converting heads to MFI at home- anyone done it?

[haycait911]

due to a lack of confidence-inspiring machine shops nearby, I'm thinking of drilling and threading the MFI injector ports on my 3.0 heads myself. doesn't seem like rocket science.

I have an MFI head to use as a template. my thought was to rig up a wooden jig that the head will sit on so that the injector is pointed straight up. plunk my 3.0 head onto the jig, use a drill press to drill the hole. thread it and, done.

am I missing something? seems like it would work well enough. the exact angle isn't really critical so a degree or two off shouldn't make a difference. any thoughts? Don.

[356RS]

Great Idea. Should work fine as long as the angle is correct and it's centered in the port.

[boba]

Theory and execution. Yes in theory. The execution has risk.

The question would be how much it would cost to ship it to someone who does this on Porsche heads and has the fixtures vs the cost of a head if you slip?

[peon77]

Ive thought about this too. Ive read that the cis injector notch needs to be filled and thats whats scared me off. Get a core head to practice on. Then let it rip.

[haycait911]

well, here's my first angle mock-up. rough, but I think I can make it come together. starting with a small bit and working up should help eliminate any 'accidents' due to a hung-up drill bit.

I've done some mock-ups with the gasket and mfi manifold, and I don't think I need to fill the cis cutout. also, I intend to use the plastic spacers under the manifold which seems to eliminate the problem. I'll post a pic.

[HarryD]

I am not a machinist but your plan makes sense to me.

However, going with my philosophy that every job I do needs to require me to buy a tool I do not currently own, I would suggest you ditch the drill press and get a proper milling machine.

To my way of thinking, if you are willing to these types of mods, you may find it handy tool for other jobs that come along and you can always use it to just drill holes.

(say 'YES" to targas!, please people, let's just admit they were a great idea and admire those who stepped up! )

[DW SD]

the jig looks WAY rickety to me. I'd come up with something that allows you to clamp the head in place and will be much more stable / repeatable. Maybe this is only the first generation. Sorry if I don't understand.

Doug

[tadd]

Wood is a fine material. Built some really big planes out of it. I would however consider using carrege bolts for 'head studs and leaving some room to clamp to the drill press table.
One other note... The typical tolerance of tap most folks have on hand (E) will be to sloppy. Order a G or H from an Internet supplier.

[haycait911]

Originally Posted by DW SD

the jig looks WAY rickety to me. I'd come up with something that allows you to clamp the head in place and will be much more stable / repeatable. Maybe this is only the first generation. Sorry if I don't understand.

Doug

hi Doug. that's not the jig, the little triangle piece of wood in front of the head is my angle gauge. the jig will be a robust item.

Harry, I'd love to pick up a milling machine, but it's just not in the card$ right now.

here are some pics of the plastic spacer to go between the heads and the thottle body. they will seal off the cis notch. with big-port heads this may be a bigger problem.

a little outline of my plan:

I'm going to use these heads on my test mule 3.0 engine to get the MFI sorted out. I have another 3.0 case, 3.2 crank, and big-port heads for the final version of this engine. once I know I can make this work, I'll get the big-ports machined professionally, cis notches filled, and twin-plugged. the final engine will be a 3.2 or 3.4 ( depending on the pistons/cylinders I can find/afford) with MFI, 10:1 compression and twin plugs.

so I don't want to get too carried away on the first version. it's just to work out the MFI bugs. then I'll probably put this engine back on carbs and stick it in my '73. the 3.2/3.4 is where I'll spend the $$ on machining, etc. and will go in my SWB hotrod. hoping for 300 hp. this engine currently makes about 250 hp on webers.

3.0 dyno day - a pleasant surprise

[haycait911]

Originally Posted by tadd

Wood is a fine material. Built some really big planes out of it. I would however consider using carrege bolts for 'head studs and leaving some room to clamp to the drill press table.
One other note... The typical tolerance of tap most folks have on hand (E) will be to sloppy. Order a G or H from an Internet supplier.

thanks Tadd. good thoughts. thanks for the tap-tip. I didn't know there were options. I can make a big wide base on the jig to clamp it to the drill press. and I like the idea of bolting the heads to the jig.

[tctnd]

Clamping it in a solid wood jig is fine for holding the angle, but I would make an aluminum drill guide that bolts to the intake studs to ensure all the heads end up the same.
regards,
Phil

[haycait911]

Originally Posted by tctnd

Clamping it in a solid wood jig is fine for holding the angle, but I would make an aluminum drill guide that bolts to the intake studs to ensure all the heads end up the same.
regards,
Phil

thanks Phil, very good idea. this is why I like this forum. this has already gone from backyard mekanik status to a semi-professional job. totally from the input/ideas of you guys.

[911st]

Sorry but I skipped over most the posts above.

I tried it and failed big time on a 2.8 I converted from carbs.

Ended up sending the heads out to be re-welded and done properly.

It did not cost much to have this done but this was years ago.

[1990C4S]

Surely you can find a machine shop with a decent machinist and a milling machine that will do a better job that your drill press. Make a decent jig and take it to someone.

[Duane V]

Don, I admire your resourcefulness but why not just send them to Lance at Hayward Performance. This is what he specializes in. He rebuild my heads, twin plugged and ported them for a reasonable cost. Plus he is located in Maple Ridge so it is not really that far to ship.

Hayward Performance I.T.B.'s Individual Throttle Bodies Individual Throttle Systems Racing Throttle Systems

Duane

[avendlerdp]

I think it's great idea to try and do it yourself. If you take some time to think it through I bet you'll do it just fine. The money you save can be spent on other stuff you will be sure to need.