2.0L race motor questions-beginning the learning curve

[jplavanjr]

Oh wise Pelican racers: I humbly seek your motor building/design advice.

I'm just starting to vintage race an early car with a '66 2.0L motor that's had Solex cams put in at some point and hydrastops on the tensioners but is otherwise stock.

I plan to build a race motor soon and am trying to learn as much as possible about all of the potential improvements one might consider to extract the maximum performance (while still staying 2.0L legal). I understand that most every performance increase is a compromise of some sort (either $ or reliability/longevity) but I want to consider all of the pros and cons as I move forward.

I will be running with VARA and possibly HSR-West at most of the road courses in the Southwest. As a rookie, the wider the power band and the greater the torque the motor can produce the better off I'll be.

I've read Bruce's book and have some experience with 912 full-race pushrod motors but I want to learn as much as possible about these old 2.0L 911 motors.

For those of you with experience with 2.0L race motors:

A) How would you spec a "no holds barred" 2.0L racing motor without compromises for cost and/or reliability?

B) What would your first compromises be to decrease cost and/or improve reliability for those things contibuting only marginal improvements at a high cost of either dollars or reliability?

One specific question I have right now concerns compression ratio. Does everyone agree with Bruce Anderson that a CR over about 10.5:1 with 2.0L heads and 81mm pistons causes an inefficient fuel burn because the piston must be domed too high to create the higher CR and the "backside" on the chamber is blocked from the flame front? Can the CR get any higher via modifications in the piston dome design and still have an efficient fuel burn with a single plug head?

Thanks in advance for your responses!

JP

[jluetjen]

jplavanjr;
The 6/94 (#46) issue of Excellence had an excellent article on racing 911 pistons. One thought that stuck with me after reading it was that while Porsche only raced with 10.5:1 CR, IMSA and SCCA racers had no qualms about going up to 12:1 or 13:1 (when using race fuel). How you get there I'm sure is a somewhat protected secret.

If I were you, I'd sit down and think of the parameters for your race engine. Specifically - time and money.

Regarding the specification of your racing engine, I've found the following process useful. Keep in mind that the pretty much all-out 906 engine developed 210 HP (carbed) to 220 HP (with MFI) which pretty well defines an agressive target for the 911 engine. This is a BMEP of 180-190 psi which is pretty good. Conversely a stock 2.0S generated 170 HP with MFI.

First: Read the preparation rules of the racing organization.

Second: Read the preparation rules of the racing organization again.

1) How long do you want the motor to last? This has an inverse relationship to the red-line.

2) What sort of intake design are you allowed? MFI? EFI? Which carbs 46's or 40's? Any restrictions on the venturi size?

3) What sort of fuel are you allowed or required to use?

4) Can you twin-plug?

Based on the answer to these questions, you can then start to map out your engine strategy...

A) Intake design will determine how much air you can pull. At this time also you might want to take a look at your intake ports to ensure that you keep the gas speeds within the optimal zone. This will pretty much determine you maximum potential HP.

B) Once you know how much air you can get into the engine, given the 2 liter capacity, you can pick out how much cam you want to use. Until you run out of air, wilder cams (ie: 906, GE80, GE100?) will generally produce more torque higher in the rev range which equal's more HP. But 8500 RPM will wear out an engine a lot faster then 7500 or 8000 RPM will.

3) Once you know the cams, you can pick out the piston design based on valve clearances and desired CR. Milder cams may not tolerate a super high CR like wilder cams will. Wilder cam's on the other hand almost require higher CR's to help fill in the hole when off-cam. A higher CR will also help if you are intake limited since it will prop up the compression at high rev's when the limited intake is choking off the air. This is why restricter plate NASCAR engines are often built with a static CR of 14:1 or 15:1 (or higher?)

4) Once you know the cams and the resulting desired rev range, you can spec out your bottom end so that it will survive what you are asking the engine to do.

That would be my approach. I'm sure that there are others which will work as well.

[Plavan]

Hurry up and get that car running! With my dad's #20 car getting a new motor and you and your dad messing with your cars.... Will I ever be able to race you guys???? I guess I'm the only real "Plavan" ....hehehehe.
Too bad you or your dad wont be around for Phoenix or Vegas. My dad should be ready for Vegas. Wonder how he is going to take it when I pass him

Also, I have my rev limit set at 7500 RPM. Shift light at 7400. I'm interested in having a motor for awhile. Dad's car is at 7300. Most of the "budget racers" keep them around 7300RPM. The "Budget Racers" are also the one's finishing at the top.

Glad to see you utilize the board.

Cya Cousin

[jluetjen]

Ohhhh - that answers the question which I hadn't asked!

Welcome aboard!

[steveW]

Whoa!

