Planning a high compression build

[flatlander757]

Been lurking this site a lot as I am hopefully going to be buying a Miata as a track car some time in the near future, and I want to put a 60 degree V6 into it because they're light and you can squeeze a fair amount of power from one naturally aspirated.

Just been looking around and reading on high compression(but 93 octane safe) builds because I want to essentially build it with the best of the best stuff to achieve perfect quench, a high static C/R, and an acceptable dynamic C/R. Of course good flowing heads and a good sized cam... solid roller if necessary/possible. I'd like to have 275RWHP with a broad torque curve over 2000 rpms... basically something that has good throttle response and can take a beating on a road course.

I know it will either take a completely done over 3500 or a 3400 hybrid... whichever I figure out is easier/cheaper to get the desired compression and quench.


For now I'm basically just dreaming up a combination and absorbing knowledge, read a lot of the stuff by Super Dave and Joseph Upson... lots of good info in their posts.

Also, I found this kick-ass calculator... it's meant for Jeep strokers but you can plug in stuff for anything really:

http://www.jeepstrokers.com/calculator/

I guess this is sort of an introduction, but moreso I may post back in here some stupid questions of mine so I don't clutter up anything elsewhere

edit: I'm trying to plug in all stock numbers into that calculator for a baseline... does anybody know what the 3500 LX9's intake duration # in degrees is? And what the dome or valve relief CC is? Thanks!

[bszopi]

Welcome!

For the static CR calculations, it probably better to use our CR calc, as the values for almost all of the engines are built in. http://60degreev6.com/content.php/101-CR-Calc

[flatlander757]

Yeah, been playing with that too, then when I find something close to usable, I'll check the dynamic compression ratio with some of the cam specs on WOT-tech.



Also I met up with CNCguy here in West Carrollton, nice guy and builds some really nice stuff... seeing how small these engines are in person and knowing the weight of the engine dressed/assembled/mated to a Ford T5(470ish lbs) makes me darn sure that it would be a perfect swap for a light Miata without adding much, if any weight.

[bszopi]

Honestly, I wouldn't really put too much effort into calculating dynamic CR. Just depends on too many variables, and there isn't a good way to actually calculate it like you can with Static. Unless, of course, you are using an actual engine simulation program.

[bob442]

I'm building a higher compression motor right now, i'm kinda on the fence as to how this motor is going to get tuned on 91 and how much the timing is going to need to be retarded to reduce knock, and how streetable its going to be, but hopefully i should have it together by june. its a 3400 with 11.5:1 pistons, but the chambers are going to get some experamental work so it will drop down about .1-3 CR in hopes to reduce detination and have more timing advance for more top end.

As for dynamic CR, it can always be changed with the cam, and basing everything off of how your going to drive it and the static CR, Ben can make you a custom cam that will work well

[trotterlg]

I have a 3.1 in the shop being bored and putting iron head pistons in it, looks like about 12 to 1 with those, picked up some coated skirt pistons for a good price. Some valve springs and cam with a roller lifter upgrade and things should be good. It may be better to just go with a bored out 3.1 and you can use stock iron head pistons and save quite a few bucks and only be down a few CC's. Larry

[Superdave]

I made 275 @ the wheels on stock 3500 compression (9.8:1)... My dynamic is down around 8.5:1, lol


You don't need to jack the compression way up to get decent power. A stock bottom end 3500 with a good cam, headers and a ported top end with a good tune will meet your goal and be reliable.

Hows this for a torque curve: http://www.3500z.com/3500/08-Dyno.gif

[mfuller]

But you also have those killer long tubes Dave.....very few of us have that know-how and fab skills.
Aren't you OBD-I also?

[Superdave]

The OP will have plenty of room for EQ-LT's.

I'm sure those helped with the torque and the peak HP on mine but even some un-equal length headers it'll still make tons of power.

[flatlander757]

I'm building a higher compression motor right now, i'm kinda on the fence as to how this motor is going to get tuned on 91 and how much the timing is going to need to be retarded to reduce knock, and how streetable its going to be, but hopefully i should have it together by june. its a 3400 with 11.5:1 pistons, but the chambers are going to get some experamental work so it will drop down about .1-3 CR in hopes to reduce detination and have more timing advance for more top end.

As for dynamic CR, it can always be changed with the cam, and basing everything off of how your going to drive it and the static CR, Ben can make you a custom cam that will work well

Thanks! Can't wait to see how it turns out... do you have a build thread or something of the sort?

