8mm vs 10mm head bolts. 1989 2.9 v6 for bronco 2

[Desmod848]

Does anyone know if there is a significant difference between the two enginse other than the bolt sizes. I need an engine for my 1989 bronco 2 , the engine i currently have has the 8mm head bolts and the only engine that I can find is the 10mm version. Are all the accessories as far as ac and the like interchangeable between the two motors ?

 

[franklin2]

I went to www.car-part.com and plugged in your 89 Bii and searched for a engine. If there are any options they usually ask you on the site, but they did not. And what came up was 2.9 engines from 1986 thru 1990. Car-part is not the end all definitive parts interchange, but they are a good reference to add to the research arsenal.

 

[Desmod848]

Thank you .

 

[19Walt93]

I don't think I've ever seen an 8mm head bolt on a vehicle, Briggs and Stratton used 5/16" bolts on their single cylinder engines.

 

[Desmod848]

The bolts in the end of the head are either 8mm or 10mm depending on which version of the 2.9 you have.

 

[Curious Hound]

This is the guy to ask.

@PetroleumJunkie412

 

[PetroleumJunkie412]

The bolts in the end of the head are either 8mm or 10mm depending on which version of the 2.9 you have.

Correct, there is some difference in accessory bracket bolts.

Does anyone know if there is a significant difference between the two enginse other than the bolt sizes. I need an engine for my 1989 bronco 2 , the engine i currently have has the 8mm head bolts and the only engine that I can find is the 10mm version. Are all the accessories as far as ac and the like interchangeable between the two motors ?

I've been through both head setups on my 2.9s. Never noticed a fitment difference, and as far as the bolts went, I replaced mine with 10mm when I installed my HD heads.

If it were me, I would be more inclined to use a 10mm version - accessory bracket holes were changed for the 89TM heads, which are superior to early 86TM heads. 86TM had the 8mm bolts, and are also the heads that are more inclined to break.



What went wrong on yours? The bottom end of Cologne engines are very stout, and have forged cranks and rods in the RBV versions. If it was just a broken head, ProMaxx makes a damn fine head, reminiscent of the World Products ones.

 

[Desmod848]

Hoping just a blown head gasket or warped head. This is my first engine rebuild I've attempted other than dirt bikes so hoping for the best but just prepared in case I messed something up. Haven't tore into the motor yet to find the issue yet.

 

[PetroleumJunkie412]

The only time a 2.9 blows a head gasket is when it blows a head....

Make sure to have your block hot tanked. 2.9s have casting residue encasing cyls 3 and 6 - Ford failed to clean the blocks, leading to broken heads.

 

[Desmod848]

So if the engine is buggered and the only long block I can get is the 10mm version , everything should bolt up as far as transmission and all the other bits I'd have to swap ?

 

[PetroleumJunkie412]

Yes.

 

[Desmod848]

Thank you.

 

[Dirtman]

You're welcome.