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#1072417 11/06/21 09:55 PM
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markg Offline OP
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i had trouble last nite with my blueprint 383 sbc.on acceleration something gave and i heard what i thought was a rodknock.i made it back to the shop 2 blocks away and let it sit till today.i pulled a vc and there were 2 pushrods missing on cyl 6 i fished them out with a magnet and only one was bent to about 30 deg.i know ive got a lot to do now but ive got a few questions.
how did the straight rod get out?
how bad was it to run with both valves closed on the same cyl?
why did the rods have a problem from the same cyl?

the lifters look fine and i cranked while holding an aluminum rod on the face and they are going up and down.
the rockers looked fine and the nuts didnt back off.
i tapped the 2 valves with a brass hammer and they seem free.


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
markg #1072418 11/06/21 09:57 PM
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markg Offline OP
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i forgot....this is an older flat tappet 383. it was manufactured 8 yrs ago and put in a project indoors that never took off.i bought it from a friend this way.ive put less than 1000 miles on it.


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
markg #1072419 11/07/21 12:05 AM
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Not sure what caused it but if it was me I would pull the head on that side. In my thinking the valves may have it the piston. Have you drained the oil to see what comes out? Remove the spark plug and see what kind of compression from that cylinder maybe. Do you hear any other noise when cranking it over? My thinking is maybe rod bolts or rod broke, piston stayed at top, valves came in contact with piston. There is a highly likely chance that im wrong, lol.

Last edited by 88ssBrent; 11/07/21 12:09 AM.
markg #1072420 11/07/21 12:35 AM
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It could be possible the cam lobes are wiping out, causing the pushrod that wasn't bent to drop out of place. Since the valve(s) weren't gaulded, If it was the exhaust side that dropped out of place first, it guess it might have been possible the intake pushrod bent when it tried to open the valve with a fully loaded and compressed cylinder???

If you have a borescope, or one of those that plug into your phone, you could check for piston damage without pulling the heads. If there's no indication of damage, then I'd pull the intake and check the cam and lifters.

markg #1072422 11/07/21 02:05 AM
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What Kevin said definitely sounds more logical than my guess.

markg #1072423 11/07/21 05:31 AM
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Also a quick check of the oil filter may tell you something. Pull it off, cut it open, look at the pleats. If nothing there that's a victory. If fine steel, not good. Run a magnet over the bottom of the pleat. A filter cutter is a great tool for engine diagnosis.
For a pushrod to jump out of the lifter that's a lot of wear on the lobe, it will be in the filter, it doesn't happen over night.

Would do a through inspection of the valve train. Would think the studs are screw in, not pressed. In the old days the press in would pull out of the head.
If the cam is wiping out there are other lobes that have gone south.
Was the valve adjustment checked/adjusted since the install of the engine. Something not to take for granted.
If using Poly locks to adjust is the setscrew on the offending rockers still tight. Have seen those locks back off if the setscrew is not buried in the stud.
Check the rocker arm where the crooked pushrod came from. May have damaged the pocket when crushing the pushrod.

It's a good chance if as you said this engine sat for a long time, flat tappet cam, breakin lube ran off the lobes, never a proper cam break in done.

If you eventually pull the intake the lifter faces will tell the story.

Chances are the pistons were never in harms way. Inspect the filter.
Bob

markg #1072427 11/07/21 07:35 PM
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markg Offline OP
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i made a big lever tool and cycled each valve to see if there were any rgh spots but they both cycled fine and smooth.

i know that not saying there is a problem there but at least i know there doesnt seem to be a serious bind.

i put two .100 shorter pushrods in ,put the rockers on loose and cranked it with the plug out.

everything seemed to cycle normally.

i put a magnet on the lifters and pulled them almost out of their bores and they came up smooth.i thought that if the cam was wiped they wouldnt come up.

my headers are in the way and i cant get the borescope or the airline to the sparkplug hole to test it.

the plug that came out is fine.

im going to call blueprint tomorrow and hopefully they will just sell me a rocker and 2 pushrods because i dont want to buy the whole set if i dont need to.

im thinking possibly the one rod bent and the rocker twisted sideways and kept the other up and the straight pushrod got out that way.

when it went the noise i heard was more of a high pitched noise like a pushrod tapping against something.

ill keep ya posted and thanks for all of the help!


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
markg #1072430 11/07/21 11:15 PM
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I suggest you pull each lifter completely out of its bore and inspect the face. A flat tappet lifter that is fine, should have a slightly convex face. A wiped out flat tappet lifter will have a concave face.


87 SS, Harwood hood, UMI trailing arms. Hooker 2050 Headers (Jet Hot Coated). Hooker Cat-Back Exhaust, Goodwrench 350, Ported TPI, Trick Flow 56cc alum heads, SLP runners, Comp Cams 260AH-12 cam, Trick Flow roller rockers, TCI 2400 stall converter, Denny's 3.5" Driveshaft, GBodyParts GNX Replica Wheels 18x8 & 18x9. F-Body Serpentine Belt Sys.
markg #1072557 11/23/21 09:56 PM
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leak test or blow air in cylinder easiest to get answers perhaps a rocker backed off if your very lucky


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