Engine rebuild coming - what to do?

[im4duke]

Recently replaced plugs and wires and decided to perform warm leakdown while in there. Here are the results:

#1 8%
#2 26%
#3 16%
#4 80%
#5 26%
#6 8%

I know, pretty ugly.

#4 leak is on the intake valve. Typical steps were taken to ensure valve wasn’t stuck open. No such luck. #’s 2,3, & 5 clearly want some attention too.

So, if I’m going to open it up, I might as well get what I want out if. Let me define that: around 500 rwhp for 80% street and 20% DE/track/AX. Keep my AC.

FYI, it supposed to be a Ruf 3.4 with upgraded cams and fueling, but I cannot verify it at this point. Car has 38k original miles.

Looking for ideas, suggestions, opinions on what to do. At this point I am considering variations on the following options:

DIY vs. shop (I’m in no big hurry and not afraid to buy tools, which I could even sell after one-time use)
Top-end vs. complete
Drop in replacement (eg. Protomotive Stage 3 3.3 litre Motronic 600 HP engine)
3.2 manifold, twin plug, crank fire, EFI, etc.

Although time is not an issue, cost is. That is, I don’t feel that I need to invest $20k to meet my goal. For example, the Protomotive engine linked to above is $12.5k. I could install that and probably sell or part out my engine to recoup a fair bit of it. In my mind, that would be financially more prudent than building my own super-duper engine for $20k+. Just an example of my willingness to consider all options here.

Anyways, would love to hear what you guys think would be the best direction.

Thanks,
Maxx

[porschett]

I have an 87 930 and was leaking a bit. Decided to do a rebuild. If you have the time and mone IS an issue, then DIY is the best route. My spreadsheet shows $2000 in parts which includes 964 cams and ARP studs and rod bolts. Subtract the cams and you're around $1400.

Tools will cost you around $700...engine stand, engine adapter plate, LM-1, 6-ton jack, sealants, P237 cam bar tool, etc...

But I'll warn you...there's a lot of "while you're in there costs" as well. Mine included replacing the rubber-center clutch with the spring-center clutch, Aluminum pressure plate, head porting/valve regrinds/new valve seats, headers, custom full bay IC, etc...

I'll be happy to share my spreadsheet with you so you can see what's involved.

David



It's very straight forward esp. if you have Wayne's rebuild and 101 book.

[im4duke]

Thanks, David. I would be interested in seeing your spreadsheet. Can you send it to maxx@alumni.duke.edu?

Is it fair to say that the primary hp-enhancing mods to your engine are cams, headers, IC w/ water and turbo? What is the hp result? 450-475?

[porschett]

Don't have HP numbers yet...still on the rebuild stage. I'll be happy if I get 400rwhp with the mods. Seems like it's reasonable with what has done here. Spreadsheet on the way...

A local shop added cams and got good gains, but when they ported the manifold/intake/plenum from 33 to 36mm, they saw an additional 50 on top of what the cams gave them.

He says my mods should net somewhere around 425-450 depending on the CIS (glup) tunning and state of the engine.

[acapella8]

I would love a copy of the spreadsheet too if you don't mind.

acapella8@aol.com

Thanks!

[im4duke]

Thanks for the sheet , David.

Had you done something like this before?
About how many hours into it are you and how many more do you expect?
Would you do it again? Maybe too early to ask...

Cheers,
Maxx

[porschett]

This is my first Porsche rebuild, although I've done other types of engines before. Being my first, I'm not really worried about hours. Things like this, I like to take my time and understand how/why things are designed and really appreciate the engineering that went into this. Compare this with a full time mechanic where they've done hundreds of these and know exactly where everything goes.

DIYs are never cost effective if you compare the hours you put into it vs. shop hours. But what you do get is experience, satisfaction of doing it right (or wrong) and bragging rights.

If you're doing an engine rebuild, then you have passion and consider it a hobby. But make sure you have plenty of time on your hands and plenty of workspace. Do a lot of research before diving in. I spent a month reading all related posts from this site and must have read both of Wayne's book 4x before actually turned a wrench.

Good luck Maxx.

[im4duke]

I definitely like the idea of doing the rebuild myself. If I go that route, it would truly only be a rebuild with "bolt-on" upgrades likes bolts, studs, springs, cams, etc. With B&B headers and a K27HFS, I’m guessing that would generate around 400hp.

On the other hand, my local shop is very supportive and has offered to kit the engine for me. That is, I disassemble, they measure, machine, etc. and give me back a kit to reassemble. They'll do as much or as little as I want them to do. That way I could get satisfaction in doing some of the work myself, learn a lot about my engine and save a little time and money.

However, I am very tempted to go EFI. I may end up tracking the car more and it would be nice to have the ability to support more HP down the road.

Again, my other option is to buy a used performance engine like the Protomotive unit I linked to before. Assuming the engine is what it is said to be, I might be able to buy it for $10k, upgrade the EFI for another $5k and sell my engine for $7k (unverified #’s). That would land me a 550-600HP engine for around $8k. That’s very tempting!

How does one go about checking out an engine like this? It’s out of the car already so I can’t run it. I could find a local shop in NJ to check it out or I could pay to have it shipped to a shop I trust and have it inspected as well. I plan to call the Protomotive shops and see if I can get the build sheet.

By the way, the pics on your website sure make it look like your rebuild is complete.