Hey guys, I’m a newbie and I’m working on my first cam degree job. It’s a SBC 350, and I’m trying to degree this thing. It’s a summit K1103 cam, and I took the old lifters and converted them to solid, finding TDC with a piston stop, measuring off the intake valve: Centerline came out pretty good on round one, 106.5 vs cam card 107. By 0.05” lift, 17 degrees, and 17 degrees before close. Cam card wants 0, 34 degrees. So naturally I decided to try retarding by one tooth, so I rolled the cam gear and camshaft counterclockwise by one tooth, and tried to degree again. This time was worse (131 centerline vs 107 cam card) and my 0.05” lift numbers were way off. Has anyone had a grind show up 17 degrees advanced? What am i missing?
You don't adjust cam timing by changing a tooth on the gears and chain, you do it with a offset bushing or an adjustable timing set depending on your application. You will get no where fast doing it your way...
Yeah I was thinking of getting an adjustable cam set, but have you had cams that far off before? It’s the same ratio, but just advanced a lot, right? Possible error from the grinder? I expected a degree or two, but...I’m just learning how to make adjustments.
Your movement is huge by just one tooth. So 17 degrees is probably just that 1 tooth by itself. You can't get any reading that has any meaning whatsoever just by moving teeth on the timing set. You need an adjustable set to get any logical readings...
If you move it one tooth,,,,,wouldn’t the centerline be wrong then ? The centerline shows the reference point of the cam to the crank . I suspect your reading at .050 is incorrect,,,,,,unless the cam is ground completely wrong . Tommy
Could you clarify your statement about taking the old lifters and "converting" them to solid? Do you mean you replaced the old hydraulic cam and lifters with a new solid cam and lifters?
Yeah I’m thinking my process is wrong, I’ve seen a few cams done and two had some advance, but only by 4 degrees. But it’s first I’m doing. Even if the cam was bad, most adjustable sets do 4/8 degrees. Just not sure if anyone had the same experience being so close but so far.
No I disassembled, removed spring, check ball and nipple, padded with two washers and replaced the cap. They were pretty tight once i repacked them. But I didn’t order solid lifters. edit: it’s a flat tappet, with hydraulic lifters. I’m hoping I repacked them well enough. All oil was out of the guts.
So you think you are going to run used lifters on a new cam? Your new cam will have flat lobes and be junk in short order. You need new lifters that are compatible with your cam type. That cam appears to be a hydraulic cam, so you will need hydraulic lifters.
Yeah I have new hydraulic lifters coming. I was trying to put in solids on cylinder 1 just for a degree job. They’re gonna get brand new lifters before break-in.
That’s what I was thinking, but so many people tell me don’t trust the centerline, keep going....I’m curious if I misread the wheel. But I went through it 5 times, and had the same result.
Well,,,,,,,you have to trust the centerline,,,,,,,that is where it is machined . The centerline can’t change,,,,unless you change it . But,,,,the lift readings can be misread,,,,,or read bad because of the lifter and it’s movement on the lobe . Sometimes the lifter will not go back to the exact bottom without a little extra effort,,,,or the indicator can be reading on a corner or side and give a faulty measurement . Tommy
I’m going to have to double check my process, I’m getting the readings off the valve with the original springs, and the original lifter from each bore. Not using checker springs. I’m going max lift, and checking 0.05” past that, and also getting measurement at 0.05” before close. It just seems odd, 17x2=34, which the cam card reads a 0 BTDC and 34 ATDC. So the range is the same, but I must be screwing up. Back to the books
You're getting a bad reading measuring off of the valve due to rocker ratio. Cam specs are based on tappet rise and not valve lift. 37.5 thousandths tappet rise equals 50 thousandths valve lift, assuming a 1.5 rocker ratio. This is probably where the bogus reading is coming from.
When hunting center line, go .080" or .100" before and after TDC, you can get a better reading since the lobe has more movement at these numbers. You have to assume equal opening and closing rates, but it will get you pretty close, quicker then looking for .050". The opening and closing rarely come out on the numbers of the cam cards, we just can't measure as close as the manufacturers, so focus on opening numbers and not total duration. Also, when adjusting the camshaft, the crank gear will only move the camshaft 1/2 the amount you adjust for. Example, 8 degree advance will only move the cam 4 degrees advance. When adding offset cam keys, the cam will move the full amount of the key offset. It's all due to the 2:1 ratio.
