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Help!!! 454 BBC Bent Intake Pushrods

  
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Help!!! 454 BBC Bent Intake Pushrods

 
canted canted
Enthusiast | Posts: 499 | Joined: 02/08
Posted: 06/07/10
04:50 PM

Good time to switch to a roller!  
Jim
70 El Camino
461 solid, m20,
pics in readers rides
thanks for over 3000 views

Dave632 Dave632
Addict | Posts: 2225 | Joined: 07/08
Posted: 06/07/10
06:28 PM

Sounds like you figured it out.
When re assembling you will also want to check the piston to valve clearance. The cam that was installed may have had enough lift to allow the valves to hit the pistons or as you said the previous owner was an idiot.
I always did the clay check. Put a layer of modeling clay on top of the piston where the valve will be nearest the piston, about a 1/4" of clay will do. Put the head on with gasket, no sealant and just enough head bolt pressure, on the cyl to be tested, to keep the head from moving when the cly is rotated thru one cycle. Then pull the head off and check the thickness of the clay where the valve made contact.  
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tuffnuff tuffnuff
Moderator | Posts: 7828 | Joined: 12/09
Posted: 06/07/10
11:16 PM

Yup,,,
Check and check again,,, or pay your money and take your chances.
I check and double check everything,,, when blueprinting an engine.
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

mikeyj350 mikeyj350
New User | Posts: 6 | Joined: 05/10
Posted: 06/08/10
07:01 AM

Yup, I will definitely be checking those clearances when putting this all back together. I actually did check the valve to piston clearance with a dial indicator when I was troubleshooting and got a little over 0.200" at TDC.

The cam I got is nothing too special as far as lift or duration goes, but it is indeed more than the stock cam. The guy at the machine shop recommended different lifters than the 'cheapies' that come with the Summit cam kit. He said they're made in China and are junk. Same thing about the entry-level Cloyes double roller chain ($17 at Summit... "A $17 chain is a $17 chain" he says.). Of course he had a 'better' chain and some slotted lifters there that cost twice as much Smirk but I do trust (or at least listen to) this guy's opinion when he starts recommending parts. Anyone have any thoughts on this? I am definitely a firm believer that you get what you pay for, but also that certain things can be considered overkill for the task at hand.

This leads me to my next question... I have to keep reminding myself this is a SUBURBAN, not a race car while considering all the upgrades I can do while it's all apart Grin ... That being said, I would like to boost what I can within reason and use parts that will last another 150k or more. What sorts of mods are acceptable, keeping the stock TBI system and computer? I.e., will a non-stock cam (however mild) and a slightly higher compression ratio (8.5-9:1) be too much for the computer to adjust for? Is it a good idea to upgrade the ECM chip too? I'd like the most power I can get and still stick with 89oct pump gas.

Again, thanks so much for all the advice and help on here, it's really appreciated!  

WRIGHTRACING WRIGHTRACING
Enthusiast | Posts: 437 | Joined: 03/10
Posted: 06/08/10
10:00 AM

Not sure on all the TBI stuff, but I do know I had a $17 double roller timing chain from Summit, and I went 5.70s with it. As for the rest of the stuff, put a good name brand cam kit in, like Comp or Lunati. Be sure to put in good rod bolts as well. Hi-tack the crap out of the head gaskets, and don't use raggedy gaskets. God luck.  
WRIGHTRACING


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huatulco huatulco
New User | Posts: 8 | Joined: 07/10
Posted: 07/23/10
09:31 AM

Hey, you ever find the missing pushrod piece? I have exact same '94 Suburban with 454 with 210k miles and the timing chain jumped a month ago. I'm down in southern Mexico with it and they never made any Suburbans with 454's in Mex it seems so all my 454-specific parts have to be brought by friends from Stateside, thus drawing out the repair agonizingly long. This thread is the most informative I found on the whole net to do with my problem, and has informed me enough to save me from taking as gospel the declarations of the really mediocre mechanics in this town. I like diagnosing the problem myself and being sure of it and telling mechanics here exactly what I want done rather than letting them come to their own faulty conclusions and waste my time and money.

