Distributor Timing Map/Curve for 65 SHP (365hp L76)?

[Joe C.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Thx Joe. How frequently should I check/set the lash?

Regards,
Dennis

GM recommended every 12K miles, I believe. Conservative to be sure. The way you probably drive your Corvette, like most of us do, this means about every 8-10 years. Set it the way I explained (or the way Williams/Hinckley describe), and use motor oil with a good amount of phosphorous, and you're good to go. Shell Rotella/Chevron Delo API service class CJ-4 or other brands are sufficient for any factory flat tappet camshaft or "blueprint" reproduction.

[Dennis K.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Post #40: "AGAIN, I SUGGEST THAT YOU REPORT YOUR ENGINE'S VACUUM AT 850 RPM. IT SHOULD BE BETWEEN 8 - 9 IN-HG, DEPENDING ON YOUR LASH. IF IT IS HIGHER THAN THIS, THEN YOUR LASH IS SET TOO WIDE, OR YOU DON'T HAVE A 30-30 CAM INSTALLED. IN EITHER CASE, THAT EXPLAINS YOUR DETONATION PROBLEM."

Recheck your lash. Set it tight @ .023/.023 to .025/.025.

Hand turn the engine in its normal direction of rotation while watching the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake valve.
After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is almost closed, stop and adjust the exhaust valve on that particular cylinder.

If you have a 30-30 cam installed, and your engine is 327 cu-in, then your vacuum at idle will be no more than 8 in-hg @ 850!!!! If it still detonates after you do this then you certainly do NOT have a 30-30 cam installed!!!

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Hi Joe,

Is you valve lash recommendation (.023/.023 - .025/.025) when the ebgine is cold or hot?Also, I was thikning of asjusting the valves as follows (starting at TDC and rotating 90 degrees):

8E 2I
4E 1I
3E 8I
6E 4I
5E 3I
7E 6I
2E 5I
1E 7I

Is this your recommended procedure?

Thx,
Dennis

[Joe C.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Hi Joe, Is you valve lash recommendation (.023/.023 - .025/.025) when the ebgine is cold or hot?Also, I was thikning of asjusting the valves as follows (starting at TDC and rotating 90 degrees): 8E 2I 4E 1I 3E 8I 6E 4I 5E 3I 7E 6I 2E 5I 1E 7I Is this your recommended procedure? Thx, Dennis

Dennis, You can set them cold, but what I like to do is to warm the engine and then set them when it's cool enough to handle without burning yourself. The 30-30 cam has huge clearance ramps, so using the standard method leaves the lobes on the ramps and not on the base circle. The method I gave you is easiest and is universally accepted as proper and accurate procedure. "Hand turn the engine in its normal direction of rotation (or use a remote switch) while watching the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake valve. After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is about 3/4 closed, stop and adjust the exhaust valve on that particular cylinder." You can also use the Williams/Hinckely method. If you don't have it I can send it to you via email. Recommend you set them at .025/.025, warm.

[Dennis K.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Hi Joe and Duke,

Tightened up the valve lash night using Williams/Hinckley method at .023" tight when cold (in fact I may have err'd on the tight side towards .022"). Also adjusted the idle screws at 1 1/2 turns off the seat. Car fired up nicely - and I had a good "clicking" sound. All of my valve lashes were at least .007" + wide before I tightened them. PROBLEM - after the car came up to normal temp (180) I let it run for a few more minutes... just to wacth everything and listen... and the car stalled. I fired it back up again (it was hard to start) and it stalled again. Car does not want to hold idle even though I have idle set at 900RPM. I got bavck into this project this morning.. and the car started and ran fine. Drove it around town... and it ran fine eve up to normal operating temp (180*). However, a few minutes after reaching 180* it stalled again at a stoplight. Just won't hold idle. It appears that the car will hlold idle and run fie... until the carb and plenum reach a certai temp (e.g. presumably above 150*). Thoughts?