427 sleeper is quicker than me I think I found the source of your confusion. When checking cam timing, you measure lifter rise, not valve opening. The dial indicator reads 'lifter rise'. It is best to have a lifter that has a flat plug it so the dial indicator has a better contact surface. Here is the 'cam card' from Summit: So, let's check your procedure. You've got checking lifters that were made solid. No slop and you can get a repeatable reading. You found true TDC using a positive stop on #1 piston. Now you rotate the crank/cam assembly until the lifter rises .050" off the base circle of the cam Note the crankshaft position on the degree wheel (should be close to TDC for your cam) Continue rotating until the lifter falls back to the .050" reading (34 degrees after BDC?) Note the crankshaft position on the degree wheel Half way between the two degree wheel readings is Intake Centerline 0 + 180 + 34 = 214 When you get your actual numbers, post them up and we can tell you your next steps.
I have two lifters brazed top to top as a checker lifter so a dial indicator has a face to register off of. Lippy
Good tips here, hopefully I’ll have time after work today, the brazed lifters are a really good idea. Thanks, I’ll reply once I have time to re-spin.
I had a different take on the extended lifter deal. No brazing, I just took the guts out of a Chevy hydraulic and stuck a .625 dowel pin in with a bit of LocTite. Of course you need to source a dowel, but at the time I was a tool room machinist at GM and we had just about everything at hand.
Ok so I was able to check my process. Since it’s a really fresh goodwrench crate (maybe 2000 miles) all the honing marks are still there, all the gaskets could hand scrape, and the exhaust bolts came out without any trouble at all. So I used comp cams heads on method. Duration check: Zero lash. Find TDC with piston stop, zero the degree wheel. My rockers are 1.5, so 1.5 x .05= .075 lift measurement for the duration check. 1)At .076 of initial lift, I got 3 degrees from TDC. 2)At .076 before close it was 30 from BDC. So...30+3+180=213 (really close to the 214 duration). Feeling good. Intake centerline check: 1)Set dial indicator to max lift and zero it out. 0.05 before max lift gives me 85 degrees. 2) At 0.05 after max lift, it shows 140 degrees. Average of these numbers gave me 112.5. Cam card says 107. So looks like 5.5 degrees retarded. Is also a 3 speed. What do you guys think? Seems good to go and I can adjust timing after break-in. Thanks for all the help!
You have to tell us where the 3 degrees and 30 degrees are, is it 3 degrees BTDC or ATDC? Same with the 30 degrees closing, before or after. To find centerline, take half of the duration ( 214 @ .076" lift ) which is 107 degrees. Count 107 degrees from either end of the duration starting at the 3 degrees opening, and ending at your 30 degrees closing. This is where the before or after effect the number. Finding centerline from max lift is not accurate, the cam lobe is not a point, so the lifter will dwell for a number of degrees at that point. You can double check using this method, but counting actual degrees of duration is a more accurate way.
I made a couple things to make checking easier: a flat button to fit on the end of a piece of pushrod, and a plastic (blue) bushing to center up the pushrod tool
Eh I didn’t realize that was a concern, but 3 degrees was BTDC because the valve was beginning to open right? Or is it more important the relationship of TDC to the crank? My same logic is also trying to say 30 degrees ATDC Since the valve was beginning to close. But I didn’t really pay much attention to whether it was before or after top dead center. I didn’t really watch the degree wheel on rotation, I kept rotating to get my numbers after the exhaust valve closed on cylinder 1. Edit: Ok after checking my photos, 3 was definitely BTDC.
So count 107 degrees from 3 BTDC. Go here, https://www.blocklayer.com/degree-wheeleng.aspx add your cam numbers, adjust size to fit your degree wheel, print it out, apply to your degree wheel, and recheck your cam.
If you are confident the readings you took were done correctly, that the 3° BTDC intake opening and the 30° ABDC are correct....you are installed 3° advanced, on a 104° intake centerline. It is advanced, because the opening point happened 3° before the cam card said it would, which the card says 0°. An easy way to think of this...lobe is 214°, 1/2 of lobe is 107°....if it opened at 3° before TDC, that leaves only another 104° left After TDC for there maining half of the lobe to reach it's peak, the lobe centerline. Thus lobe centerline is 104° as installed right now. You could leave it slightly advanced like that, knowing the timing set does wear and stretch a bit with use and the cam will retard back 1-2° over time and use.....or you could decide to get a multiple keyway timing set or a set of offset dowel pin bushings and drill out the cam gear pin hole for replaceable bushings and use either method to correct it to exactly what the cam card suggests. Personally, I would leave it right where it is now unless you are riding the edge of the maximum compression ratio for the grade of gas you plan to use....if this is a 9.5:1-9.75:1+ compression engine and 87 octane is planned the 3° might give you detonation problems....if it is just a 9.25:1 or less engine then it will be fine.
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