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Update - The windage tray is on and the balancer needs attention.
GM never used flat washers under the prevailing torque windage tray nuts but I have added some. If you do not use washers, the nuts will tear metal shards from the sheet metal windage tray when you tighten them up. Just can't live with that.
The nice 8" damper (balancer) has a very typical wear groove on the nose from riding on the lip of the front cover seal. Not a big deal but it does need to have a sleeve pressed on to repair it good as new.
My wife has left for work so I sneaked into her sewing basket and pilfered her cloth measuring tape. The damper measured out to be 25.25" in circumference. If you divide that measurement by 10 you will get 2.525" which is actually 36 degrees on the damper. (360 degrees/10 = 36 degrees)
Measure to the right of the "0" mark on the damper 2.525" and place a mark there.
You can use this new mark to set your timing at 36 degrees at the top of the advance curve. Poor mans degreed damper. If you have the smaller damper, the method is the same but the dimensions are different.
To check the chamber sizes, a glass burette and a piece of plexiglass comes in handy. The valves get a light coat of assembly grease to seal them up and the flat surface of the head needs it too. Need to install a spark plug. I used a clamp but it isn't always required. The plexiglass has a hole in it that needs to be positioned so all the air will be forced out as the water fills the chamber. Fill the chamber with water and read the burette to see how much water fit in the chamber. These factory big valve heads are usually quoted as (assumed to be) 64cc's but these here are actually measuring out larger at 67cc's or so. That makes a difference in your compression calculations.
Glass burette. Bought a cheap one online from a scientific supply house years ago.
Grease seals the plexiglass to the head. Water is added through the hole near the top of the intake valve.
Because at 5000 rpm.....a std. volume oil pump requires 4-5 horsepower to turn (as much as the average lawn mower produces TOTAL).....and the hole that it goes through is sloppy so the neoprene collar is the only thing keeping the shaft from walking off the pump drive......and as an added bonus.....after about few thousand heat cycles, this part becomes brittle. I believe that an engine that is designed to rev over 5000 on occasion should have the steel collar shaft.....it is just an engine builder staple at $11 a piece. You can do build it how you see fit but I would change this out. You are all over it by removing the bypass spring for brazing and installing the Z-28 spring, brazing on the pickup and checking for pickup height.....but leave this part stock.
Just an observation and am not bashing in any way......
BTW.....for $6 more dollars you can use a stud to hold on the oil pump and for free you can chamfer the oil port on the main cap for less turbulence at high RPM. I love the stud because it leaves NO way to pull the threads out of the main cap when torquing the bolt....which on old stuff I have seen many times.
Jebby
Jebby,
It's kind of a choice between the devil you know vs the devil you have not met. This oil pump shaft will never see much more than 3500 RPM on a good day...it rotates at half crank speed. The nylon sleeve has been used in literally MILLIONS of GM engines and they have never been failure prone - Even when used in the screaming DZ 302. The top of the shaft fits inside the recess in the bottom of the distributor gear and the other end is held in place by the oil pump and sleeve. Its not going anywhere.
I generally tend to dislike and avoid cheap aftermarket replacement parts because they frequently disappoint me. So much off-shore manufactured crap out there. I know GM spent a LOT of time and money designing and manufacturing these pieces for many years so I sleep well at night knowing the work was done and the parts will fit and function as intended. No pins to fall out, no cheap plating to flake off, No questionable metallurgy with potential for excess wear.... If it works, I don't want to spend money to change it for something that might work and toss out the one that does work. Just how I like to roll.
To check the chamber sizes, a glass burette and a piece of plexiglass comes in handy. The valves get a light coat of assembly grease to seal them up and the flat surface of the head needs it too. Need to install a spark plug. I used a clamp but it isn't always required. The plexiglass has a hole in it that needs to be positioned so all the air will be forced out as the water fills the chamber. Fill the chamber with water and read the burette to see how much water fit in the chamber. These factory big valve heads are usually quoted as (assumed to be) 64cc's but these here are actually measuring out larger at 67cc's or so. That makes a difference in your compression calculations.
