critique my 2.5/2.6 plans

[Shuie]

Ive thought a lot about having a high compression twin plugged hand grenade of a motor built, but I just dont want to deal with the extra cost and the BS that a lot of you guys seem to have to go through. I want to end up with a motor that is reasonable on the street and has a lifespan measured in miles, not hours.

Im buy starting to buy engine parts for a 2.5 or a 2.6. Let me know if Im headed in the wrong direction.

7R case - from a later 2.7 - got it
2.0 CW crank & rods - buying it
SC oil pump - I want a sump screen and a drain plug - not bought yet
P&Cs - J&Es @ ~9.5:1, maybe nickies - not bought yet
S spec top end - not bought yet
crank fired single plug - got it
ITBs - not bought yet
max redline 7200-7500RPM


As always, thanks for the help!

[Plavan]

Shuie,
You are on the right track. 2.5L motors are VERY fun. You really do not HAVE to get a CW 2.0L crank. A non counterweighted crank will work fine. The bearing journals are huge! I know some people have different thoughts on this, but on the race cars we have used both. The non counterweighted cranks spin up faster. Your not going to be zinging it to 8K rpm so you will be more than fine.
My motor is single plug also. I will be dynoing it on the 22nd so I will post the results.
I have J&E's in my car but 10.5:1 but your 9.5:1 will be perfect for the street.
I have PMO 46's but you will be fine with the 40mm webers. My uncle may have a set to sell you. He just upgraded to 46mm PMO's
You can get a Carrera oil pump. My mechanic makes a sump plate with a drain plug.
Just grab any 2.2 -2.7 heads and use those. Maybe open up the ports a tad. I have stock valves in my race car....They are perfect.
I hope this helps. If you have any questions let me know.
Regardless of what you pick, you will never forget the first time you fire it up and go for a drive with your 2.5L
-Chad

[Shuie]

Thanks Chad! I know you guys drive your cars a lot harder than I ever would, so if its good enough for you, Im sure it will be fine for me.

What kind of redline is a non CW 66mm crank good for? Occassional runs up to 7200? Which rods do you use with these cranks? Is there a certain year that is the best one to use?

thanks again!

[bavaria911]

You see the 2.5 twin plug on ebay for $5K.

Bavaria911

[Shuie]

sure, I saw it. sounds pretty cool.

[kenikh]

Definitely go 2.6 and why not twin plug it while it's apart? It is really very cheap to do since the motor is disassembled and with the crankfire, adding another plug is elementary; all you do is add a signal splitter and another coilpack. Then you can go w/ 10.5:1 and really have a hot motor.

If you think Nickies are in your price wheelhouse, I'd rather spend the money on twin plugs and take advantage of the gains of higher compression. Also, build the motor w/ a CW crank and SPIN it!!! This motor will rev forever. 7500 RPM is still super safe for a 66mm CW crank and the valve train should be fine, too.

Don't be conservative on the came either. An 'S' cam on this motor will be surprisingly torquey so if you want to make power high, a Mod-906 cam might be just the trick. A motor set up like this should make a very reliable 250 HP while still being highly tractable, from everything I have read. (Can you tell I have been planning a short stroke big bore, too )

Regardless of your selections, I can't wait until you start building it. Mine is still about a year away.
Have fun!

[Plavan]

Ken is right about the twin plugging. You may want to consider that since the motor is already apart. But I understand it is a bit more $$$ getting a 993 distributer conversion. I may go twin plug next time I have the motor out. I have an extra set of heads I could work with before I take the motor out.
I take my car to 7500rpm. It could easily go to 8200RPM because of all the goodies I have (Racing springs, Ti retainers etc). I like my motors to last a bit though. This motor will probably be good for 3 seasons of racing before a teardown. If you keep the stock springs and retainers, 7300 RPM is safe. You could probably even go to 7500. Just becarful of missed shifts
I have cams similar to the GE-80 profile. That may be a bit much for the street. My power comes in at 5300 RPM. Once I get the dyno results we will see exactly. S+ cams may be a good alternative for the street.
We use the 2.0L rods because they are lighter weight and you can get the ARP rod bolt hardware for them (A "must" do not skimp on this). You cant get the hardware for the 2.2l rods. Do a search on 2.0L rods vs. 2.2 rods. We have never had a 2.0L rod just "break".... We threw a rod because of a problem happening before the rod went (oil starvation). Any rod will break then. We even threw Carillo rods because of this. We stick with stock rods now without problems. Needless to say we fixed the oil starvation problems and have super happy motors now (and wallets).
You are just going to use 90mm pistons right? That would be the most cost effective way. If you want true compression figures, have one of your heads CC'd. that way you can tell J&E what your head CC is and they will make it a "true" compression ratio instead of generic of the shelf 9.5:1 etc.
Zoom Zoom
You can see the build process of my 2.5L below.
http://www.plavanracing.com/racemotor.htm
Have fun.

[kenikh]

Plavan, w/ crank fire, he has no distributor, so the 993 conversion doesn't come into play.

[Plavan]

Doh- forgot that part. We cant use crankfire (dumb rules) so I was not thinking that way.
Twin plug your beast.

[Shuie]

I already have the twin plug setup. I was just starting to try to think a little more conservatively. CW crank, light valvetrain, bigger valves, etc, etc, start to add a lot of $$$. Trying to minimize the 'slippery slope' factor if possible

I would have to lug a motor like that to drive it on the street, right? Would there be any real gain to bumping the compression and twin plugging without opening up the ports and running the hi rev valvetrain with a hotter cam like? Does it make sense to have 10.5:1 2.5 or 2.6 w/S ports, S+ cams, and stock valves that rarely if ever spins past say 7000RPM?

Im going to call the engine guy Ive gotten my parts from and EBS today about the P&Cs. I know EBS can source the 90mm & 92mm sets w/J&Es. the case is a later 7R, so the spigots dont have to be opened up for either and I dont believe the higher CR costs any more.

Thanks again.

[rswannabe]

Shuie,

I have been told by very experienced race mechanics that the stock S valve train is good to 7,500 regularly and occasional runs to 8,000 without incurring too much float. Of course with the stock S cam, there is no point in spinning it that high.

The higher compression is definitely worth it. It really improves the responsiveness of the motor. So, even with an S cam, I would say go for the higher compression and twin plug setup. I am planning a 2.6 and am going to go for at least a GE60 cam to start. I love the peaky/revvy nature of my 2.2S and want the same character, but with more power. There is a guy in the Portland area who has a 2.6 twin plug MFI motor with GE60's and he is wanted to go to a hotter cam still.

Brooke

[vanwyk4257]

Sherman, is this for your tangerine car? I'm actually thinking very seriously of a 2.5L in mine as well. By the way, do you still have those steel wheels. PM me if you would be interested in selling them. Thanks!

[Plavan]

Here are my dyno numbers for my 2.5 Short Stroke. Pretty much what we figured. 217.2 HP/ 170 Torque at the rear wheels. So figure 250 HP at the flywheel. Zoom, Zoom on my <1900 pound car

[Shuie]

nice. that just made my day. Ive been hoping for 180-190 as I plan my 2.5.