1 (edited by drewmatthews208 2021-04-23 09:08 PM)

Topic: How reliable is the ej25 motor in racing conditions?

I know that on the street, other than head gaskets, the ej25 is a pretty good (stock) engine, or at least in my experience. What about in racing conditions however, how do they fare from what y'all have seen. I plan to run a first gen Forester next year at Road Atlanta, I got the car for free from my dad, so that leaves quite a bit of room for the build so we are doing head gaskets, water pump, thermostat, and oil pickup tube for on the reliability front. Is there anything that we should be expecting fail during the race and prepare for? I used to daily the car and never had any issues, but that was obviously totally different conditions, thanks.

Re: How reliable is the ej25 motor in racing conditions?

Have you watched any videos from the 24 Lemons?  I'd say...

Up in smoke
That's where my money goes
In my lungs
And sometimes up my nose
When troubled times
Begin to bother me
I take a toke
And all my cares
Go up in smoke

However I am not an expert and if you want stonk advice ask a professional...I just have diamond hands...

Re: How reliable is the ej25 motor in racing conditions?

(Assuming your EJ25 is NA.)
Don't change the head gaskets unless they're bad because you overheated the motor.  Instead, put that money into upgrading the radiator.  Keep the engine cool and the head gaskets won't fail.

PS: My team, Hopes and Dreams, runs an EJ25 and we haven't had to change any head gaskets yet...

If you have a 4wd model, one issue you're going to face is the fuel flowing over the tank hump on hard right turns, which will starve the fuel pump and give you the equivalent of a hard lift in the middle of the corner.. Just plan to top up your fuel every hour and your fuel pump should survive / you won't spin out.

Re: How reliable is the ej25 motor in racing conditions?

DefectiveLemon wrote:

(Assuming your EJ25 is NA.)
Don't change the head gaskets unless they're bad because you overheated the motor.  Instead, put that money into upgrading the radiator.  Keep the engine cool and the head gaskets won't fail.

This.

Head gaskets are the effect, not the cause. So many people jump on the "DERP - MUHST BE TEH HEAD GASKETS!! - DEPR" bandwagon, nobody ever bothers to realize WHY the head gaskets blew out in the first place.

Radiator
Radiator
Radiator

Actually, Subaru used a VERY dense condensor core for the A/C system in front of an already mediocre radiator. As the condensor clogs with road grime, dirt, bugs, etc. the already over stressed radiator can no longer keep up. It also doesn't help that the Subaru engine temp "gauge" is anything but. That son of a bitch will point straight up right smack dab in the middle from 130°F all the way up to 250°F. That's right, at 250°F, the temp gauge will still be reading happily in the middle of the "normal" range.

So my recommendations:

1. Ditch the A/C condensor (if you haven't already)

2. Buy the largest and thickest aluminum radiator you can find

3. Install a real water temp gauge in the block somewhere

The Pentastar whisperer

Re: How reliable is the ej25 motor in racing conditions?

Uhhh...Have y'all ever done any study on Subi head gasket failure?
The printed sealant often fails on the factory MLS gaskets.
However, that is usually on the SOHC motors.

Now, my personal experience:
I have overheated my EJ257 twice with cooling system failures. yikes
But, it was after I installed Cometic MLS gaskets and ARP studs.
Those went in around 40K miles when I had a ring land failure.
The latest overheat was a couple of months ago with 95K miles.
Both times it was fix the cooling system, refill with coolant, and go back
to driving as usual. big_smile

If it were my EJ25 entry, I'd install studs with Cometics,
perform the Cylinder 4 cooling system mod,
change out the oil pick-up tube, or reinforce the stock one,
enlarge the oil pan, and delete any signs of A/C components.
A windage tray would hurt, either.

If it was a turbo EJ25, I'd do the fuel rail supply mod that fixes the dead-end problem.
I'd also bring a full set of ignition coils.

Lastly, consider some trackside human sacrifices in hopes of completing the race.

Capt. Delinquent Racing
TRUMPACO XR4Ti
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: How reliable is the ej25 motor in racing conditions?

Bayley wrote:
DefectiveLemon wrote:

(Assuming your EJ25 is NA.)
Don't change the head gaskets unless they're bad because you overheated the motor.  Instead, put that money into upgrading the radiator.  Keep the engine cool and the head gaskets won't fail.

This.

Head gaskets are the effect, not the cause. So many people jump on the "DERP - MUHST BE TEH HEAD GASKETS!! - DEPR" bandwagon, nobody ever bothers to realize WHY the head gaskets blew out in the first place.

Radiator
Radiator
Radiator

Actually, Subaru used a VERY dense condensor core for the A/C system in front of an already mediocre radiator. As the condensor clogs with road grime, dirt, bugs, etc. the already over stressed radiator can no longer keep up. It also doesn't help that the Subaru engine temp "gauge" is anything but. That son of a bitch will point straight up right smack dab in the middle from 130°F all the way up to 250°F. That's right, at 250°F, the temp gauge will still be reading happily in the middle of the "normal" range.

So my recommendations:

1. Ditch the A/C condensor (if you haven't already)

2. Buy the largest and thickest aluminum radiator you can find

3. Install a real water temp gauge in the block somewhere


Yeah I have noticed that water temp gauge issue before, we are running with an Ultragauge and I have water temp right on the main screen, the head gasket doesn't allow water in the combustion chamber, but id does leak oil pretty bad. Would you think I need to change it?