Maximum revs for std EA81

Buddyboy · Post by **Buddyboy** » Sun May 27, 2012 7:40 pm

Hi Guys, Can anyone tell me what should be the maximum rpm of a std EA81 Motor?
Regards Buddyboy

Brumby Kid · Post by **Brumby Kid** » Sun May 27, 2012 8:35 pm

Not sure sorry. Why do you want to know?
There is one easy and very fun way to find out....
Anyone got a spare EA81 they would like to donate?

Post by **TOONGA** » Sun May 27, 2012 8:56 pm

mmmmmm flat top pistons ... mmmmmm, only problem with over revving and EA81 is bending valves. Oh apparently you can safely rev one to 4800 rpm or unsafely to around 6500

EA-81

The Subaru EA-81 engine was produced from 1980 to 1989 and is a stroked version of the EA-71.
Specifications

Displacement: 1,781 cc
Bore: 92 mm
Stroke: 67 mm
Compression Ratio: 8.7:1
Valvetrain: OHV Pushrod
Horsepower: 73 bhp (54 kW; 74 PS) at 4,800 rpm
Torque: 94 lb·ft (127 N·m) at 2,400 rpm

TOONGA

BBoypebs · Post by **BBoypebs** » Sun May 27, 2012 9:09 pm

Untill you hear the valves hit the pistons.

Good mechanical motor should handle 6500rpm easy.

Post by **TOONGA** » Sun May 27, 2012 9:24 pm

BBoypebs wrote:Untill you hear the valves hit the pistons.
Good mechanical motor should handle 6500rpm easy.

If the valves in an EA81 hit the pistons, a conrod has given way or a valve and/or a collet has broken

I've heard a rumour they will rev to 8000 rpm, never got one there though :0

TOONGA

steptoe · Post by **steptoe** » Sun May 27, 2012 9:33 pm

Put a tacho on one and take it for a drive - use your ears as a rev limiter - pretty nasty beyond 4800 which is poor for an inline Jap 4 pot. 8 grand ? That'd be the infamous EA81S !

Silverbullet · Post by **Silverbullet** » Sun May 27, 2012 9:38 pm

steptoe wrote:8 grand ? That'd be the infamous EA81S !

I'll let you guys know when I've broken mine in and put a tacho in-cabin

Brumby Kid · Post by **Brumby Kid** » Sun May 27, 2012 9:56 pm

Same. Not that mine is an s. just highly modded.
Oh spoilers... Will post pics tomorrow. Got it back Friday night.
Just need to wait till I can put it in.

Cheers Cam

BBoypebs · Post by **BBoypebs** » Sun May 27, 2012 9:59 pm

TOONGA wrote:If the valves in an EA81 hit the pistons, a conrod has given way or a valve and/or a collet has broken
TOONGA

Too true. Had a mate's engine at 12500rpm while stationary.

RSR 555 · Post by **RSR 555** » Mon May 28, 2012 9:51 am

If in total standard form (i.e. tyres, rims, driveline, etc) the MY have revlimit marks on your dash which show the maximum speed at which gear can be held at. I don't have a tacho gauge on mine but working through the rolling diameters, ratios and simple maths you should get something pretty close.

Silverbullet · Post by **Silverbullet** » Mon May 28, 2012 6:02 pm

RSR 555 wrote:If in total standard form (i.e. tyres, rims, driveline, etc) the MY have revlimit marks on your dash which show the maximum speed at which gear can be held at. I don't have a tacho gauge on mine but working through the rolling diameters, ratios and simple maths you should get something pretty close.

This is true, I never noticed them until dad pointed it out

But I think these numbers are optimistic even if the car was brand new; 80 km/h in 2nd?

I've had mine nearly up to 70 in 2nd gear for a split second down a shallow hill and that is absolutely revving it's tits off.

Matt · Post by **Matt** » Mon May 28, 2012 8:34 pm

I have had mine up to 8 grand, was screaming, and i think may have had more, but i wasn't game...

Brumby Kid · Post by **Brumby Kid** » Mon May 28, 2012 8:41 pm

Was that the turbo or dual port heads engine?
Btw what does dual port heads mean?

Gannon · Post by **Gannon** » Mon May 28, 2012 9:47 pm

There are no 'true' dual port EA81's, some EA81's had the intake and exhaust valves in opposite positions and the divider in the exhaust port came all the way to the surface.

The EA62 was the only engine to have dual exhaust ports

Matt · Post by **Matt** » Mon May 28, 2012 10:51 pm

The Dual port, EA81T runs out of power long before 8 lol

Matt · Post by **Matt** » Mon May 28, 2012 10:51 pm

Also search on Google there is some good pics on there showing the differences in the heads.

sublime · Post by **sublime** » Mon May 28, 2012 10:52 pm

Gannon wrote:The EA62 was the only engine to have dual exhaust ports

Ahhh... No (Don't Believe Wikipedia)!

The Subaru flat four engines all had dual exhaust ports up until the revised EA63 in 1975/76... That means EA52 through to EA63 had an exhaust port on the front and rear of each head. Once the revised EA63 was released most EA engines had siamesed exhaust ports that exited from the bottom of each head.

Incidentally they also went from extremely quiet engines to extremely loud, like a certain chaff cutter four...

Brumby Kid · Post by **Brumby Kid** » Mon May 28, 2012 10:57 pm

Cool, didn't think these existed, surprised the twin carb doesn't have them.
Dual intake as well?
Where can I get some?
Will have to see how my ported heads do compared to the dual ports.

Cheers Cam

Silverbullet · Post by **Silverbullet** » Tue May 29, 2012 7:09 pm

Don't think the 63 heads would be compatible with 81 engine, there's also the fantabulous contraption of an exhaust manifold you'd need to make; 4 pipes coming from each corner in opposite directions

Brumby Kid · Post by **Brumby Kid** » Tue May 29, 2012 7:14 pm

I mean the heads that Matt has. Those twin port.