Had a new timing chain installed (at least labor is a bargain, about $130) and that got it running, but like hell, 1/3 power. Mechanic declared the valves were bad, never even popped the valve covers to look at the pushrods. Another younger mechanic I'd talked to about it happened to be walking by and shook his head and said "the valves aren't bad" because he knew it was a non-interference engine. I got it home and popped the valve covers, two rocker arms were floating loose on one bank of cylinders because the intake valve pushrods were broken and the other ones were severely bent.

Anyway, I've got the same problem of having to chase the pieces inside the engine, I'm assuming they may be safely down in the pan because I drove all around town without (seemingly) further destroying anything. Wonder if you found your piece in the pan eventually. I was hoping to do the minimal amount of work - I don't plan a long future with this truck - to get it running again so am hoping that I can just replace the pushrods without ever pulling the head and it'll be okay. At minimum though it seems I need to pull the intake manifold to look for pieces in the cavity and check the lifters, though.

What remains a mystery to me from everything I've read is how valves get bent on a non-interference engine when a chain jumps. It seems to happen enough that I know it's possible, but no one seems to explain why, they blithely say "piston to valve contact" when there's no way that should be possible. The only way it seems possible is as someone suggested on this thread, something was replaced that caused improper clearance and allowed interference. Can anyone tell me with stock cam and valves how it could be possible to have contact and bend valves? Cause I'm going back to the States next week and going to buy the pushrods and manifold gasket and other sundries, but would hate to come back and put all that in and find the valves bent and not be able to get valves down here. But without a set of good pushrods I can't check things by hand turning the engine and seeing if the valves are moving up and down okay.  

chevelle83 chevelle83
Addict | Posts: 2280 | Joined: 11/09
Posted: 07/23/10
10:03 AM

My best recommendation it your situation,,,,,,,,,

Go ahead and pull both heads and check all the valves before you get any parts, you might as well get the full gasket set cause you will spend just as much piecing it together. With that kind of miles all the gaskets and seals are way! past their life expectancy.   I dont think the bottom end on these engine ever wear out.  I have opened up a 99 model 454 with 149K and the bores looked really good and it still had good oil pressure.

 With the heads off it will be easy to tell if the valves touched the pistons, I am almost dead sure these are non interference engines though.


 A set of pushrods is obvious.  while you have the cam exposed check the lifters cause I have been told that  these lifters usually are done around the 150-175K depending on how it was treated.

 The lifters are the only thing that I can think of that will cause bent pushrods once the plungers collapse this allows lots of slack in the rocker arms and at speed, catastrophe happens.  Oh,,, I have also herd LOUD ticking in high mileage late 454s    However I am still not 100% sure on this cause I have physically not worked on one that actually came apart like this.  

tuffnuff tuffnuff
Moderator | Posts: 7828 | Joined: 12/09
Posted: 07/23/10
10:31 AM

No interference means that a stock Big Block will have adequate piston to valve clearance engineered into the engine.
However, when your valve eventing gets scrambled from a jumped timing chain,,, this safety factor is eliminated. Your engine turns clockwise and when the chain jumps, the crank gear/sprocket keeps movin for one or two teeth,,, your cam gear/sprocket, gets left behind.
This causes your intake valve eventing to be late,,, and your exhaust eventing to be early, in relation to the piston TDC.
Think of it as a revolving door that you wish to go thru,,, your entrance timing determines whether or not you can gain access.
IF,,, you are late for one entrance,,, you'll find the next one comes early,,,
kind of draws a word pic for you, I hope.
I include a link below, cuz there are 3 block deck heights possible and you'll have to determine what exactly you have. Cuz the pushrods are different lengths, depending on the block you have..
Broken pushrods are no big deal if the pieces are in the pan sump,,, BUT, if they are still in the lifter valley,,, the pieces could slide forward under hard braking, and end up getting tangled up in your timing set!!! Not good!!!
TO verify that there are no pieces in your vally, simply pull the intake and check,,, for peace of mind.

