I'm building a 5.0 HO twin turbo and am having a MASSIVE ball-ache trying to sort out the heads.

Basically the original 5.0 heads are scrap. I've since sourced some early 302 heads (from a '75 Mustang) and I'm trying to make the whole thing work. Obviously the 5.0 heads have the later 'saddle' type rockers which are bolted to the head, whereas the '75 heads have rocker studs and 'rail' type rockers. Two of the rocker studs are damaged (one bent and one snapped off) so I thought it would just be a case of removing the studs (didn't realise they are pressed in) and simply bolting on the 5.0 rocker set-up.

Now I find myself at a loss as what to do. Do I pay to have the studs machined off and the heads tapped to fit the 5.0 rockers and bolts, or machine the heads to accept ARP rocker studs, or do I scrap all of them and try and find another pair of 5.0 heads?

Everyone I talk to in the UK doesn't know jack shit about these engines, let alone turbo'ing them, so all they keep telling me is to buy aluminum heads and fit double valve springs. I know stock heads can work, and can give good power, as this forum is full of people who have done just that.

I just want some advise - what would you guys do (remember parts for these engines in the UK are very rare, so if it involves buying parts from the US and shipping them over it can get expensive)

Thanks in advance

 

you have 2 choices.

1. replace the 2 damaged studs and buy rail type rockers.

2. pull all the studs out (pita) have a machine shop cut about 3/8 off the bosses and tap the holes at 7/16 coarse thread. then buy your new rocker arms studs and pushrod guides.

as for putting petestal ty rocker on it is never gonna hapen. you can't thread a 3/8 hole to fit a 5/15 bolt.

 

Choice #3: same as #2 but instead of milling the bosses have them use a Doorman "cheater" stud. It doesn't have the hex at the bottom like an ARP and uses stock rockers. I put them on some late 60s heads and they worked great. They'll work fine with a mild cam and near-stock spring pressure. Stock D5 heads have no business with big cams/spring anyway

FWIW, I do believe those D5 heads will be worse than the E7 heads from a flow perspective. You might want to research that.

 

I would also like to see the flow numbers on the 75 heads...