1969 427/435 ignition and timing questions
 

I just purchased a 1969 Corvette L-71 (427 V-8, 435 hp, Tri-Power) and will soon be doing a full tune-up on the engine.

1. What are the stock timing specs for a 427/435 engine? I am wanting to know what initial timing is along with total timing ... and at what rpm full advance should be in. Example: 12 degrees initial, 23 degrees centrifugal, all in by 3,000 rpm.

2. Does a 1969 427/435 Tri-Power engine's distributor feature a traditional points setup (or does the transistorized ignition do away with such)? If so, what is the stock dwell time for a 427/435 ... 28-degrees, 30-degrees or ??

3. The 1969 427/435 engines came with a transistorized ignition. I have never worked on such an ignition so I am wanting to know more about it. Can anyone share info on this ignition system along with special items associated with it (special spark plugs??, special spark plug gap??, different timing specs, or ??).

1. 4 BTDC
2. No points with TI
3. R43N .035 gap

4-degrees BTDC ... really?! That sounds like a very smog-era spec ... especially since a small-block would use about 12-degrees BTDC.

Although 4-degrees may be stock, is there a recommendation on a "real world" spec that should be used that works better? Maybe 6, 8, or 10 degrees BTDC??

Any insight on the factory spec for total ignition advance?

Also, although an R43N (at 0.035 gap) is stock ... is there something else that is highly recommended to use instead? Hotter/colder, platinum/iridium/etc. core, more/less gap, etc.

My big block (390 horse), and most I have owned run real well with around 12 degrees initial/36 total all in around 3,000 RPM's. If you get any detonation you may have to dial it back a bit.

I like a 5 heat range in both big and small blocks that are street driven. I use AC R45 XLS. I gap at .035

capevettes,

Thanks for the info. And to all others ... keep the suggestions/info coming!

In other news, is there any adjustments to be made to the transistorized ignition setup? Does it require an occasional tune-up, rebuild and/or adjusting?

Does anyone know of other threads dealing with this topic?

Thanks for your help.

John

A good street and all around plug is R45XLS or Champion RN12-14Y with a .035 gap...initial lead will vary according to the octane of fuel your using and will range from 8-14.....all in somewhere around 3 grand as the 3 grand will almost immediately be reached as soon as you press on the gas.....Idle is 800-850. Too much lead will cause spark knock if the proper octane is not used

4 degrees lead for a 435 car is not enough although the hydraulic cammed 427`s ,ie 390-400 hp engines are best at 2-8 degree range....you will find the engine smooth out and increase RPM as you increase the lead...then just adjust the carb idle speed back to 800-850. Excessive idle speed is not necessary....

Hi John,
New 69, 435!!!!! Very Nice!!!!
If I may, I'd like to suggest you think about buying the GM 69 Chassis Service Manual for your car. It'll have lots of information on many aspects of working on your car. Most people find it well worth the money. Many of the larger Corvette vendors sell it.
How about posting some pictures? It's always enjoyable to see what people have in the garage.
Regards,
Alan

Alan 71,

It's a 1969 Corvette L-71 (427/435 with Tri-Power), 4-speed, 3:70:1 Posi, tilt/tele, factory sidepipes (sidepipes are since removed by a previous owner ... but the tank sticker and Protect-o-Plate verify the car as an original RPO N14), etc.

The car is largely unrestored (but needing some TLC) with 46,000 miles. Plus, the car came with a stack of paperwork (including original sales paperwork) that goes back to the first three owners.

I'm looking for a very nice/clean set of stock/original side pipe covers if anyone out there has a set that they are looking to sell. Also, I will need a set of re-chromed or reproduction valve covers as the stock covers are looking a bit shabby (I would prefer to put the original covers in a box rather than re-chrome them). I have a possible lead on a new set of reproduction F70-15 redline tires ... but if anyone out there has a set they want to sell then let me know.

If someone will be kind enough to tell me how to post a photo then I will share a look at the car.

