[1969GPSJ]

Originally Posted by HWYSTR455

Ok, elaborate on the comment ' I put a timing light on it (I have a dial back light, so I can check the timing throughout the range) and it was in spec. '

What's 'in spec'?

What's your initial, total, and timing at 3000 rpm? And how much is the can adding?

When/where does it ping? Rolling of a dead stop, under load at 1800-2800, or above 3000?

If it's not been apart, the pistons are def in the hole, how much is the question.

If you haven't had the heads off, you don't know what the heads CC are.

Rated static CRs are exaggerated.

'sounded like ball bearings in a tin can with just the 93 at 9-10 degrees of timing' . You're obviously talking about initial, which doesn't mean jack.

Definitely need more (accurate) info to make any type of recommendation. If you're willing to change gaskets, you can pull the heads and determine exactly what you deck height is and head volume. Without that basic info, I don't think anyone can give any valid recommendation.

Now, just to say, most shops finish deck and head surfaces to 50 RA or better as SOP, which supports an aluminum head/iron block combo with MLS type gaskets. If it's iron/iron, it's a lot more forgiving, and you could possibly get away with an MLS gasket. Or, you could try 'smoothing' the surface some if you feel brave and lucky.

Another option is you could stack composite gaskets, that too would be if you feel brave or lucky. Neither would be advisable with a performance build, but if you're just trying to 'get away with it' for a short period of time, you could take a shot at it.

This could all be moot if whatever cam in there now is compromised or there are other factors that could be contributing, like heavy carbon build up. You could go through the trouble and try to get 'lucky', but you may end up having it fail and be forced to rebuild.

Can't cheat physics, might be better to just ride it out until you can go through and properly rebuild.



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Thanks for the reply HWYSTR455. I am just looking for some up to date information on something I have not paid a whole lot of attention to in the past few years. I thought that perhaps the thicker head gaskets may be a possible short term solution to get the car on the road until I do more to the engine. I was looking for some solid unemotional, knowledgeable advise about the workability of a thicker head gasket in the short term. The heads have to come off for broken exhaust bolt removal anyway, so I thought I would see what the community has to say about the thicker Cometic head gaskets.

It has been over 15 years since this engine has been run, and even longer since I drove the vehicle it was in on a regular basis. So in spec would mean no more that 30-36 (ish) degrees total timing. It did ping on 93 with the initial set at 9-12 degrees from a start through the operating range. It didn't stop with more throttle, and it still pinged at part and light throttle. Vacuum can attached made it worse, but it did not go away with it disconnected. Because of the ping/knock, this engine spent most of it's time running on 93 octane fuel and seriously retarded timing to avoid the ping/knock. The only time (no pun intended) it did not ping when set at 9-12 initial was when I would run it with (about) a half tank of turbo blue mixed with a half tank of 93 octane unleaded. So in this case the difference in how the engine behaved on 93 octane with 9-12 degrees of initial vs having the initial retarded by 14 degrees does mean "jack".

This isn't my first rodeo, I have had my hands on dozens of '67 through '70 Poncho cylinder heads over the years, and have had about 6 sets of my own on a variety of cars. I used to do some flow bench work and porting 30 years ago. I have cc'd many of the big valve 400 and 428 heads, and most were nominally 72 ccs (give or take a few cc's in the 68-74 cc range).

As far as the engine's current state, I did stick a bore scope in every bore recently to assess cylinder wall, head and piston condition. The pistons had the typical non-428 HO piston dish, intended to yield a 10.5:1 compression ratio with the 16 casting head. There was light, wet carbon build up ("wet" because I have fogged the engine several times over while it was in storage the past 15 years) , typical of a 428 running a little rich, but it was not excessive, and the piston tops and chamber all showed significant areas that were base metal without carbon deposits - so relatively clean. There wasn't any obvious valve, piston or chamber damage, even in # 7 and #8. I didn't take pictures because I was not anticipating any discussion about the condition of the engine. It is fairly apparent that none of the previous owners had done anything internal - I changed some gaskets (intake, valve covers, timing cover and oil pan) and probably replaced the timing gear - but didn't do a cam change and I don't think I even removed the valley pan when I first put this engine in my car about 35 years ago. Darn thing still has the short water pump ( but for not much longer).

Gach suggested that a more aggressive cam may help overall.
The engine will be going back on the road with a Edelbrock Pro Flow IV, so the fuel/air and spark will be managed better than in the past. It looks like a cam change (which was in the works anyway) may be the best solution for addressing the ping/knock issue, but still nobody has really presented a good case about why a thicker head gasket would be a good or bad idea - other than the issues about cylinder head and deck surface quality, which has nothing to do with the thickness of the gasket and what the pros and cons are for a thicker head gasket.