OEM Head/Main bolts vs ARP Studs
 

Morning,

I´m working on my 250/300bhp engine and i would like to know safety power for OEM bolts.
I don´t know if ARP would be a must to use under 300. I didn´t read anything about crushed OEM bolts.

Same for healthy OEM oil pump vs Boundary one.
I still have a 5v gearbox so i would be under 250 for a time and will jump to 300 next year. Maybe could keep OEM pump and change it next year, with 6v gearbox...

Thanks !

They are cheap insurance. Same with the pump. Imo.

You should be ok on stock ones for now, but most would replace anyway just so you don't have to tear it apart later to do that.

OEM main bolt + 300whp = https://www.miataturbo.net/engine-pe...n-motor-57653/

250-300bhp is what, 220-270whp?
Either way, seems like a waste to build an engine without em only to go back in later and tear it apart to replace.
Subtract cost of labor/gaskets/fluids/etc. and it's just silly not to do it.

There are those who claim that you can't install ARP main studs without line boring the block. I dunno, I've done it twice and didn't line bore and had no problems, but maybe I just got lucky.

--Ian

Thanks for all answer and advices.
I think i´ll go with ARP Head and Main studs but keep with OEM oil pump. I can´t pay for all items and OEM will be "ok" before 5v gearbox crush... so i will change gearbox, clutch and oil pump at time (I hope this happens later 250bhp).

You know that changing the oil pump requires pulling the oil pan off, right? And that pulling the oil pan is best done by pulling the motor out of the car? It's basically the first thing that goes on the engine after you've installed the rods, pistons & crankshaft. It's easier to install head studs later than it is the oil pump.

No way would I put a motor back together without replacing the oil pump unless it's got very, very few miles on it. And if I'm buying a pump anyway, I'd buy a boundary one, not an OEM one.

--Ian

Technically you can do it under the car by taking the subframe off.. but it's a fucking terrible idea.

Yes i know that but pulling gearbox and change clutch / flywheel with out pull out the engine would be madness so i think would be easier to pull the engine out and to change oil pump without remove engine head, just the oil pan.
My actual OEM oil pump is healthy (check it with gauges) and i can rise up the pressure little more just putting a washer in the damper... in other way BF is so expensive.

Is there any problem with oil pan (1.6 1991) clearance and ARP studs?

I think everyone made an assumption when you said 250/300 HP it was a 1.8L... Now, you say 1.6L?

Has anybody ever broken a main cap when running studs?
I just got my first look at a set op BP main caps...Not very inspiring!

Huh? If you're just doing the clutch & flywheel then it's a lot easier to just pull the tranny out and do it there. There's less than half as much stuff required to get the tranny out by itself as to get the whole motor out.

...you're not building a 1.6, are you?

--Ian

I'm building my 1.6 without forged pistons (i think not necessary under 300 bhp).
I´ll mount OEM pistons, new rings, forged rods, ACL race bearings in all parts, ARP rod bolts and full head / block work.

You can check photos here: https://www.instagram.com/gn0m4/

Just thinking about ARP Head studs vs ARP Main studs vs BF Oil pump... the money the problem. Just want to create best engine "upgrade stages" for the money and for the other parts of the car.
My OEM Oil pump healthy is perfect and BF is sooo expensive, so in my opinion to mount ARP studs in all engine would be best option.
I never changed gearbox without pulled engine... so i don´t know how harder is.

Next year could change clutch, flywheel, gearbox, oilpump... all at same time.

What about re-use main bolts? would be possible with safety? and... re-use head bolts?
I see a lot of people with 250whp with stock internals and pumps.

That´s my goal so has any sense to build a forged 1.6 engine with oem pistons, oem head bolts / main bolts and oem oil pump?
has more sense to build it with oem pistons, ARP head bolts / main bolts and oem oil pump with ATI damper?
or to build it with oem pistons, ARP head bolts / main bolts and BF oil pump?

Just thinking about throwing cash to finish my 1.6 project with oem pistons (to rise 300 bhp) vs to forget it and keep with my actual items (forged rods, ACL race bearings in all parts, ARP rod bolts and full head / block work).

First off, on a project that you are going to spend a lot of good money....I would toss that 1.6 in the dumpster (OK sell it to some sap) and get a 1.8.
Once you start a project it is hard to stop...and then you have a bunch o money in a crap engine.
Maybe that is just me.

So you are going to rebuild an engine? You want to put a 30 year old oil pump back in service? Those pumps came with fragile cast gears (utter shite for high performance) from the factory?
Now it is 30 or however many years old.
You are under the impression this pump is somehow OK? If the pump was a proven design...the best there was....and it had 30 years on it? In the Fking dumpster!
The oil pump is the heart of the motor...it has a jammer and all you have spent is gone. It wont warn you either!
Good pistons and rods...What are they $750.00 now? No you don't "have" to used forged goodies, but you have to pay for the other factory hardparts..I bet they are more money!
You weren't going to rebuild with 30 year old pistons right?
Dude the gaskets are near $250.00!

Building these things is expensive. Do it once, do it right, and with any luck you wont have the grief of a blown motor.
You can turn up the boost when you get your 6 speed without fear of popping a rod. From there octane and tires (you are going to burn them off) will be your only concern
Everybody has to stack up parts and wait until they have enough money.
Save a few extra months, sell the running 1.6 to offset costs.

What I would do...What my son Is doing right now.

How do you have a 1.6 in a 99 miata?
Did you get another car since you made your profile 2 days ago? :)

So worried about your budget that you're willing to ignore all the advice you asked for. Nothing breaks the budget like building your motor twice because you were willing to delude yourself into thinking you didn't have to do it right the first time.

Gotta love it.

Thanks for your advices dudes.

If I were building a budget motor, and I could only afford to change a few things, I would do a stock motor + forged rods, hone + new rings, new quality gaskets, plastigauge the bearings. If any extra money, new bearings. If any more money, ATI Harmonic damper. After that, forged pistons and ARP head studs would be my upgrades going in the motor. My current motor is all of this and nothing more. I run a stock oil pump and have never had a failure, but apparently I'm the luckiest guy in the world because the forums say the stock pumps are fragile. Mine have seen a lot of RPM and power and been fine, but I do run an ATI damper and I think that is probably the reason my stock pump lives. People boost stock 20 year old stock 100K+ mile engines to 230-250whp all the time, you don't need to spend thousands of dollars to make 250-300bhp. But if you have money to burn, sure it's nice to have everything built to hold 600+.

EDIT: oh yeah, I have the ARP mains studs too. Not sure those are needed, but I did them.

If I ever break my current motor, the next one will have steel caps, probably build a custom girdle for them as well.