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  1. #1

    Default 8 bent intake pushrods

    Scratching my head on this one. Any advice appreciated.

    NOTE: The motor in question came out of my 86 that was previously rebuilt and driven approx. 15k miles with no issues. The only thing changed before installing in the '84 was the camshaft. I went from an 'F' motorsport cam to a stock 'speed-density' (86-88 HO) cam.

    The combo is roller 306 block, GT-40 iron heads, 1.7 motorsport roller rockers, push rod length unknown at this time... I still need to measure although i suspect stock.

    I installed this engine in my '84 over a decade ago and have just now recently gotten back into the project and got it *sorta* running. It was making some valve-train noise and running overall poorly (rough idle) so I pulled the covers to adjust the valves. In the process of doing so, discovered all 8 intake push rods were bent. Exhaust are fine. It's been 10 years but i'm willing to bet I installed the cam correctly. I did not degree the cam when installing... just brought up to TDC on #1 and matched the dots on the cam & crank sprockets per the shop manual instructions. Didn't think it would be an issue with a stock cam. Nothing binding or felt strange when turning over by hand before the initial fire-up.

    Did I make a mistake in assuming going from the lumpy 'F' cam down to a stock smooth-idle cam that my pushrod length would not be an issue? Nothing else was changed. Heads were not pulled, just front cover & intake for cam removal/installation. I am unaware of what valve springs it currently has. I'd guess they'e a little stiffer than stock, but that shouldn't pose an issue here, right?

    Can't seem to find any specs on the speed-density roller cam. Does anyone happen to have the lift/duration #'s for that particular cam? I know they were slightly different than the later 'mass-air' roller cams from 89-93. I need to do the math with the 1.7 rockers to factor out if that's my issue.

    Thanks!
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  2. #2
    Moderator wraithracing's Avatar
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    Everything I have seen shows the 86-88 camshaft as 0.444 lift and 266/266 duration.

    I would recommend checking your pushrod length first to verify what you have before making any assumptions. Good luck!
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  3. #3

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    Quote Originally Posted by wraithracing View Post
    Everything I have seen shows the 86-88 camshaft as 0.444 lift and 266/266 duration.

    I would recommend checking your pushrod length first to verify what you have before making any assumptions. Good luck!
    Thanks, Trey. That's definitely the first thing on my to-do list this afternoon.

  4. #4

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    I gather the engine was previously fired and running and underwent a cam swap and was left sitting? What if the problem is unrelated to the cam swap?

    I've heard of and seen instances where an engine sittings for time can encounter issues where the valves get gummed up at the valve stem/valve guides.

    This very thing happened to a 79 5.0L coupe that sat for 4-5 years owned by Doug Kielian.

    I agree -- do measure pushrods. But I would carefully take the pressure off the valve springs and see how much effort it takes to turn the valves in the guide.

    Thinking back to an old engine I worked on while I was a kid. The valve seals basically turned into glue after they were left without oil for years.

  5. #5

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    Quote Originally Posted by erratic50 View Post
    I gather the engine was previously fired and running and underwent a cam swap and was left sitting? What if the problem is unrelated to the cam swap?

    I've heard of and seen instances where an engine sittings for time can encounter issues where the valves get gummed up at the valve stem/valve guides.

    This very thing happened to a 79 5.0L coupe that sat for 4-5 years owned by Doug Kielian.

    I agree -- do measure pushrods. But I would carefully take the pressure off the valve springs and see how much effort it takes to turn the valves in the guide.

    Thinking back to an old engine I worked on while I was a kid. The valve seals basically turned into glue after they were left without oil for years.
    Hey erratic50 -

    You are correct in this engine ran 15k miles with a different cam with no problems. When pulled, it was swapped to the stock cam and put in the car and not fired until several years later. I would occasionally rotate the crank by hand to keep things moving.

    Great point on sticky valves. I have encountered this before as well with solid lifter y-block engines that sat for years and would get sticky and bend pushrods left and right. The fact that it bent all 8 intake pushrods and none of the exhaust leads me to believe sticky valves is likely not a factor here.

    I did measure a straight pushrod last night and it came out to 6.25" (approx. as i couldn't find my caliper and used a ruler). Based on what I've read here, that's stock length.

    For grins, I put in 2 good pushrods on #1, got it on TDC, adjusted to zero lash and rotated the motor by hand about 10 revolutions. No binding was observed. Rods stay dead center in their guides and in the holes in the head.

    Since all the initial work was all done so long ago and I can't recall specifics, could it be that I set the valves in the incorrect sequence and ended up not being on the base circle of the cam and intakes were simply over-tightened? User error? Wouldn't be the first time...

    Thoughts?
    Last edited by graphicdesigner80; 11-05-2019 at 12:14 PM.

