Pushrod problems

[joemac1000]

I am looking for an answer that would prevent my pushrods from bending. I am rebuilding a 65 mustang. This is the first engine I rebuilt and have read every article and called every auto tech in my city for answers but really no one wants to help nor have the correct solution. Here is the run down of what my specs are:

66 ford block 289
351W CAM performer edelbrok
302 crank, connecting rods/ pistons, and 1972 302 heads (valves 1.94 and 1.6)
66 hydrulic rockers
screw in rocker arm studs

When I first assembled this engine and turned the key I got several popping noises through my carb. I was told it was a timing issue. After further investigation, I found out that your firing order is determined by the type of CAM. I changed my firing order and it still ran rough. I then noticed that my rocker arms and pushrods where not tight. So I tighten to zero lash on the firing order and it still ran rough. Then my neighbor stopped by and said your pushrods (6.905) are too small since the rocker arms were almost sitting on the screw in stud bolt and I couldnt tighten them any further. So I purchased some 7.3 pushrods and started my engine up. It started great until I hear something rattling in my heads. I removed the valve covers and one of my pushrods snapped one of my studs and ALL MY PUSHRODS were bent. I set all my pushrods prior to starting the engine to zero lash without even giving the nuts an additional 1/4 turn. Whats going on????

I am at a lose and really can not afford to keep buying new rods. I would appreciate any help or some sort of answer.

Thank you!!!!!!!!!!

 

[69Rcode_Mach1]

Time to get a custom pushrod length checker. You need to tighten that down with it set so that the rocker is pressing at the center of the valve, or you will bend pushrods, possibly drop a valve, or mushroom the head off the valve.

 

[TOM B]

give us a pic of the valve train with rockers and pushrod installed.also a pic of
the studs you installed, might have the wrong studs, the noise you heard was the valve hittingthe top of your pistons, hence the bent pushrods.
When you adjust the valve lash bring up number 1 to TDC on the COMPRESSION stroke, If its not on the compression stroke then the cam is in the wrong possition, this sounds like like what you did wrong as you said the valves were loose after you just adjusted them.
With the 289 and the 351w heads swap you shouldnt need longer pushrods.

 

[D.Hearne]

Did you have guide plates installed along with the screw in studs ? 7.3" pushrods are WAY too long.

 

[SoCalCruising]

For a guy who has "read every article and called every auto tech in my city" you have indicated a real misunderstanding about how to choose pushrod length. You MUST determine proper pushrod length using conventional methods - an adjustable pushrod checker.

http://www.carcraft.com/techarticles/116_0401_push/index.html

This references a decent article on this topic.

Keep trying to find a knowledgeable person to look over your shoulder when you set up your valvetrain geometry. This is a critical area of engine building.

 

[joemac1000]

Thanks everyone. The article was really informative. I will let you know how it turns out. The reason why I went with a 7.3" pushrod was because the 6.9" (stock) pushrods were not long enough to prevent rubbing the bottom of my rocker arm on top of the stud base. In other words when I tightened up my rocker nuts the arms would bottom out on the stud before my pushrods were relately tight on TDC. I also installed guideplates.

 

[D.Hearne]

Usually when it's necessary to change pushrod length, it's done in smaller steps. Like in plus or minus .060 (about a sixteenth inch) You went almost a half inch in going from 6.9 to 7.3. If you don't use checking pushrods, then try a 6.906 length next time.