rocker arm broke
- Thread starter johnnyrod
- Start date
In view of the other problems you have had with the valve train I would think that the rocker arms would be pretty much beat up! With this in mind I would not let this be a concern. Aftermarket rockers are weak and stock exhaust rockers would go first. Replace the rocker and move on, no the stock rockers were not prone to breakage.
John,I would get rid of your stamped rockers and replace them with Roller tip rockers IMO 
BB Chevy 1.72 ratio, 7/16 stud.
Mr Goodwrench
Well Known Member
you will have to use some sleeves unless you have upgraded you rocker studs to 7/16" DQ posted a picture of them once I think.
Show Cars also sell rockers for 3/8" rocker studs.
I copied this from Show Cars catalog,Internal Engine section
ROCKER ARMS 03.370
Manufactured by Elgin, Comp Cams, Scorpion, Angus & Crane.
*Steel shoe stock type, guaranteed unbreakable.
3354 348/409 rocker arm, bolt, and nut assembly*... Set $107.12
3354A 348/409 rocker arm bolt, and nut assembly*... Ea. $8.92
5460A 348/409 Comp Cams roller tip rocker arms for 7/16 studs (16)... Set $190.00
5460 348/409 Comp-Cams roller tip rocker arms for 3/8 studs (16)... Set $234.00
Note: when installing roller rockers on a 348 or 409 you must machine the stud boses and install screw-in studs.
5823 348/409 Scorpion 3/8" Roller Rocker 1.75 ratio... Set $232.97
5824 348/409 Scorpion 7/16" Roller Rocker 1.75 ratio... Set $232.97
6719 Scorpion 7/16 big block roller rocker 1.70 ration... Set $218.94
6720 Scorpion 7/16 big block roller rocker 1.80 ration... Set $237.97
6738 348/409 Scorpion 3/8 stud, 1.70 ratio roller rockers... Set $232.97
6937 34/409 Angus 3/8" Roller Rocker 1.75 ratio... Set $199.00
6938 348/409 Angus 7/16" Roller Rocker 1.75 ratio... Set $199.00
6068 348/409 Crane Gold Race roller rocker arms for 3/8 studs... Set $Call Special Order
ROCKER ARMS 03.370
Manufactured by Elgin, Comp Cams, Scorpion, Angus & Crane.
*Steel shoe stock type, guaranteed unbreakable.
3354 348/409 rocker arm, bolt, and nut assembly*... Set $107.12
3354A 348/409 rocker arm bolt, and nut assembly*... Ea. $8.92
5460A 348/409 Comp Cams roller tip rocker arms for 7/16 studs (16)... Set $190.00
5460 348/409 Comp-Cams roller tip rocker arms for 3/8 studs (16)... Set $234.00
Note: when installing roller rockers on a 348 or 409 you must machine the stud boses and install screw-in studs.
5823 348/409 Scorpion 3/8" Roller Rocker 1.75 ratio... Set $232.97
5824 348/409 Scorpion 7/16" Roller Rocker 1.75 ratio... Set $232.97
6719 Scorpion 7/16 big block roller rocker 1.70 ration... Set $218.94
6720 Scorpion 7/16 big block roller rocker 1.80 ration... Set $237.97
6738 348/409 Scorpion 3/8 stud, 1.70 ratio roller rockers... Set $232.97
6937 34/409 Angus 3/8" Roller Rocker 1.75 ratio... Set $199.00
6938 348/409 Angus 7/16" Roller Rocker 1.75 ratio... Set $199.00
6068 348/409 Crane Gold Race roller rocker arms for 3/8 studs... Set $Call Special Order
Mad Dog Racing
This is about the right price. 409 chevy.
I think Ford 1.7 3/8 shaft will also fit. Anybody know for shure jump in here.
http://cgi.ebay.com/ebaymotors/Scor...ryZ33624QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
This is about the right price. 409 chevy.
I think Ford 1.7 3/8 shaft will also fit. Anybody know for shure jump in here.
http://cgi.ebay.com/ebaymotors/Scor...ryZ33624QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
models.thats a good price.
unclebrad
Active Member
Main question:
• How would I go about identifying the broken rocker arm from my engine and finding a single one arm to replace it? (Picture below.)