  6. #6

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    Are the GT40 heads stock explorer fare? Those heads have notoriously weak valve springs and even with the stock HO roller cam would likely float the valves at over 5k rpm's, let alone when you had the F cam in it.
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  7. #7

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    Quote Originally Posted by Zap's 85 GT View Post
    Are the GT40 heads stock explorer fare? Those heads have notoriously weak valve springs and even with the stock HO roller cam would likely float the valves at over 5k rpm's, let alone when you had the F cam in it.
    Zap - They are not the exploder version. Springs were replaced with stiffer ones when it was rebuilt, but can't recall what rate were used.

    I'll have to dig in my receipts.

  8. #8
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    If the engine has stock 86' pistons, they are flat tops without valve reliefs. 1.7 rockers increase lift, GT40 heads have larger valves. Everyone of these items tells me you have a valve to piston clearance problem Since all 8 pushrods are bent. Stock pushrods are not hardened and bend easy. Even if they didn't touch just running the engine, at higher rpms they will touch. If you pull the heads, you will see the valves have hit the piston and there will be smiley marks on them.
    You stacked the deck against yourself when you used the 1.7 rockers.

  9. #9
    FEP Power Member gmatt's Avatar
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    If the pushrods are bent, you better check the valves too.....

  10. #10

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    Quote Originally Posted by dynodon64 View Post
    If the engine has stock 86' pistons, they are flat tops without valve reliefs. 1.7 rockers increase lift, GT40 heads have larger valves. Everyone of these items tells me you have a valve to piston clearance problem Since all 8 pushrods are bent. Stock pushrods are not hardened and bend easy. Even if they didn't touch just running the engine, at higher rpms they will touch. If you pull the heads, you will see the valves have hit the piston and there will be smiley marks on them.
    You stacked the deck against yourself when you used the 1.7 rockers.
    dynodon64 & gmatt -

    I should've been more specific. It's not an '86 engine, it just happened to come out of my other car ('86). The pistons have valve reliefs. This combo was run with a motorsport F cam (.512 lift) with 1.7's with no issues. Going to a stock (.444 lift) with the same 1.7's would give me even more clearance. This is all with stock length pushrods.

    I'm pretty sure at this point I adjusted the valves incorrectly when the stock cam was installed. Going to do a compression test and go from there.

    Thanks for the help.
    Last edited by graphicdesigner80; 11-06-2019 at 11:43 AM.

  11. #11
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    Just because the newer cam has less lift, doesn't mean that the duration and open/ close events are the same for both cams. You have to look at all the timing events of the cams, not just max lift. If the cam was installed advanced or retarded, it will also cause a clearance problem. You have a piston to valve clearance problem or you are having spring coil bind with the intake valves because you bent every pushrod. One other possibility is the 1.7 rockers don't have a long enough opening in them and they are binding on the stud or bolts. Remember, the piston is chasing the intake valve as it closes. That's where it will hit the valve.

  12. #12

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    Quote Originally Posted by graphicdesigner80 View Post
    dynodon64 & gmatt -

    I should've been more specific. It's not an '86 engine, it just happened to come out of my other car ('86). The pistons have valve reliefs. This combo was run with a motorsport F cam (.512 lift) with 1.7's with no issues. Going to a stock (.444 lift) with the same 1.7's would give me even more clearance. This is all with stock length pushrods.

    I'm pretty sure at this point I adjusted the valves incorrectly when the stock cam was installed. Going to do a compression test and go from there.

    Thanks for the help.
    Wow Iím interested in why this could happen. You said you turned motor over by hand right? You didnít notice any strange binding? Compression build? I have seen before the pushrod not seated properly in the middle and possibly once you get the motor running you have a whole lot more lift and the lifters arenít forgiving when they are primed. I donít think itís a cam issue. 1.7Ēs donít do that with a stock cam. At the same time you would notice less oil pressure.

    Or 2nd guess. Wrong timing set up. Donít flame me but make sure #1 piston is correct not like chevy right... if your setting timing up on the wrong side you just opened valves at the wronnnggg time...

    Locked in for further details


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  13. #13

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    I think hint #1 was the valve train noise.

    There is another side to this coin...

    Which rockers? Assuming stud-mount (adjustable) rockers... what was/is your sequence? The procedure I use is: mark the balancer at zero/TDC, at 180/BDC, and then the two 90-degree locations between TDC and BDC. Then with the crankshaft at #1 TDC on it's compression stroke, adjust #1's rockers - rotate crankshaft clockwise 90-degrees, adjust for the next cylinder in the firing order - rinse and repeat until all are done... which is really only best for starters, because the actual best way to adjust rockers (lifter preload) for a hydraulic cam setup is to adjust them with the engine running and warmed up. If you did somehow happen to mess up with your sequence of statically adjusting for the lifters' preload, each not being on camshaft lobe base circles, you would not end up with too much preload or binding in the valve train WHEN AT camshaft lobe base circles, but with valve train slop when at the base circles, and less overall valve lift... see first sentence. There's great possibility of push rods getting bent if they're jumping around with slack in the system.
    Last edited by Walking-Tall; 11-07-2019 at 06:10 AM.
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  14. #14

