SBC cam help

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Ericnova
Pro
Pro
Posts: 231
Joined: Tue Jan 01, 2008 2:56 am
Location: Southern Michigan

Re: SBC cam help

Post by Ericnova »

You could have avoided all the clearancing and offset lifter hassle, valve pocket hassle if he had just bought the 220cc instead.
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: SBC cam help

Post by CGT »

The picture of that piston indicates something went wrong in the notching process, that is not the direction of the 60-40 spacing. Most I've had to do was nothing near that radical or out of place. Turn an old valve down to a center punch, punch piston at, and around tdc through the valve guide, measure your valve diameter out from punch mark average with a protractor etc from there. You shouldn't be anywhere in the neighborhood of that notch you made.
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: SBC cam help

Post by prairiehotrodder »

sounds like some good advice here. The offset lifters and better pushrods especially should be done. Don't know what to say about my notch. Its done with the piston at TDC with a cutter that goes through the exhaust guide. The pistons are just Cheap forged ICON flat tops obviously not made for the 60/40 deal. The plan was to use this 383 shortblock for a season then build a more dedicated 427 next winter.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
User avatar
MadBill
Guru
Guru
Posts: 15024
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: SBC cam help

Post by MadBill »

What ~TDC exhaust lift does this engine have with the cam indexed as intended? Besides being wildly displaced from the factory notch location :-k , your notch looks hugely deep. How much crown thickness remains under it?
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: SBC cam help

Post by prairiehotrodder »

My friend went ahead and ordered some pushrods and lifters from Chris Straub so hopefully we can get this sorted out asap. Supposed to race this weekend!
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
gnicholson
Pro
Pro
Posts: 482
Joined: Tue May 06, 2008 9:59 pm
Location: kansas city mo

Re: SBC cam help

Post by gnicholson »

The valve notch should be made at the crank angle where the valve comes closest to the piston not tdc
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: SBC cam help

Post by prairiehotrodder »

gnicholson wrote: Tue May 22, 2018 6:21 pm The valve notch should be made at the crank angle where the valve comes closest to the piston not tdc
I considered doing it that way. That would have required a smaller notch but it would have been even farther from the factory notch which wouldn't have mattered i guess. My instructions just said to do it at TDC and that was easiest so thats what i did. I did a .125 deep notch because we had zero p-v clearance and the cam instructions called for a minimum of .100 clearance on the exhaust valve and .080 on the intake.
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: SBC cam help

Post by Walter R. Malik »

prairiehotrodder wrote: Tue May 22, 2018 6:48 pm
gnicholson wrote: Tue May 22, 2018 6:21 pm The valve notch should be made at the crank angle where the valve comes closest to the piston not tdc
I considered doing it that way. That would have required a smaller notch but it would have been even farther from the factory notch which wouldn't have mattered i guess. My instructions just said to do it at TDC and that was easiest so thats what i did. I did a .125 deep notch because we had zero p-v clearance and the cam instructions called for a minimum of .100 clearance on the exhaust valve and .080 on the intake.
Brian
That is an aftermarket piston and they usually don't exactly mimic the factory valve notches. Usually they are made considerably larger to be able to accept any over size valve diameter for that engine.
http://www.rmcompetition.com
Specialty engine building at its finest.
User avatar
MadBill
Guru
Guru
Posts: 15024
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: SBC cam help

Post by MadBill »

In this case, it appears the notches were not a match for the valve location(s) :-k

Also, assuming the radial clearance is adequate, 5° CA either way should not affect the location enough to be a concern.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
user-17438

Re: SBC cam help

Post by user-17438 »

cstraub wrote: Mon May 21, 2018 2:01 pm To run those heads you need an offset lifter. If you don't the side loading the lifter will experience will take out the needle bearings very quickly. Can't use a hyd roller lifter as you can't have an offset pushrod seat in the lifter.

If running OEM .842" Diameter with a .750" wheel, I highly recommend a bushing style roller assemble. If not, it is not a question of "if" it is going to come apart but "when".

Note I see it is now a solid roller. .750 wheel I highly recommend a bushing lifter when using OEM sized lifters. If not, it will wear out parts. Second based on head CS and the camshaft this thing is going to be spun. You need a heavy wall 3/8" pushrod minimum in this thing to get any type of reliability out of it. The offset lifter will help with larger pushrods. Need a 210 radius also with shaft rockers.

