I'm slowly finding out things about my new to me Shovel.

I did some measurements and found I may have an 88" inch stroker motor. .020 over standard bore with a 4 3/4 stroke. Comes out to 89.22 inches.

The cam in it is an Andrews AB grind. I'd like to see if this is a good cam or if I need to make another selection. Problem is, I have no idea what the static compression is. I don't know what typical combustion chamber volume is on a Shovel. I've seen numbers like 110cc to 135cc. I know the proper way is to "cc" the heads. But I'm just looking for a range right now.

I also need to find out the dome height for the pistons. They are S&S pistons that are TRW forged 2900 series. I also get numbers like 135cc when I do a search.

I think just the average numbers will be adequate for picking an off the shelf cam. Actually, I hope the existing Andrews AB grind will be acceptable so I don't have to buy another cam.

 

the 2900 S&S piston is a fit all to all the different strokers today, they use a spacer under the jugs for a 4 3/4 stroke < do you have this set up or do you have the longer barrels ,200 longer is required

an AB andrews is not a stroker cam the duration is too narrow and the motor static compression is too high with it, making it kick starting a bitch and the older starters dont like it as well -- 2900 piston with that stroke is at least 9.7 to 1 we shy away from that much compression today, as guys are looking to putt and not street race like years ago

lineweber has the best cam today for a stroker shovel plenty of power and lots of noise from everything

 

I have the S&S 495 cam along with the 2900 series pistons in an older 86" build. It doesn't like anything but PREMIUM fuel. It's a hard starting beast but still runs strong after years of use. I did this long before "kits" were available and love how it came out.

 

I must have the longer barrels. There are no plates under them. It looks like the flanges on the bottom are a lot thicker than stock ones. There are no parts numbers on them either. I'll measure them to be sure. What is the stock length for the barrels ?

When you say 9.7 to 1 compression, are we talking static ? This might not be too bad if I get the right cam and get the dynamic compression down to 8.7 or so. When I saw the advertised duration numbers on the AB, I thought it might not be the correct cam.

I only run premium fuel anyway but who knows what we will have in the future.

I want this bike to start easy. The heads are set up as dual plug heads. I was thinking of running two plugs and using compression releases on the carb side.

 

I made a new post on this but I scored a used cam with 260 duration on the intake and 270 duration on the exhaust. I think the advertised duration is 262 and 272. Lift will come out at .455. Hope this works out. it's the only thing i could find in both the duration and lift I wanted. Plus it was $49.

Correction: 260/270 is the duration @ .053. 262/272 is the duration @ .050. I have no idea what the advertised duration is.

 

Yes , the big boyz calc

 

Definition: Advertised duration is the most common form of listing specific duration figures. It is measured in crankshaft degrees and basically expresses the length of time that a given valve is open. Unfortunately, this particular figure can be more optimistic than theoretical valve lift. A good portion of the discrepancy regarding advertised duration figures is due to the fact that many manufacturers tend to include the camshaft Lobe clearance ramp in their duration figures. For example, a Chevrolet ZL1 camshaft has an advertised duration figure of 359 degrees on the exhaust side. Obviously, this is an extremely stout number and, when you give it some consideration, you can clearly see that the powerplant could hardly run with such a radical camshaft. This is where 0.050-inch duration figures come into play. Measured with the 0.050-inch method, the very same ZL1 grind features a duration figure of 273 degrees. That's a significant difference.

Definition: The 0.050-inch duration figure is determined when the valve lifter has risen 0.050-inch off the camshaft base circle (opening side) and closed to within 0.050-inch (closing side) on the ramp. This particular duration figure is quite accurate for comparison purposes and in most areas is much closer to true duration than the advertised number. Airflow in the intake or exhaust port is minimal at low lift figures, especially when the clearance ramp numbers are included in the discussion. Since this airflow is almost nil in most situations, the camshaft manufacturers began using the 0.050-inch method to determine a universal number that could be used for camshaft comparison. The newer 0.050-inch number is more accurate and can, at least, be compared without worrying about variables such as ramp clearance.

Definition: Several camshaft grinders have begun to use the 0.020-inch duration figure in addition to the previously mentioned 0.050-inch number. It is primarily a seat duration figure and most often is used to determine valve timing at the seat. This figure is helpful when plotting a specific cam profile on graph paper and also can be of some assistance when comparing various camshaft profiles.