I have worked on many Astro vans and most have a 4.3 litre V-6 engine. So I will give you the torque specs and sequence for that engine. If you have another one. Just let me know which one you have.
There are 13 bolts in each cyl. head. If you can see the bolts and notice from front to back there are 3 rows of bolts. On the outside closest to the spark plug there are 6 bolts in this row.There are 4 bolts in the middle row and 3 in the top row. We can number these bolts by which ones you torque first to last. Okay starting with the bottom row the first one towards the front is # 11 the next is # 7 then #3--#2--#6--#10. The middle row starting in front.. #12--#4--#1--#13 Then the top 3 from front to back are #8--#5--#9
I hope this is easy to understand. I have some more tips for you if you want. Such as if you use a metal head gasket, make sure you use some special sealant such as K&W copper coat. On both sides before installation. Also use some Permatex no. 2 on the threads of the head bolts. Torque all the bolts in sequence to 22 ft. pounds. Then on the long bolts an additional 75 degrees... on the medium length bolts...an additional 65 degrees... on the short ones... 55 degrees...I will tell you a secret no one seems to realize. Any bolt you torque and then put another degree turn on are STRETCH bolts. You should never reuse these bolts if they have been used. New bolts are supposed to be used. I know lots of people reuse the old bolts and have luck doing so. But why risk it. Do it right every time and you never need to worry. (as much) Good luck my friend and let me know how it turns out and if I can be of any other service.
Foot pounds (Final torque)
Note:
Torque sequence --------- | 6 2 3 7 | | 5 1 4 8 | --------- Step 1: torque in sequence to 33 Ft/Lbs Step 2: turn an additional 90 degrees Recheck final torque in sequence *** CAUTION ***engine uses Torque To Yield head bolts (TTY) thatpermanently stretch during the initial installation.New head bolts must be used when cylinder head isreplaced or re-installed to obtain proper torque.
Foot pounds (Final torque)
Note:
Torque sequence --------- | 8 4 1 5 | | 7 3 2 6 | front --------- of engine | 6 2 3 7 | | 5 1 4 8 | Step 1: torque to 40 Ft/Lbs --------- Step 2: turn an additional 90 degrees Recheck final torque in sequence *** CAUTION ***engine uses Torque To Yield head bolts (TTY) thatpermanently stretch during the initial installation.New head bolts must be used when cylinder head isreplaced or re-installed to obtain proper torque.
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