4AGE top end rebuild

[*E9*]

I need to part rebuild my smallport 16V 4age fairly soon as it either has worn piston rings or valve stem seals (It burns a signifcant amount of oil)

While the head is off, I will be getting it ported, flowed and decked (not 100% sure how much I will have decked off yet) plus run a 0.8mm headgasket for some extra compression.

I have two options concerning cams:
-Leave the stock cams in, rebuild with a bit of extra flow and compression, and enjoy a non oil burning 4AGE
OR
-Throw in a set of aftermarket cams, which will give a difference that can be felt in the seat of the pants, but still remains very suitable for daily driving, as the car is a daily driver. Standalone ECU is not an option, and I would like to avoid a piggyback if possible.

I have done a little bit of research, and it looks like 256 cams work quite well for the street, or 264in and 256ex, which apparently helps spread out the powerband more.
I wish to keep the powerband similar to OEM spec, an upward shift toward redline is ok, but as I will most likely not get a piggyback ECU, I have a maximum of 8000 rpm to use. And I usually stay below 3000 rpm for my daily commute. I also don't want my fuel consumption to go up much.

Can anyone shed some light as to what I can expect with a pair of 256 cams or 264/256 power deliver, driveability, torque and fuel economy wise?

And would a 2" header back exhaust be restrictive if I ran those cams?

[Subaru_Kid]

IMO go for a 2.25 on the exhaust, its what I run with 240deg bigport cams in my smallport and its got more power and torque.

Fuel use will increase with the cams, power delivery will move up in the rev range and the car may need to be revved harder in everyday driving. Not sure which gen 4AGE you have, but if it is your daily driver then just place a set of bigport cams in as its easy on the budget. It wont ruin your economy, or your driveability and add a small amount of power over smallport cams.


Also when did the car smoke, form a stationary point as you drove off or was it only when you floored it?

[xero]

if you want to keep it as close to stock as possible while not being a pig and standard ECU 256 deg is the go. the small increase in compression (you MIGHT get to 11:1 if you try really hard with a head skim and thinner gasket, at best your gonna get ~10.5:1) with those cams will give a nice pokey package without sacrificing drivablility. fuel consumption would have a marginal increase as where you spend most of your time in the rev range will have a marginal effect. in fact you may find the engine is running a bit leaner than it was before...

alternatively, and a better idea in my opinion, is you go for a pair of 264s at ~8mm lift, along with the head work and fit a programmable ECU. something cheap-ish and easy like a haltech sprint 500, adapt e420c, microguess LT10 etc etc have it wired and tuned, not only will you see gains in power but will often see increases in fuel economy (if tuned correctly) and it definately wont be a pig to drive

[ctrain]

have you made sure that its the valves that are stuffed and not the rings? you can do a wet compression test to see if its the rings or the valves, you dont wanna rebuild a head hoping to fix it and find out it was the rings all along.

[*E9*]

IMO go for a 2.25 on the exhaust, its what I run with 240deg bigport cams in my smallport and its got more power and torque.

Fuel use will increase with the cams, power delivery will move up in the rev range and the car may need to be revved harder in everyday driving. Not sure which gen 4AGE you have, but if it is your daily driver then just place a set of bigport cams in as its easy on the budget. It wont ruin your economy, or your driveability and add a small amount of power over smallport cams.


Also when did the car smoke, form a stationary point as you drove off or was it only when you floored it?

I have a 16V Smallport, aka Redtop. General consensus is that a bigger cam moves powerband further up the rev range, hence I am toying the idea of mixed degree cams to spread out the powerband more.

The car mainly smokes when I floor it and have the revs up high, I can actually see white smoke in the rear view mirror, I think it also smokes a bit on takeoff too but I rarely see this myself in the mirrors.

if you want to keep it as close to stock as possible while not being a pig and standard ECU 256 deg is the go. the small increase in compression (you MIGHT get to 11:1 if you try really hard with a head skim and thinner gasket, at best your gonna get ~10.5:1) with those cams will give a nice pokey package without sacrificing drivablility. fuel consumption would have a marginal increase as where you spend most of your time in the rev range will have a marginal effect. in fact you may find the engine is running a bit leaner than it was before...

alternatively, and a better idea in my opinion, is you go for a pair of 264s at ~8mm lift, along with the head work and fit a programmable ECU. something cheap-ish and easy like a haltech sprint 500, adapt e420c, microguess LT10 etc etc have it wired and tuned, not only will you see gains in power but will often see increases in fuel economy (if tuned correctly) and it definately wont be a pig to drive

You reckon the pair of 264's with a piggyback ECU would retain low end power, while I would love more mid-top range pull, and a faster revving engine, I drive quite conservatively most of the time, so I want to retain similar performance levels in the low rev ranges, as a healthy stock smallport would.

have you made sure that its the valves that are stuffed and not the rings? you can do a wet compression test to see if its the rings or the valves, you dont wanna rebuild a head hoping to fix it and find out it was the rings all along.

I am looking to get a compression test done to see what I am working with, would I be able to see the piston rings once the head is removed (I'm not that good with engines) ?

[Javal]

I am looking to get a compression test done to see what I am working with, would I be able to see the piston rings once the head is removed (I'm not that good with engines) ?

No. You need to have at the bare minimum a compression test done, a leak down test would be better. Get thus done before you throw your money away having the head redone when it could well be a problem in the bottom end, launching straight into it without doing the appropriate testing is downright foolish.

[*E9*]

If all goes to plan this weekend, there will be a dry and wet compression test done, and a leakdown test.

If the piston rings are stuffed, what sort of cost am I looking at to replace them and fix up the bottom end to good OEM spec?

If the rings actually are stuffed, then I will be considering a few options...

[Subaru_Kid]

Sounds like the rings are your main culprit but the valve seals are on their way too...

Ive used the Bigport cams on the track and can tell you there is a definite increase in response and the power band is stretched over a slightly longer rev range. It still picks up power between 4500-5000 and toque is still good. Your looking at 1/8th of the price of aftermarket cams which is why i am suggesting it to you...



Here is a cut out of a motor. the rings are located around the pistons (see the 3 lines on side of piston) and are in the cylinders. so you wouldnt be able to see them.