I made 275 @ the wheels on stock 3500 compression (9.8:1)... My dynamic is down around 8.5:1, lol


You don't need to jack the compression way up to get decent power. A stock bottom end 3500 with a good cam, headers and a ported top end with a good tune will meet your goal and be reliable.

Hows this for a torque curve: http://www.3500z.com/3500/08-Dyno.gif

That's a very nice torque curve, and pretty much exactly what I want in an engine

But bumping the compression up will never hurt... I'm going to get a Miata and just build the engine on the side... I am also looking to do this because frankly I've never "built" a motor's bottom end before, I'm a mechanic(have been for 5 years) and have done a bunch of stuff, but working in a dealership you simply don't do that kind of stuff.

But you also have those killer long tubes Dave.....very few of us have that know-how and fab skills.
Aren't you OBD-I also?

The OP will have plenty of room for EQ-LT's.

I'm sure those helped with the torque and the peak HP on mine but even some un-equal length headers it'll still make tons of power.

Exactly... Long tubes should be no problem.

I'm not new to fab work... this is my current daily driver:








I'm merely looking to get into a fun car to enjoy on the road, and then as a project put a hot motor in it while keeping weight in mind. Also because I'm a mechanic, putting something in there that is nice and open, and easy to work on will be a huge plus... an LS1 is a bit tight.



I'm still doing a TON of reading on the different options for tuning, none of which will be super easy since it's going into a vehicle it's not meant for. I'm familiar with how OBD2 systems work, and with Ben offering tunes via HPTuners if you can give him feedback seems like a good plus... on the other hand Megasquirt could be a fun learning experience too... but that's for consideration WAAAY down the road.




I do have one question for you guys though... should you not bother with "building" a motor until you're nearly ready to use it? Or could you safely store it without risk of anything being messed up when the time comes for a year or so?

[pocket-rocket]

That, my friend is some sexy flex...

[bob442]

I do have one question for you guys though... should you not bother with "building" a motor until you're nearly ready to use it? Or could you safely store it without risk of anything being messed up when the time comes for a year or so?

I went a head a pulled my motor before i had the funds to buy all the parts, its best to get set on building the motor one way (which can be very hard) buy all the parts you will need (or atleast as many as you can plan for, and then build the motor up starting with getting all the machine work done. How ever, it would be a good idea to have the block machined before you buy pistons, as you might have to have it bored out, so if you buy ..020 over pistons, and actually need to bore it out to .030, your SOL.
Build thread will start when i actually get it back together and finish buying the parts lol

So the jeeps got links in the front and springs in the rear? did you get the kit that had binding issues in the rear?

[flatlander757]

That, my friend is some sexy flex...

Thanks haha!

I went a head a pulled my motor before i had the funds to buy all the parts, its best to get set on building the motor one way (which can be very hard) buy all the parts you will need (or atleast as many as you can plan for, and then build the motor up starting with getting all the machine work done. How ever, it would be a good idea to have the block machined before you buy pistons, as you might have to have it bored out, so if you buy ..020 over pistons, and actually need to bore it out to .030, your SOL.
Build thread will start when i actually get it back together and finish buying the parts lol

So the jeeps got links in the front and springs in the rear? did you get the kit that had binding issues in the rear?

What I moreso meant was... if I could build the entire motor at once... complete longblock and all, then would it be a bad idea to let it sit for up to a year or even 2 before firing?

Nothing was any sort of kit... they're all a bunch of generic brackets from various companies, with the exception of a few that I made myself.

It's an 03 TJ, I built a 3-link w/ panhard front, and the rear uses Cherokee XJ springs which are flipped around so the long side is forward(pin is offset 2" IIRC).. and to combat axle wrap it's got a traction bar that is a slip-and-twist style... basically the front is machined so it sleeves inside the rear triangle portion to allow for forward/backward movement of the axle and twisting... it works great. The only downside to the leafs is the ride on-road... offroad they're great... they're very stable but if they must flex, they will(as seen in that pic).

Here's the build thread on the Jeep:

http://www.pirate4x4.com/forum/showthread.php?t=768019

[trotterlg]

If you are planning to store an engine for a long time there is preservitive oil and spark plugs the will absorbe moisture out of the cylinders. Aircraft engines are stored like this for years and years. I wouldn't see a problem, you could even turn it over by hand once or twice a year. Larry