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Pontiac of the Month

dues70's 1970 Pontiac Bonneville

2020 July
of the Month

BearGFR

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BearGFR last won the day on July 4

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About BearGFR

  • Rank
    Learning to Fly
  • Birthday 03/21/1953

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  • Website URL
    http://www.garrettfamily.us/gto

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  • Location
    South of Springtown, TEXAS

Forever Pontiac

  • Name
    Rob Garrett
  • Gender
    Male
  • Year
    1969
  • Car
    GTO
  • Trim
    FAST
  • Engine
    "400" :)
  • Style
    Coupe
  • Color
    Black

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  1. Very true. I hadn't thought of that.
  2. Sounds like you're finally catching a break or two on this. That's good. It was me who suggested cutting open the oil filter. There are some nice tools available for doing it, but you may not want to buy one yourself. They look and work like large tubing cutters. The manual way to do it is described here: What you're really interested in is removing the paper and spreading it out so that you can eyeball it for "shiny bits". This video shows inspecting the filter out of a Cat, but the principles are the same.
  3. Double check your pushrods for straightness. Rolling them on a flat piece of glass works really well. If one wobbles at all, you know it's bent. Keep everything in order so you can reinstall in the exact same location. Especially important for all the valve train components and bearings, since part of the 'break in' process involves mating parts (pushrods, lfters, rocker arms) wearing in together. "Moving things" on reassembly makes them all have to go through that again and causes additional wear. When you've got it all back together and ready to fire up, prime the oiling system first. Pull the distributor and use a tool chucked into a reversible drill to spin the oil pump (counter clockwise) to move oil all through the engine. When you see it coming out the ends of the pushrods, you're ready. I have an old distributor body that I removed the gear and advance mechanism from and spin with my big 1/2" drill. I've also done it with a "spade" wood boring bit that I cut the point off of, so that it fit down into the oil pump drive, but that's a little harder because there's nothing to keep it centered and engaged in the slot. Rear main seal: The achilles heel of Pontiac engines. Whichever one you decide to use, I recommend getting the engine back together then overfilling it with oil and letting it hang from your hoist tilted downwards enough to completely submerge the rear of the crank. Let it hang like that for a couple days or so to make sure it's leak free before you go to the trouble of putting it back into the car. Don't forget to drain out the excess oil first. Front timing cover seal. If your engine is missing the alignment sleeves in the block on the bottom two timing cover bolt holes, install the timing cover "loose" - don't tighten the bolts. Install the balancer before you tighten them down. Leaving the bolts loose like that will cause the cover to "self center" on the balancer snout when you install it, then you can snug down the timing cover.
  4. I do believe I see some bent valves.
  5. I thought I replied to this last night, but I don't see the post now so I must have been hallucinating. Wrongway, using that smoke machine was genius. I'd like to know how you made it. So what you have there is confirmation that your compression is escaping through the intake valves in both 5 and 6. By any chance were the intake pushrods also damaged in those cylinders? I'm betting you've got bent intake valves on those two, either from them jamming against the heads of the exhaust valves or from trying to close with pieces under their seats. 5 and 6 are adjacent to each other in the firing order, so that makes sense as well. Keep us all in the loop - and again I'm impressed with your smoke machine idea. Bear
  6. That recommendation to pull the motor came from your report of definitely hearing leakage at the exhaust. I'd hate for you to go to the trouble of pulling it and that not be the problem. If you have the chance to test those cylinders again before you get too far along, make sure both valves look completely shut and apply air. Listen for leakage - at the carb, at the oil filler, at the exhaust - hopefully you'll be able to hear it hissing from at least one of those three spots. Also remove the radiator cap and listen there - look for bubbles while you've got it hooked up to air. Listen around the tops of the valve stems on those cylinders and see if you can hear it hissing there around the guides too. With zero compression, it's got to be going -somewhere-.
