|
'69 427 Bent Push Rod
Sold my 2004 CE Z06 about a year ago.
I just purchased a 427 69 coupe. I changed the oil and filter, gave her a tune up with air filter,new plugs, wires, distributor cap and rotor. I Decided to go through the valve train by starting to adjust valve lash because of some valve train chatter. I found the #1 intake push rod bent! and ran ok but didn't know extent of the problem. So, what should my course of action be. Get a new push rod? How can I be sure the valve is not bent. Your feed back would be appreciated. Thanks Mike |
The stock pushrod is the weak link when slightly over-rev'ing the engine. Just because the pushrod is bent does not mean there are other serious problems. If the pushrod is not badly bent, it can be straightened across V-Blocks with a dial indicator and a rubber mallet (this method is FAA-approved for straightening aircraft engine pushrods, believe it or not..). Or you can replace it. If this is a near-stock engine with a 5500 rpm redline, and there are no other engine problems or symptoms, I'd straighten it, run the engine, and have fun. :cheers:
Don't over-think it... Don't make the problem worse than it is... Lars |
Must be why GM had 7/16 pushrods available for the BBC's.. But they are heavy compared to the 3/8..
|
The push rod is bent pretty bad. The rockers are rollers, which is not stock. They have Poly locks. The guy I bought the car from said it had a higher performance cam in it what ever means because I don't know the specs of the cam.
I will take some pics of the bent push rod and the rockers that are on the studs. Maybe someone can identify them. |
Different cam and roller rockers. On an otherwise stock 427 when you use a higher lift cam you have to change out the stock valve springs as with higher lift, you can get coil bind. Coil bind results in bent pushrods. Check the rest of them very closely. Roll them on a piece of glass. Your wife's glass coffee table works perfectly for this but don't get caught. If it's just the one, fix or replace it but make sure it is only the one pushrod or you probably have a spring bind problem with the aftermarket cam.
|
Originally Posted by CanadaGrant
(Post 1599008065)
Different cam and roller rockers. On an otherwise stock 427 when you use a higher lift cam you have to change out the stock valve springs as with higher lift, you can get coil bind. Coil bind results in bent pushrods. Check the rest of them very closely. Roll them on a piece of glass. Your wife's glass coffee table works perfectly for this but don't get caught. If it's just the one, fix or replace it but make sure it is only the one pushrod or you probably have a spring bind problem with the aftermarket cam.
|
Replacement Cam and you don't know what. you need to know the valve lift. You can get pretty close with a good little steel ruler. Stand up next to a valve and have somebody bump the starter. obviously subtract up from the down measurement go around and check a bunch of them. Intake and exhaust separate. 20 buck digital caliper would be better. What 427? Head casting numbers? Orig o-ring valve seals or umbrellas or positive seals under springs? You also want to get a cheap lever style spring compressor and feel the valve that bent the rod for binding. Is valve bent? Compression test. https://www.ebay.com/itm/OEMTOOLS-25...cAAOSw7thb-KAa
|
Call Trend in Michigan and get a set of .080 radial wall 3/8" pushrods.....8.280 intake and 9.250 exhaust.......nobody really uses 7/16" anymore and your guide plates are probably 3/8" already......I would also pop for a set of Comp Magnum rocker arms......even though they are a ball/stud design, they are LIGHT YEARS better than GM or rebuilder spec stamped rockers that actually have a 1.7 ratio (Stock can be anywhere from 1.63 to 1.7) and don't deflect when revved over 5000 rpm.
BBC's in the day were classic for breaking rockers and bending pushrods due to crap valve spring, float, and the previously mentioned installed height. You will have a few bucks into doing this (about $300) but at this point you can be SURE the lash is right and that you have solid components up top. I like to use polyloks even on stamped rockers as it is so much easier to feel where you are at with the lash on a hydraulic..... Jebby |
Bent push rod pic
https://cimg8.ibsrv.net/gimg/www.cor...9c086d16e9.jpg
https://cimg5.ibsrv.net/gimg/www.cor...a657f82706.jpg https://cimg6.ibsrv.net/gimg/www.cor...8a1c8b5af2.jpg Damage from rod guide https://cimg7.ibsrv.net/gimg/www.cor...39c206b5fb.jpg https://cimg8.ibsrv.net/gimg/www.cor...71e2c318b7.jpg Comp cams 1411 1.72 ratio |
Those appear to be two piece pushrods. In laymans terms: crap.
