[glhs#116]

I don't know much about engine internals except that most of what I've seen looks stock. Certainly, when I had the heads off the pistons looked completely flat on top which I think is what stock ones look like.

I plan on doing the compression test this weekend when I do the timing cover.

Sam

[GonicGM]

As hot as it sounds it is there, I'd go even colder than a 45, maybe an AC 44 or Champion 11 or equivalent. I can't remember all the prefixes and suffixes that indicate reach, extended tip or not, although the 'R' is for resistor.

[GonicGM]

Does the car have a fresh air intake? If not, I would rig up a cold air intake either through a factory or aftermarket hood scoop or fresh air tube to your radiator support, front of wheelhouse or cowl plenum. You can also block your intake manifold heat riser port and get some heat out of the intake manifold.

[glhs#116]

My cold air intake modifications consist of a piece of styrofoam wedged into the intake snorkel of my air cleaner. It's not airtight but it blocks most of the flow. The air is then forced to come form the open shaker. It's a stock shaker but doesn't have any of the factory solenoid pieces, or hinge for the air flap, or the air flap. It's just open. Of course, sometimes driving with the window open here is kinda like having someone blast you with a 50ft hair dryer so cold is a relative term...

Crossover is also kinda partially blocked in a mickey-mouse way. I pounded some copper pipe into a shape that almost blocks the passages and re-assembled. Again, some hot air probably circulates but quite a bit less than stock, I'd say.

Yeah, this is probably something I'm going to have to attack from all sides.

Maybe some sort of moon lander-looking kitchen foil heat shield for the carb...

Sam

[Jack Gifford]

No, AC45 isn't the coldest- they go down to at least AC43, which a lot of guys used to run in racing. The 'S' suffix is the extended-tip version- but it's only extended about .085" more than normal, so there should be no "interference" issues. I think the extended-tip is a good idea in Pontiacs.
Anybody know for sure what the "ACF" prefix means?

[glhs#116]

I'm doing my timing cover today. Compression test results are in.

Method was: no spark plugs, engine warm, WOT, cranked (by ear) through three compression strokes. I found that my earlier readings were lower and I think I wasn't doing as many as three strokes. Unknown if more strokes would have yielded higher numbers. I was just looking for a consistent technique.

1- 165
2- 139
3- 145
4- 146
5- 147
6- 145
7- 153
8- 145

I really had to do a double-take on how consistent the middle cylinders were. They are dead nuts on each other. I know see why I heart the knock mainly on passanger side. Number seven is high and number one is super high. Other than that the only standout seems to be a slightly low number for number two.

Is this too high? What's a good possibility for the two high spots? I also found some sharp edges where I trimmed the spark plug electrodes and I've wire wheeled them smooth. Pics of the plugs to follow later.

If these compression numbers are too high is there anything I can do about it whilst I have the front of the engine off?

Sam

[Jack Gifford]

I think someone already suggested that you could consider retarding the cam a couple of degrees, to slightly lower the dynamic compression ratio.
(Those higher static compression numbers are on the driver's side, not passenger).
Higher static compression readings result from things that make the cam look "milder"- hydraulic lifter not staying fully pumped up while cranking, cam lobe going away, etc.
Actually, those compression readings shouldn't cause "rattling"- unless the fuel is really crappy, or maybe a cam lobe is going away on #1.

[glhs#116]

Yeah, thanks for the heads up. I got myself completely convinced that I'd been looking incorrectly at #1 as #2 all these years. Hence my cylinder numbers are all wrong. The high numbers ARE on the passanger side. I just have all the odds and evens swapped.

Must be the heat!

Revised:
1- 139
2- 165
3- 146
4- 145
5- 145
6- 147
7- 145
8- 153


Sam

[sixt8bird]

Try disconnecting vacuum advance and take for a drive. Do this and post what detonation exists.

[glhs#116]

Sixt8bird - I've tried taking out over ten degrees of total timing. I've also tried no vac advance. Apart from performance getting worse the pinging didn't change.

OK. I've got the timing cover back on. Hopefully this time we will be leak free. I was very slow and deliberate this time. I had to reuse my old balancer because when I took the new one off I found that it was cracked lengthwise along the collar either side of the slot for the key. The crack was big enough to make a path for leaking and doubtless the balancer would have eventually loosened up on me. Second thing I found was that the seal had a "hump" in it - kinda like a bump in a heart monitor graph. No leaks on first start.

So, the mistakes I made first time were:

1. Didn't know about the dowels for timing cover so didn't use them
2. Didn't bother to mark TDC so didn't know how to put balancer on straight
3. Didn't properly lube seal before balancer install

Hopefully I didn't make any particular mistakes this time. I tacked all the gaskets to the timing cover before putting it on with some RTV. I gooped in the corner where block and pan meet. As I was assembling the pan lip gasket slid forward. Hopefully there was enough goop there to cover it. No leaks to see yet!

Drove the car to the local shop. Idles a little lower and belts want to slip more easily. I do have an alternator and PS belt of slightly different widths so drive to the water pump pulley is not ideal. I replaced the stock water pump and worn divider plate (which had a large clearance) with a FloCooler aluminum one and new divider plate that I had carefully clearanced so I think the pump is moving much more water and probably takes a little more oomph to turn over at idle speed.

Tendency to ping seemed a little less but it was very early morning so also cooler air. Could be that the rounding of the plugs helped. I'm still trying to get some cooler ones. Have "ACF-R43" plugs on order. Waddayouknow? Summit had them... Hopefully arriving this week.

That's all for now!

