Pushrods

bezerk

bezerk

New member
On the last day of 2014, the year almost couldn't posssibly have ended as bad as I thought it did. I took the Sy out for a spin and after a nice WOT run, the engine sounded like crap like a dead cylinder.

Today I found the problem; a bent pushrod. (Hope that's all).

So I think I still have stock pushrods in mine, but I happen to have a spare set of 7955 comp. The cam is 7.400 .080.
They are slightly longer as you can see in the pic. Can i use these if iI change them all out?

(Vortec heads, 1.52 rollertip rockers and an 422"ish cam)

 
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Syclone#2960

Syclone#2960

What ever it takes!!
Re: Pushrods

What? You just gave me a head ache. You need to check geometry with a pushrod length checker. Otherwise you could have another bent rod issue.
 
bezerk

bezerk

New member
Re: Pushrods

Syclone#2960 said:
What? You just gave me a head ache. You need to check geometry with a pushrod length checker. Otherwise you could have another bent rod issue.
Click to expand...

Truck has been running for 7yrs (best of 11.2 with 1.8 60ft). Never had a problem. Ran out of alky what i think ihas been the problem, or just on the edge??
 
Syclone#2960

Syclone#2960

What ever it takes!!
Re: Pushrods

bezerk said:
Truck has been running for 7yrs (best of 11.2 with 1.8 60ft). Never had a problem. Ran out of alky what i think ihas been the problem, or just on the edge??
Click to expand...

then u need to run the same length pushrods as before and if it was me I would check them with a "adjustable pushrod check" tool. The stock pushrod was the weak point in this scenario and gave way instead of a lifter or valve. Things could have been a lot worse if were using the 1 piece hardened pushrod instead.
 
randy merritt

randy merritt

Donating Member
Re: Pushrods

Syclone#2960 said:
then u need to run the same length pushrods as before and if it was me I would check them with a "adjustable pushrod check" tool. The stock pushrod was the weak point in this scenario and gave way instead of a lifter or valve. Things could have been a lot worse if were using the 1 piece hardened pushrod instead.
Click to expand...

x2 and I will go ahead and x3 this statement.

I just checked my pushrod length requirement when I swapped out my cam. Very easy to check, and then I ordered some good correct length pushrods from Hood who beat everyone's (including Summit's) prices. I got my pushrod check tool from summit, and it was only about $15 or so.

Turns out I had a bad lifter also that was causing my knocking under hot start symptom.
 
Don W.

Don W.

Stab it and steer it
Re: Pushrods

Probably shooting myself in the foot here but I'm gonna follow this. To my way of thinking a bad lifter won't bend a pushrod. If the lifter was bad (not pumping up) then I suppose the puchrod could come out of the rocker then somehow force the valve to open to far, binding the spring or hitting the piston. I have a bet with myself there is more to this story.

FWIW I recently had my motor out and, among other things, checked the valves. All were worn/marked as show in the vid. But checking length with a yardstick? Notoriously inaccurate.
 
Quickstop [UK]

Quickstop [UK]

Combating adversyty.
Re: Pushrods

I thought you would measure the length with either a set of calipers or an adjustable push rod tool. You set up a length then use the blue dye to see if the PR is sitting in the right place thn adjust as necessary. You then measure the correct length and that is your figure.

I agree Don, a lifter could drop out and allow play which then causes a bind but that seems unlikely. The only mechanism I can understand here is detonation causing a valve to close at the wrong time and bending the rod. But I :dunno:
 
12secondSY

12secondSY

Syty Killer :(
Re: Pushrods

I've bent pushrods in SBC engines before. Replaced with stock and all was good. I believe it was from overrevving/floating valves. The tach wasn't working when I was at the track. Kept sticking at 3-4k.
 
12secondSY

12secondSY

Syty Killer :(
Re: Pushrods

Don W. said:
Outstanding!

Thanks

And 12secondSY, yup, over-rev will definitely do it. I had not thought of that. I haven't floated any valves in a long time...:rotf:
Click to expand...

That's because rev limiters take away all the excitement now :)
 
Don W.

Don W.

Stab it and steer it
Re: Pushrods

I think I have some. I'll post the length if someone doesn't beat me to it.
 
Icarus-54

Icarus-54

Donating Old Member
Re: Pushrods

Which cylinder was it? If it was #3, check and see if the rocker hit the valve cover baffle. This has happened before on a few trucks. Comp Cam rockers are notoriously loose on the valve stem.
 
bezerk

bezerk

New member
Re: Pushrods



Found a stock pushrod, same lenght. Runs good...
Dont upgrade your stockpushrods if u can stay with stock lenght! It acts like a fuse!! :D
 
D

Davemc1963

93 Ty Owner
Re: Pushrods

If it were me, I would be worried not knowing the root cause of the problem, if the same thing happens again, you could take a head out. Possible causes are as simple as a rocker stud adjuster nut coming loose or a collapsed lifter, but you are running again, so...? You would probably have noticed these on tear down. More worrying is if you have press in studs (probably not) that the stud is pulling out of the head. Other causes are a weak spring causing valve float. Once this happens, the springs temper can be affected due to it geting too hot and wont recover. With our trucks though they're not really high rpm motors, but if the spring is weak, it may re-occur. Have you checked spring rate and and installed length? Your new cam may well have a different base circle diameter and require non stock push rods, as has been suggested. Not trying to be a smart arse, just trying to offer an opinion so it dosen't happen again. Another simple tool I have used is this http://www.summitracing.com/int/parts/man-42137. Handy bit of plastic. Good video though, I will try that, I have my vette sbc to put back together soon. I have always used a dti and witness marks, but will try that and compare my results next time. Every day is a learning day!
 
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bezerk

bezerk

New member
Re: Pushrods

Davemc1963 said:
If it were me, I would be worried not knowing the root cause of the problem, if the same thing happens again, you could take a head out. Possible causes are as simple as a rocker stud adjuster nut coming loose or a collapsed lifter, but you are running again, so...? You would probably have noticed these on tear down. More worrying is if you have press in studs (probably not) that the stud is pulling out of the head. Other causes are a weak spring causing valve float. Once this happens, the springs temper can be affected due to it geting too hot and wont recover. With our trucks though they're not really high rpm motors, but if the spring is weak, it may re-occur. Have you checked spring rate and and installed length? Your new cam may well have a different base circle diameter and require non stock push rods, as has been suggested. Not trying to be a smart arse, just trying to offer an opinion so it dosen't happen again. Another simple tool I have used is this http://www.summitracing.com/int/parts/man-42137. Handy bit of plastic. Good video though, I will try that, I have my vette sbc to put back together soon. I have always used a dti and witness marks, but will try that and compare my results next time. Every day is a learning day!
Click to expand...



I get your point but the way it rans ans runs for the last 6yrs is wicked, and i"m at the edge with this.
Fixing things before they break will break something that didnt need a fix
Ill order some alky and let you know
 
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