[eldorado99]

I have a 472 with 91000 miles in my 1970 Sedan Deville which I purchased recently. I need to know what to do for a tune-up. I have already done the spark plugs and oil change (10w-30). What else would re-awaken the beast? spark wires? filters? rebuild the carb? I know when I step on it if its cold the engine stalls for a second then roars, and if its warm it'll still do this but it is less noticeable. Also when I snap the gas down neither tire breaks they are new tires but... seems to me a 472 ought to be able to at least break the right rear. I heard something about hooking the vacuum advance to the manifold vacuum for always on advance, what does this achieve exactly? Also how do I tell if I have HEI? and if not, what would going to HEI benefit? How smooth should this engine be at idle when warm? I can feel it rumble when its in drive with my foot on the break, should it be just about not noticeable and silky smooth or will the big block always rumble a bit? I have been running 94 octane on the 10:1 compression. Sorry for so many questions but I am eager to get this thing purring (and roaring when necessary :burn: )

 

[davesdeville]

Plug wires, cap & rotor, points, check the mechanical and vacuum advance, fuel filter, PCV breather filter, check PCV valve... although I'm not sure when PCV systems started being installed in cars. You don't have a HEI distributor (although it would be a good upgrade to install one) if it's the original. HEI units are easily identified by the coil in the cap. It shouldn't rumble much at all.

 

[jk1000]

My 2 Cents:

It sounds like you covered the basics. But you may consider looking at the following:

1.) A carb rebuild may be in order at this mileage.
2.) Old fuel pumps tend to become weak and cannot keep up with demand at certain times.
3.) Don't overlook the timing chain. It's amazing how much better a car will run with a new timing chain, even if the old one is "still good". They usually become loose and sloppy at the 50,000 mile mark (sometimes sooner). If it's the original, it probably has a nylon cam sprocket. The teeth often break off and end up in the oil pan.

Good Luck

 

[guidematic]

Good advice, but I'll add:

Use an open air cleaner, if only you put on a smaller lid. Those air cleaners only flow 380 cfm.

Go to 10 degrees initial advance.

By-pass the transmission controlled spark if it has not already been done.

If you go with HEI, you will also need the 8mm wires. Use R44XLS6 plugs gapped at 0.060"

If you have the carb done, bebuild the carb that is on your car DO NOT go with an off the shelf exchange. And have a competent carburetor mechanic do it for you.

I would also recommend using 15W40 oil in the engine with an AC/Delco filter.

Mike

 

[jk1000]

Yes, listen to Guidematic. Do not exchange that Rochester for another, learn to rebuild it yourself or find someone who knows carbs of that era. Even if you decide to put a different brand carburetor on the engine, keep that Rochester.

 

[Kev]

If you replace points and condenser (highly recommended) DO NOT use the combination points and condensers! (Common for Chevys, not sure if they are available on Caddys) If there is a choice between combination points and condenser or separate points and condenser go with the separate set! Many GM cars were left along the roadside as a result of failed combo units.

Brings back horrible memories! :ill:

 

[Nrets]

Interesting bit O info about the combo points. There IS a combo set of points for the 472. It is the same Borg Warner part # as the Chevy points. I know this because I installed those a few monthes back in my 70 coupe. Good thing I'm going to HEI, I guess

 

[eldorado99]

What is the purpose of HEI?

 

[Kev]

Interesting bit O info about the combo points. There IS a combo set of points for the 472. It is the same Borg Warner part # as the Chevy points. I know this because I installed those a few monthes back in my 70 coupe. Good thing I'm going to HEI, I guess

That's what I thought. I used to use the Standard Blue Streak label for points and condenser. They always did a good job for me. The HEI is a better choice though. I'd replace that combo set ASAP if I were you.

 

[Kev]

What is the purpose of HEI?

Stronger spark, improved burn, better performance.

 

[eldorado99]

So what does going to HEI involve, the purchase of a new distributer, wires, plugs? How difficult is it to pull the old distributer and put in the new one? Just pull it out, put in the new one and set the timing? And how do I tell if the one I pull from a junker is worn out?

 

[Kev]

So what does going to HEI involve, the purchase of a new distributer, wires, plugs? How difficult is it to pull the old distributer and put in the new one? Just pull it out, put in the new one and set the timing? And how do I tell if the one I pull from a junker is worn out?

Replacing a distributor is relatively easy, the most important things are to properly align the shaft into the oil pump gear and get the rotor pointed in the right direction for cylinder #1. (get it back in the same position the old one was when you pulled it out)

Not sure what's involved with the conversion but regarding a distributor from a junker, how about checking on a rebuild first? I'd rather spend a few bucks more (depending on how much more) for a rebuilt distributor than take a chance on a used one from a scrap yard.

Just a thought...

 

[eldorado99]

Replacing a distributor is relatively easy, the most important things are to properly align the shaft into the oil pump gear and get the rotor pointed in the right direction for cylinder #1. (get it back in the same position the old one was when you pulled it out)

Not sure what's involved with the conversion but regarding a distributor from a junker, how about checking on a rebuild first? I'd rather spend a few bucks more (depending on how much more) for a rebuilt distributor than take a chance on a used one from a scrap yard.

Just a thought...

That sounds like a better idea, especially because I'm doing this as a tune-up as well, no point in putting on worn out parts if the whole point is to refresh the engine. This system remained the same for a long period of time no? For instance the same system from an '80 Deville w/ 368 would be interchangeable? The reason I ask is that I may have an easier time trying to find a rebuilt HEI from 1980 rather than 1970 though I'm not sure. About how much is this likely to cost me?

 

[Kev]

Before you make your descision to swap give this page a read.

http://www.rowand.net/Shop/Tech/BuickHeiConversions.htm

 

[eldorado99]

Thanks, that page told me a lot. Of course I might still consider staying original and just keeping the old points. If I do would it still be a good idea to put in a rebuilt distributor?

 

[Kev]

Thanks, that page told me a lot. Of course I might still consider staying original and just keeping the old points. If I do would it still be a good idea to put in a rebuilt distributor?

If your distributor is working and not sloppy it should be fine. If you use good quality points and tune them properly you will be happy with it. You might want to think about using a performance coil for hotter spark with the points.