JB_Sonic_197

According to the Sean Hyland book "4.6-Liter Ford Engines" an aluminum block (the original Teksid casting, Cobra and Mark VIII blocks) can only go .040 overbore. However the WAP (Windsor Aluminum Plant)blocks likethe Mach1, Maurader, Explorer and2005-08 Mustang don't have the cylinder wall thickness of the Teksid blocks. Both blocks have a 3.552 inchor 90.2mm bore

Basically if you want a big bore 4.6 you have a few options. Find a Teksid block and bore it out and install sleves. Buy a FRPP 5.0L block ( 3.70 inch or 94mm bore aluminum or iron)or a World Man-O-War 5.0L block. Big money either route.

Like most people have said, 2 or 3cubic inches is not worth the money or effort. If your engine was making 1-hp per cubic inch, you would see the gain of 2 to 3-hp for the cost of machine work and new pistons.

Pwny

Stroke it. The cylinder walls are too close to safely bore the cylinders.

lyyroix

Actually Rodeo its for the SCCA E Street Prepared class in the dreaded autox which has become my fav hobby in the last couple years. I will also use it in HPDE's at CMP which is just an hour away from me. Aside from that it will be my daily driver to the tune of 30 to 40 k miles a year. Clearly no boring and unfortunately no stroking

Norm Peterson

0.040" overbore on a 4.6/281nets you just over 6 cubic inches, so you *might* get 7 hp and a similar amount of torque from the displacement increase. Sometimes, an overbore finds a few more hp and ft-lbs than the displacement increase suggests due to unshrouding of the valves, but that puts you back to needing some actual dyno results.

My take todayis that it probably isn't worth it in terms of overall block life for a dual purpose car. Or this soon in your autocrossing career. Save the forty thousandths for a rebuild or two, given that you're running up a lot of street miles on it. Unless you absolutely have to for reasons of what it takes to properly recondition it, don't use the entire allowance all at once. Unless, perhaps, you become (a)a serious National-level competitor, and/or (b) pick up a generous and understanding sponsor.


Norm

spyder7724

I'll go against the grain here for the purpose of taking the rules to the max. obviously if you didn't have rules you would build a big bore stroker etc. but when you have very specific rules you will want to take everything they allow cause if you don't someone else will. The reason for boring a block is not so much for increasing size it's to straighten the cylinder walls and make them true. Also there are some honing tricks that combined with a good piston/ring package can make a considerable amount of extra power compared to stock. while you are doing it if they don't mention coatings then go ahead and have everything coated (they make a ton of different coatings for every area of the engine) and mikronited. you may have to use stock cams but what about valves or lash adjusters/rockers and spring/retainer combos?
if you have the resourses then you can round up a few sets of stock heads and flow test them to find the best set and same for the intake manifold if porting isn't allowed.
there's a ton of ways to make power within the rules but it isn't cheap. Thats part of racing. they make rules to keep costs down but there's always one guy in the class with enough money to do all of the tricks and make more power than everyone else. that then sets the standard for the class cause if you wwant to win you've got to find a way to keep up with the Jones'