Head bolt differences

GangreneSpleen · Nov 18, 2014

So I searched the topic and could not find a straight answer. Are 6 bolt and 7 bolt head bolts different? All the chain stores (autozone, advance, o'reilly's) list the same part number for all 1st gen's and satan lists the same number for both 1g and 2g, but I can also remember running into a problem with this 7 or 8 years ago while working on a friends 6 bolt engine. He bought the felpro oem replacements listed for 90-94 and they wouldn't work at all in his engine (yet they came from autozone so could have been labeled or boxed wrong). Any info on this would be much appreciated. Also, I'm well aware I can buy ARP studs but they're not needed for what I'm doing.

synthetek · Nov 18, 2014

Yes they are different, 6 bolt are 12mm 7 bolt are 11mm

GangreneSpleen · Nov 18, 2014

Ok thanks for the quick reply, all I needed to know. Looks like I'll have to buy ARP's since no one lists anything different for the 6 bolt. Prime example of why you have to be careful buying crap from the parts store, and in this case even the dealer has it wrong (doesn't surprise me).

19Eclipse90 · Nov 18, 2014

Fel-Pro part numbers are ES71175 for the 6-bolt (without washers).
ES71177 for the 7-bolt (with washers).

Dealer part numbers MD121887 for the 6-bolt (without washers).
MD191470 for the 7-bolt (with washers).

If, perchance, you're looking at parts for a '92, that may be why everything looks like the same number as there were both 6- and 7-bolts that model year.

GangreneSpleen · Nov 24, 2014

Yes, I usually look up engine parts for a 91 to avoid running into the 6/7 bolt differences. The chain stores list ES71175 for 90-94, but upon more research I have found they are actually for a 6 bolt, so the bolts I bought will actually work. The system lists ES71177 for 2g's, so I'm willing to bet the ES71177 will work in the 1g 7 bolt engines (92.5-94) as well seeing they're the right thread pitch, but I'm not 100% sure on it.

19Eclipse90 · Nov 24, 2014

GangreneSpleen said:
The system lists ES71177 for 2g's, so I'm willing to bet the ES71177 will work in the 1g 7 bolt engines (92.5-94) as well seeing they're the right thread pitch, but I'm not 100% sure on it.

There are a lot of similarities and shared components between 1G 7-bolts and 2G 7-bolts. Head bolts are one of them. That is why there is one part number for 6-bolt and one part number for 7-bolt.

I am 100% sure on it.

GangreneSpleen · Nov 26, 2014

That confirms everything then! Hopefully if someone else ever searches this topic (regarding felpro head bolts) they come across this post. My engine is a 6 bolt so the bolts I bought are good, but anyone looking for head bolts for a 1g 7 bolt (92.5-94) would actually need to look them up for a 2g, as all the parts stores list them wrong and have the 6 bolt part number listed for all 1g's. Thanks for all the responses guys.

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Head bolt differences

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