Top end rebuild - need help on choosing upgrades
 

Guys,

I'm rebuilding the top end of my '87 Carrera. I'm not planning on splitting the bottom end, as I've got no leaks and only 75K miles on the car. I'd like like to build a strong, reliable street engine that will be fun at the occasional DE event. I need your help to discern between meaningful upgrades and overkill.

Here's what I've got already:

3.2L Case/Crank/Rods/Oil Pump
ARP Rod Bolts
Mahle 98 MM Cylinders & RSR Pistons - 10.5:1 compression - great condition
Supertec Head Studs
3.2L Heads w/ Valve Job and twin plugged by Supertec - stock springs/retainers - NOT ported/polished
3.2L Carrera Cams
3.2L Intake/Throttle Body/AFM/Air Box
Motronic ECU/Andial Splitter/964 Dizzy/Steve Wong Chip/Stock Fuel Injection
993 Heat Exchangers with Flowmaster muffler (modified for pre-89 911)
Engine-mounted oil cooler and auxiliary cooler in front wheel well

I do not want to change the stock Motronic this year. That's a possibility for down the road. The engine needs to be built to last. There are lots upgrades that I suspect are more for track cars than street cars. How would I benefit from these or others?

Stronger Rods (Pauter/Carrillo/R&R)
Titanium Springs/Retainers
Ported/Polished Headers
Extrude Honed Intake
Bored Throttle Body
Mass Air Flow sensor to replace AFM

Some of these things seem more performance-oriented than reliability. I'm going to be on the street with this car 90% of the time. What upgrades will help me meet my goal?

Thank you!

Andy,

Most of these modifications will not do you any good with the mild cams you would be using.

Stock Carrera heads support up to 325BHP.

Stock rods and bolts are safe to 6750 RPM and you'll not turn the engine higher, even with 964 cams, since thats well past the power peak.

A MAF can improve throttle response IF,..... IF the software is perfect. Talk to Steve Wong @911Chips about this.

Now,....if you ditch the OEM intake system, Motronic, and stock cams, that's a totally different situation and some of those items would be mandatory for reliability. :) :)

Steve - Thanks for your reply. Keeping my goal of street performance and reliability in mind, what upgrades would you recommend to make the car more enjoyable to drive on the street and track, with the constraint of keeping the stock Motronic? Emissions are not a concern.

Other than your current listing I think I would just go for the 993SS cam and some new (stronger) rod bolts.

As Steve W. says... Changing the engine management will open up a world of possibilities.

Hi JP - Can you describe how the 993SS cams deliver power? Where's the sweet spot on these guys? Is there a shop you'd recommend to buy these or get a regrind?

I've got ARP rod bolts with stock rods currently.

This is a possibility for down the road, but I'd like to limit the scope of the project this year so I can drive the car. I've been off the road too long!

3.2 crank and 98 mm piston makes a 3.4. With 10.5:1 and twin plugs you could run a pretty aggressive cam (.500 lift or so) and PMO carbs and have a rocket of an engine. Easy and cheap compared to custom EFI. You won't know it's the same car. Once the PMOs are set up, which isn't very involved, you're done. This would be a 6500 rpm stump puller...

I have a 3.0 set up roughly the same way with GE 60 cams and it's all I want. Great bottom end and it rips on top; my only complaint (which isn't really a complaint) is it gets about 18 mpg if I'm real easy with the loud pedal.

Interesting. So the PMO carbs would replace my Motronic ECU? Is there a kit to somehow interface the carbs to my fuel injection system? Or would that need to be replaced? What controls spark in a PMO carbs setup? As you can tell, I'm not familiar with this option!

What's your recommendation on cams for my engine if I did not go PMO carbs?

The ignition would be triggered from the crank. You already have a distributor; it simply needs to be triggered and advanced for operation. The PMO carbs would replace your entire induction system. There is a carb throat for each of the six cylinders which is why they perform so well.

Look at your engine bay and then compare it to the picture attached. You'll see a lot more "blue sky" with carbs.

http://forums.pelicanparts.com/uploa...1327099138.jpg

I don't believe that my 964 twin plug dizzy can be manually advanced. I believe that is done through changing chips in the Motronic today. So I imagine I'd have to get twin plug dizzy with adjustable advance. So it looks like this upgrade would cost roughly $5400 to source new on Pelican:

JB Racing twin plug dizzy - $1500
PMO Carbs (46mm) - $3900

I'd be able to sell my entire induction system... that'd bring maybe $1500? So call it a net $4000 price tag. Would I need anything else?

What kind of power difference should I expect? I imagine I'd feel a difference across the entire rev range.

I don't know the specifics with the 964 dizzy but I think it can be mated to an MSD with programmable advance. The right way to do it is with two MSD boxes and two coils, one for the top and one for the bottom set of plugs. I think I would use PMO 50s.

Power wise, I'm guessing with everything you've mentioned +50hp but it'll feel like 100...

50 additional HP is about the same increase I'd get with a Carrera intake, motronic and steve wong chip. So the throttle response is the big difference9 is need to be more convinced of the difference before dropping $4k.

Guys - is anyone familiar with running PMO Carbs with a Bosch motronic to control ignition? Does Steve Wong create custom chips for this?

So if I plan to run PMO carbs on my car, should I plan to change any internals further?

From what I've read, I'd be able to run hotter cams with carbs, which would allow me to rev to 7K no problem. Even though I COULD run to a higher RPM, what's a safe plan for a car used mostly on the street? I'd like to identify a reasonable red line for a street engine with carbs, and then build to support that. Thoughts?

If you make a move to twin plug and PMO carbs, the entire Motronic goes away. The fuel side of the equation is replaced with the carbs and the ignition side replaced with the new dizzy and MSD CDI. I like two MSD boxes running the 12 pin distributor and two coils.

For the street, I rarely see 7,000 with mine although it pulls there easily. 7,000 rpm in 3rd gear is approaching triple digit speeds, but that's where mine is set up to run. The combination I used pulls like stock from idle to about 3,000. Once there it is a different engine and can / will spin the rears in first and second without manipulating the clutch. Loads of fun. Raceware or ARP rod bolts should be on your build list.

I've got ARP rod bolts with a stock rods and 3.2 case/crank/fuel pump. Aside from the rod bolts, should anything else be upgraded if I'm going to spin up to 7k RPM once in a while?

Cross-drilling the crank is cheap insurance but I didn't do it. I plan to do it though later. Other than that you should be good.