out there:

• Is it worth fussing about this difference? It looks like the actual profile has the same duration as a CB2238, but less lift... And that is still a performance cam...

• If I accept what I have, what does one dial the cam according to? Intake or exhaust timing, or the middle of the two?

• And out of curiosity, does anyone know where to find a cam card for the 2238? I haven't had much luck.

TDC - had to make up the marker after finding it difficult to repeat readings due to some slop and difficulty with parallax.


Intake open


Intake close


Exhaust Closes


Exhaust Opens

[Wentzel]

I don't have a lot of experience on degreeing myself but found that the pulley I had was off from true tdc. Did you check that the pulley is accurate.

If I remember correctly Bob Hoover had a trick to adjust the cam a few degrees by drilling bigger holes and some mods to get the cam spot on.

[Simmy]

Thanks Wentzel - I have read his article on degreeing the cam several times over, so I am hoping I am working according to his method.

So the pulley is off by 0.75deg, and the "needle" you see in the images is set to point to true TDC. Anything I measured from that point is relative to TDC, not the case parting line and the marking. I am not sure if that difference makes things better or worse... I would need to have the assembly in front of me to confirm.

You are correct on the Hoover mod - he basically suggests you open up the holes a little to get 1-2deg play. If I am working according to intake timing, then I am within the 0.5deg tolerance, but anything else will probably need that treatment. I could also have the holes slotted and counter-bored in an arc if I need more, but I will try avoid that.

[Tony Z]

Measured: IO-15.5 IC-11.5 EO-51.0 EC-47.5
Card: IO-19 IC-12 EO-55 EC-48

There is no way that this is right. I've had to take what you wrote and guess at what you meant.
According to that, IO to IC is 27deg. That isnt right, that I've had to guess at as being your overlap - IO to EC

but as you say, it looks like both lobes open late.
Are you setting the dial indicator to zero on the back side of the lobe?
Then when it lifts 0.05", reset to zero and measure from this point?

Just looking at things and seeing what they do, we can say the following:
Late exh opening gives a slightly improved torque band and fuel economy (an emissions but I'm sure you not worried about that), but does reduce time for the exhaust to get out.
Late inlet opening reduces the amount of time for overlap to "pull" in fresh air (and fuel) reducing peak power, but also allowing the cam to "come on" earlier in the rpm range and also less fuel will get spilled over into the exhaust.
From the quality of parts I have seen you using thus far, I can only assume that your exhaust will be a good quality item too. Thus reducing the negative effects of the slightly less duration. It'll "pull" easier and harder.
Also keep in mind, those Panchitos, even though very good heads, are too much head for your 1776. They can flow to 160hp plus, your engine on a good day will be making around 120hp on the coast. That said, the heads will be flowing pretty damn well as they are, so if your aim was to have a 110 cam with the right heads, you might even find that this inconvenience will put you right to where you wanted to be. If however, you were hoping to buy a 110 cam but wanted to be closer to a 120 cam, then you'll be a little disappointed.
So not all is lost, in my eyes, you are going to end up with pretty much what you hoped for but likely with a slightly wider torque band and improved fuel economy.
I'm just thinking of how each part works and its result to the whole picture.

My opinion only.

[Simmy]

You are right Tony - I must have written that before my first cup of coffee this morning!

Should have read (after unswapping closing figures) (and taken @ 0.05" lift for both, reset to 0 on the heel of the cam)
Measured: IO-15.5 IC-47.5 EO-51 EC-11.5
Card: IO-19 IC-48 EO-55 EC-12

Putting this through an online calculator gives:
Your Actual has an Overlap of 26.50 degrees and has in Intake Duration of 242.50 degrees. The Exhaust Duration is 242.50 degrees. Your Lobe Separation Angle is 108.00 degrees. The Inlet Cam has an Installed Centerline of 106.25 degrees ATDC. The exhaust cam has an Installed Centerline of 109.75 degrees BTDC.

So, this means to me that it is a flatter cam profile with less duration? hence it will err towards the performance of a W100 as opposed to a W120 (supporting Tony's view). But this still leaves the issue of whether to adjust according to opening or closing... so did some reading and found these two resources:
https://www.enginebuildermag.com/2016/0 ... mportance/
https://www.mechadyne-int.com/app/uploa ... ssions.pdf

But all of this leaves me a little confused still, but I think this is where i am:

1. The cam profile is flatter, specifically on the intake side (if lobe centres are still at 108deg).
2. If true, there should be more overlap?! Not less???
3. If I adjust to suit the IC point (only 0.5deg difference) which is easier and also apparently preferred according to the second article, then both intake and exhaust will open early resulting in:

• More exhaust recirculation... which has some impact on efficiency which doesnt matter to me
• Lower full-load torque
• Higher low-speed torque

I am not sure if that makes any sense... but between the 2xgearing, changes in direction of rotation and insufficient caffeine its very likely i am missing something.

[Tony Z]

you are confused...
Remember, the exhaust valve opens before the intake, not the other way around.
As you wrote, IC is 47.5 but the card says it should be 48. Why would you even want to modify things to change this when it is basically spot on?
Duration is when both the inlet and exhaust are open. IO = 15.5BTDC, EC=11.5ATDC, overlap=27deg which is less than the cards 31deg.
This will make the car more drivable and smoother (as I mentioned earlier) at lower rpm and your high flowing heads should be able to make up for any duration losses at the higher rpm levels. As you noted, inlet closing is likely the most important factor in the cam profile, and yours is spot on to where it was designed to be.

If the cam is unmarked and undamaged, we can swap it out for another 110 if you wish.
Otherwise, if you are still unhappy, then consider stepping up to a set of 1.25 rockers.

And, if you ever turbo it (I think you once spoke about that), then the later inlet opening will give the exhaust more time to blow down, thus further reducing any chances of the exh flowing back into the inlet port

[Simmy]

Thanks for bearing with me... But I think I have this now!

I had the datums wrong on my head, and the fact that rotation means you read the graph backwards also threw me off.

Anyways, this is what I should have started with (red line is the actual profile, whilst blue is design):



So, overall I think I am comfortable with what I have. I want a torquier low end and, like you say, I can make up for losses in the top-end later with ratio rockers and certainly with a turbo.

[Tony Z]

thats better...
and if you want to sound fancy, you could tell people in the future that you have a custom spec cam

[Haans]

Jeeezzz,...you guys can confuse the hell out of me with facts !,

Very interesting though !!

Have you ever thought of taking up gardening !,....much easier on the brain !! Just a joke !

Haans

[Donovan D]

Jeeezzz,...you guys can confuse the hell out of me with facts !,

Very interesting though !!

Have you ever thought of taking up gardening !,....much easier on the brain !! Just a joke !

Haans

Agreed...when reading all of this, this is what it sounds like in my head

[retrovan]

Let me as an engineer decode this for you and explain what he is talking about......

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Its a Adendorff Generator.......



Herman





Joking

[Riaan.N]

Sound like a sales man that uses too much technical jargon to give the appearance that he actually knows what he is talking about and to make it sound that what ever that contraption is that its highly technically advanced. The last door he opened looked like just normal control circuitry of an electric motor to me.... nothing wow there.

The world of spin doctors... like our own Eskom that says our coal powered electricity generating stations can't operate with wet coal..... BS... excuse my sneezing, must be dust!