283ci and cam timing wheel

[Lugnutz65]

I’ll get right to the point.

Is there a way to determine whether or not my current cam has 4° of advance already built into the cam? The cam has no markings and I don’t have a cam card.

I’ve read a few articles that tell me it is very important when choosing a cam for an engine, to know the cam timing. For my particular situation, I want to install the cam with 4° of advance so that I have better power and torque at lower RPMs than if the cam was straight up. This engine will not be running above 2500 RPM’s unless I am rowing through the gears.

Here’s the problem. I do not have a cam card. The information below will help you understand why I believe the cam in this engine is a factory cam for a 1966 283ci SBC.

What I need help with is determining if the cam I have already has 4° of advance built into the cam. I called Jasper, and the guy on the phone seemed to believe that a factory rebuild by Jasper would not include 4° of advance already built into the cam.

I’m assembling a 1966 283ci that was rebuilt by Jasper years ago but never run.
Rebuilt and assembled by Jasper so long ago they have no record of it. It was still bolted to the shipping crate and wrapped in plastic.
1966 block and heads.
New pistons 0.040 over and fresh crosshatch on the cylinder walls.
Rebuilt powerpack heads.

I’ve read articles about cam timing. I removed the cam but it doesn’t have any markings that indicate the lobe separation or duration.
Here’s what I have learned using a timing wheel.

Here are the conditions.
I lubricated and installed a solid lifter with light weight oil. Then installed it in the intake position for cylinder #1 and tightened down the rocker to zero lash. Just tight enough that I couldn’t spin the pushrod with my fingers. No slop.
My dial indicator was carefully lined up with the pushrod and resting on the rocker.

1. I calculated the centerline of the cam intake lobe of cylinder number one. I did it several times with repeatable results.
I got the dial indicator reading maximum lift and reset the dial to zero. I then turned the crank clockwise until it read 0.050 inches less than zero and recorded that degree mark. I then turned the crank counter clockwise until the dial indicator went past zero and then past 0.050 and stopped at 0.020. I then turned the crank clockwise again to take up any chain slack and stopped again at 0.050 and recorded that degree mark.

Jasper cam
150* - 60* = 90 90/2 = 45*
So 60* + 45* = 105* So 105* ATDC is the intake lobe centerline.

I repeated everything with a 1958 283ci cam I have from another engine.
1958 283ci cam results were essentially the same.

153 - 62 = 91 91/2 = 45.5
So 62 + 45.5 = 107.5* ATDC = intake lobe centerline for the 1958 cam.

2. Jasper cam lift was 0.244 and slightly less at 0.238 for the 1958 cam. I guess from cam wear. Factory spec in 1963 was 0.2658.

3. Duration
The Jasper and 1958 cams both had these same numbers.
Intake valve begins to open at 25* BTDC
Finishes closing at 260* ATDC (yes 80* ABDC)
These numbers were taken down when I saw even 0.001* of movement of the dial indicator. The numbers likely include the acceleration ramp and closing ramps.

[Lugnutz65]

The duration of 285* I got likely includes the ramps. This document supports that and says 300* including ramps.

[AussieinNC]

I have always measured cam timing when I have 0.060 of lift on the lifter itself.

This figure eliminates the opening and closing ramps on the cam lobe.

Your figures show a normal 293 cam.

As far as it being 4 degrees advanced...I doubt that Jasper...(or any mass production rebuilder), would custom grind a cam plus 4 degrees....

The usual mechanism to install a cam plus or minus is to use a special upper gear and an offset bushing to move the cam itself. There are kits around that have a lower gear with three keyways cut, one straight up, one plus 5 and one minus 5.

The accuracy of these figures is always assuming there is zero slop in the cam chain and gear set...

Even a new set often has up to 3-4 degrees crank of slack....thats why performance engines usually use a precision gear set.

Have fun....

[Lugnutz65]

Thanks for the input. I’ll measure stuff again using the 0.060 as a reference. A friend gave me a new double chain SBC timing set. It has the 3 keyway slots on the lower gear like you mentioned.
Before I install it, I thought I should figure out if the cam had any advance in it.
Having gained all this “knowledge” about my stock cam, I’ve decided to install a GK390 cam I have on the shelf. It came out of that frankenstein 307ci I tore down that had the large journal 302 Camaro crank. Everything I’ve found on the web indicates it would really work well in my 283ci. Here’s the specs.

[AussieinNC]

Measure at 0.060 60 thou....not .6 which is 600 thou

Typos just suck....

[Lugnutz65]

Typo corrected. Thanks. I had it right in my head.
What do you think of the GK 930 cam?