Glass burette. Bought a cheap one online from a scientific supply house years ago.
Grease seals the plexiglass to the head. Water is added through the hole near the top of the intake valve.
perhaps those older heads' valves have sunken from a valve job or three... seems the more they sink, the more the volume goes up,
The only difference between a stock GM pump and a high pressure Z/28 pump is the oil pressure spring..
This needs to be changed. I have one that I blue printed in my garage many years ago. The gears are physically wider in the chevy high performance oil pump. I used to completely polish the inside and the gears. Then shim the spring to get a true 10 psi per 1000 rpm's
So the wider gears makes it a higher volume and pressure pump. My present stock 4 bolt higher nickel motor also uses drilled out morroso oil restrictors the make it a priority mains oiling system
perhaps those older heads' valves have sunken from a valve job or three... seems the more they sink, the more the volume goes up,
There could be several reasons. If it is the valves, we could see a correlation between larger measured chambers and higher valve spring heights. These original GM exhaust valves were in great shape and with the new valve job they sit nicely down in the chamber, as I would prefer. The original intakes were replaced because they were getting thin. Not too much recession.
These are the measurements I took before final assembling of the heads.
The chambers are cut for better flow at the factory on 2.02" x 1.60" SHP heads. Never hear anyone tell you how many cc's of metal is removed when the factory cut the chambers around the periphery of the intake valve.
A good amount of metal was hogged out.
I really appreciate a traditional build, were it is kept as close to as was! I squirreled away all kinds of Bow Tie NOS, enough to build two entire GM part number engines as I like F5000, 1980/90s Trans Am or IMSA GTP stuff!
The best identity of the stock parts, is a Chevrolet Parts Number book that I have to go find! It is a series called By The Numbers! I think it is 65-69 and then they have a 70-75, and a 60-64 edition and I think one more. The 65-69 covers the LT-1 also, if I am correct. Will have to go look, but I also have the 70-75 book too!
I have X and O rods, floaters, presses, and both the 91s and the 83s in the 4340 6 inch! I see the X rods called pink rods, but those aren’t! The pinks got shot peened and had 3/8 bolts.
Last edited by TCracingCA; 02-24-2019 at 08:36 PM.
Jebby,
It's kind of a choice between the devil you know vs the devil you have not met. This oil pump shaft will never see much more than 3500 RPM on a good day...it rotates at half crank speed. The nylon sleeve has been used in literally MILLIONS of GM engines and they have never been failure prone - Even when used in the screaming DZ 302. The top of the shaft fits inside the recess in the bottom of the distributor gear and the other end is held in place by the oil pump and sleeve. Its not going anywhere.
I generally tend to dislike and avoid cheap aftermarket replacement parts because they frequently disappoint me. So much off-shore manufactured crap out there. I know GM spent a LOT of time and money designing and manufacturing these pieces for many years so I sleep well at night knowing the work was done and the parts will fit and function as intended. No pins to fall out, no cheap plating to flake off, No questionable metallurgy with potential for excess wear.... If it works, I don't want to spend money to change it for something that might work and toss out the one that does work. Just how I like to roll.
That's cool man.....but I disagree.....there is not an engine builder in this country that uses the nylon sleeve. Melling is a respected USA part and the 55IS is made for a reason.
So for a cost of less than $20.....you can use a premium steel collar shaft, an ARP stud on the oil pump and port the inlet. These are accepted bread and butter parts and mods....and IMHO kinda foolish not to do as they are proven.
BTW....have you ever primed the pump with a drill pre-startup? Ever notice how much drag the drill gets when the oil finally starts pressurizing? 1hp per 1000RPM is what the shaft requires.
Too me that is a lot.....
I don't care what GM ran in their 302 DZ......if something can be made obviously better for next to nothing then why not do it?
Ok.....carry on
Moving on.....are you going to bowl blend and gasket match? A chance for huge gains here. Another thing we found out later was that removing even more material around the intake valve is worth a lot of flow.....it takes advantage of the large valve......hold a head gasket up to the head and scribe to see the difference.