Three main engine block deck heights that require different
length pushrods have been used:
Std height blocks are from cars and light duty trucks to 1984.
454 Car 1976 and light truck 1985-90 use shorter push rods.
Tall blocks are from heavy duty trucks and use longer push rods.

www.amotion.com

www.northernautoparts.com

Good luck

Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

huatulco huatulco
New User | Posts: 8 | Joined: 07/10
Posted: 07/23/10
07:44 PM

I'm pretty familiar with engines though big block pushrod engines are new to me, most I've worked on in my life have been overhead cams. I usually do my own work on 'em but if it's more labor than worth my time I'll take advantage of the $10/hr labor mechanics charge here. No question this is a non-interference engine. I mean, was any stock 454 ever made an interference engine? I thought the Vortecs might be that I believe they switched to in '97, but even they seem to be non-interference. But regardless, how I understand non-interference engines work is it doesn't matter if the crank and cam get totally out of sync, the pistons still cannot contact the valves. They are engineered so that even if the intake valve was fully open when the piston was at top dead center, there is no contact. What you described to me sounds like an interference engine, where there is no clearance between the piston at top dead center and a fully open valve, thus if wildly out of time, there is contact. Anyone else on this?

Now if I'm right about that, my only theory for bent valves on a non-interference engine when a chain jumps is that when the chain reconnects, the cam suddenly turns again so abruptly that a cam lobe slams a lifter upward extra hard, making the valve open a little more than usual and completely out of time and thus allowing contact with the piston (that force would also buckle the pushrod at the same time). My Dad - we're both mechanical engineers, he's the better one though - doesn't buy that and only sees the pushrods buckling as an out of time result of the intake valve trying to open during the compression stroke and the gas explosion in the cylinder trying to force it closed, thus buckling the pushrod. He doesn't see any way possible for there to be piston to valve contact. But enough people have slightly bent valves on non-interference engines from chains jumping teeth that there has to be something happening to force the valves open beyond their usual range.

Anyway, had already planned on pulling the intake manifold tomorrow to see what I find - agreed, I do NOT want those pieces flying into my timing set or my cam! There appear to be big enough holes in the lifter valley for them to fall through into the cam but luckily if they did go through there they fell down below and missed the cam. Now as far as length of pushrods, they appear to be 8.179 and 9.166 for those mid-90's 454's, I'll double check a straight one I pull out just to be sure. I know pulling the heads is the best way to be sure about everything, but I'm going to try to avoid doing that unless I have to.  

tuffnuff tuffnuff
Moderator | Posts: 7828 | Joined: 12/09
Posted: 07/23/10
07:57 PM

I see you know how all this works, so I'll leave you with your theory that there will never be piston to valve interference, regardless of where the piston TDC is in relation to max valve lift or valve eventing.
Furthermore, hydraulic cams are constant contact profiles and the lifter "NEVER" leaves the cam lobe,,, so what do YOU think, caused pushrods to get bent,,, on your "no interference" engine,,, if my facts are incorrect.
I also suppose there is no need for blueprinting an engine,,, nor is there any need for valve reliefs cut into piston crowns,,, to clear valves at max lift.
Guess I'm still learning after almost a 1000 engine builds, huh.
Thanks for schooling me bud, I appreciate it.
Guess I should junk my engine blueprinting tools too, and just start slapping things together any old way, from now on... Cuz there is no interference,,,
until pushrods get mangled and bent,,, mebbe valves too
Confused  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman2 Pontiacman2
Moderator | Posts: 8956 | Joined: 09/08
Posted: 07/23/10
08:06 PM

Grin  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

tuffnuff tuffnuff
Moderator | Posts: 7828 | Joined: 12/09
Posted: 07/23/10
08:55 PM

+1
Confused
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

tuffnuff tuffnuff
Moderator | Posts: 7828 | Joined: 12/09
Posted: 07/24/10
12:11 AM

Icon QuotePontiacman2:
Grin

And what is that grin all about Pman, LOL
Crazy
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman2 Pontiacman2
Moderator | Posts: 8956 | Joined: 09/08
Posted: 07/24/10
06:43 AM

You all ready know T-man.  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

Pontiacman2 Pontiacman2
Moderator | Posts: 8956 | Joined: 09/08
Posted: 07/24/10
06:43 AM

Grin
Grin  Smile  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

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