My 1965 manual that came with the car says timing for the 327 ci. 360 HP and 375 HP Fuel injected should be set at 10 degrees BTDC. My Chilton's Corvette Stingray Repair & Tune-up Guide 1963-76 second edition says timing should be 12 degrees BTDC for the 360 and 375FI horse power engines. Which should I set it at? Thanks for your input.
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Re: 1965 375HP Timing
You're splitting hairs. Corvette News Vol.8 No. 2, which lists tuneup specs for all '65 engines says 12 nominal with a range of 10-14.
Generally, small blocks make best power with 36-38 degrees of total WOT timing - the sum of initial plus full centrifugal. Your OEM distributor should provide a maximum of 24 degrees centrifugal at 2350 RPM, so this implies initial timing of 12-14, but this could be limited by detonation depending on your fuel octane rating.
The best way to set the total WOT timing is to use an accurate dial back light or accurate timing tape/marks on the balancer and set the timing at above the speed that centrifugal is all in, which would be about 2500 for your engine. Set the total timing at about 37 and the variation should only be about one degree. Of course, the vacuum can must be disconnected to do this job.
Then, if you want, you can check to see where the initial ends up. Also, since your centrifugal starts at 600-700 RPM, initial timing must be checked well below normal idle speed, or you must tie up the centrifugal advance to be sure the centrifugal advance has not begun to deploy.
The '64-'65 SHP/FI ignition map setup is ideal for a high performance small block, and I recommend it for all high performance small blocks with either a factory or aftermarket high performance cam. The igntion map includes the centrifugal advance and the vacuum can, which provides 16 degrees advance at 8". This vacuum can is available from NAPA/Echlin under the part number VC1810. The original Delco can is marked 236-16.
Duke -
Re: 1965 375HP Timing
Either way will work. So will 8-14. If it rattles at the higher setting, start backing it down. Make sure there is no vacuum pulling on your can when you are setting timing.
In my opinion, the best way to do it is to set your maximum advance to 36-37 degrees with a dial back timing light and lock the distributor down. Then whatever initial advance you have is what you have. But it will probably be around 10-12 degrees. If it isn't, it could mean your advance weights are sticking or somebody has modified your distributor. I forget the RPM where your full centrifugal advance kicks in. Some are as low as 2500 to as high as 4800. Your book should tell you.
MikeComment
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Re: 1965 375HP Timing
Centrifugal advance does not "kick-in", whatever that means. Centrifugal starts at some point low in the rev scale and maxes out at a higher point, and the increase is not necessarily linear.
For 64-65 SHP/FI engines with mechanical lifters (other than very early versions, which may have had carry over '63 distributors) the centrifugal curve is as follows:
0 @ 700 (start)
15 @ 1500
24 @ 2350
These are crankshaft advance and engine RPM. Sometimes specs are quoted in distributor advance and RPM, which would be half these amounts. Also, figure that tolerace is +/- a couple of degrees and a couple of hundred RPM.
Because the centrifugal starts at below where these engines will idle with acceptable quality one must be careful when checking initial timing to be sure that the centrifugal has not begun to deploy. Thus my caution in my earlier post. You either have to drop the engine speed to the point where it is barely running or tie up the centrifugal to be sure it does not deploy.
Of course, checking total timing is the best way to go, but you have to know the point that the centrifugal is fully deployed, which is in the range of 4000-5000 PRM for some Corvette engines.
DukeComment
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Re: 1965 375HP Timing
"The RPM where your FULL centrifugal advance kicks in" means the same as "The point that the centrifugal is fully deployed". "Deployed" is military jargon for "kick in".
"Some engines (Corvette) are as low as 2500 to as high as 4800 RPM" means the same as "Which is in the range of 4000-5000 RPM for some Corvette engines".
What part of this don't you understand? JC! The man just wanted to know what timing spec was correct!
Besides that, he didn't ask what linear meant and he's probably like me. He don't care!
MikeComment
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Re: 1965 375HP Timing
From the three, plus year that I have been closely monitoring and contributing to this Board, it is clear to me that many vintage Corvette owners do not understand engine timing requirements as a function of speed and load, which is implememted by the combination of initial, centrifugal, and vacuum advance on vintage Corvette engines.
Further, most don't have the post-graduate training in internal combustion engine research and design that I have, nor do they have the professional engineering experience, nor 40 years of racing, tuning, and restoration that I have.
Thus, I endeavor to go beyond one line answers to questions in order to educate owners on the entire subject that their question relates to.
Some owners do not know that the vacuum advance must be disconnected to check initial timing, and many do not understand that an aggressive centrifugal advance curve may give a false initial timing readout at idle speed, and very, very few understand the vacuum advance requirement as a function of the engine's load/manifold vacuum characteristics, including idle vacuum.
