'77 3.0 turbo camshaft upgrade

[930turbo]

I'm looking for feedback on the use of SC grind cams in a 3.0 liter turbo. I want to know a couple of things; what kind of performance increase can I expect and how will it affect the off-boost drivability. I've read a few articles where this upgrade was applied to the 3.3 but that engine has a half-point higher comp. ratio and 10% more displacement. I am a little concerned with the smaller displacement and very low 6.5:1 compression ratio. My car is currently very lazy prior to the big boost hit. I am assuming the reduction in dynamic compression may adversely affect an already anemic 0-25 mph experience. You have to think carefully before pulling out in front of the city bus. However, is it possible the improved area under the valve curve will offset the loss of dynamic compression? Rumor has it this upgrade is worth somewhere between 60-100HP on the 3.3. Is this true or over optimistic?
The engine is a fresh crankshaft-up rebuild with the addition of an Andial intercooler, Borla muffler and 1.0 BAR wastegate spring. The thermal reactors and air pump have been removed.

[dean]

IMO, you won't gain much with a cam change. The people who claim a hugh change must be high or very hopefull. I think your biggest problem with the lazy off boost is your gearing. It is very tall.

When I installed my stock ROW 3.0L in my SC I took a friend out for a ride. He said "gee your off boost performance is just like an N/A SC". And it was. So the only difference that I can see is the gearing. I had the stock 915 which has shorter gearing.

Then I did a bunch of mods on my car. Shorty headers, EFI, big intercooler, K27, G50 tranny. One of the last things that I did was SC cams. Honestly I didn't notice much change in the car from the cams. I think I did the cams a couple winters ago and that was the only thing that I did that winter.

Last week I took that same friend to a party in my car and he was very impressed with the power. We could accelerate away from a car going 70 mph very quickly. I think he love it

So I would say gearing my friend. If you were to do one thing to your car to change off boost performance. Put a N/A G50 in it.

[john walker's workshop]

i find the SC cams sufficiently improve throttle response at lower RPMs so the car is easier to drive in town. i installed a '79 5 speed in my 77 930 which made it easier yet.

[Tom F2]

SC cams and an 8:39 final drive seem to make a big difference in my 77 930, despite a pesky and hard to find vacuum leak, but I can't really separate out which is most effective. My big problem with driveability turned out to be a WUR from a 3.3 car, which gives all the wrong control pressures for our 3.0 cars.

[john walker's workshop]

if you use the superceeded WUR on a 3.0 car, the top port must be left open. the original setup had a vacuum hose there.

[Tom F2]

Originally posted by john walker's workshop
if you use the superceeded WUR on a 3.0 car, the top port must be left open. the original setup had a vacuum hose there.

John, I found that the control pressures, hot and cold, were way too high with the WUR (Bosch number matched for a 3.3 Turbo) that was on my car. I got a big improvement in driveability by opening the bottom of the unit, and loosening up on the spring for the boost adjustment. After that, my control pressure was perfect, hot and cold. However, I still have driveability issues. Would you, please, clarify what is the superseded WUR? Also, I found that my car, a 77 930, has a hose for the boost control on the WUR. However, the workshop manual does not mention anything about what control pressure should be with boost. Thanks.

[930turbo]

I tried the superceded WUR from the 3.3 and never was successful enough to drive the car without fear of stalling coming away from a light. It was horrible. The later model has an additional opposing spring below the diaphragm and I was not successful at properly tuning with that WUR. My project came with teh new one so I put it on for the first time I ran the motor. I have since changed back to the original that still functions OK. I disassembled both WURs for comparison and inspection. The older simplified version is working the best for me thus far. However, I'm convinced it's still not right. The '77 appears to be a little mysterious even to the experts.

[930turbo]

I had a thought; what if I used the later WUR from the 3.3 and just plumbed it as such? Instead of trying to adapt the later WUR to the 3.0 and match the original connections. If this would work, does anyone have knowledge or photos of the vacuum line routing and connections of a '78-'79 turbo??