1968 GTO set base timing and total timing?? - Pontiac GTO Forum
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post #1 of 16 (permalink) Old 05-19-2018, 01:36 AM Thread Starter
 
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1968 GTO set base timing and total timing??

Hello All: New member. I got a 68 GTO 400 engine. Just bought. Not stock. Got Elderbrock mandifold with Elderbrock cfm 600 4 barrel. Hooker headers. No cam. A MSD 6200A electronic ignition. No points or vaccum line going to distruibutor. A matching number 68. Flow master exhaust system. I've read alot of your post on setting the timing??? I'm asking what I did is ok for the engine. I started out with my total timing at 36 degrees pulling in at around 2700 RPM's. Base timing is set at 15 degrees. What I did was subtract 36 degrees from 15 degrees, and got 21 degrees. With engine running at around 2700 RPM's the engine tab at zero matched the balancer BTDC (0) perfect. My timing light is the one you can preset the dwell. So I set it on 21 degrees, and both zero's hit perfect. I did have my base timing at 12 degrees BTDC, but the engine runs smoother at 15 degrees, and excellerates much better. No back fire which I had with Manufacture base timing at 9 degrees BTDC. Wondering if what I did is OK???? Question one: Is my base timing to far advanced? Don't want to burn a cyclinder head. No pinging. Also I hooked up a fance vaccum gage, and that was in the Green at Idle, and stade in the green at 3000 RPM's. I'm a old 66 years old disable Vet, and had one of these in high School. Back then we use to take out the termostate, and just ran her that way. Took off the Air cleaner. And just ran the shit out of her. Now at 66 years old I wash, and wax her. Vaccum the car every other day. This is the last thing on my Bucket list. LOL LOL So I hope the engine isn't going to blow up. The car is a His, and Her automatic.

Thank you, Bob :-)
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post #2 of 16 (permalink) Old 05-19-2018, 09:47 AM
 
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Each engine combo can be different with regards to timing. The factory settings were just that, for the factory engine. Often the initial can be set higher and run better. You also no longer have the vacuum advance, so your initial setting wants to be higher without it. Vacuum advance adds to better fuel mileage when cruising under light load/high engine vacuum.

The key is not to have too much total timing, as that is where you destroy the engine - ie burn a piston or hammer the bearings away. Personally, 36 degrees total in my book is about the limit and I would feel safer with 34, but from what I read, the ethanol in the gas will allow for slightly more timing advance - so IF you are not hearing any "pinging" then I suspect you are OK. A stop limiter could be added to the mechanical advance in the distributor if you like your distributor's initial timing and it's curve, but find some pinging due to too high total advance.

The problem arises when you don't here the audible detonation. Outside temps & under hood temps can rise and this can create a problem that leads to detonation. Modern cars have knock sensors and can automatically adjust timing to compensate. Our older cars don't have this feature.

If your car starts well at 15 degrees initial, then that is also fine for your application. It is when you have starting problems, the engine struggles to turn over, that it may be too far advanced for the initial. So if it starts good and runs better as you stated, then leave it.

If you can lug the engine and it does not ping/detonate, then it should be OK - old school way of timing for maximum advance, right?
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post #3 of 16 (permalink) Old 05-19-2018, 09:29 PM Thread Starter
 
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1968 GTO intial, and Total timing.

Hello PontiacJim: I first would like to Thank you for your reply. Very Good.
Have a Question Jim: Would you like if I turned back my Total Timing to 34 degrees, and Intial Timing at 13 degrees???? Would this be a safer adjustment??? The car is running great. No hessitation on acceleration. Starts right up in the mourning with the choke on. It takes the gas right off the bat.
Runs very fast. I believe if I had some pinging I could hear it at Idel?? It is Ideling at 850 RPMS. As you can tell I'm a little nervous.. :-( Engine was rebuilt 20,000 miles ago. I put a Vaccum gage on it, and it read in the green at Idel, and in the green at 3000 RPMS. Does that mean any thing. Well again I Thank you for the good advice. Have a great Weekend.

The "Z" Man :-)
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post #4 of 16 (permalink) Old 05-19-2018, 11:04 PM
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If it's not pinging/detonating, don't worry. Put it under some load at low rpm, like pulling up a long hill in high gear for instance with the engine nice and warm. If it's going to detonate, you're most likely to hear it under those conditions. Pull a couple of spark plugs and examine them really closely with a magnifying glass. If you don't see any shiny specs - sort of like bits of glitter - on your plugs, that's more evidence that you're not getting into detonation and more confidence on your part that things are ok. Every engine, every build is a little different. Rules of thumb are exactly that - rules of thumb. That doesn't mean that a specific engine won't be happy with a little more timing than usual. It's the total and how fast it comes in that matters. The initial setting is nothing more than a way to 'get to' what you want for the total. As long as the engine isn't running so much initial that it's hard to start, and it's not detonating, you're good.

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post #5 of 16 (permalink) Old 05-20-2018, 08:51 AM Thread Starter
 
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1968 GTO intial, and Total timing.

Hello Mr. Bear: Great information... I pulled 3 spark plugs, and looked at them with my magnifier glass, and everything looks OK... :-) Your right I should be
OK with the way I have it set up. My spark plugs are ACDELCO R45S... Gap is .045 inch. In fact I still had the Spark Plug Gap tool from back from 1965... LOL LOL
Is this spark plug ok for this car????? What would be a better spark plug????
The old days back in 1969 we use to use a cold plug. I believe it could of been
a CHAMPION R16 ???????? Does this bring back the old days???? I've been adjusting this timing for a month. Manual says. 9 DBTD.. Then I went to 12 DBTD... Engine ran better. Now I went to 15 DBTD, and engine runs great....
Your question about a Hill to put a load on the GTO would be hard to do in Florida... LOL The biggest hill in town is my driveway... I got this car just like the day it came off the assembly line. If you can think of anything else I should do or check let me know... You have been a great help.

