Old Olds Fan

Friends, Ive been reading the engine thread for a while now and I'm surprised that there's so little talk about available fuel(octane) , timing, exhaust value seat recession (for the pre-71 cars out there) and value adjustment? I just purchased a 65 442 with 92,000 miles and am thinking about what needs to be done about these issues. I read the other day of members running as much as 36+ degrees total? I'm a 30yr marine mechanic, we didn't deal with vacuum advance but, I think I understand how it works, but again recently some one mentioned 50 degrees with vacuum? I've checked and the original timing spec. is 7.5 BTDC and I'm good with a distributor putting in a max of about 24 degrees=32.5 total and vacuum pulls in what?
Has anyone suffered value recession to the point where it effected value adjustment. I know there isn't any way to adjust the values on a 400 (shim the pedestals, or tip the values) ?
I'm going to build the engine, because I'll have to do exhaust seats and larger ex. values at a minimum, I'm thinking new Edelbrock heads instead of the work on the originals. I want to build a torque monster for the street, but it needs to run on 93octane or less God only knows what we'll be able to get in 10 years. I know the the Olds engine is detonation resistant but how much compression and how much advance before trouble begins? Any Input?

oddball

With iron heads, compression over 10:1 can detonate easily. Good spark control is the key, though. For me, changing to an MSD 6AL-2 and doing the curve in the box helped tremendously.
Vacuum cans are widely different, can pull anywhere from 10 to 20 degrees. Aftermarket ones are adjustable. Vacuum is critical for cruise efficiency, not terribly important otherwise unless your build requires it at idle (some do...).
If you're working the heads, might as well install hardened seats just so it's never a problem. I've heard of folks running on the street without just fine, though. Good detonation and temp control is probably key.
The cam and final CR will really drive how careful you need to be.

oldcutlass

You were reading my or others posts. Those are not initial timing settings, they are total. Total is initial + mechanical + vacuum advance. The general rule of thumb for most V8's is 36 degrees (plus or minus) total mechanical advance all in at 2800 rpm. Most HEI distributors have 15-18 degrees built in, so that would put your initial timing somewhere between 18 - 21 degrees BTDC. If you realize detonation at these settings due to altitude, fuel quality, or any other reason, you should back it off a bit. These settings are for performance.

When you add vacuum advance the optimum figure was 52 Deg. BTDC @ 2800-3200 RPM. Since there are a great number of vacuum advance cans, stock and aftermarket adjustable available there are a great many ways of setting it for efficiency. Some engines like that much others do not, so experiment.

Points distributors had so many different variations of weights and springs but have more mechanical and vacuum advance. That's where the lower initial settings were derived. The total 36 deg BTDC @ 2800-3000 rpm rule still applies.

Old Olds Fan

oddball, I understand the issue that's why I chose to go with aluminum heads. I am interested to hear that some people are running non-hardened heads without problems. As I said, I'm a marine mechanic and 32 degrees is about all you can get in a marine engine without knocking it apart and I've seen lots of sunk values, also badly tulip-ed values, oldcutlass, I'm surprised by 36 but there are big load differences between a car and a boat, so I'll go with it. Doesn't 18-21BTDC initial lead to starting problems (difficult cranking)? Where might I get info on what's available on the vac side, I'm guessing the higher the vacuum the more advance it pulls, is there any rule of thumb here. Hay thanks guys for your input.

oldcutlass

I've never worked on boats, but yes I would think the load on the engine is much different but I would assume the fundamentals are the same. I would think the timing curve would be different. What's the compression of the marine engines?

With aluminum heads your timing may differ a bit. The adjustable vacuum advances are great, most aftermarket distributors come with them, or you can purchase them separate as improvement to an older distributor. The advance weight and spring kits are available to control when and how much advance for your engine requirements.

I have not seen many valve or seat issues do to fuel. Most older street cars are not daily drivers and don't accrue the annual mileage so these issues aren't that prevalent. The performance builders are building their heads according to their budget and/ or individual engine requirements.

As always every engine is different and all need to be tuned individually. Altitude, humidity, temperature, barometric pressure, and fuel quality play a major part in effecting the way you engine runs also.

Starting problems can arise, but can also be caused by worn components. Octane requirements have always been a fundamental of compression ratio's. The higher the compression the higher the octane needed.

cutlassefi

No they're not detonation resistant, at least not with stock heads.

Do the aluminums, you'll be glad you did. Either the Procomps or Edelbrocks would be a good choice. Redoing the old irons is a waste of time and money these days, not worth it.
You can make good power with that 400 and the right parts. Those heads would be a good start.

oddball

Aftermarket heads will come with hardened seats.

Also, marine engines - at least speed boat engines where I'm used to seeing V8's - tend to run all day at high RPM. That'll kill the seats pretty easily. A street engine has a very different usage.

Initial over 16 can get hard to start. For points-style dizzys, initial tends to be around 12. You will have to sort out the details with your particular build.

Stock vacuum cans are build to certain specs, and there were a wide variety of them. So they have different maximum advance that comes in at different levels. e.g., one can will have 10deg advance at 15", while another can will have 12deg advance at 12". I think it's very worthwhile to get an aftermarket adjustable can. They have a set screw that changes the maximum advance and also somewhat alters the advance curve.