Thx,
Dennis

[Joe C.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Hi Joe and Duke,

Tightened up the valve lash night using Williams/Hinckley method at .023" tight when cold (in fact I may have err'd on the tight side towards .022"). Also adjusted the idle screws at 1 1/2 turns off the seat. Car fired up nicely - and I had a good "clicking" sound. All of my valve lashes were at least .007" + wide before I tightened them. PROBLEM - after the car came up to normal temp (180) I let it run for a few more minutes... just to wacth everything and listen... and the car stalled. I fired it back up again (it was hard to start) and it stalled again. Car does not want to hold idle even though I have idle set at 900RPM. I got bavck into this project this morning.. and the car started and ran fine. Drove it around town... and it ran fine eve up to normal operating temp (180*). However, a few minutes after reaching 180* it stalled again at a stoplight. Just won't hold idle. It appears that the car will hlold idle and run fie... until the carb and plenum reach a certai temp (e.g. presumably above 150*). Thoughts?

Thx,
Dennis

You don't want your lash tighter than .023/.023. Better a little too loose than too tight. Repeat.......recommend .025/.025. In any case, you'll have to reset your idle speed with the new lash settings.

.022/.022 will work, but allows no margin for error and a tight valve, especially an exhaust will burn a valve fast. After resetting to .025/.025, warm the engine and adjust idle speed to 850 RPM. Next, adjust your mixture screws to achieve highest idle speed, making sure that left and right needles are within 1/4 turn of each other. Recheck idle @ 850-900 RPM. Check and report idle vacuum, and now I'll bet that it will be closer to 8 - 9 in-hg. Detonation should be non-existant if your timing is set properly at 10-12 initial plus 16 - 17 degrees vac advance plus 24 centrifugal.

If your idle speed screw is set too low, it will stall. The engine will not run once idle vacuum falls below about 6-7 in-hg.

[Duke W.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

This has been a long and confusing thread because others have jumped in with their own questions, so lets review.

How do you know for sure that it has a 30-30 cam? Idle vacuum @ idle speed will give a clue. Have you measured it? Post the data.

Is the dwell angle and initial timing in the ballpark?

Does the installed VAC a 236 16 or B28, and does it meet spec?

Is the heat riser wired open?

With the lash set at about .023" there should be virtually no valve train noise from a 30-30 cam. You could almost believe it's a hydraulic lifter cam.

I'll be back in San Diego tomorrow by 10 AM so I can catch Jim Gessner's seminar. Let's hook up after that and check out your car. Do you have all the requisite "Tools of the Trade" from my powerpoint slide or should I bring mine.

Do you have fender covers?

Duke

[Dennis K.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Hi Duke and Joe,

Thanks again. Certainly would appreciate the help tomorrow. I have all the tools (including golf tee, tiing light, and one fender skirt, etc.)... except for the ohmeter. Not sure we need it though. Anhyway... I called the engine builder (my father - he and I built the engine 12 years ago, but I was not involved in the cam and/or overall design - just assembly)... anyway.. a few points:

1. The heat riser block inbetween the intake manifild and valve heads was not blocked off. I am thinking this could be causing my carb to rise to a heat that would vaporize the fuel at idle (e.g. fuel under low pressure)??

2. My cam is a BLUEPRINTED 30-30 cam. My dad happened to know the actual cam grinder for GM 30-30 cams (back in the day)... and had him grind a blueprinted 30-30 cam. It came sent to us in a GM box. Wondering how this affects how we setup valve lash?

Duke - my personal email is dkurimai@hotmail.com. Can you please send me an email and I will forward my cell number? THANKS again for your assistance... there's a bottle of nice wine in it for you (from my part of Northern California near Napa). Again - THANK YOU for your kind offer to assist.

cheers,
Dennis

[Duke W.]

Re: Distributor Timing Map/Curve for 65 SHP (365hp L76)?

Okay, we can talk tonight, and I'll see you tomorrow. Let's close out this thread until we figure out what's going on. You can start a new thread with the results of the analysis and whatever corrective action is taken once we get it sorted out.

Duke