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Yes the shoulder style are best. Typically, the pushrod holes are drilled open, the rocker arm stud bosses are cut down and guideplates are added. Its not an expensive operation but it is a requirement to upgrade pressed in studs. I have a set at the machine shop getting this done right now. Should be finished today.
L-46 did not get screw in studs originally but when the LT-1 came out in 1970, they got the screw in studs. The studs were pulling out in higher RPM applications so they were needed. The L-82 replaced the L-46 and used the same cam as the L-46 so the L-82 got the screw in studs as well.
Last edited by stingr69; Apr 23, 2021 at 07:33 AM.
I have run .480 lift on small blocks with press in studs for 30 years or better......no issues.......BUT, no more than 120 on the seat and 320 over the nose....which coincidentally is what the Elgin "Z/28" spring is......
Another point is to not run a modern FT cam with high ramp rate.....use an older grind like the 268H.....or the Elgin E-1784-P 230/230 .480/.480......
A buddy with a bridgeport can convert a pair of heads in about two hours with the right tool...cast iron is easy to machine.....from there you just tap 16 holes and done.....and I have power tapped cast iron as well.....once you have the head setup on the table at the right angle.....the rest is cake.
Lift is not a huge concern with stock "186" heads. The springs will run out of lift before the heads will. Stock valve spring pockets and retainers measure out at about 1.75" so if your springs will accomodate the valve lift with enough safety margin, you will be fine. You can get retainers that set up a little bit higher if needed. Valve spring pockets can be opened up for larger diameter springs but there are plenty of springs out there that will fit the stock pockets.
Later stock Vortec heads are lift limited but the guide bosses can be cut down to fix that.
These 186 heads have had the bare minimum modifications done to them. In my opinion, you always want bronze guides, screw-in studs and guideplates. This also allows you to run positive valve stem seals and loose the HEAVY stock retainers and steel umbrellas. Any other mods are optional. You can see the machined pads and pushrod holes below.
186 head with bronze guides, cut and tapped for screw-in studs, and pushrod holes drilled open to use guideplates.
These heads also have GM swirl polished SHP valves in them. (Not a requirement)
Yes the shoulder style are best. Typically, the pushrod holes are drilled open, the rocker arm stud bosses are cut down and guideplates are added. Its not an expensive operation but it is a requirement to upgrade pressed in studs. I have a set at the machine shop getting this done right now. Should be finished today.
L-46 did not get screw in studs originally but when the LT-1 came out in 1970, they got the screw in studs. The studs were pulling out in higher RPM applications so they were needed. The L-82 replaced the L-46 and used the same cam as the L-46 so the L-82 got the screw in studs as well.
Originally Posted by Jebbysan
I have run .480 lift on small blocks with press in studs for 30 years or better......no issues.......BUT, no more than 120 on the seat and 320 over the nose....which coincidentally is what the Elgin "Z/28" spring is......
Another point is to not run a modern FT cam with high ramp rate.....use an older grind like the 268H.....or the Elgin E-1784-P 230/230 .480/.480......
A buddy with a bridgeport can convert a pair of heads in about two hours with the right tool...cast iron is easy to machine.....from there you just tap 16 holes and done.....and I have power tapped cast iron as well.....once you have the head setup on the table at the right angle.....the rest is cake.
Jebby
Thanks both
I was thinking about installing the heads on a 1973 Z28 engine.
The engine is a 9:1 in compression, and as I understand it, the only difference, between the 2 heads are the chamber size, I will from from 76ccc to 64cc with the 186 heads.
So I will bump up the compression to 10
I do have a new set of Elgin Z28 springs in stock, but also lifters and 1.5 rocker arms, all new, and from Elgin.
But I also have a brand new L46 camshaft, GM number 3896962 please see below.
What will be the effect of using the parts, in the engine, will they work "good together"?
Regarding the camshaft, I assume it this one.
Will that be a better solution??
Lift is not a huge concern with stock "186" heads. The springs will run out of lift before the heads will. Stock valve spring pockets and retainers measure out at about 1.75" so if your springs will accomodate the valve lift with enough safety margin, you will be fine. You can get retainers that set up a little bit higher if needed. Valve spring pockets can be opened up for larger diameter springs but there are plenty of springs out there that will fit the stock pockets.
Later stock Vortec heads are lift limited but the guide bosses can be cut down to fix that.
These 186 heads have had the bare minimum modifications done to them. In my opinion, you always want bronze guides, screw-in studs and guideplates. This also allows you to run positive valve stem seals and loose the HEAVY stock retainers and steel umbrellas. Any other mods are optional. You can see the machined pads and pushrod holes below.
186 head with bronze guides, cut and tapped for screw-in studs, and pushrod holes drilled open to use guideplates.
These heads also have GM swirl polished SHP valves in them. (Not a requirement)
They should work Great together. You will almost have exactly duplicated the L46. Do you have the 73 Z28 cast iron manifold and quadrajet as well? Or going aftermarket? A good running quadrajet works terrific on this engine.
Crane has a duplicate of the OEM L46 cam and they rate it at 224/224 at ..450/.459 lift and a 114 LC. RPM range of 2000 to 5600. WIth a 10:1 CR you should wind up with 8.0 - 8.2 DCR about perfect.
The Elgin is a little hotter at 230/230 at .480 lift and a much tighter 109 LC. Says lopey idle, 2200-5400 but great power from 3000-6000.
So the L46 will have better all around street manners, broad powerband, idle with a little lope, good low end TQ, etc.
