orlmiata

iTrader: (1)

My new built engine is being rebuilt only after 30 minutes of running due mistakes of an incompetent engine builder. I will chalk it off to expensive learning experience. I am trying to get some questions answered so that I am not blindsided again.

1. I am thinking of replacing the 83.5 Supertech pistons (8.5:1) and M-Tuned rods that I currently have with 83.5 CP pistons (9.0:1) and Manley rods. I have read that Supertech pistons expand less so tighter clearances are necessary.

Is a rebore necessary to use the CP pistons or can I can get away with the existing bore since both pistons are 83.5? Are there any other "Gotchas" that I need to be aware of?

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2. The head is getting new +1 Supertech Inconel exhaust valves, new valve guides, Supertech valve springs and 3 Angle valve job. I will be using the Miata OEM head gasket to bolt it to the block.

Should I be concerned with Piston to Valve clearance since there has been head work done?

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3. I also had to get a crankshaft from a MSM block to replace mine (my existing one was out of tolerance). I will be using the SuperMiata crank pulley.

Is it necessary to balance this new crank?

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4. I will be using the stock 99 cams and Toda adjustable cam gears with the rebuilt head.

Is it necessary to degree the cams?

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The machine shop is willing to assemble the long block for $550.00 and degree the cams for additional $150.00. I am thinking if some the steps above are not necessary, then I can assemble the block myself with help from a mechanic friend.

guttedmiata

Block should always be bored to match pistons.

The motor in non-interference with stock cams and low compression pistons.

Balancing the crank isn't a bad thing but not necessary. Doesn't do any good to balance the crank without clutch/flywheel assembly being balanced with it.

There is very little to be gained playing with cam position. Even less if you're running the factory ECU.

Ryan_G

iTrader: (8)

What exactly happened that forced a rebuild? Did you spin a bearing or something? Why would the pistons and rods need to be replaced? Did they sustain damage?

orlmiata

iTrader: (1)

After running the car for about 30 minutes we noticed white smoke out the tail pipe. So my mechanic friend checked the plugs and found that coolant was leaking thru to piston #4. We took the head off and in the process found that the head bolts were not torqued down to spec.
Fearing that other bolts may not have been torqued down as well, we decided to dismantle the block. In the process we discovered the main bearings were installed wrong and the caps were not torqued to spec as well. The bearings were done and we noticed some scratch on crank shaft as well. The machine shop told us the crankshaft had to be resurfaced. I opted to get a used shaft from another block and machine shop verified it to be good.

I am looking to run about 300 - 350 HP ( and whatever PSI that can achieve that with BW 6258) and maybe more (and E85) as I build the car out. So after talking with a few folks locally, I am thinking of ditching the Supertech and M-Tuned for CP and Manley. PS: The Supertech pistons and M-Tuned rods have no damage -- they are in almost new condition.
I have read mixed reviews about Supertech and M-Tuned. I bought them from another member here without having much of an idea of what I wanted to build. Just want to make sure I have right arsenal if I decided to go "ALL OF IT". Comparing with the amount of money that has been spent to date, the cost of CP pistons and Manly rods would be minimal.

I have the money to let the machine shop build the block but I would like to have the experience myself (that's what hobbies are for right ).

So what did I learn from this whole experience?
"Duh..Should have had a V8".

patsmx5

iTrader: (16)

I have a VVT head, did +1 inconel exhaust valves, did NOT have the head or block skimmed, but did sand both just enough to get them smooth (maybe removed 5-6 thousandths between BOTH. I now have an interference motor.....

guttedmiata

So before you loosened the head bolts, you set the torque wrench and turned in a tightening direction to check torque?

BTW, I'm running over 300hp on M-Tuned rods.

guttedmiata

Doesn't seem right. With oversized valves AND 11:1 pistons AND custom cams, I can move the cams 12* before interference. With 8.5:1 there would never be interference. What pistons do you have and how much timing range does the vvt operate through?

Ryan_G

iTrader: (8)

The ST pistons and mtuned rods will be more than adequate for your power goals. No need to change them out unless you just like spending money for no reason.

orlmiata

iTrader: (1)

We were able to remove the head bolts with little effort which let us to believe they were not torqued down spec of torqued down at all.
My engine is non VVT. I currently have 99 with 83.5 Supertech Pistons (8.5:1).

I was just checking to see if piston to valve clearance needs to be checked and how well Supertech and M-Tuned rods combo hold up in 300 ho or higher range.

patsmx5

iTrader: (16)

All I did was "discover" that at TDC, when cylinder 4 tries to open the exhaust valves, they hit close to peak lift. Did not "test" cylinders 1-3.

patsmx5

iTrader: (16)

also no idea if VVT side is interference, didn't check.... Running stock 03' pistons on this motor, new shortblock is FM Weiscos' they go in one day when I swap the shortblock.

orlmiata

iTrader: (1)

Here are pictures of the condition of pistons

psyber_0ptix

iTrader: (4)

Use what you have, reassemble crank with new bearings, triple check torque specs and get on with troubleshooting.

If you're spending money on splitting hairs, just get some carrillos.