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Pulled all rocker studs out. Started tapping all bosses for threaded studs.
Noticed on the second head that 1 boss is broken.
The damage is about 4 threads deep. I think there are around 7-8 threads that fully engage below it.
should I repair this? Perfect excuse for aluminium heads afterall? Or machine the boss down for a stud (studs?) With a nut?
if these heads are important then that can be fixed by a good welder.
My choice would be to clean the complete head ,then the area. the head area has to be heated and athe stud screwed in and cold. Weld and remoce stud. If you can't remove stud then pin it with a taper pin. Back in the day we ised taper pins to keep the studs from pulling out when heavy springs were used.
Cast is tricky to weld and a experianced welder is needed. I use a silicone bronze rod for cast. then it needs to be peened with a sharp pointed peener to stretch the molecules. If not peened then it will crack. If it doesn't unscrew then you actually have what you want.
Yep. Repairing that damage is do-able...but probably costs more than they are worth. Go with some nice aluminum heads and ask you buds if anyone needs a good 'boat anchor'...
You could weld a stud in the remains of the existing boss....but you would still need the upper surface of the 'missing' piece for the valve train to work right. So, you need welding and machining to correct the problem. Not justifiable, IMO.
Those type of studs are not a great choice. The broken bosses are a known risk when the tiny ring on the top of the new stud tightens up on the top of the boss.
The much safer way to strenghthen the rocker arm stud is to cut 3/8" off of the top of the boss and install a stud with the itegral hex base that you tighten up to the pushrod guide plate. The obround pushrod holes in the head need to be drilled open wider and you use the guide plates to align the rocker arm with the center of the valve stem at final assembly. It looks like you need a machinist to do this. If the damage can mostly be removed with a 3/8" deep cut, the head can be saved and strengthened better than new. You will need a new set of guideplates and a new set of HARDENED pushrods for use with guideplates. Not the cheap rebuilder pushrods with the pressed in "ball bearing" looking ends. Around ~$120 US. 5/16" are fine and be sure to match the guideplate slot size to the pushrod diameter.
Time to cut the boss down 3/8" and add the proper hexed shoulder studs. Boss cracked when rocker arm stud was tightened. This way is possible but I do not advise it. The pushrod to valve stem alignment is not adjustable this way. Too late now since the bosses are already cracked anyway.
Last edited by stingr69; Sep 26, 2021 at 10:18 AM.
stinr69 knows exactly what he is talking about. Your studs look like they could be cut down, if you want to.
I don't think a machine shop would charge to much for this, they have been doing this for 50 years. Stock 1970 LT1 head with original screw in studs & guide plates.
Press in stud head being cut down.
Notice how the cut down boss almost goes down to the level of the headbolt boss. I do not think your chip goes far beyond that so yours could be saved, if desired. It may be the cheaper way out, or maybe not. Your budget and desires are just as important.
I would price up a set of aluminum heads, and compare to fixing yours, include pushrods, etc. You may find the total cost is not too much more. And newer chamber design al heads will give you an instant 30 HP just by the one part swap alone. And if you increase the compression, even better.
Oh, and as you are in Belgium, could you find a machinist over there comfortable with or has experience doing this?
Last edited by leigh1322; Sep 26, 2021 at 12:22 PM.
I've looked into getting them machined. When I'm picking up my block I'll be taking the heads to get the machinist to take a look.
I have been looking at aluminum heads, AFR ENFORCER looks affordable. https://www.airflowresearch.com/195c...cylinder-head/
Do they always need guideplates? Or is this only for when you use a solid lifter cam with non self aligning rockers? (If I'm correct I think the original rockers are all self aligning except those on the LT1?). I don't have a lot of experience with these rocker styles. All my European cars Im used to working on are either OHC or use a rocker shaft. Thanks in advance
I've looked into getting them machined. When I'm picking up my block I'll be taking the heads to get the machinist to take a look.
I have been looking at aluminum heads, AFR ENFORCER looks affordable. https://www.airflowresearch.com/195c...cylinder-head/
Do they always need guideplates? Or is this only for when you use a solid lifter cam with non self aligning rockers? (If I'm correct I think the original rockers are all self aligning except those on the LT1?). I don't have a lot of experience with these rocker styles. All my European cars Im used to working on are either OHC or use a rocker shaft. Thanks in advance
Nice heads. That said, you will need some hardened push rods to run the guide plates. You could run a "guided tip" self aligning rocker arm without using the guide plates BUT the heads are already machined for the guide plate thickness so....Might as well just run the guide plates.
Do not run a "guided tip" self aligning rocker arm WITH a guide plate.
You need to purchase an adjustable length push rod tool so you can measure for the custom length push rods you will need to order.
I've looked into getting them machined. When I'm picking up my block I'll be taking the heads to get the machinist to take a look.