Anyway...nice build.
Moving on.....are you going to bowl blend and gasket match? A chance for huge gains here. Another thing we found out later was that removing even more material around the intake valve is worth a lot of flow.....it takes advantage of the large valve......hold a head gasket up to the head and scribe to see the difference.
Anyway...nice build.
Jebby
Jebby,
No grinding initially. Maybe after the build is shaken out and I get tired of it.
Moving on.....are you going to bowl blend and gasket match? A chance for huge gains here. Another thing we found out later was that removing even more material around the intake valve is worth a lot of flow.....it takes advantage of the large valve......hold a head gasket up to the head and scribe to see the difference.
Anyway...nice build.
Jebby
If you can find a 4.00 or 4.030 bore gasket. You open up the casting below the valves to the diameter of the seat material and radius into the port
You can buy cam Valley vent tubes that eliminates the windage of all the oil pouring down on the crank
That's cool man.....but I disagree.....there is not an engine builder in this country that uses the nylon sleeve. Melling is a respected USA part and the 55IS is made for a reason.
So for a cost of less than $20.....you can use a premium steel collar shaft, an ARP stud on the oil pump and port the inlet. These are accepted bread and butter parts and mods....and IMHO kinda foolish not to do as they are proven.
BTW....have you ever primed the pump with a drill pre-startup? Ever notice how much drag the drill gets when the oil finally starts pressurizing? 1hp per 1000RPM is what the shaft requires.
Too me that is a lot.....
I don't care what GM ran in their 302 DZ......if something can be made obviously better for next to nothing then why not do it?
Ok.....carry on
Jebby
But when you think that GM made millions correct is not good. Corporate design is with planned failures. For instance, I had a 76 with the cheap junk nylon timing gear and it wore away and finally broke. The cam chain was also such cheap junk that it was all strethed out. GM WAS never looking out for you. Planned obsolescence was the company model.
Looks like the actual measured chambers negates the need to retard the cam. With all the measurements and adjustments taken into consideration the DCR will be 8.21 with the cam timed "as ground". Going back to the zero offset bushing and wrenching on with it.
If you can find a 4.00 or 4.030 bore gasket. You open up the casting below the valves to the diameter of the seat material and radius into the port
You can buy cam Valley vent tubes that eliminates the windage of all the oil pouring down on the crank
George,
I know you have spent a lot of time at the track. I have heard that road race SBCs would need to run about 1 quart over full for hot laps with the factory pan, pump and baffle setup. Can you confirm? For my street car the oil drain back is probably not going to be much of an issue but actual track experience is quite different.
If I were headed to the track I would probably spend a lot of time focusing on the oil drain back concerns. Tubes, glyptal paint, grinding to smooth the return passages, etc.
George,
I know you have spent a lot of time at the track. I have heard that road race SBCs would need to run about 1 quart over full for hot laps with the factory pan, pump and baffle setup. Can you confirm? For my street car the oil drain back is probably not going to be much of an issue but actual track experience is quite different.
If I were headed to the track I would probably spend a lot of time focusing on the oil drain back concerns. Tubes, glyptal paint, grinding to smooth the return passages, etc.
Yes, way back when I had my 355 ci with "186" casting double hump heads. In a sustained high "G" turn I would get my oil pressure light flickering red. Adding an extra quart is something I tried. I went to 7 quart kick out road racing pan and used to run an extra quart because my oil pressure light would flicker. During a historic event a few guys came into the pits with rod knock from oil starvation at our local 4.2 mile road racing track and it scared me enough that I bought an Accusump 4 quart system.
Accusump can also pressurize your oiling system just before you turn on the key. the 4 quart is kinda over kill. At the shop we usually installed a 2-3 quart on non dry sumped American V-8 motors
02-22-2019, 10:04 AM
But when you think that GM made millions correct is not good. Corporate design is with planned failures. For instance, I had a 76 with the cheap junk nylon timing gear and it wore away and finally broke. The cam chain was also such cheap junk that it was all strethed out. GM WAS never looking out for you. Planned obsolescence was the company model.
