Going 4.6 DOHC on a budget (don't laugh).

[Jdufour]

Looking to go from carbed 351 to a 4.6 DOHC w/auto in my 85 coupe. This will become a turbo build eventually, but not all at once. Mark VIII's and Aviators are pretty easy (and cheap) to find in the salvage yards around here, but Cobras and Machs, HAHAHAHAHA!!!!!!!!! Looking to see what my best bang-for-the-buck options would be. My coupe is pretty much a clean slate right now.

 

[Jdufour]

So far, my research is leading me towards a Mark 8 shortblock, ECM, and wiring, with the heads and intake from an Aviator. Looks to be a poor man's Cobra motor, minus the forged bottom end of course! 96-98 mustang k-member is no problem. Will not be using the PS, AC, or any creature comforts. Business only!

 

[Bill]

How budget is budget? If I were on a tight budget, I would go with the 96-98 Mark Viii motor, computer and wiring, and a 96-98 Cobra intake. You might be able to swing the entire build for a net of less than $1000 if you get a decent Mark Viii and sell off what you don't use.

 

[Jdufour]

Around here, i can get the mark viii engine, tranny, ecm, and any wiring and supporting hardware I want for $450 loaded in my truck. I was hoping I was on the right track with that setup. Appreciate the info! By the time I sell off all of my 351w stuff, it should fund the swap with enough left for h-beam rods, studs, and forged pistons.
So in your opinion, the Aviator top end isn't worth the effort? I can probably get all that for $250 or so.

 

[Bill]

The Mark Viii uses the same head castings as the Cobra. I have seen the support 2000 hp, with a lot of work. The block also. On a budget, put the engine and transmission in and get it running, with a Cobra intake. When you do the hardened bottom end, change the cams and put the cool stuff on. I've seen them 450 N/A with a lousy idle and lumpy cam set. Spend your money in chunks and fix what you break.

 

[Jdufour]

Awesome!! Should scream with 2 7.3 diesel turbos shoving air down it's throat. Thanks!!

 

[Jdufour]

The best part is that no one knows I'm doing this swap besides my best friend (we've built MANY pushrod cars together). Everyone thinks I'm just rebuilding my iron-headed 351. Nobody really does this kind of stuff around here.

 

[cpearson1342]

That's what I did with my swap... it's great. I tell most people but my friends don't know (one has a ws6 and one has a 91 mustang). They think I still have my 86 302 and all I did was change to 5 lug with 3.55, o/r x-pipe and underdrives. I went on the track for the first time ever and ran 13.8 and my friend is still telling people it's the gears.

 

[Jdufour]

That's with a stock Mark VIII motor? Pretty good, and I bet it's a great driver, too.
I wonder what the weight difference is between an iron head 351w w/ a C6, and the Mark VIII setup? 150lbs or so maybe?

 

[cpearson1342]

No, sorry it's a 2003 mach 1 engine. All that is done is the o/r x, magnaflow catback, tune and aluminum driveshaft

 

[Jdufour]

Still great for a basically stock engine. Love the car by the way!!

 

[cpearson1342]

Thanks, just went to the drag strip again today and ran 13.38 so definitely coming down on the times. I'm hoping with some stickier tires I could do high 12's

 

[Jdufour]

If that was on street tires, then you should be able to crack 12's with some DOT slicks.
I hope to do the same. My old combo ran 12.65, and I'm hoping I can get close to that on the motor. Probably will run 4.10 or 4.30 gears

 

[cpearson1342]

It was, I have sumitomo htrz II's. Going to build the rear end this winter most likely to make sure we don't have any problems.

Anyway if you need any help with anything feel free to ask

 

[Jdufour]

I appreciate it!