[burnin oil]

Most the off the shelf cams for SBC come with 4 degrees advance ground into them. Been like that for years. Not a big deal since most people buy a cam that's to big. Reading lift depends on the cam manufacturer and lifter type. 50 readings became the standard for comparing cams but the ramps could be doing anything before that. Depending on how old that rebuild is it may have a true cam grind. As for cam choice I would keep it in the RV cam range and you will be happy. 283s are small and that short stroke makes them have a higher power band than the cam is rated. It doesn't take much to need to go to deep rear gears! Back before vortec motors I knew a guy that built a 283 with RV style cam and large valve 305HO heads. Good power and was knocking down 20mpg in a square body daily driver. Large valve heads are iffy on a 283 since the valves are really close to the cylinder walls. Valve shrouding can be an issue and cause a loss in power. Worth checking while the motor is on the stand. Depending on usage I would consider upgrading the heads. Power pack heads were good back in the day but there are alot better now. Other than the intake cost I think vortecs would be a good match for a 283. Plenty of flow with good velocity without being over sized for a smaller SBC. Would love to hear others opinions on this.

[Lugnutz65]

Do you think this GK 930 SBC camshaft that I plan to install has 4* of advance in it? It should improve performance compared to the original factory cam.

[burnin oil]

From my memory it looks a little small for a 300hp 327 cam but is probably spot on. I loved that cam in a 400sb. It would Rev to 6k on the shift and still run at 400 rpm off roading. I had it hooked to a granny low 4spd with 3.07 gears and that sucker would shred a 31x10.5 tire. Talking 4 inch wide black marks. It really narrowed the tires like a dragster. Best motor I ever had! That being said it was a 400sb that has a 3.75" stroke and not a 3" 283. With a good 10:1 compression or higher I think it would be a blast in a 283 but you would need atleast a 3.73 gear in my opinion. Torque for me was good but I think it would be a little shy on the little brother. I would run it and install straight up. Knowing that it is going to like moderate rpm I would do a little port work to the heads right at the valve but leave the runners alone to keep some velocity. Honestly I would try to run a factory qjet intake and carb but you would need to adjust the pvc system. If running a carter or edelbrock I would probably shoot for a 500cfm model. For a holley I would try and find a 390 cfm double pumper. A little small but the right foot controls the throttle and I think it would be a blast. I actually have a 390 on my circle track 400sb right now after my 830 had some issues as a keep it running deal. It really surprised me on how well it performed, light years ahead of a 750 vac secondary carb. The cam is dated as are the heads but of you are good with old school it will still be a blast to drive. If its hooked to an auto I would up the stall a few hundred rpm and enjoy. Nothing to radical. I think the motor will be perfectly streetable but will need to driven with a little spirit to it. As a combo I think you will be able to beat it hard and never have an issue with durability. A 3spd Saginaw may say something different. You never did say the application.

[Lugnutz65]

I will put this Jasper 283 in my 1965 C10 short stepside. I have a Rochester 2Jet and cast iron manifold. The truck currently has a T5 manual tranny with Camaro V8 gears and a 3.73 12 bolt rear axle. Daily driver with good MPG is my goal.

[burnin oil]

That will be a fun ride for sure. I don't think the 283 will be to hard on that T5 if you treat her right. Definatly will have the potential to tear it up if you get on it aggressively. Keep us up on how she runs. I am curious how much you will end up in 5th. You may need a little more rear gear to keep it happy but Columbia is pretty flat as I recall.

[Lugnutz65]

I know the 283ci makes power in the upper RPM band. I’m a T5 guy and rebuild them. So I have a few options on gearing. The 283 might like a 0.86 OD gear better than a 0.73 OD gear on the highway. The V8 Camaro gear set is a close ratio T5 gear set and the best of the bunch, but there’s no way to change it to a 0.86 OD gear. I have an S10 gear set in my 1963 C10 and it’s a fun driver for sure, so no worries if I have to change.

[burnin oil]

I think that they have a bad rap also. I enjoyed the one I put in a v6 camaro alot and beat it hard. Had a few in s10s and one in a v8 camaro that I only drove a few times before I had to get rid of it. All served me well. Then again I had a friend with a mustang that tore them up all the time. He lost one coming off a stop sign on a hill by rolling back slightly and coming off the clutch. Honestly it was probably already damaged and that was the last straw. Another light duty trans that I really like is the NV3500. They have a similar reputation yet I never had an issue with it behind a small block, including a vortec 350.

[Lugnutz65]

Here’s an update on this 283. TWO VIDEOS BELOW
Found all the pieces I needed. That part was NOT easy. Got her buttoned up and on the run stand yesterday and again today. She’s alive! A few leaks need to be addressed and then getting installed in my 1965 C10 with a T5. WooHoo!
https://youtu.be/PuU_gY58kPw
https://youtu.be/zmXjeAMFQ3I