3.0sc what to do?

[Matt_West]

I have a 3.0 SC engine that was rebuilt by a respected member of our community 60K miles ago. The rebuild included new pistons, cylinders, oil pump, rod bolts, etc...

The problem is that it now exhibits low compression on the number 4 cylinder. All other cylinders are remarkably consistent and show good numbers. The car still runs strong, but I am thinking that I am going to have to do something about number four eventually.

The delema is what to do while I am in there? It would seem that I have a reasonably solid motor that needs a little cylinder head TLC, however I would hate to tear it apart without improving it.

Having read the forums I would love to do something like a high compression 3.2 short stroke with 46mm PMO's. However there are two concerns: would stock rod bolts be a liability (remember they are 1mm fatter that the 3.2 carrera long stroke) Cost of 98mm PC's.

So is there a middle road that will allow me to make some upgrades that can be re-used further down the road. Specifically I am wondering about:

1. Twin plug heads and open up ports (???)
2. JE pistons for high compression and valve clearance ($900)
3. Rowdier cams than CIS pistons would allow ($650)
4. 46mm PMO's ($3K)
5. Crank fired twin plug ignition ($1K)

My thinking is that a flat six should not have CIS, but individual throttle bodies. The PMO's could support a wide range of future upgrades. The twin plug heads could be re-used (right??) on a future rebuild. Basically when the bottom end wears out I could do a 3.2SS or 3.4 if a Carrera crank was in the picture.

So what kind of torque and power would my proposed recipe make? Am I delusional in thinking that I could reuse the Carbs and heads.

[Porschekid962]

Ditch the twin plugging and crank fired ignition. Its useless if your running under 10:1 CR. Stick with your dizzy, put on some carbs, hotter cams, port match your heads to intake and exhaust, 9.5:1 CR pistons. Spend the money on a better exhaust if your not against swapping back to your stock setup to smog it every other year.

Before you really get into the motor ask yourself this, what kind of driving do you do, what kind of motor do you want, is your suspension setup well i.e. polybronze bushings, sport dampers, lowered a tad with some neg camber?
If your happy with your suspension and the rest of your car then go ahead and open the motor up a bit.

Best of luck.

[Mysterytrain]

Been there done that..well, thought that! I think P-kid is right, you need to think about what you are going to do with the car. My car [78 ] needed a rebuild and I bumped it up to a 3.2SS, 964 cams, SSI's and 2/1 dansk. My concern was NJDMV and passing emissions so I kept the CIS and still have the original cat and exhaust if I need it. I got around the testing by registering my car as a collector vehicle which limits me to 3000 per year. I guess I could go to carbs but its been great as a street car and a major improvement over what I had. You will be shocked at how much money you can dump into an engine project.

[Steve@Rennsport]

Matt:

Do a leakdown test that locates the precise location of the compression loss. You need to know WHERE the leakage is; valves or rings.

P-kid offered sound advice,.....you should define the car's usage and whether smog compliance is a factor here so you can plan the performance upgrades you want and assemble a realistic budget.

Although its fun to build a 'hot-rod' type 3.0-3.2-3.4, in many cases, its cheaper to install a 3.6 that is smog compliant and outperforms most anything for street and track,.....

Please let me know if I can help as this is our specialty.

[Matt_West]

Thanks for the replies.

I have installed poly bronze bushings all around plus mono balls front and rear. 22mm front and 28mm rear sanders torsion bars. For exhaust I have installed SSI's and am waiting on a Monty. Smog compliance is not an issue for me.

I took the car to the track last weekend and liked how it handled. I felt the greatest weakness of the car was that it was under powered. No mistaking that it was very fast and I could carry a lot of speed, but I was giving up ground all day to a 2002 Boxster S when it came to the straights.

Second to power were brakes, but those only really became a minor issue when the car was run two sessions back to back and I asked the instructor to drive and demonstrate maximum braking capability for the second session. I think for my skill level I should be able to get by with some additional cooling for a very long time.

Ultimately I want more torque and power. I love the look and sound of individual throttle bodies and hear great things about what they do for throttle response.

If I go the 3.0 9.5 to 1 compression, single plug ignition, 46mm carbs, cams, and have some head work done; what can I expect in the way of an improvement? What do you think this will cost?

What does a good 3.6 conversion run?

[Porschekid962]

You thought it fealt underpowered, ok. With my dads 74 911 with 78 3.0, CIS, SSi's, 20/21 cams, 2 in 2 out muffler, msd single plug I kept up with a 996 turbo at willow streets hehe! I really dont know what 3.6 conversions cost but you need a decent motor, wiring harness, new engine tin, figure out the exhaust, I am not all that savvy with these conversion but I am sure things add up quickly. If you are going to rebuild your motor why not drop in 98mm p and c's, hotter cams, carbs, keep your exhaust, keep your dizzy, coil, i think the fuel pump needs to be changed but by and large there is less to do to get the motor back in the car.

Of course the torque or power wont be the same as a 3.6 and the money is getting close to a 3.6 conversion, unless you build the motor yourself and save some bucks. I say decide what you would do to the 3.0, price it out, then price out a 3.6 conversion and compare. happy hunting.