3.3 RSR Engine re-build advice needed
 

I've acquired a 74 914 with a 3.3L IROC spec engine that has sat for 15 years after experiencing a "big bang and black smoke" during a track day in 2007. Not much more information was provided so I've been disassembling the engine to determine the source of the incident.

Some details on the build.
It was built by a local indy shop back in 2002 and saw about 7 track days (20-30 hours) of runtime.

1978 3.0 case
Twin Plug heads
Mahle 100mm pistons & Cylinders
Genuine RSR 3.0 MFI pump
Genuine RSR High Butterfly throttle bodies
Genuine 906 cams
Stock 3.0 valves and rockers
Stock rods
Electromotive HPV-1 Ignition

The pistons and heads had heavy carbon buildup. The exhaust valve on cylinder 4 had carbon built up around the seat and the valve was not sealing during a leak down test. All the rest had no issues. Mechanically everything seems good.

There were no valve stem seals installed on any of the valves.

The spark plug wires used were standard off the shelf copper wire of which 3 of the 12 had no continuity. My theory is there was issues with spark that caused a backfire.


I plan on using the 914 as a weekend mountain cruiser with the occasional auto-X and track day. I don't plan on racing it.

There are some very rare expensive RSR parts in this build that make this somewhat unsuitable for street driving.


Now on to my questions.

- Would I be better off putting the engine back together, getting it running and selling the entire engine to someone building an RSR tribute? I could then source a stock 3.0 or 3.2 which would be plenty of engine for my purposes.

- Keep the engine but install a milder cam? Would the MFI need to be tuned to work with a milder cam or is it more related to the displacemtent.

Anyone have ideas what the RSR fuel injection and the 906 cams would be worth?

I'm new to the Porsche aircooled scene so any advice or opinions would be appreciated.

Dave

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Unless you personally value having cool rare RSR items on your engine (which would be valid, by the way), you might consider selling the RSR and 906 parts since you could probably replace them with some carbs or EFI and better suited cams and be way ahead in terms of $$$.

If you keep the RSR MFI, it would probably be wise to have it at least calibrated by a specialist and possibly retuned for whatever cams you choose.

As for the Big Bang event the motor supposedly had, you may have gotten lucky if the oil was clean and the top end did't reveal anything other than being dirty.

I am feeling pretty lucky about my findings. I've purchased new plug wires and a trigger wheel from Clewett which should be an improvement over my current saw blade.

I really would like to experience the MFI so I'll look into getting it calibrated once I determine which cams would work best. I guess I should find out what the parts are worth though.

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You might talk to Richard but I've heard of some issues with the HPV1 not holding timing very well. I run the later XDI on a couple of cars with success but it has recently become obsolete.

I talked to Richard about the HPV-1 and he had nothing but good things to say about that system. I'm hoping a set of his plug wires and the new trigger wheel and sensor will keep things running smooth.

If all your information is accurate you have a mishmash of parts.
The pump looks genuine. Could be worth a boatload to the "right" guy.
All 906 cams had 47 cam journals and were designed to run solid rockers.
The 47 mm housings when fitted to a 3.0 type head offers some dimensioning issues. 3.0 cams [49mm) have a larger base circle facilitating the use of a shorter valve.
This miss-match causes the issue. Solid rockers won't work.
I this was my project, I would look to selling the pump, high butterfly and Carrera 6 cams to finance a more appropriate performance engine for your purposes.

Just my 2 cents mind you.

You would not regret a nice mostly stock 3.2 in your 914. Great low end grunt and power. I have an '87 3.2 in my original 914-6. I went with 964 cams, large-tube SS heat exchangers, a custom Steve Wong chip and it runs great with the stock Motronic injection. Lean into the window and turn the key (in neutral of course with brake set) and she fires right up. No gas smell and decent mileage as a bonus.

Thanks for your thoughts on this Henry. I sent you an email with some follow up questions.

Dave

This sounds like a great solution. I may just reassemble the engine and sell it off to fund a stock 3.2. I'd rather be driving the 914 than tuning the racing engine.

Here's an option. We can use your parts for a down payment...



https://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1126035-77-porsche-rebuilt-2-8-engine.html

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