John
Sounds like a cool car. :cool: Does it have the original engine? We need to see some pictures before answering any more questions...absolute requirement of this free help forum.
Dennis

Quickest way is to:
Go to User CP
Click on Pictures & Albums
Click on Add Album
Upload all the photos you want...up to 50
Select the photo you want to include in your post
Select the 2nd option at the bottom, right click (BB Code) and copy
Go to your post and paste it in there
Repeat with additional photos

Faster Rat,

The car is all original ... including the engine. The numbers have been checked (and verified) by two NCRS judges and the car was deemed "the real deal". Being that it is a "survivor car", I don't want to restore it too much. However, there is lots of cleaning and detailing to be done.



http://forums.corvetteforum.com/pict...ictureid=82317

The 1969 chasis service manual lists for the distributor
4 degrees BTDC, and 30 degrees total mechanical at 3,800 RPM, plus another 15 degrees vacuum at 15.5 HG.
If you start modifying things the typical curve would be 12 degree's initial and a total of 36 degrees mechanical. You could use another 10 degrees in the vacuum unit.
Problem is you have an 11 to 1 compression and gas typically is no more than 93 octane unless you can find Sunoco 100 octane in your area and pay big bucks per gallon. Last summer it was going for $8.99/gallon in Connecticut. That being said you may have to lower the total mechanical advance to about 32 degrees.

MelWff,

I have no idea if the engine has ever been rebuilt (maybe the compression has been lowered??), but this weekend I will do a compression check and use my dial-back timing light to determine:

1. initial timing advance
2. total timing advance
3. RPM at which all advance is in

I will also check the carb float levels and make sure that all carb hoses/lines/connectors are properly attached.

I am trying to burn out all of the old gas in the tank so that I can fill it with fresh fuel, and I'll soon change the oil/filter as well. As I drove the car home it ran better and better, and the amount of smoke (from rich jetting??) gradually decreased. Because the car had been sitting for so long it probably just needed a good run to clear it out.

With regards to the power valve(s) ... is it only on the center carb, all carbs or what? Is it a traditional Holley PV? Regardless of what was stock, what vacuum level PV should I install?

Hi John,
Sounds like a very interesting car.
ONE picture is a TEASE!!!!
Paragon Reproductions reproduces the side exhaust covers and insulators on the original tooling. You might need to get second mortgage on your house to buy them.
I'd think a very nice set of production line originals that don't need to be re-chromed will be even more $$$.
Have Fun!
Regards,
Alan

Looking at the 69 overhaul manual, only the center carb, list 4055-1, has a metering block with a power valve. Holley lists a 125-65, so 6.5 power valve and I would stick with that.

Hi Alan
But John has bought "the bomb" and has no choice but to head up that slippery slope. Too late now. :D

John
Allen's Stainless Exhaust sells the pipes and same covers as a package for around $2500. They can be ordered with 2-1/2" tubes in aluminized steel, slightly more $ for stainless. Extremely loud but you need the least restriction possible for that L71. Either way there will be a deduct in judging points. They are not mandrel bent (were the originals?) and need to be shipped with the pipes and brackets loose for fitment and welding on the car. Ask me how I know this.

What did the previous owner do to the rear valance? What do you have to do in order to put it back to side exhaust?
Dennis

I have owned My 427/435 Trans Ign. Vette for near 43 year The Magna Pules is awesome it will throw a 1 inch hot blue spark, I use all the Chevy (for Vettes) standard tuneup specs.
main thin is to keep the standard cap and rotor clean.
My Car is a Virgin 99% original has only 39K
I have and do help any one that needs advice on this series C3 vettes.
aldelisle2@aol.com 727.480.0700

My 69 has the GM TI system. The PO had unhooked it and installed some other amplifier, I pulled that and installed a Mallory (Summit) CD box. Worked OK. I got curious about the original TI so I hooked it back up. Works way better than that CD box. easier starts, better idle, and seems to run a bit cleaner. Just make sure you have the correct coil for the TI if the amplifier is the original. Mr. TI, Dave Fielding, states that a coil with the wrong impedance will degrade the amp.