Thank you, The "Z" Man (Bob)
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post #6 of 16 (permalink) Old 05-20-2018, 09:19 AM
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Hey Bob (my name is also Robert) -- As long as the plug is getting the fire lit (and it sounds like yours are fine in that regard), the other considerations on choice are that you want a plug that will stay hot enough to keep itself clean, yet not so hot that it becomes a 'hot spot' that can lead to detonation and/or have a shortened life. If your plugs fit all three of those concerns, they're fine.

My 69 likes lots of initial too. I'm running a Davis HEI that has 20 degrees centrifugal in it, and my heads (Edelbrock RPM 72cc round ports) seem to like 36 total, so I set my initial at 16. I might need to retest after I finish the current build because I'm making a significant cam change, also an intake/carb change.

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post #7 of 16 (permalink) Old 05-20-2018, 09:40 AM
 
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Originally Posted by rob40999 View Post
Hello Mr. Bear: Great information... I pulled 3 spark plugs, and looked at them with my magnifier glass, and everything looks OK... :-) Your right I should be
OK with the way I have it set up. My spark plugs are ACDELCO R45S... Gap is .045 inch. In fact I still had the Spark Plug Gap tool from back from 1965... LOL LOL
Is this spark plug ok for this car????? What would be a better spark plug????
The old days back in 1969 we use to use a cold plug. I believe it could of been
a CHAMPION R16 ???????? Does this bring back the old days???? I've been adjusting this timing for a month. Manual says. 9 DBTD.. Then I went to 12 DBTD... Engine ran better. Now I went to 15 DBTD, and engine runs great....
Your question about a Hill to put a load on the GTO would be hard to do in Florida... LOL The biggest hill in town is my driveway... I got this car just like the day it came off the assembly line. If you can think of anything else I should do or check let me know... You have been a great help.

Thank you, The "Z" Man (Bob)

The factory plugs for the 1969 400 ('cause I have the specs handy) is AC R44S. A colder plug may be right for Florida weather. So you may want to try the R44S and see how that works. As long as you don't experience plug fouling - then you have gone too cold.

You will not hear pinging at idle, only under load, whether it be light load or heavy load. An engine will ping under light load if it is way too advanced. Heavy load testing is done under Wide Open Throttle. As Bear stated, a hill can be best, but Florida is indeed flat for the most part. If you have an automatic, His/Hers trans, you should be able to manually keep it in second gear. If so, accelerate from about 10 MPH under WOT for a short blast and listen. If a 4-speed, same deal, but try 3rd gear to lug the engine. This should produce the same results. So that is the key, WOT under load is where you want to listen for the pinging
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post #8 of 16 (permalink) Old 05-20-2018, 09:49 AM Thread Starter
 
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1968 GTO intial, and Total timing.

Hello Mr Bear (Robert): You sound like you know what your doing. I being a retired Military Aircraft mechanic have some Idea what's going on. Plus having one of these car's (1968 gto) Back in High School. I was Hot back then. Now at 66 years old I just think about what's for Dinner. LOL LOL

About the spark plugs. The plugs where really clean, and looked like there fairly new. I've only owned this car since March. It's starting to come back to me. Back in 1969 I spent more time adjusting the points, and playing with timing than I wish to do now. Use to race the car. It was a 4 speed, and I blew that clutch a few times. Changing it in the street. Driving it up on the curb, and getting under there, and doing the work. Back then we did this stuff our selves.. Now I wash and wax the car, and call the Mechanic...

Got a Question for you Mr. Robert: I got the Elderbrock Model 1460 which is 600cmf. Would It be OK for me to put on a bigger Carburator??? Say a 750cfm???? Or this should be just fine. When I hit the throttle, and she shift down to second, and the 4 barrell opens up??? Hang on.... My other car don't sound like that. LOL LOL

So Thank you, Robert, and have a great weekend.
The "Z" Man (BOB)
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post #9 of 16 (permalink) Old 05-20-2018, 10:21 AM Thread Starter
 
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1968 GTO intial, and Total timing.

Hello Again Mr. Jim: Your Idea about putting the car in 2nd gear is a good Idea. I have a Automatic, His and Her shifter. So I'll do that load test. This is going to be interesting. Maybe I'll do it with the Hood open so I can hear better???????? LOL LOL

The spark plug that you suggested I'll give a try. Give me something to do...

I guess it's a big deal changing the car from 12 degrees TDC to 15 degrees TDC??? I've been using 93 Octane, and adding a Octane booster with every fill up. Also some STA-BIL 360 Performance for the Ethanol in our Gas.. I've read here on this site that some people are using a Lead Substitute??? My mechanic was very puzzeled about adding a Lead Substitute??? The car runs great, and start's right up Cold or Hot. So as that worry wart that I am I'll do the load test Jim. I'll get back to you. It's raining today here in Florida. I'm waxing the GTO AGAIN in the garage. LOL
So I wish you a great weekend.
Thank you, The "Z" Man (Bob)
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post #10 of 16 (permalink) Old 05-20-2018, 03:23 PM Thread Starter
 
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1968 GTO intial, and Total timing.

To PontiacJim: Did load test on car. Put it in second gear at 10 mph, and gave her a lot of gas. You could hear the Engine trying very slowly trying to come up in RPM's. No Pinging at all... Just a smooth very slow upward RPM's. I guess I'm out of the weeds. I'll try those new spark plugs...

Have a great week,
Thank you, Bob
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