How badly have I messed up my nice engine block? Need Advice

[roadsterdude1600]

Installing head studs on my 1970 1600 rebuild. Dumb-ass me figured that a late engine being metric, also had metric head bolt threads in the block. I have chased the threads using M10 X 1.5 chaser and wondered why the head studs are so stuborn to go in. Finally figured out that I must be dealing with 7/16 SAE threads. CRAP! before going any further and trying to re-tap the holes back to 7/16 X 14 which I believe they should be, is this a fools errand? Is this thing ruined, or can it be salvaged? Shudda, Cudda, Wudda.....(this part metric part SAE thing is a royal PITA - I was so used to the early cars)

[Linda]

I would just let a machinist do all the tapping at this point, because they practice all day long I am sure you are pretty competent , but the machinist could use the Time Serts to get it correct. I had my machinist do one block hole at his suggestion during the rebuild.
Linda

[keith0alan]

I would recommend helicoils. If you pull out a helicoil you can go to tineserts. If you pull a tinesert out you are pretty much done. The early head bolts are sae threads and sae head, the late head bolts are still sae threads with a metric head. IMHO humble opinion 65 ft/lbs is plenty for the head studs. The 85 ft/lbs mentioned is 75% of the yield strength and has nothing to do with the clamping force needed by this engine.

[redroadster]

How many Did you retap ?
Cast iron is about as hard as the tool steel tap
How much metal broke off in the process
Try a set up and see if the bolt torques down ....if it still threads

[Linda]

My machinist said the Time Sert was better. Guess there is some discussion about pros and cons. Here is a YouTube video on it:

I was going to use ARP studs also so that may have been a factor for Time Serts.

Linda

[roadsterdude1600]

Thanks for the replies. Here is an update. I researched Time Serts but figured that if I will need to drill out anyway, there is no harm in trying to clean up the threads again with a 7/16 X 14 chaser and see how it feels. The threads are pretty close but 10MM is a little narrower than 7/16, so maybe I did not mess them up a lot. (it is surprising how very similar the threads are) Anyway, I carefully chased all the affected threads with a good 7/16 chaser using WD-40 and what ARP assembly lube was left in the holes and they cleaned back up nicely so that the studs could be seated without any undue pressure or torque. I did use an allen wrench to run them in, but did not have to fight them like before. They feel nice and snug. My understanding is that you should be able to hand tighten them anyway with just a final twist to make sure they are bottomed out. And that is what I have. I think I dodged the bullet this time because the 10MM tapping did not really remove much if any material because of the smaller diameter. I will not go any further however until I get some opinions that are in agreement with my observations. Since this is a 1600 head, and not a 2000, my final torque using the ARP lube will be about 41 ft-lb which should equate to the 50 ft-lb spec. Any opinions are welcomed. I am pausing until I am confident. Fingers crossed.... While I am at it though, is there supposed to be a locking tab with a nut locking ear on the timing chain tensioner for a 1600? Scott's book mentions this but I think my tensioner that I removed just had lock washers...

[JT68]

because the 10MM tapping did not really remove much if any material because of the smaller diameter. I will not go any further however until I get some opinions that are in agreement with my observations. Since this is a 1600 head, and not a 2000, my final torque using the ARP lube will be about 41 ft-lb which should equate to the 50 ft-lb spec. Any opinions are welcomed. I am pausing until I am confident.

I think you took the best course of action. Helicoils and especially keensert/timeserts are the not a great plan for headbolts/studs. I think you are correct, since the 10m1.5 is undersized and very close to 7/16-14, you probably actually did minimal damage to the threads. 41 with ARP lube should be right on. If nothing goes into yield when you torque it, you probably have no issue.

Cheers, jt

[david premo]

Do NOT bottom the studs out, finger tight is all you want.

[mraitch]

question re torque (1600) - 41 with lube - what about no lube.- somewhere I thought I heard 81 dry??

[roadsterdude1600]

50 in 3 steps: 33, 48, 50. 65 for the U-20