Let's talk boosted M42's

[Vivek]

I've been wanting to start this thread for a while. Everyone on r3v says not to do it, while most people who've boosted an m42 are all for it.
With a .140" MLS gasket, I believe the compression ratio is down to 8.52:1, so resurface the head and you should be at under 8.6:1 compression. That's not bad at all for boost.
The crank and rods are forged stock. How much can the cast pistons take?
Is there anything to know about the head? Are stock cams a limiting factor, or do they just adjust the power band?

Please share any knowledge and tips that you may have. If you've boosted an m42, what do you think of it?

-Vivek

[e304me]

you have to be careful using a thicker mls on a m42 because of the profile gasket

[Vivek]

I've heard that. People tend to use some liquid gasket makes like hondabond generally, right?

[decay]

the stock M42 engine has been shown fine for ~10psi. didn't you say you didn't want a lot of boost? i think in your position i'd spend that money on megasquirt-

that way if you hole a piston learning what detonation sounds like, you find another block at the junkyard rather than building again or hoping that your next combo of MLS, gaskets, and RTV tolerance-stacks like the last one did.

[jntar]

I am in the same thought process you are Vivek. I have everything but injectors and engine management to build a boosted M42. However, I dont have the funds for a full rebuild right now. I'd love to do it right and go forged lower compression pistons, but that wont happen for a while. What I'm doing now is as dk posted above. Sticking to stock head gasket, ARP studs, and 10psi for now (should be ~180whp). I have a second M42 in my garage I am working on, but it will be a year before it's finished. Eventually I'll go low compression/high boost and try to get close to 300hp or so. From what I've read the stock head/cams are good up to around that level.

[Dj Buttchug]

bro, in all seriousness fuck that mls idea and just do a refresh with stock everything and run 10psi. maybe splurge on some arp head studs but thats it.

From what I've read the stock head/cams are good up to around that level.

this is true. ask me how i know

[Vivek]

the stock M42 engine has been shown fine for ~10psi. didn't you say you didn't want a lot of boost? i think in your position i'd spend that money on megasquirt-

that way if you hole a piston learning what detonation sounds like, you find another block at the junkyard rather than building again or hoping that your next combo of MLS, gaskets, and RTV tolerance-stacks like the last one did.

I am in the same thought process you are Vivek. I have everything but injectors and engine management to build a boosted M42. However, I dont have the funds for a full rebuild right now. I'd love to do it right and go forged lower compression pistons, but that wont happen for a while. What I'm doing now is as dk posted above. Sticking to stock head gasket, ARP studs, and 10psi for now (should be ~180whp). I have a second M42 in my garage I am working on, but it will be a year before it's finished. Eventually I'll go low compression/high boost and try to get close to 300hp or so. From what I've read the stock head/cams are good up to around that level.

This is the kind of stuff I wanna hear. Thanks guys. I've heard MS is easy to learn, but it's really another $6-800 up front, and I have no clue what I'm doing (but that's my personal issue and not the point of this thread). If 10PSI is fine on a fully stock motor, that's over 200 at the crank and around 200hp at the wheels with a good tune.

[MF DOOM]

innovates pnp megasquirt system for m42 is $850 i think.

keep the stock compression, o ring the block, arp studs, e85, 20psi 8)

I never asked if this was your only car? Is this going to be done in a weekend or will you have time and a place that the car can sit while you work? What are you going to do if you break something?

[Vivek]

innovates pnp megasquirt system for m42 is $850 i think.

keep the stock compression, o ring the block, arp studs, e85, 20psi 8)

I never asked if this was your only car? Is this going to be done in a weekend or will you have time and a place that the car can sit while you work? What are you going to do if you break something?

Hopefully it won't take too long but I have no real rush. It's personally my only car but my dad has an e30 and an e46 so I can borrow one of necessary. It can be in my garage, storage is no issue. I'll probably pick up a spare m42/g240 from a friend who should be swapping his around when I boost mine.

How does e85 work and what are the benefits? I know that it needs higher compression, but will the setup you described be close to as reliable as a stock engine running 91 octane gas at ~10psi?

[MF DOOM]

e85 burns collllllllld. less chance of detonation. and its much cheaper then race gas. It wont eat your fuel lines. umm.. gotta tune for it of course. I was actually joking about that set up :p do they have e85 at the pumps where you are? i havent seen any since ive moved here.

[Vivek]

I just googled it, there seems to be enough around San Jose. Do you know any more about e85? I know nothing about it other than that you can go with high compression and high boost when you run e85. Does it give similar power gains to a built engine and a 20psi setup on pump gas?

[MF DOOM]

i know that you dont always have to run it. have a map for e85 and a map for 91. and it smells good. My uncle runs it in his 1500hp 442. Ive read that its better on engines, people have cut time off of their 1/4 miles, more power while running cooler. Im not sure if it would be a good idea to run it or not. it wouldnt hurt to look into it more.

[Vivek]

Definitely something ill look into. If anyone else knows, feel free to add. I'd like to make this thread less about me personally and more of a resource for anyone who's interested :)

[jntar]

E85 is a decent option if you have access. In my state we only have 3 stations with it so it's pointless for me. A good substitute is meth/water injection.

[wazzu70]

this is true. ask me how i know

What is your power level? I dont see any way the stock cams are your limiting factor unless you are pushing major power. Im sure the issue is elsewhere in your system.