Background:
Since my last post in Oct 2021, I did get the engine running but not long afterward, she started popping and screeching one day, while warming up in the driveway, so I shut her down. I drained the oil to check for metal and, although it was fairly clean, an extra quart came out and the oil smelled very strongly of gas. (When I purchased this engine, it had just been rebuilt, and it is still in the break-in phase, so I was not surprised to see a little metal suspended in the oil, but there were no "bits" in the bottom of the pan.) Apparently, the carbs had been draining into the crankcase after driving, adding a quart to the oil after a few weeks of that.
At that time, I pulled off the valve covers and found some very loose rocker arms. A buddy came over one day and we re-adjusted the rockers and put in new oil and filter. Oddly, it fired up and seemed ok, but there were now massive clouds of smoke coming out of the tailpipes.
Damn.
So, it has been sitting in the garage for almost a year. I haven’t been able to bring myself to work on it until today, when a couple friends came over to try to get me going on it again. In addition to loose rocker arms (again), we found a couple things that we hadn’t seen before, one being a broken rocker arm. (cyl #6)
• Any ideas about what would cause this?
• Is there any way this rocker arm can be identified, and a single one purchased to replace it or do I need to replace them all?
• If I have to replace them all, can you recommend good ones? (I see that it has been a couple years since the last comment in this thread, but roller tips were suggested as an upgrade? Would that still be a recommendation, and is it a straight swap with no other changes?
Another thing –
During today’s session, after cranking the engine (coil lead off) until after the gauge was reading 50lbs, we didn’t see any oil coming to the rockers. Could be just because it has been sitting a while, and needs more cranking.
• Are there other possible reasons?
Thanks!
• How would I go about identifying the broken rocker arm from my engine and finding a single one arm to replace it? (Picture below.)
Background:
Since my last post in Oct 2021, I did get the engine running but not long afterward, she started popping and screeching one day, while warming up in the driveway, so I shut her down. I drained the oil to check for metal and, although it was fairly clean, an extra quart came out and the oil smelled very strongly of gas. (When I purchased this engine, it had just been rebuilt, and it is still in the break-in phase, so I was not surprised to see a little metal suspended in the oil, but there were no "bits" in the bottom of the pan.) Apparently, the carbs had been draining into the crankcase after driving, adding a quart to the oil after a few weeks of that.
At that time, I pulled off the valve covers and found some very loose rocker arms. A buddy came over one day and we re-adjusted the rockers and put in new oil and filter. Oddly, it fired up and seemed ok, but there were now massive clouds of smoke coming out of the tailpipes.
Damn.
So, it has been sitting in the garage for almost a year. I haven’t been able to bring myself to work on it until today, when a couple friends came over to try to get me going on it again. In addition to loose rocker arms (again), we found a couple things that we hadn’t seen before, one being a broken rocker arm. (cyl #6)
• Any ideas about what would cause this?
• Is there any way this rocker arm can be identified, and a single one purchased to replace it or do I need to replace them all?
• If I have to replace them all, can you recommend good ones? (I see that it has been a couple years since the last comment in this thread, but roller tips were suggested as an upgrade? Would that still be a recommendation, and is it a straight swap with no other changes?
Another thing –
During today’s session, after cranking the engine (coil lead off) until after the gauge was reading 50lbs, we didn’t see any oil coming to the rockers. Could be just because it has been sitting a while, and needs more cranking.
• Are there other possible reasons?
Thanks!
Another possibility is how high is the lift of your cam? Chevy made long slot rockers for HP SBC's and BBC's for a reason, inspect your rocker studs for witness marks. Where yours broke is right where the rocker would run into the stud. As far as the smoke, if there was contact in the valvetrain causing the failure it may have wiped out your valve stem seals. If so I would be inspecting everything under the valve covers checking for spring coil bind, retainer to guide contact and condition of guides and seals. It will require removal of the valve springs, but can be done in the car 1 cylinder at a time.