Non GS, rather swap a cam or complete head?

[wkmpt]

Okay.
This related to the other thread I posted a little bit ago.

1987 BMW 325i. Currently has hot cams.

Am wanting to return to stock for the time being, to improve fuel economy.

To those that have experience doing both, my question is:
Would you rather swap a complete head, or just swap the camshaft?

A fellow on a different forum suggested that they *should* take about the same amount of time either way, and he'd rather do just the cam so he doesn't have to fiddle with the head gasket.

Ultimately, I'm shooting for fastest transition so my car is non-op for as little time as possible.

Thoughts? Opinions?

 

[Nessism]

I'd do the cams. Head gaskets are expensive.

 

[tkent02]

I'd do the cams. Head gaskets are expensive.

+1, anytime the head comes off it can turn into a bag of worms. I'm pretty sure the cam can slide out on that model by just raising the front of the engine a little bit.

 

[Baatfam]

Are you really going to save enough gas to make it worth the trouble? And your time? And the cost of parts?

Just askin'....

 

[wkmpt]

Are you really going to save enough gas to make it worth the trouble? And your time? And the cost of parts?

Just askin'....

I'm fairly sure. Right now I'm getting in the neighborhood of 12-15/city with a really genuinely (I promise!) soft foot. I'm dropping around $100 every 5-7 days of driving.

Conservatively, I can snag a replacement stock cam in the vicinity of $150, and snagging a lower-geared (lower ratio?) differential should be around $250. My time doesn't cost me anything, and most of the time I find working on mechanical stuff enjoyable time well spent.

I figure if I can gain even 25% better economy, than at 20-25+ bucks a week ($80-100/month) I can net back the cost of the parts in a few months. I don't see gas prices dropping 25% in the next few months.

I'm not sure how much gas I can save with the stock cams, however most mpg statistics I can find for the 325i put city driving in the low-->mid 20's stock. The stock differential is for manual transmissions is a 3.73:1, other available bolt-on differentials are a 3.25:1 (drops approx. 200 rpm at speed) and a 2.97:1 (drops approx. 400 rpm at speed). So with any luck the combination should net me at least fair gains in economy.

So that's my logic. Help me iron it out if anyone sees any kinks in it.

 

[Baatfam]

So that's my logic. Help me iron it out if anyone sees any kinks in it.

I find it hard to believe that a hotter cam would move you from low/mid 20s to 12-15...
I could see a 2-4mpg shift, maybe...

12-15 seems real low for that car, my 4K lb caddy with a 3.6 gets 18 around town....
Are you sure there isn't something else amiss?

To be honest, I really don't know anything about BMW cars, so your logic may be perfect...

 

[tkent02]

My daughter's 325i gets about thirty mpg, if you are just cruising at a reasonable speed.
In town 25 or so but she's aggressive. That E30 is my favorite car by the way.

 

[wkmpt]

I find it hard to believe that a hotter cam would move you from low/mid 20s to 12-15...
I could see a 2-4mpg shift, maybe...

12-15 seems real low for that car, my 4K lb caddy with a 3.6 gets 18 around town....
Are you sure there isn't something else amiss?

To be honest, I really don't know anything about BMW cars, so your logic may be perfect...

I might be a bit pessimistic on the mpg, might be consistently closer to the 15 than to the 12, but either way I know there are v8's out there doing as well or better...

I know I'm due for an oil change, but air filter's good, new dist/plugs/wires end of last summer/ can't think of too much else to be wrong...I hope.

Biggest thing about bimmer's in general is that they'll run almost indefinitely with basic maintenance, if the electrical gremlins are kept at bay...

 

[wkmpt]

My daughter's 325i gets about thirty mpg, if you are just cruising at a reasonable speed.
In town 25 or so but she's aggressive. That E30 is my favorite car by the way.

E30's are close to my favorite, they're such awesome little cars.

My true favorite, though, is the E28 535is.

 

[tkent02]

Yeah, those are nice too.

 

[fastpakr]

Test drove a 535is once, but never had a chance to own one. Great machine. I owned a 528e for a while and it wasn't bad, but the 535is had a lot more to offer.

For what it's worth, I agree that there has to be more at play here than just a hot cam. Have you checked your compression recently? Tested spark at each cylinder?

 

[7981GS]

Replace the timing belt while you are at it.
They are interference engines and if it jumps timing,
all of your valves/rocker arms get bent and broken!
Then, you WILL be pulling the head.

Just sayin'

Daniel

 

[tkent02]

Sometimes guys trying to get more power will put in much bigger injectors, or bump up the fuel pressure. That doesn't normally do any good but it would certainly kill the gas mileage. A clogged catalytic converter can do the same thing.

 

[wkmpt]

Fuel delivery sys is stock.

How do you know if the cat is clogged? The exhaust seems to be flowing freely.

Replace the timing belt while you are at it.
They are interference engines and if it jumps timing,
all of your valves/rocker arms get bent and broken!
Then, you WILL be pulling the head.

Just sayin'

Daniel

Forgot about that, thanks for reminding me. I'll order one.