Sam

[loggerhead]

"However, I have no choice in fuel and as we all know octane boosters don't work."

Octane booster does work...If you use the right stuff!!!
It's called Torco Accelerator. This stuff works BIG TIME!!!!!!!
However, it is not cheap! Checkout Torco website for pricing.
Best way to buy this stuff is in the 5-gallon pale.
This way it's around half the cost of the quart cans.
I use it in my E-Head 455 whenever I want to run the timing
up where it's supposed to be. I have pinging issues also and can't
figure out why. I'm running the Comp 276HR cam and have been told
that it builds too much cylinder pressure at low RPM. Have also been told
that 288HR would cure this problem. Here's the kicker...Compression test
shows around 115 PSI +or- on all cylinders. SOOOOO....why is this thing pinging
at anything above 26 degrees total BTDC???

David

[glhs#116]

Got the plugs pics done. Also, got my new plugs in the post. Will try to install them soon.

First pic is 1, 3, 5, 7
Second pic is 8, 6, 4, 2

To me they don't look too bad...

Sam

[Jack Gifford]

Looks to me like they make great glowplugs- but what do I know?

[glhs#116]

Originally Posted by pontiac jack

Looks to me like they make great glowplugs- but what do I know?

Man I hope you're right! Got my ACF-R43S plugs via FedEx yesterday. Going to try to get them installed at lunch time. Would be fantastic if that fixes it!

Sam

[glhs#116]

OK. This was a definite step in the right direction. I put in the R43S plugs and now have significantly less pinging. However, it's not gone. The fuel here is in two grades. They are labeled as 97 octane and 92 octane. I believe that (like England) this is a "RON" number. In the US the "pump" number is an average of the "RON" number and the "Motor" octane number. In fact, a lot of the pumps have stickers showing the octane is "R+M/2". Anyway, since I'm using the "97 octane" stuff here I'm sure that it is at least comperable to 92 or 91 octane "US gas".

Therefore, there's probably something else at play, yes?

I'm running out of things to check here. The timing chain looked good. Cooler air seems to help. Am I going to have to put a different cam in this beasty???

Sam

[Jack Gifford]

Now that you've "improved" the situation, I'd go back to dropping the timing back (and disabling vacuum advance) to determine if what you're left with is "spark knock" or not.
Before replacing the cam, you could try the suggestion of retarding your cam. Just need to pull the front apart (again!) and buy an offset key for the cam sprocket.

[glhs#116]

Update!

I had a slight D'Oh moment when I again noticed how the idle changes when I slam the hood. I'd previously inspected the carb mount and changed the carb gasket but I suddenly realised it could be my intake gaskets.

So night before last I took off the intake. I found that the rear intake bolt hole near number 8 cylinder weeps oil. The bolt was also loose. The oil had been migrating between intake and gasket and into the number 8 intake. It looked pretty gross looking down the port. Guess that explains the high compression readings for number 8.

So, I replaced the gaskets, lok-tited the bolts and poured two cans of carb cleaner down the carb throat at idle. Car runs better now but I still have ping (though less). I think I need to de-carbon.

Sam

[glhs#116]

Well, my car passed emissions with flying colours. I've also tried disconnecting the vac advance. No difference in pinging. Only things I've noticed:

Some (usually slower) rates of opening the throttle induce a lot of ping.
The R43 plugs helped - but not as much as I had hoped.
Some (usually fast at first, then held) rates of opening the throttle induce little or none.
Light throttle is always OK.
Full or any throttle is usally fine over 2500rpm
Less pinging just after a fillup. (Possibly this is when my summer fuel temps are lowest)
Full mechanical advance in by 2300-2400rpm and is about 32degrees
Car runs and sounds great when not pinging.

Still scratching my head but would love to fix!

Just a reminder -- it's mothering hot here in the summer and humid too. It's just as hot at night so I really can't say if it runs any better in cooler air.

Sam

[sixt8bird]

Originally Posted by glhs#116

Well, my car passed emissions with flying colours. I've also tried disconnecting the vac advance. No difference in pinging. Only things I've noticed:

Some (usually slower) rates of opening the throttle induce a lot of ping.
The R43 plugs helped - but not as much as I had hoped.
Some (usually fast at first, then held) rates of opening the throttle induce little or none.
Light throttle is always OK.
Full or any throttle is usally fine over 2500rpm
Less pinging just after a fillup. (Possibly this is when my summer fuel temps are lowest)
Full mechanical advance in by 2300-2400rpm and is about 32degrees
Car runs and sounds great when not pinging.

Still scratching my head but would love to fix!

Just a reminder -- it's mothering hot here in the summer and humid too. It's just as hot at night so I really can't say if it runs any better in cooler air.

Sam

I had a 1985 full size Blazer with a 305 and carburated. Talk about gutless. Anyway I thought I would change the advance springs to a lighter spring and man talk about ping!!! I got ping on the lightest throttle throughout the rpms. I put back the stock springs after a day of driving it very easy and no more ping. Just like the 190 thousand other miles it had on it.
Try a stiffer spring on the advance to slow down the timing. Its an easy step even if it doesnt work. But like I said, sometimes bringing to much timing in at low rpms even on low compression engines is to much.

[Kenth]

"Full mechanical advance in by 2300-2400rpm and is about 32degrees", no wonder it pings?

Please try factory ignition settings, and adjust the fuel curve later......

These are the original ignition timing settings checked at crank for a 1971 455HO,
12 degrees initial, 24-28@4500rpm in distributor for a total mech advance of 36-40@4500rpm, add to that 20 degrees from vacuum advance connected to a ported source.