The Elgin 109 LC especially and +6 duration means it gives up a lot on the bottom end <3000, strong lopey idle, but pulls better and longer upstairs. With the Elgin you may want higher static CR to keep your DCR over 8.0. The 109 LC makes it a little bit of a racey sounding / feeling cam.
Your choice depending on what you are looking for. Some people "need" a bad-*** idle, others don't. Looking for an all around street car? Or reving and racing it a lot? Personally the L46 is one of my all time favorite Chevy engines, for good reason,. And I owned an LT-1 for 27 years, that's another. Just changing your idle rpm 100 or so changes the way it sounds at idle anyway.
I was thinking about installing the heads on a 1973 Z28 engine.
The engine is a 9:1 in compression, and as I understand it, the only difference, between the 2 heads are the chamber size, I will from from 76ccc to 64cc with the 186 heads.
So I will bump up the compression to 10
I do have a new set of Elgin Z28 springs in stock, but also lifters and 1.5 rocker arms, all new, and from Elgin.
But I also have a brand new L46 camshaft, GM number 3896962 please see below.
What will be the effect of using the parts, in the engine, will they work "good together"?
Regarding the camshaft, I assume it this one.
Will that be a better solution??
Perfect. I run a setup simmilar with the 962 cam in my Vette. Find the FelPro thin steel shim head gasket if you still have not decked the block yet. Zero decked blocks can use the thick composite gasket that already comes with the gasket set. You want about .035" - .040" quench height ideally for detonation resistance.
They should work Great together. You will almost have exactly duplicated the L46. Do you have the 73 Z28 cast iron manifold and quadrajet as well? Or going aftermarket? A good running quadrajet works terrific on this engine.
Crane has a duplicate of the OEM L46 cam and they rate it at 224/224 at ..450/.459 lift and a 114 LC. RPM range of 2000 to 5600. WIth a 10:1 CR you should wind up with 8.0 - 8.2 DCR about perfect.
The Elgin is a little hotter at 230/230 at .480 lift and a much tighter 109 LC. Says lopey idle, 2200-5400 but great power from 3000-6000.
So the L46 will have better all around street manners, broad powerband, idle with a little lope, good low end TQ, etc.
The Elgin 109 LC especially and +6 duration means it gives up a lot on the bottom end <3000, strong lopey idle, but pulls better and longer upstairs. With the Elgin you may want higher static CR to keep your DCR over 8.0. The 109 LC makes it a little bit of a racey sounding / feeling cam.
Your choice depending on what you are looking for. Some people "need" a bad-*** idle, others don't. Looking for an all around street car? Or reving and racing it a lot? Personally the L46 is one of my all time favorite Chevy engines, for good reason,. And I owned an LT-1 for 27 years, that's another. Just changing your idle rpm 100 or so changes the way it sounds at idle anyway.
Thanks
That is GREAT :- )
It started by, "I want to install a new chain set", then I thought, well I also have a Edelborck 2701 intake, lets put that on also.
To now where I also find my camshaft, lifters, rockerarm (and chain set) have have in stock.
So the only thing I have to buy, it a set of Fel Pro 1094 (I also have Fel pro 1204 in stock :- )
Yes it is a factory 1973 Z28 engine, that I have in my 1973 Z28 RS
Perfect. I run a setup simmilar with the 962 cam in my Vette. Find the FelPro thin steel shim head gasket if you still have not decked the block yet. Zero decked blocks can use the thick composite gasket that already comes with the gasket set. You want about .035" - .040" quench height ideally for detonation resistance.
Thanks
I will go for 1094 head gasket, the block has not been decked yet.
This is just great, I can use a lot of parts I have in stock, that is nice :- ))
Sure I will hit .035 - ,040 in quench for sure, I HATE ping :- )
Here’s a thought. There used to be a tool available that slipped over the stud and gave you a hole that acted as a guide to drill the boss and stud. Then you hammered a pin in to hold it. It was called drill and pin. I haven’t seen one in a long time but you might check around. Cheap and very effective.
John,
Be sure to get some HARDENED pushrods to use with the guideplates. The stock length pushrods should be fine but any time you run guideplates you need the better parts.
Here’s a thought. There used to be a tool available that slipped over the stud and gave you a hole that acted as a guide to drill the boss and stud. Then you hammered a pin in to hold it. It was called drill and pin. I haven’t seen one in a long time but you might check around. Cheap and very effective.
Thanks
Originally Posted by stingr69
John,
Be sure to get some HARDENED pushrods to use with the guideplates. The stock length pushrods should be fine but any time you run guideplates you need the better parts.
Thanks, yes for sure I will use guide plates, and some hardende pushrods, thanks for the advice !!
I was thinking,with the GM cam, and a set of 1.6 rocker arms I have in stock, will that be too much?? (with the Z28 springs)
It will be 0.490 on the exhaust.
Those "Z/28" springs were originaly designed for the "first design off-road" cam. The stock Z/28 used the same valve springs as every other small block Chevy. You can add some extra RPM capability using those springs with the "962" cam. The higher ratio rockers increases the spring requirements so you already have it covered.
I was thinking,with the GM cam, and a set of 1.6 rocker arms I have in stock, will that be too much?? (with the Z28 springs)
It will be 0.490 on the exhaust.
Don’t forget with stock GM heads going to 1.6 rocker will probably require opening up the pushrod hole or pushrod will rub the head.
John,
FYI - The pushrods in your parts photo are not guide plate compatible. They have the ball ends which are not reliable and more important, they are not hardened for guide plate usage.
