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#21
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Hi all, new to the forum, not new to Pontiacs. I had an experience a while back with an engine that break or bend the same pushrod, twice. The engine would warm up to operating temperature just fine, then bang. Finally it hung the valve open and crashed the piston and valve. Turned out to be a small crack running through that valve guide. It would warm up, pinch the valve, game over. Just a possibility. Good luck with it.
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#22
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North Star I can see that happening if the the head your taking about had been fitted with a 1/2” OD cast iron replacement guide, but we need more details on these casting 62 heads on his motor.
For one thing Pontiacs have there guides just drilled into the cast iron of the head, and these days unless the guides are incredibly worn a ,030” non cast iron guide liner in installed and the n reamed or better yet honed to size. This type of guide would have a hard time pinching a valve it would seem! In terms of the motor you have posted about pinching a exh valve, what type was it, and was it a iron head ?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#23
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steve25, the motor in my case was a warmed up inline 6 Chevy, based on a brand new service replacement long block. We just did some minor bowl work and did nothing with the guides, so I’m sure they were just drilled into the iron. So, yes, it would be good to know the history of those 62 castings.
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#24
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In terms of jetting you are dealing with heads that flow 10% more then what the 389 heads did, your displacement has gone up by 4% and your running a much bigger Cam.
All these factors consider I would want my jetting to be on the safe side and start off with 70s in the center Carb and 72 jets on the end carbs. This is up from a stock 62 on the center and 68 on the end carbs.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#25
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What these guys said about it being mechanical vs a lean mixture. I pulled the tripower off of a 428 engine in 1987 and bolted it on a 389 without even opening the carbs up and it runs fine to this day. Yes, jetting and calibration is important, and can lead to issues if out of range, but it is not your issue here.
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Jeff |
#26
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I am onboard with "no oil" seen in the valley area. With conventional oil, you should readily see this in the pockets in the valley. So I would check oil level, then pull the distributor and use a drill motor and pre-oiler shaft and prime the engine and watch for oil to appear.
Pontiac engines need the correct valve guide-to-valve stem clearances - they are designed to provide oiling to the valve stems. If they were made too tight, it could cause the valve to stick once expansion takes place when hot. Lean condition? BS in my book. An extremely retarded timing at the distributor can cause a lot of heat in the engine to the point of making the exhaust glow, but your engine temps will also go high and you'll know its cookin' hot as when it cools down, you'll here creaking/popping of the cast iron exhaust manifolds as they cool - trust me on this one. |
The Following User Says Thank You to PontiacJim1959 For This Useful Post: | ||
#27
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Great catch on the oiling. I didn’t even think about that. Now that picture was taken after it sat over night but I would still expect there would be some oil?
I thought the lean condition was a reach. Possible yes; probable no... |
#28
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Many years ago when I put a new cam and lifters in my high mileage 400 (YS), when I pushed it real hard it would often bend those exact two pushrods. Being a kid I just carried a couple of spares and would toss in two new ones on the side of the road. Almost always in my case you could just flop the rocker out of the way and pull them out. I actually put the T handle valve cover bolts on so I could get the cover off quick and easy Have no idea what the problem was.
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#29
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Sounds like the story with your YS 400 was the new Cams valve lift combined with the stock amount of retainer to guide clearance , factory production machining tolerances adding up to be not in your favor and in heavy throttle , added heat followed by expansion of parts with the end result of collision, with maybe some valve float thrown in the mix just for more fun, lol!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 03-02-2021 at 08:02 AM. |
#30
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To the OP here, I am not saying that your condition your dealing with was brought about by lean part throttle jetting by any means, but once you get it back up and running again your full throttle jetting will without question need to richer then stock dispite what others have said in there postings to you here.
certainly it will not hurt any to start off on the rich side and then back down as needed.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#31
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Where did the pushrods come from? I can see that they are used..I agree with most here..wrong pushrod length or valve spring bind. I'd like to see a picture of the rockers and valve springs.
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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#32
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Quote:
Bottom line, focus on the oil. |
#33
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FWIW my high school hot rod street racer and class racer 409 Impala used to break rocker arms intermittently. Machine shop was supposed to check valve springs/retainers for clearance for the big solid cam. Fast forward 20 years ago when I got my own valve spring tester. Probably coil binding! If you can always double check every shop if you can. Also learned another potential cause on the 348-409 board with their weird chamber in the block the exhaust valve gets real close at .550 lift-my cam had. .590 - lash. Why the new motor I built recently has a notched block!
I also bent a 11/32 Melling RAIV pushrod just turning over my motor by hand checking clerances when the roller rocker got in just a slight bind was hitting the hex on the stud. So it does not take much to tweak a pushrod.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#34
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No reason to worry about using an original 1965 Tripower on a 400 engine running lean.
I have used an to my GTO the original 1966 Tripower on my current 1969 RAIII engine for about 25 years w/o issues. By nature of the beast a larger engine pulls adequate amounts of A/F due to the stronger signal (pressure differential) thru the venturies. F.e. Pontiac used the same #7029268 carb (with same jetting) in 1969 for 350 H.O.-400 H.O. and 428 H.O. A/T. Also in 1970 all A/T RamAir III, RamAir IV and 455 RamAir used the same #7040270 carb (and jetting). BTW, for your issues it seems like coil bind. FWIW |
#35
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So Kenth, so when in your world does there come a need for jetting changes?
In mine, to make the best average Torque and HP numbers on a number of dyno pulls when just switching to different octane level and different blend type fuels we had to change the jetting to achieve our goals.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#36
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Higher volume fuel pump
Quote:
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#37
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Quote:
It´s or never was like anyone buying a new car in the 60´s-70´s or using an original used street car nowadays checking for best average Torque and HP numbers every time they went out for a ride. For most of these folks they were happy if their ride started and drove well. And they did thanks to the people building them. |
#38
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Ok folks the word has come down from on high, Kenth as spoken !
It’s a new day in the automotive world and in our hobby!! It’s one carb fits all now,! So Holley you look here!, do away with all of those different part numbers for Carbs that are within 50 cfm of each other and all of you other folks spending hours and a tank full of gas on getting your fuel injection map just right, just screw it, shut up and live with the out of box results, or that original program that came in your car’s computer before that cam and exh system change you made!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 03-03-2021 at 04:03 PM. |
#39
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Valve guide clearance too tight. Valve guides not concentric with valve seats.
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#40
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Quote:
Do you really believe Pontiac would mount wrong non-functional carbs on their vehicles? |
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