  7. I just had a thought (yeah, sometimes it happens - even to me - lol). When you put air into 5 and 6, did you turn the engine to a point where you were sure both valves were closed on those cylinders, I hope?
  8. Any of the name brands work well.
  9. They won't be hurt by soap and water. Just look then over to make sure they aren't damaged. You mentioned grease. All the bearing surfaces need liberal amounts of assembly lube when you're putting it all back together.
  10. Well alrighty then. Sounds like you got two exhaust valves that aren't sealing. That explains the rough idle and the wonky/low idle vacuum. Count your lucky stars it's not worse, although I think you mentioned at least one piston had a pretty good divot in it. I'd get that checked out and try to determine how thick the metal is there before reusing it. You'll "probably" be ok driving it back inside - cross your fingers The best way to clean the block is to remove all the gallery plugs, then use copious amounts of good old hot soapy water combined with a collection of bottle brushes. There are two plugs in the front behind the cam gear, and 3 in the back. Unless they've already been redone, the two in front are like mini-casting plugs ("freeze plugs") that have been staked in. On the back drivers side, there's a screw in plug. On the passenger side, there's another pressed in plug "behind" the distributor and another screw in plug in front of the distributor. That's the famous Pontiac "hidden" plug that people forget to put back in and then have no oil pressure on startup, so don't forget that one. Use bottle brushes to chase all the holes --- lifter galleries front to back, lifter bores, lifter oil feed holes, oil pump passages, main bearing feed passages, all the passages in the crank --- everywhere you see a hole, clean it. Take the end plate off the oil pump and look for damage/scoring on the gears and in the housing. Open it up and clean out the passage where the check ball is and make sure there's nothing in there that might jam the ball. It's boring, time consuming, somewhat tedious work but it's oh so important to make sure everything is clean. Make sure you keep everything "in order" so it can be reinstalled in exactly the same place. Examine all your bearings for signs of damage/scoring. Same with cylinders, piston skirts, etc. Hopefully everything is fine and you'll be able to re-use everything, but you won't know until you look. Good luck! Bear
  11. Ok great! Thanks for the explanation. So, if I understand correctly - after the exhaust valve problem you replaced them all yourself right? Congrats on being not afraid to jump in and do things yourself. That's getting rarer by the day. If I've understood right, that does open up some possibilities. The 'fit' between the valve head and the valve seat is critical and must be precise. When those valves let go it's very possible that you also bent an intake valve. It wouldn't take much of a bend to destroy its fit to the seat so that it can't seal even though you wouldn't be able to see it even if you tried. You -might- be able to spot it if you shined a light at the back side of the valve through the intake port and did that in a completely dark room - maybe, but you'd have to know to look for it. It's also possible that during the "loud noise" you heard when those valves let go, the exhaust valve seats on those cylinders got nicked. Again it wouldn't take much damage to destroy the sealing ability and cause the problem you're seeing now with no compression. Also new valves need to be "fit" to the seats. That's what a valve job that a machine shop does is all about. They use fixtures and matched grinding stones to match both the valves and the seats together so that they'll seal. You can approximate that at home using a valve lapping compound and a hand tool, but that's usually only done as a final step after the valves and seats have been ground, otherwise it can take a very long time and a lot of work to fit valves to seats and you won't be able to control the width of the seat very well. So what now? At this point considering what we know, I think it's a done deal that the heads need to come off and everything looked over, but I'd still do that air pressure test first to try to isolate where the leak is. In fact, if it were me I'd probably pull the engine and do a complete tear down, remove all the oil gallery plugs at both ends of the lifter gallerys, tear down the oil pump, and do a thorough inspection/cleaning of everything looking for damage or scoring. There's no telling how much shrapnel went into the oil pan when those valves let go or where it is now, and it'd be a shame to get it all back together and running, only to have a piece of metal circulating around in there take out a bearing, seize a rod, and destroy the engine. Failing that, at least stick a bunch of very strong magnets on the oil pan, passenger side, rear, and hope that they'll trap and hold onto whatever's in there before it can get sucked