Finally, as a retired Air Force officer I cannot recall any kind of relationship between the word "deploy" and "kicks in" in a military context. I interpret "kicks in" to be an informal expression to denote "when something begins" as opposed to "when something ends".
DukeComment
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Re: 1965 375HP Timing
The key word you are missing is, I said when FULL kicks in. Not a LITTLE, not a LOT, FULL, FULL, FULL. That's hillbilly talk for "deploy". Do you know what a hillbilly is?
Most members of this board don't know/care about the effects of timing whatever on their engines. They don't need a degree in internal combustion engines. They just want to know "how to"? Although, I will admit I do not "know" most of the members of this board.
Jim's question was simple. What do I set my initial at? That answer does not require Internal Combustion 101 and 102. I've never seen him post a question before, don't know anything about his experience or knowledge and tried to keep my answer simple. You, on the other hand, wanted to write a book and then chastise my use of the English language. That's not your place. If Jim didn't understand what "kicks in" means, he could have asked and I would be happy to tell him. I can imagine your answer to simple questions, even though generally accurate, overwhelm the knowledge threshold of many of these Corvette neophytes.
And if you do this, they turn off. The short answer is the BEST answer. If someone needs more information, they will generally ask for it. Corvettes, refrigerators, lawn mowers, garbage disposals, grass seed fertilizer, etc,etc.
It might interest you to know that at one time, back when I played basketball for Bobby Knight at Indiana University, I was an aspiring young Air Force officer candidate. I walked into class one day in my Air Force uniform with a Army cap on turned backwards. We marched in formation for 5 minutes before someone spotted me, threw me out of ROTC and flunked me for the semester. So much for my Air Force career. I joined the Indiana Army National Guard for 8 years and did rather well. Tell me, as a retired Air Force officer, do you think I missed my calling with this outrageous behavior?
MikeComment
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Re: 1965 375HP Timing
Duke - I have always appreciated your thoughtful, complete,insiteful feedback. Being an engineer, I can realte well to your posts, but they always are stated in a way anyone can understand. It takes time to convey a thorough answer, and, you have always done that without reservation. I have many posts of yours, Joe Lucia, John Hinkley, Jack Humphrey, and others saved in files for future reference. Thanks for your help, and I hope I have been able to help a few folks as well...CraigComment
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Re: 1965 375HP Timing/Duke Thanks for the effort *NM*
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Re: 1965 375HP Timing
Duke has always been an invaluable addition to this board. I have always read his posts with interest, as he always adds valuable explanations that are easy to understand yet quite technical. Much better than a "Yes" or "No" answer that will invariably raise further questions. When you know the "Why" behind an answer, you find yourself educated enough to solve the problem yourself rather than being capable of only blindly following advice and hoping for the best.
Keep up the good work, Duke. I don't post much, but I don't miss many of yours.
-Michael
The HampsonsComment
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Re: 1965 375HP Timing
I agree with mike Hampson.Comment
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Sometimes a simple answer doesn't give enough info
That's exactly the case here. Just telling someone to set the initial timing a X deg is a real disservice. With these old high compresion engines and today's crappy gas, it can spell disaster if one doesn't fully understand engine timing and what you are really doing. The initial timing spec is only good if the entire ignition system is exactly to factory spec. No change in either mechanical or vacuum advance and everything working just as specified.
Duke is entirely proper in fully explaining the whole timing proceedure and I for one am grateful that we have folks on the board who are willing to take the time and effort to fully explain some of these issues. I wish my 62 had a vacuum advance so I could take advantage of some of the knowledge I've gained from the "long answers".Comment
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Re: 1965 375HP Timing
I will add some information here prior to Dukes informative post's on timing.I used to set my timing to the recomendations from tune up manuals.I now own an ajustable timing light and think I understand how to use it properley.THANK YOU DUKE
I also feel that the folks who are asking questions on this board are looking for an education and are looking for the long educational answers that members of the board are nice enought to share with us.
And as some one who has teach my staff how to correctly repair some thing mecanical,I know it is most important to teach them how and why some thing works.With the better mecanical understanding they are able to diagnois problem they encounter in the future.This way we have more mecanical tecnitians and less parts changers.A real terrible thing will be when all of the true mecanics stop sharing there information with us.
PS Duke
that was a most Excellent and informative article in the latest issue of the restorer magazine this month.Comment
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Re: Sometimes a simple answer doesn't give enough
Amen... Thanks Duke, et alComment
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Re: Sometimes a simple answer doesn't give enough
I want to thank everyone for there input. I am the type of person that wants to fully understand why things do what they do and I want to know how to do things correctly so I always ask alot of questions. I never fully understood the relationship between initial, centrifical and total timing but I do now and because of that my car runs great!!! Thanks Again!Comment
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