Summit has the one piece rods you need. Just match not only the correct length obviously, but the correct guide plate diameter slot too. And I wonder if those are 1.7 rockers instead of 1.6 causing binding at the fulcrum? |
Pushrods bend from some valve train interference. There is something binding. The bent pushrod is not the culprit, it is the evidence of the other problem not yet identified.
|
those are "roller tip" rockers not roller rockers, there is a significant difference
|
They're 1.7 ratio , thats what is stamped on the rocker.
|
Originally Posted by HeadsU.P.
(Post 1599009076)
Those appear to be two piece pushrods. In laymans terms: crap.
Summit has the one piece rods you need. Just match not only the correct length obviously, but the correct guide plate diameter slot too. And I wonder if those are 1.7 rockers instead of 1.6 causing binding at the fulcrum? |
THAT! I don't know. Just sayin' like in post 8, you need to know what size guide plates somebody put on there, 3/8 or 7/16. Should be 3/8, but measure your guide & pushrod dia.
Those 2 pc rods are a accident waiting to happen. Sometimes they separate. And its not pretty. |
Originally Posted by HeadsU.P.
(Post 1599009076)
Those appear to be two piece pushrods. In laymans terms: crap.
Summit has the one piece rods you need. Just match not only the correct length obviously, but the correct guide plate diameter slot too. And I wonder if those are 1.7 rockers instead of 1.6 causing binding at the fulcrum? |
A few thousandths. Mebbe .010. If 7/16 guide and 3/8th pushrod, there will be 1/16th wiggle room. 1/32 each side. It will be pretty obvious if wrong size.
|
Any overheating?
Any overheating? As others have mentioned a bent pushrod is a symptom not a cause. Overrevving is one possible cause Miss matched parts and Clearence is another. One that nobody has mentioned so far is overheating if an engine is overheated sometimes a valve can stick in a guide and the pushrod is where the damage occurs
|
Ok...so you have the Comp rockers that I mentioned......that is why the pushrod bent because those particular rockers are pretty tough with a thick cross section.....GM rocker would have probably broke right off......
So......you have a crash going on....you need to determine if it is the retainer to boss or spring coil bind.......I personally pop one off the I and the E (use air holder or the rope trick) and start inspecting....you can put a light tension spring on both I and E and use an indicator to check distance to bind and distance to retainer crash. Record these number and compare with the cam lift. Don't know your cam? Take the same indicator and go off the tip of the pushrod while rolling the engine over.....it will move like .300, record the movement and multiply by 1.7.......subtract that number I and E from both the retainer and spring bind number.....you need at least .060 :) If you do not have clearance.....you will have to find a retainer/spring/locator setup that works...... But buy new one piece pushrods......99% of them are made by Trend no matter what brand name is on the box. Jebby |
Originally Posted by Jebbysan
(Post 1599009621)
Ok...so you have the Comp rockers that I mentioned......that is why the pushrod bent because those particular rockers are pretty tough with a thick cross section.....GM rocker would have probably broke right off......
So......you have a crash going on....you need to determine if it is the retainer to boss or spring coil bind.......I personally pop one off the I and the E (use air holder or the rope trick) and start inspecting....you can put a light tension spring on both I and E and use an indicator to check distance to bind and distance to retainer crash. Record these number and compare with the cam lift. Don't know your cam? Take the same indicator and go off the tip of the pushrod while rolling the engine over.....it will move like .300, record the movement and multiply by 1.7.......subtract that number I and E from both the retainer and spring bind number.....you need at least .060 :) If you do not have clearance.....you will have to find a retainer/spring/locator setup that works...... But buy new one piece pushrods......99% of them are made by Trend no matter what brand name is on the box. Jebby I'm at work so I can't examine the rods. |
| All times are GMT -4. The time now is 04:00 AM. |
© 2024 MH Sub I, LLC dba Internet Brands