up into the pump. Leave them there until you have a chance to pull it and go through it for cleaning. Also change your oil, including a new filter - cut the old filter apart, cut the element out of it and spread it out, inspect it to look for metal that it may have already trapped. The same process I told you about earlier on how to make a piston stop using an old spark plug, you can duplicate to make your own air fitting - but I think I remember you said you'd already ordered one. After you figure out where the leak is, I'd recommend you pull both heads, take them to a machine shop, and get a full valve job done on all 16 valves. Make sure they check the all the valve guides too because they could have been damaged when the valves went. Something else to be careful about when dealing with machine shops: unfortunately there are some 'out there' who tend to have an opinion like "Oh, it's only a Pontiac so it's not important to be precise". I've got the engine out of my '69 right now with the block at a different shop as a direct result of that kind of thinking (grrrr - long story). Another thing to check since you've got some aftermarket valve train parts: Pushrod length. Back off a few rocker arms so that you can see the tops of the valves, and look for the wear pattern on the top of the valve stem where the rocker tip meets the valve. What you should see is a wear pattern that is very close to being exactly centered on the valve stem. If it's offset significantly to either the high side or the low side, that's an indication that you need different length pushrods. That's not going to cause any of the problems you're having now, but it can be a concern for long-term wear on the valve guides if it's not right. Don't worry about it now, but I wanted to mention it so that you don't forget when it's time to put it back together. Let us know how it turns out whenever you're able to do put compressed air into those cylinders. Cheers, Bear
  12. Well, "should" and "should not" at this point are both out the window. You already know through direct testing that you've got two dead cylinders that aren't making any compression so what "should have happened" no longer applies here The question now is - why? What's going on with those two? In order to make compression, the intake valve has to open and allow air to be drawn in. Both valves have to close, the piston has to riise in the bore, and everything has to seal so that air can't leak out. In your case, on two holes, at least one of those things isn't happening. The intake isn't opening - or at least one of the valves is never sealing - or the seal in the piston + rings isn't capable of holding pressure - or the piston isn't moving at all. If it was just "bad" or worn rings, you'd see some pressure rise in those holes, they'd just not make as much pressure as the others. IN youc case you've got zero pressure rise. That tells me something is broken. Intake isn't opening, or at least one valve (or valve guide) is never sealing, or the cylinder can't be sealed (broken piston, cracked/holed cylinder wall, something major. Breaking those exhaust valves was a very catastrophic event and very likely to have caused more damage than just the valves. Could you walk is through in detail exactly what was done to repair things after the problem you had with the valves? Here's on possible scenario: Heads break off exhaust valves. One or more of those heads gets caught between the intake valve and its seat the next time it opens and tries to shut Intake valve is bent but not broken, and no longer seals on its seat. Viola - no compression in that cylinder
  13. Well sir, that cylinder pressure is escaping to somewhere and that's a fact. I assume that after you had the mishap with the exhaust valves that you had the heads redone including having all the guides checked, and the seats reground, so if that's the case then it's not likely the leak happening at the valves. You mentioned a divot in at least one of the pistons. Maybe it weakened the metal there enough, made it thin enough, so that it wasn't able to hold up to combustion pressures. Do you have an air compressor? If so, maybe get a hose fitting you can connect to a spark plug hole and try to pressurize those cylinders. You probably won't be able to - and you'll hear the air hissing out from somewhere. Where you hear it leaking from will tell you where the leak is. If it's loudest at the carb, it's an intake valve. etc. If it's loudest at the dipstick tube, that means it's getting past the piston.
  14. I've got one of these. Not too pricey... https://www.amazon.com/dp/B00I4I92G8/ref=cm_sw_r_cp_apa_i_7U3-Eb2X29JC9
  15. Sorry, Misunderstood did I You know, I didn't even think about using a borescope, and I even have one. Duh. Wrongway, You might consider getting yourself one. They are handy to have around for all kinds of things.
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