Make it stop and go round corners better first. Actually the easiest and cheapest route is to make it lighter and thus improve power to weight ratio which results in less work on brakes, suspension and everything.

[TimT]

Like other said make the chassis and brakes solid.

About the engine, I believe the 66 has an aluminum case.Which is stronger than magnesium but will still benefit from being shuffle pinned so it will stand up to sustained high RPM running. Also install case savers, and have the case machined for a bearing for the intermediate shaft.

You should have the oil-bypass mod done to update the oiling, and installling a higher volume oil pump (from a carrera or SC) can only help. Installing pressure fed tensions would be great, exept that I dont know if it can be done on a 66.


If cost is no object some Pauter or Carillo rods would be nice.

If you do all the above youll have a bullet proof bottom end.

Now you can build the top of the engine to make power

[TRE Cup]

Here is a little on the motor:
Carillo rods, Call Jerry at JE pistons and discuss how high you can go- there are a lot of 2.0 racers that have done that already with great results. No need to reinvent the wheel. Also - look into welding up 2.7 heads and cutting them for the 2.0 barrels. Get some 4 bearing cam housings (911SC or Carrera 3.2) and buy a set of cams from Jerry Woods. Have Jerry set up the heads as well. Early S heads are impossible to find, so the mod 2.7 route seems the way to go. 3.2 or 964 oil pump with oil bypass mods on the case. Raceware hardware throughout. Case mods- shuffle pin, boatail the webs, polish the inside (hey you asked for cost no object!)EBS for the springs and retainers. Headers- there are a couple high dollar sets out there Cox and Dave Mclaren. They extract the last few hp you need to blow off the families' doors
Good luck

[jplavanjr]

Thanks for the tips so far guys.

I'm comfortable with the chassis & brake setup options and lightweight issues so that's a given. I've got the car down to about 1970lbs now with more to go but HSR-West rules require a 2000lb min. so I'll have to ballast some when I'm running with them.

Regarding induction limitations: no MFI, etc. allowed. I will build the motor to max the potential of the Weber 40IDA carbs. Will also use '69 S spec heads with the biggest valves avail for 2.0L heads and port them aggressively.

Still looking for some comments from 2.0L racers with the rest of their preferred motor specs (and lessons learned!)

Thanks guys. This board is great. Long time lurker, first time poster.

Look out Chadler. Your older, wiser, and soon-to-be-faster cousin is on your tail.

JP

[jplavanjr]

Thanks for the info Dave. I didn't know I could do that with the 2.7 heads. I'll have to check the VARA and HSR rule books on that one.

I've got a good set of early heads on my stock motor now and also a good set of '69 911L heads to play with. We'll see.

I'll talk to Jerry and Jerry.

JP

[TRE Cup]

if you look closely at some of a certain shop's cars you will see those heads (or so I've been told.. heh heh)

[jplavanjr]

[QUOTE]Originally posted by jluetjen

The 6/94 (#46) issue of Excellence had an excellent article on racing 911 pistons.

jluetjen: I can't find my Excellence mags back that far.

Anybody know the web site for Excellence or have a copy of that article they could send me?

Thanks

JP

[Wayne 962]

My new book has a neat table with "Wayne's Picks" engine combinations listed. These are guaranteed to work, and produce a good engine. Here's my pick for HSR-spec 2.0L engine. This engine was actually built by Tom Woodford, and used in the white 914-6 with the cut-off windscreen that was at the Ventura German AutoFest. It may be at Dunkle's on Sunday too!

Here's the info on the HSR-spec engine:

Case Crank Pistons Cylinders Cam Fuel Heads Disp Ratio
2.0L Aluminum 2.0/2.2 11:1 Mahle 81mm RSR 40 Weber 36mm Venturis 1969 S 36mm Port 2.0 11:1
(66mm) High Dome Mahle
2.0L HSR-spec Race Engine. Shuffle-pinned, boat-tailed, cylinders mooned, crank is knife-edged. Pauter lightweight rods, RSR cams in 4-bearing cam towers (originally 3.3 Turbo cams reground to RSR specs). Lightweight flywheel & puck-type clutch. Tall Weber manifolds, racing headers and megaphones. 180-200 HP in the 6000-8000 RPM range. Race gas only.

The early 911S engine achieved the highet HP/Liter of any of the later-model 911s, in the range of 80HP/L, so some great engines are possible...

-Wayne

[jplavanjr]

Thanks Wayne. That's exactly what I was looking for.

When can I get your book? I've been waiting for publication instead of ordering the preview 'cause it should be soon right?

Some specific quests from your specs above:
What years/models had the 4 bearing cam towers?
Same for the "tall" Weber manifolds. What cars do I find those on?
What year RSR cams are you referencing & what are the grind specs?

JP