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    Quote Originally Posted by 82MoreDoorFox View Post
    Wow Iím interested in why this could happen. You said you turned motor over by hand right? You didnít notice any strange binding? Compression build? I have seen before the pushrod not seated properly in the middle and possibly once you get the motor running you have a whole lot more lift and the lifters arenít forgiving when they are primed. I donít think itís a cam issue. 1.7Ēs donít do that with a stock cam. At the same time you would notice less oil pressure.

    Or 2nd guess. Wrong timing set up. Donít flame me but make sure #1 piston is correct not like chevy right... if your setting timing up on the wrong side you just opened valves at the wronnnggg time...

    Locked in for further details


    Sent from my iPhone using Tapatalk
    No flaming at all! I'm second guessing myself on everything at this point. Set a lot of ford valves successfully, never chevrolet, so hopefully didn't resort to that! #1 is always passenger front! lol.

    The motor ran but sounded like an old solid-lifter 'ticky' motor. It's very possible that the sequence was done incorrectly.

    I put in two good pushrods on #1 and set lash correctly. Pulled all the spark plugs and spun the motor over by hand a dozen times watching and feeling for anything strange. No binding. Pushrods stayed dead-centered in their guides and in the holes in the head. Could hear and feel compression.

    I don't recall what sequence everything was set initially (been 11 years). Just to be totally sure, I pulled the intake to see if all the lifters are up against their snap-rings. All of them are up and feel about the same (no oil pressure). I've already purchased 8 new pushrods. Will go ahead and reset lash per the shop manual and rotate everything by hand and watch and feel for issues. Then go to rotating with the starter. Then run a compression test.

    Having the intake off will make adjustment easier and will be make it less likely to screw up something.

    Maybe I'll get lucky here.

    Thanks to everyone for the helpful suggestions. I'll have an update sometime this weekend.
    Last edited by graphicdesigner80; 11-07-2019 at 10:24 AM.

  15. #15

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    Quote Originally Posted by Walking-Tall View Post
    I think hint #1 was the valve train noise.

    There is another side to this coin...

    Which rockers? Assuming stud-mount (adjustable) rockers... what was/is your sequence?
    The rockers are Ford SVO 1.72 rollers on pedestal stud-mounts. Can't remember how I did the initial setup. Been over a decade.

    Name:  FullSizeRender.jpg
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    Not the best pic, but gives you an idea.

    Quote Originally Posted by Walking-Tall View Post
    If you did somehow happen to mess up with your sequence of statically adjusting for the lifters' preload, each not being on camshaft lobe base circles, you would not end up with too much preload or binding in the valve train WHEN AT camshaft lobe base circles, but with valve train slop when at the base circles, and less overall valve lift... see first sentence. There's great possibility of push rods getting bent if they're jumping around with slack in the system.
    I think you're onto something here. I agree that this is probably what happened here.
    Last edited by graphicdesigner80; 11-07-2019 at 10:34 AM.

  16. #16

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    That solid lifter noise you're hearing is the valves kissing the pistons.

  17. #17

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    Quote Originally Posted by gt pony View Post
    That solid lifter noise you're hearing is the valves kissing the pistons.
    Guess i'll find out when i do the compression test.

  18. #18
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    Spring coil bind is a possibility. Do the GT40 heads springs support the lift you have? Since all 8 intake pushrods were bent, it's due to the lift being too much for piston to valve clearance, spring coil bind or rocker arms not having enough clearance to rotate through it's arc. Are there any marks on the rockers in the pivot slot or are they hitting the spring retainers behind the roller tip? You have a bind going on somewhere due to the lift in your set up.

  19. #19

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    Quote Originally Posted by dynodon64 View Post
    Spring coil bind is a possibility. Do the GT40 heads springs support the lift you have?
    Good question. I'm still digging through my old receipts to see if i can find the spring rate #'s.

    Quote Originally Posted by dynodon64 View Post
    Since all 8 intake pushrods were bent, it's due to the lift being too much for piston to valve clearance, spring coil bind or rocker arms not having enough clearance to rotate through it's arc. Are there any marks on the rockers in the pivot slot or are they hitting the spring retainers behind the roller tip? You have a bind going on somewhere due to the lift in your set up.
    No marks on rocker pivot. The only marks are on the bent rods where they rubbed the passage inside the head after they bent.

    If you were me, would you just go back to 1.6's? I'd really rather have the stock ratio since 1.7's aren't benefiting me much at all with a stock cam anyway. That and i'd rather run stock valve covers with oil baffles intact.

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