Piston fly cutting
Ok. Need some suggestions. I have a new set of heads that have a 2.02 intake valve. Pretty sure they are not going be within tolerance and needing some advice on fly cutting the pistons in the car. I am currently running a 96 Ford Explorer 302 block and pistons etc....
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Use an old head and a valve slightly larger than 2.02 oversized valve that you've machined cutting edges into.
you might want to cut it so it's a one hole at a time fixture- up to you
cut the top of the guide off for additional depth is desired or more length is needed. I prefer added length because it helps with stability. Putting a fresh seal in it helps too
Drop the valve down until it touches the piston. Mark this point. Run the piston down the bore and Measure the depth you need to cut plus a margin of safety. put a stop on the valve at this depth.
Tape and a washer works. Other options exist that will work better.
Bring the piston back to TDC and spin the valve with a drill and plunge cut it.
There are varied opinions on applying grease around the piston to keep shavings away from the rings. Personally I'm a fan of it if you neck down a shop vac with some tape and an old ink pen and suck the grease away - don't wipe it.
Best advice I can give short of new slugs or paying a machinist to do it for you. Hotrod or car craft published articles on doing this back about 20 years ago.
If you go to a twisted wedge head you might not need anything at all
also don't assume. Mock it up and bar it over easy with clay and see where you are at. Depending upon if the block is near zero deck or not and how thick your gaskets are, etc, the results could surprise you.
Good luck.
Thank you for the advice. I have seen a video about this and wondered how well it would actually work. Think I will go this route. Still deciding on head gaskets and gasket thickness or, what will be the best gasket for longevity under boost. Would a thicker gasket kill the compression ratio but, then again I don't think that will be a bigger deal under full boost.. hmmmm
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Stock 86 is 9.2:1 compression with flat tops. 87-93's dropped down to 9.0:1 due to the notched pistons. You should expect slightly less with notching for the 2.02's provided the heads are chambered the same.
Now take your old head bolts and toss them. Buy ARP studs or at least ARP bolts. Factory head bolts are torque yield and not supposed to be reused - ever.
Stock style gaskets will be good at the boost levels therefore power levels your block can hold.
You will likely want no more than 9:1 if you are going to boost and run premium pump gas in your motor. Less compression will help you cram in more air and fuel to a point. Most boosted street motors fall in the 8.5-9 range. Higher boost usually starts with lower compression. But you stock block is your limiting factor.
Some guys explore options to go to E85 too because it's cheap and tolerates a lot more timing advance. but remember E85 requires 35% more fuel per revolution of the motor. This drives up cyl pressure because liquid does not compress but is good for 12-15% more power in N/A form. Supercharged I believe there are gains to be had but less and remember your block is the limiting factor
Given the limits of a stock block vs what you can get out of a healthy bolt-on motor you won't be able to add a lot of boost but it will sound and look cool.
If you are going to add boost I strongly suggest doing an EFI speed density to MAF conversion on the car. When I explored mods on my 86 I literally couldn't find anyone that would tune a speed density setup- period. An A9L ECM for stick only or A9P can handle stick or auto are the computers programmed with the most aggressive tunes.
You could go up to a cobra computer with 24lb/hr and a standard (often called 19 lb/HR) MAF for a less angry advance curve but you'll still need to upgrade injectors and tune with a boosted combo. 70 MM MAF is often sufficient in blow through setups. 65MM throttle body is sufficient for a 5.0L also.
EV6 style injectors with EV1 to 6 adapters will give you better fuel atomization.
Binary Editor and logging software and a wideband will help tune it. I'd try running with a Moates Quarterhorse. Fast and Megasquirt have systems that you may prefer - it's up to you.
I would call comp cams or Anderson and discuss your goals. They will tell you which cams will work best with your setup.
My guess is when you tell them your heads and induction and a stock block they will tell you to skip the supercharger as the blocks are the weak link. They did when I discussed my combo and goals. 400 HP to the rear tires is completely doable in NA form with good heads and intake and E85. That should be good for 11's with a good 60' time and great driving.
Happy tinkering. Send us pictures!
Definitely measure, because depending on your cam and the events you may only need to cut intake or exhaust. The PO of my 85 did this to a 88 shortblock he put in. Only the intakes needed to be cut. (big cam with E7's). When I put Pro Comp 2.02 heads on it with a even slightly bigger cam, I didn't have to do any more. The exhaust is slightly tight....most recommendations are for .100 on the exhaust and I had .91-.95 on mine.
1985 GT, Sunroof, 5 Lug, Rear Discs, 01 Graphite Bullets, 88 forged piston shortblock, 2.02/1.60 Alum heads, Weiand Stealth, Holley C950 TBI, BBK Long tubes
A lot of good information from folks. Thanks! I have owned and built a vortech v1 car before but ran a gt40 aluminum heads that requires no mods from smaller valve size so I have never preformed this task before. I know I definitely don't want to convert my 85 to a 86-93 injection system due to an insane amount of issues, cost factors and restrictions. Kinda a been there done that also. I am running a fitech blow thru system that has 8 injectors and will support an insane amount of power and 25lbs of boost. The fuel is an e85 set up with a Paxton novi 2000 with a cog set up. I will put some previous pics up and also progression pics also. Building to run competitive in nmra/nmca true street class. Hopefully
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Current progress being done.
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More progress.
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Nice rides.
I've heard of guys going soft tune and going north of even 600HP on stock shortblock setups but IMO it is a ticking time bomb. My luck is it would go at the least opportune time. Get through many rounds at a nearby strip the blow it up before or during the final, etc, and lose.
I enjoy seeing a wide variety of approaches to going fast and keeping stuff together. It's what this car hobby of ours is all about really
that cage looks more tolerable than most. I haven't caged mine because it can make them uncomfortable to drive for anything but short blasts.
Ive always wanted to build a nearly invisible cage. Cut it into and hide it in the cars existing structure as much as possible. Do door bar assemblies that interlock but are part of the door and door frame, etc.
My last car was caged and definitely not a pleasure to get in and out of ( and was a lot younger then). I have three kids now and needed to make sure the back seat is easily accessible for my 10 and 11 year old. With them and safety in mind this is the best I could come up with. We finally managed to get all of the plastics out of the rear hatch Sunday and have started building the shock tower boxes. I will post pics hopefully Wednesday night of those completed and hopefully have the interior completely assembled back in the car by this Sunday. Then time for checking piston to valve tolerance.
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P.s. The red asc is my wife's baby! The blue 88 is my buddies car.
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