380 ci sbc bending exhaust valve

General engine tech -- Drag Racing to Circle Track

Moderator: Team

gsbrown83
New Member
New Member
Posts: 32
Joined: Sun Jun 02, 2019 8:30 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by gsbrown83 »

Roller
F-BIRD'88
Guru
Guru
Posts: 9802
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: 380 ci sbc bending exhaust valve

Post by F-BIRD'88 »

The roller lifters you have may be restricting oil flow up the pushrod.
PRH
Guru
Guru
Posts: 1501
Joined: Fri Sep 08, 2017 4:16 pm
Location: S. Burlington, Vt.

Re: 380 ci sbc bending exhaust valve

Post by PRH »

Might be something here you could use:

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=56757
Somewhat handy with a die grinder.
Kirk600
New Member
New Member
Posts: 10
Joined: Wed Apr 17, 2019 9:36 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by Kirk600 »

PRH wrote: Wed Jun 19, 2019 2:48 pm Might be something here you could use:

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=56757
That's a pretty interesting read, thanks
gsbrown83
New Member
New Member
Posts: 32
Joined: Sun Jun 02, 2019 8:30 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by gsbrown83 »

Problem seems to be solved. Our engine builder re assembled the motor and got us into a Dyno shop. Upon warming the engine up on Dyno setting timing etc. They wanted to take valve covers off and inspect for oiling. We we're shocked when we took the covers off and after running for 2-3 minutes the top of heads were dry. So we fired the motor with the covers off and oil barely trickled out of the pushrods on both heads. We went back through all old receipts to make sure it had all original part numbers in it. Then called dart and talked to there techline. They said the lifter to lifter bore clearance has to be to tight. Recommend cutting a two thousanths of an inch groove from oil band to oiling hole in lifter. Did that to all lifters fired the motor oils like crazy. Two weeks at track has ran perfect. Dart said comp has probably made a design change and not changed part number. Looking at them they look identical but obviously 2 thousandths to big which caused our problems thanks for the help guys
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: 380 ci sbc bending exhaust valve

Post by prairiehotrodder »

that would be a hard thing to figure out. I hope its fixed. I wonder how many other guys have had the same problem ? I'd like to see a picture so i can understand exactly where you made the cut.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
Schurkey
HotPass
HotPass
Posts: 1858
Joined: Sun Mar 01, 2009 2:42 am
Location: The Seasonally Frozen Wastelands

Re: 380 ci sbc bending exhaust valve

Post by Schurkey »

Reminds me of "Edge Orifice" flat-tappet lifters from Chevy...about forty years ago. They were suggested for roller rockers only, as I recall.

The Chevy Power books talked about grinding a flat on the side of the lifter from oil band to the oil entry hole in the lifter side (which is usually IN the oil band, but not on the Edge Orifice lifters) if additional top-end lube was desired.

The Edge Orifice lifters were said to reduce oil flow to the top end to a trickle, which somehow wasn't supposed to lead to overheated valve springs. The primary benefit was oil pressure/volume directed to crankshaft instead of rocker arms.
gsbrown83
New Member
New Member
Posts: 32
Joined: Sun Jun 02, 2019 8:30 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by gsbrown83 »

We are fairly positive it's fine now. It never lasted this long and seeing if run with no oil to the top we we're assured that was what was overheating the valve/ guide. It's like anything else now days just bcz it's new doesn't mean it's good
PRH
Guru
Guru
Posts: 1501
Joined: Fri Sep 08, 2017 4:16 pm
Location: S. Burlington, Vt.

Re: 380 ci sbc bending exhaust valve

Post by PRH »

Is what was preventing adequate oil flow to the top end a secret?
Somewhat handy with a die grinder.
gsbrown83
New Member
New Member
Posts: 32
Joined: Sun Jun 02, 2019 8:30 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by gsbrown83 »

Darts techline told us that it had to be the lifter to lifter bore clearance was to tight. They said on all there big blocks they have a tech bulletin to cut relief slots in the lifters but have never seen it on sbc. We did exactly like they said 2 thousandths of an inch from oiling hole to oil band and it fixed it. So it's a issue with the lifter outer diameter being a touch to big.
allencr267
Pro
Pro
Posts: 362
Joined: Wed Nov 07, 2012 6:28 pm
Location: Tallahassee Florida USofA

Re: 380 ci sbc bending exhaust valve

Post by allencr267 »

Are there sharp edges on the lifter bore's lube ports and the lifter's band?
Never been deburred/wire brushed/radiused?

dart... ...techline. They said ... bore clearance... ... a two thousanths of an inch groove...

Thanks for the update, I shudder to think what 3 thou would do. :?
PRH
Guru
Guru
Posts: 1501
Joined: Fri Sep 08, 2017 4:16 pm
Location: S. Burlington, Vt.

Re: 380 ci sbc bending exhaust valve

Post by PRH »

gsbrown83 wrote: Tue Jul 02, 2019 4:56 pm Darts techline told us that it had to be the lifter to lifter bore clearance was to tight. They said on all there big blocks they have a tech bulletin to cut relief slots in the lifters but have never seen it on sbc. We did exactly like they said 2 thousandths of an inch from oiling hole to oil band and it fixed it. So it's a issue with the lifter outer diameter being a touch to big.
I’m not exactly sure I have it right.......
you put a .002” deep groove in the lifter body connecting the oil band to the pushrod feed hole?
Somewhat handy with a die grinder.
ClassAct
Guru
Guru
Posts: 1024
Joined: Wed Dec 05, 2018 11:55 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by ClassAct »

PRH wrote: Tue Jul 02, 2019 5:45 pm
gsbrown83 wrote: Tue Jul 02, 2019 4:56 pm Darts techline told us that it had to be the lifter to lifter bore clearance was to tight. They said on all there big blocks they have a tech bulletin to cut relief slots in the lifters but have never seen it on sbc. We did exactly like they said 2 thousandths of an inch from oiling hole to oil band and it fixed it. So it's a issue with the lifter outer diameter being a touch to big.
I’m not exactly sure I have it right.......
you put a .002” deep groove in the lifter body connecting the oil band to the pushrod feed hole?


That's how I understood what he is saying. I mean, dang...if the lifter is that tight in the bore that would make me nervous.
PRH
Guru
Guru
Posts: 1501
Joined: Fri Sep 08, 2017 4:16 pm
Location: S. Burlington, Vt.

Re: 380 ci sbc bending exhaust valve

Post by PRH »

We had a puller motor in the shop a couple years ago.
Sbc, blower, roller, etc.
Customer bought the short block assembled, put the rest together himself, went to prime it........ no oil out of one pushrod.
Primed and primed and primed...... turned motor over, etc...... not a drop.
Swapped rockers and pushrods with another hole........ still nuthin.

Had 20/50 in it....... drained and put 5/30 in...... still nothing.

Brings motor in...... after verifying the stuff he tried, pulled intake off.
Swapped lifters with another pair, still nothing.

That one hole only had a couple tenths clearance to the lifter....... oil couldn’t get from the band to the feed hole.

All the bores were tighter than they should be....... but that one was extra tight.
Somewhat handy with a die grinder.
gsbrown83
New Member
New Member
Posts: 32
Joined: Sun Jun 02, 2019 8:30 pm
Location:

Re: 380 ci sbc bending exhaust valve

Post by gsbrown83 »

Prh that's exactly what they ended up doing a 2 thousandths groove from oiling hole to oiling band. Fixed it both engine builders said by feel the lifters felt great not to tight they would have never thought that's what it was. They are comp cam lifters I will have to get part number later
Post Reply