I have been looking at aluminum heads, AFR ENFORCER looks affordable. https://www.airflowresearch.com/195c...cylinder-head/
Do they always need guideplates? Or is this only for when you use a solid lifter cam with non self aligning rockers? (If I'm correct I think the original rockers are all self aligning except those on the LT1?). I don't have a lot of experience with these rocker styles. All my European cars Im used to working on are either OHC or use a rocker shaft. Thanks in advance
Originally Posted by stingr69
Nice heads. That said, you will need some hardened push rods to run the guide plates. You could run a "guided tip" self aligning rocker arm without using the guide plates BUT the heads are already machined for the guide plate thickness so....Might as well just run the guide plates.
Do not run a "guided tip" self aligning rocker arm WITH a guide plate.
You need to purchase an adjustable length push rod tool so you can measure for the custom length push rods you will need to order.
As said, Never run any guide plate with any self-align rocker.
FYI, No OE C3 rocker is self-align.
As indicated, with aftermarket heads like AFR, you are likely to have most success with guide plates + hardened push rods + NON self-align rockers.
As said, you MUST correctly measure for proper pushrod length Before ordering any pushrods. Depending upon manufacturer, PRs usually available off-the-shelf in 0.050" Or 0.100" increments; which is close enough for street motors. FWIW, rocker arms with NO roller tip are less demanding of correct PR length. There are any number of instructions for measurement on web.
And, with any valve train part, it's penny wise and pound foolish to risk chinesium.
As said, Never run any guide plate with any self-align rocker.
FYI, No OE C3 rocker is self-align.
Another data point I came across on my 73 with World Products SR 082 heads;
- Don't run non self-aligning rockers on a aftermarket head that has no guide plates.
From a GM OEM parts standpoint you can only purchase self-aligning rockers (10089648) as the non self-aligning rockers (3974290) are no longer available. Even the Sealed Power non self-aligning rocker made from GM drawings are no longer available. Used or NOS is the only option for these rockers.
Another data point I came across on my 73 with World Products SR 082 heads;
- Don't run non self-aligning rockers on a aftermarket head that has no guide plates.
Why? do those SR have HUGE pushrod guide-holes that're part of casting ?
From a GM OEM parts standpoint you can only purchase self-aligning rockers (10089648) as the non self-aligning rockers (3974290) are no longer available. Even the Sealed Power non self-aligning rocker made from GM drawings are no longer available. Used or NOS is the only option for these rockers.
Seems, both Elgin and Melling still manufacture conventional, NON self-align stamped rockers for 73 sbc & others.
Yup, except for lifters, seems sealed power/SP have dropped all related valve train.
Not really a big deal GM stopped manufacturing Gen 1 SBC parts a long time ago. They have been supplying many service parts manufactured by others (Melling, TRW, etc) and putting them in GM boxes for years.
Seems, both Elgin and Melling still manufacture conventional, NON self-align stamped rockers for 73 sbc & others.
Yup, except for lifters, seems sealed power/SP have dropped all related valve train.
Correct, I was looking for GM or Sealed Power. As for the World Products SR 082 heads there is a WP bulletin that states if you install guide plates you have to open up the push rod holes.
If you really want to 'save' the original cylinder head, you can have your machine shop mill down the broken boss [to below the end of the cracking...very important!] and braze a steel spacer of the same length as what was milled off. Drill and tap new hole for the stud [in correct location] and you would be good to go. (You SHOULD NOT weld the spacer to cast iron.)
I agree that when the shop does this work they could also just mill a good top surface for ALL the rocker studs by just 'cleaning up' the top surface. Exact boss height doesn't matter as lifters are adjustable.
I'll look into the brazing as well, the block should be ready this week so should go collect it coming weekend. Was tempted to braze in the stud, but that would probably destroy the steel stud.
In terms of hardened pushrods, are they all the same?
comp cam 7812-16 is what I have my eyes on ATM. I've read different storie, some people saying all SBC pushrods are hardened from factory ( someone said to take a file to them and test), some say hardened 1010 steel is fine, some say you NEED chromemoly steel.
FWIW, some years ago the USA-made cast iron brake pedal on my 1967 USA diesel tractor broke; a clean break. I had a pro welding shop braze the two pieces together. The first day I used the tractor the pedal broke right at the braze as the OE spring snatched (quite normal) the pedal against OE stop. I took the pedal to another welding shop & they arc-welded it together and it hasn't failed in many years. FYI, replacement brake pedals are quite rare; unlike non-performance iron sbc heads.
I would Not braze the rocker stud boss; there's a fair amount of stress on those bosses. In fact, I wouldn't spend what it'll cost to successfully weld it AND machine it ... because those heads are very poor performers. Get better heads or just find another similar sbc head. They don't HAVE to perfectly match.
7812-16 PRs will be fine for mild sbc. Hardened PRs are Required whenever sbc/BBC has guide plates; otherwise , hardened not required.
Broken rocker stud boss