Also that head is a 60/40 valve spacing. It requires pistons specific to that spacing.
'
Why is a heavy wall 3/8 needed with under .650" and why would the need for a 210 radius on shaft rockers with specified cam? also. why is a bushing a must? asking for a friend.
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: SBC cam help

Post by prairiehotrodder »

MTENGINES wrote: Wed May 23, 2018 6:34 am
cstraub wrote: Mon May 21, 2018 2:01 pm To run those heads you need an offset lifter. If you don't the side loading the lifter will experience will take out the needle bearings very quickly. Can't use a hyd roller lifter as you can't have an offset pushrod seat in the lifter.

If running OEM .842" Diameter with a .750" wheel, I highly recommend a bushing style roller assemble. If not, it is not a question of "if" it is going to come apart but "when".

Note I see it is now a solid roller. .750 wheel I highly recommend a bushing lifter when using OEM sized lifters. If not, it will wear out parts. Second based on head CS and the camshaft this thing is going to be spun. You need a heavy wall 3/8" pushrod minimum in this thing to get any type of reliability out of it. The offset lifter will help with larger pushrods. Need a 210 radius also with shaft rockers.

Also that head is a 60/40 valve spacing. It requires pistons specific to that spacing.
'
Why is a heavy wall 3/8 needed with under .650" and why would the need for a 210 radius on shaft rockers with specified cam? also. why is a bushing a must? asking for a friend.
The new cam is a comp 12-863-9 with nearly .650 lift.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: SBC cam help

Post by CGT »

prairiehotrodder wrote: Wed May 23, 2018 10:20 am The new cam is a comp 12-863-9 with nearly .650 lift.
That cam appears to use TK lobes. Those lobes are vtp clearance eaters, and "other thing" eaters if your not careful.
prairiehotrodder
Guru
Guru
Posts: 1602
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: SBC cam help

Post by prairiehotrodder »

Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
steve cowan
Guru
Guru
Posts: 2253
Joined: Wed Jul 27, 2011 5:22 am
Location: brisbane AUSTRALIA

Re: SBC cam help

Post by steve cowan »

prairiehotrodder wrote: Sat May 26, 2018 10:40 pm Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.
i think the 227 will be nice on the 427sbc
personally the biggest valve i will use on a 4.030 bore is a 2.05'' after that there is alot of valve shrouding going on and i dont have the experience to make a 2.08 valve work correctly,i am not saying it cant be done,i am am saying i have not done it.
doesnt the 227 head have a 2.10'' intake valve ??
383 ci @ 7000 rpm is looking at 2.61'' MCSA
the 227 afr has a MCSA of 2.340'' so you would think it should work but it looks like not the case here probably due to big intake valve,bigger and slower intake runner and not enough time (rpm) to make it work,there is alot more to the whole package but this is just my observation regarding the 227 head
steve c
"Pretty don't make power"
GARY C
HotPass
HotPass
Posts: 6301
Joined: Tue May 14, 2013 10:58 pm
Location:

Re: SBC cam help

Post by GARY C »

steve cowan wrote: Sun May 27, 2018 2:21 am
prairiehotrodder wrote: Sat May 26, 2018 10:40 pm Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.
i think the 227 will be nice on the 427sbc
personally the biggest valve i will use on a 4.030 bore is a 2.05'' after that there is alot of valve shrouding going on and i dont have the experience to make a 2.08 valve work correctly,i am not saying it cant be done,i am am saying i have not done it.
doesnt the 227 head have a 2.10'' intake valve ??
383 ci @ 7000 rpm is looking at 2.61'' MCSA
the 227 afr has a MCSA of 2.340'' so you would think it should work but it looks like not the case here probably due to big intake valve,bigger and slower intake runner and not enough time (rpm) to make it work,there is alot more to the whole package but this is just my observation regarding the 227 head
The AFR 227 I dealt with for a 421 had a 2.100, they were pre eleminator versions.
Here is a simple method Vizard taught me for unshrouding valves consistently.
https://www.speed-talk.com/forum/viewtopic.php?f=1&t=46308
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
Post Reply