I've been toying with this idea for a while. Months, actually... The note is partly thinking out loud, partly asking opinions of Jake, and partly asking opinions of anyone else who wants to chime in.
I have a 2.0L 914. My local PCA (Zone 7) rules have a particular class that I want to run in. In this class, the engine has to stay stock in most large respects. However, modifications that are specifically for the purpose of increasing the reliability of the engine are explicitly allowed. ("Methods of ensuring oil flow" and "external oil coolers" are listed as two examples.) So I am trying to come up with ideas for a motor that would be prepared to the limit of the rules.
The purpose of this motor would be to go as far as possible between overhauls--even just re-lapping the valves--while keeping stock or better power. (95 HP DIN.) The engine would see all manner of use, from daily-driving in the city, to 4-hour freeway trips (probably running 4000 RPM in top gear), to 20- to 30-minute lapping sessions which are almost constantly at WOT from 4200-5000 RPM. All of these in air temps ranging from about 30 degrees (very rarely) up to 110 degrees.
Restrictions:
Stock-grind cam
7.6:1 compression ratio
Max. 94.5mm bore (allowed 0.5mm over stock)
71mm stroke
Stock size valves
Must run D-jetronic fuel injection
Must use 914 heat exchangers and a muffler of some kind; SSI exchangers are OK
Stock distributor (points replacement and/or CDI is allowed)
No porting of the heads, though if that were somehow
only done for reliability that might possibly be allowed
Stock cooling system
...And for my own personal convenience, it must also be able to pass current California smog tests. (It won't go exempt until 2004.
And I'm not completely confident that the jokers in my legislature won't change that again soon!!)
From reading on the Shoptalk Forums, it seems that Jake believes that using the stock cam, stock compression, and D-jet FI are very good ways to heat the heads up until you run into problems. I have dropped three intake seats (mostly due to mixture problems I think) so far, so I am worried about overheating the heads. But those are the rules I run under...
I had been thinking to run LN Birals in the stock size initially. But the prices of the production Birals came out somewhat higher than I had been anticipating, and it seems the step up to Nickies might actually be something I could stomach.
It is my hope that using cylinders with superior cooling properties would help on the head temperature front. I was also considering some kind of coating on select parts of the heads...
Since 914s, particularly on "sticky" tires, can generate significant lateral G forces, I need to address the oiling issue. I have been using the Weltmeister Oil Trap, AKA "the tuna can", which is a small sump extension with an oil pickup extension. It has proven OK so far, and it does not seem to be in much danger of hitting anything. But Jake disapproves, and I can see that I might be very unhappy if I go over the rumble strips a little too enthusiastically and rip the thing off. So a less-vulnerable method may be in order, like an Accusump. I figure a 1-quart (or whatever the smallest size they make) would be more than adequate.
What other oil system modifications would be in order? An external oil cooler is often recommended for time-trial cars (20-30 minute run sessions at Wide Open Throttle, 4000-5000 RPM the whole time). Would it still be necessary with the other mods mentioned? Would it be a better idea to block off the stock cooler location and only run the external cooler? If an external cooler is recommended/required, would a large fan-equipped cooler in an area with mediocre air flow that is heated by the exhaust being below it be good enough, or would a cooler with lots of cold air flow be required?
Would other coatings be recommended? Cryogenics or heat treatment? I am still, quite frankly, rather skeptical of most of the claims made for cryo treatment (my research has turned up quite a few people on each side of the debate) but I am willing to give it a try if it really will help.
Stock valves or aftermarket? They must be the stock sizes, of course, but whose?
Will having a lightweight valve train help the engine be more reliable? I can see how it could help if I miss a shift and over-rev the motor (to a limited extent, at least) but is there any point with the stock mild-mild-mild cam?
Would tightening up the deck, while still maintaining the 7.6:1 CR, be worthwhile from either a reliability or a power standpoint?
Pretty obviously I would want to use the 911 swivel-foot valve adjusters, have all of the moving bits balanced, and so on.
And finally, of course, is the question of money. Nickies will cost--yes indeed they will!! And all of the other detail work (balancing, CC'ing, 911 valve adjusters, match-porting the oil pump, etc., etc., etc.) all takes time which means money. I wonder what kind of ballpark all the above would land me in?
Thanks for any thoughts on the above!!
--DD