Differences in Heads

[Crumm]

I was doing a little part searching and came across the following information.

F4TZ6V049BARM Use ONLY to replace heads with 8 hole intake manifolds.

F5TZ6V049AARM Use ONLY to replace heads with 10 hole intake manifolds.

The early 8 hole intake is for 94'-95' and the 10 hole is for 95'-97'. What are the extra holes for? Why did they change? Do the 10 hole heads provide more air? Just one of those "because I am curious questions".

 

[BJS]

the extra holes provide for a couple extra bolts to hold the intakes on which will warp and leak under high boost. There are some of the guys with the 8 bolt heads that have added an extra brace to span where the extra bolts are on the 10 bolt heads.

As far as the air flow passages and the combustion chambers I don't think there is any difference, or none that I've heard of anyway

 

[Crumm]

Well now that makes a little more sense. It didn't click that they were talking about bolt holes, duh.. I spent way to much brain power trying to figure out where they would put two more holes

 

[Renegade]

You can also do a direct bolt on of the later model 99.5 & up bigger inlet intakes with the 10 bolt heads instead of modding the intakes for an earlier model. Theres actually a lot of other differences in the head casting itself that was changed thru our model years but most of it had to do with making it quieter & not really a durability issue.

Oh - under higher boost - a intake leak at the wide spot between the bolts will sure make a wild shrill that makes you want to think youve fried a turbo I had to do mine a while back as it got louder & louder at lower boost pressure.

the pass side is easy to reseal but the drivers side will require turbo removal to get to the rearmost bolts

theres some pics in my somewheres showing the bigger intakes & the use of baby powder to find boost leaks.

Cheers