motor questions advice......

#1

once race weekend left this year, question for the offseason (besides making car look prettier) is what to do with the motor.

motor has made a low of 140hp 148tq at nasa mid-atl dyno at the track, and made 146 hp 148tq at performance autosport in Richmond.

leakdown was between 2 and 9% with #4 at 9% the worst, compression was 150-150-170-170-150-150

.

So question is on a limited budget:

  1. screw it, race it as it is and don’t worry about it
  2. buy a used motor and hope its better than the one in the car (cost less than $1000 for motor plus cost of engine swap
  3. refresh the head?
  4. take the spare motor (block and head) that came with car, throw it in there and see what happens
  5. Win the lottery and buy Gags spare motor?
  6. spend spare racing budget on beer?
  7. ??
#2

win the lottery??? have you seen your daily driver lately??

#3

Damn - I would be happy with those HP numbers (mines a dog, with big fleas.)

Just learn to drive a slow car fast…

…and spend the rest on GOOD beer.

#4

#5 - but wait. I won’t sell you that motor for good reason even if you do hit the lottery.

I have a brand new (literally brand new head from the factory) head with cams/& new rockers arms etc for sale. But your cheap ass won’t buy it. :wink: That will probably be the best bang for the buck. If you are worried about the bottom end, I also have a 75k mile auto that might be for sale as well. I recall the one that came w/ your car was a junk build, so I don’t vote for that.

And spend the remainder of your racing budget on making that heap of junk better. :wink:

#5

I guess you never heard of Harper. The dude can wheel. That’s a fact.

#6

Unless there is reason to suspect the bottom end, just do the head. $100 for a gasket set, tbelt and head bolts, and $300-$800 depending on who you have do your head, and you’ll get the most bang for you buck.

That assumes that you R/R the head yourself, which is pretty easy.

#7

Options 2 and 4 are bad ideas; option 6 is a given. If leak down doesn’t indicate bottom end leakage, refresh the head with new rockers and a Febi cam then dyno. Pick a shop that other racers with strong motors are using for the machine work! When money permits, build a .020" over bottom from your spare motor, remove head from old bottom end, lap valves, and re-install head on new bottom end.

#8

How do u tell if leak down indicates bottom end leakage?

#9

Air will go into the engine block and come out the dipstick port and intake. It’s not an exact science. The important place for no piston leakage is around tdc. So suspect piston needs to be in the right place. Engine needs to be hot for a good test so you have to run the engine a bit and then work fast.

I’ve dicked around with leakdown tests quite a bit for a hobbyist type. I’ve learned to not trust my leakdown test too much until I’ve done it about a hundred times and removed every possible variable that could possibly confuse my test. Our bottom ends are pretty tough. Refresh the head and call it a day.

#10

Regarding using a new Febi Cam, are you guys seeing that much wear on the OE cam? Meaning, is it a pretty noticeable difference in performance (hp or tq) between a used and a new cam?

The reason I ask, is because I am thinking of the same approach over the winter of swapping the head on the bottom end I have in the car right now (engine #4 since last season…)

#11

In my experience, cams can wear significantly with very little visible indication of wear (upwards of .010"). If the cam has any visible sign of wear, I junk it. The only way to measure the cam for wear is with the cam installed in the head while using a dial indicator to measure valve movement then compare to a new cam. I have never encountered a used cam that I was comfortable with re-using and comment on actual performance numbers. I will say that a new cam is not that expensive (bimmerparts.com) and the cylinder head is not a place to make sacrifices in any engine build.

#12

Rich,
Any advice on which brand camshaft to use? Lifters? The pricing makes me want to replace damn near everything in the casting with new.

#13

I am pretty sure he put a brand new Febi camshaft in my motor.

#14

[quote=“RRhodes” post=74318]Rich,
Any advice on which brand camshaft to use? Lifters? The pricing makes me want to replace damn near everything in the casting with new.[/quote]
I always use Febi camshafts and have recently switched to using the IE HD rockers. OEM BMW rockers are a bit more expensive than the IE units; stay away from Febi rockers.