I am planning an engine build after my unfortunate cracked piston in the Mustang.
The current plan is:
-Dart SHP block, 4.125” bore, 9.5” deck height
-Scat Forged Crank, 4.00" Stroke 2.75" Main, internally balanced
-Scat 6.250 H-Beam Rods
-Diamond Forged 2618 Pistons, 1.25” Comp Height (0 deck), 6cc
-AFR 205 Renegade, 72cc chambers
-AFR 8019 Springs (for hydro roller, .650” max lift)
-Morel 5323 Hydro Roller Lifters
-MLS .044” Compressed, 4.125” bore (this lands me at 11:1 comp on the dot)
-Double Roller Timing Set
-FRPP Road Race Oil Pan (has windage tray, baffling, and crank scraper), pickup, gasket
-Melling 10833 High Volume Pump/ARP Driveshaft (planning for an oil cooler down the line)
-Will need to measure for pushrods later, of course
-ARP Head Studs
-Aluminum flywheel and better clutch, FRPP pilot bearing
-Victor Jr Intake
-Holley Sniper 800cfm EFI
-Bullet Custom Cam
-BBK 1-¾” LT Headers, will be 3” pipe back to the rear end, then turned down
Here's my full calculations:
View attachment 9155
This will add some weight over the nose, but we are going to try to counteract that by moving the engine back 1". The MM K Member moves the wheels forward 3/4" and the MM control arms add another 3/4". So in total, the engine will end up being 2.5" further rearward than stock. Obviously, that's not a ton of shift, but that also moves the trans/clutch assembly back too. Might as well do whatever we can and want while the engine is out and on hold.
In addition, I've done my best to do the math on the weight of the rotating assembly, etc. Here's what I have come up with:
View attachment 9154
Obviously, it's not possible to get an exact comparison of the weights, and I have ignored things that DO matter, like the addition of hydraulic roller lifters, shorter pushrods, etc etc, but it is nice to see that the approximations of the big things are fairly equal. I am reusing some things like roller rockers off the old engine. With an aluminum flywheel, this engine will be about 10 pounds lighter on rotating weight than the 357 it's replacing.
Speaking of, I found a good deal ($150!!) on CJ Pony Parts for an SFI Certified aluminum flywheel. This should be a helpful addition in autocross. Some people have had iffy experiences with aluminum flywheels, but with a stroked 427" engine, I'm not too worried about torque or power off the line.
I picked up the LMR ABS delete block. So that will be going on this weekend. That takes about 10 pounds off the nose of the car. I am also going to pick up a Wilwood proportioning valve. The front brakes lock up much faster than the rears, probably because of the 13" Brembo setup in front and the 10.5" stock GT in the rear. This problem was exacerbated by stiffening the car up all the way around.
The AC compressor removal will take out another 20 pounds.
The MM K Member will net me another 23 pounds.
The MAF Racing front bumper takes another 14 right off the nose.
So even though the Dart block is about 30 pounds heavier, I'll still be pulling some weight out of the front, not to mention moving the weight around.
Obviously, with the MM K Member and control arms, there will be some other changes. Bumpsteer kit, sway bar relocation, etc.
Once all the hard parts and engine are back in, the plan is to corner balance the car to get the best symmetrical handling we can.
When all of that is said and done, we should have a much better-balanced car than we had before. Not to mention a ton more power at RPMs more suited to autocross. With a 6800 rev limiter, there will still be plenty of range when we do hit the road courses.
I've reached out to both Kuntz and Craft Performance engines here in Arkansas to do the work. Kuntz has been incredibly responsive and answered the questions I had upfront. Even did some math on the engine out of the gate, quoted me two different cranks to match my budget up to my goals, etc. I asked Craft some questions by email and then had to call 3 times over the course of 2 weeks to talk to them. Not as good of a feeling as Kuntz gave me, and being comfortable with the engine builder is something I'm looking for.
The plan is to head down one day next week and get them some money to start building it.
From my own experience, I have an 86 I put a 351W in that Kuntz built back in 2001, its still running great, and is a beast. Jim Kuntz was a great guy, I did business with him a lot, I heard they got sold and Jim passed away but if the same folks work there its a top notch shop.