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jdahl
I'm building an engine (2 actually) to run in my 914 for SVRA Group 3 road racing. I've done a lot of research, built a spreadsheet, shopped around, done more research, etc. Before I start spending money on parts, I would appreciate any experienced advice/critique of my build(s).

Conservative
Bore 94 mm - flat top Type 1 "stroker" pistons 35mm pin height
Stroke 71 mm
Rods 5.325"
Heads 59 cc, 2.0 42/36 valves, single valve springs (porting/polishing TBD)
Rod Ratio 1.905:1
Deck Height .04" (1mm)
Compression Ratio 8.5:1
Cam 86a

Creative
Bore 95 mm - 14cc custom dome pistons 25.8mm pin height
Stroke 71 mm
Rods 5.7"
Heads 56 cc, 2.0 44/38 valves, double valve springs (ported/polished)
Rod Ratio 2.039:1
Deck Height .04" (1mm)
Compression Ratio 11.5:1
Cam 86b/c or 163/86b

Induction Weber 40 IDF
Exhaust Kerry Hunter 1.5" header

Again, I appreciate any and all constructive feedback.
Brett W
QUOTE(jdahl @ Dec 5 2015, 10:16 PM) *

I'm building an engine (2 actually) to run in my 914 for SVRA Group 3 road racing. I've done a lot of research, built a spreadsheet, shopped around, done more research, etc. Before I start spending money on parts, I would appreciate any experienced advice/critique of my build(s).

Conservative
Bore 94 mm - flat top Type 1 "stroker" pistons 35mm pin height
Stroke 71 mm
Rods 5.325"
Heads 59 cc, 2.0 42/36 valves, single valve springs (porting/polishing TBD)
Rod Ratio 1.905:1
Deck Height .04" (1mm)
Compression Ratio 8.5:1
Cam 86a


Please No. No reason to re-engineer the wheel. That cam is a baby and needs more compression, Unless you are going to turn a zillion RPM there is no need to run a rod that long. The engine will be a dog everywhere.

QUOTE(jdahl @ Dec 5 2015, 10:16 PM) *

Creative
Bore 95 mm - 14cc custom dome pistons 25.8mm pin height
Stroke 71 mm
Rods 5.7"
Heads 56 cc, 2.0 44/38 valves, double valve springs (ported/polished)
Rod Ratio 2.039:1
Deck Height .04" (1mm)
Compression Ratio 11.5:1
Cam 86b/c or 163/86b

Induction Weber 40 IDF
Exhaust Kerry Hunter 1.5" header

Again, I appreciate any and all constructive feedback.


If this is truly a race motor and not a wanna-be race motor, use a solid combination that has proven its reliability for decades. Again no reason to reinvent the wheel. Start with the following:

71mm Counterweighted crank

96mm Keith Black or forged pistons with stock pin height. (You can get tricky here if you want and run smaller wrist pins, but that typically means custom pistons and special rods) Don't use the Hastings junk rings, go low tension on the rings. If you do custom pistons, go 1.0mm or less on ring thickness and 1.2mm on the oil rings. Compression needs to be in the 11:1+ range, depends on what you can get to clear the valve lift

Bore the stock 2.0 cylinders as they are better quality than the garbage for sale new.

Rods, Run the stock rods with ARP bolts or buy a nice set of SCAT lightweight rods. (stock rods are really heavy)

Cam: Web 86B/163 on a 102-104 centerline, to keep it easy, You could go bigger but you get into sprint race motor territory and the cam is hard to setup. Only use Web cams (although Elgin has done some interesting stuff)

Call Len and get him to port a set of heads, replace guides, replace seats, etc. Expect to spend over $1000 to get a good set of heads done with new valves, new springs, Titanium retainers, bronze guides etc. Expect that stock heads will be junk and start with the new castings. Have him do all the tricks, small stem valves, small plugs, etc. These will be real money and they will be where the power is made.

Carbs (if you have to run them) 44IDF Webers 36mm Chokes

Header, Tangerine if he still makes it or a custom copy of the Finch header. Kerry makes a nice street header, but not a good race header.

If you want to get really silly with it:

100+mm Nickies and custom pistons. Use the most current design strutted piston they offer. Stick with JE or Wesisco for custom pistons. Maybe CP if they will work with you.

Stroker crank. take the engine out to 2318ish. You know the Datsun guys will be running 2.3 stroker motors.

If you want to race a T4 there really isn't a cheap way to do that. It will take work and you will blow a few pieces to bits. These engines don't make good race motors. Not trying to burst your bubble, but having been down this road, you will find the six is cheaper and faster in the long run. The four is a good street engine, but when you start asking it to go racing, its a grenade.
stugray
QUOTE(Brett W @ Dec 7 2015, 01:55 PM) *


If you want to race a T4 there really isn't a cheap way to do that. It will take work and you will blow a few pieces to bits. These engines don't make good race motors. Not trying to burst your bubble, but having been down this road, you will find the six is cheaper and faster in the long run. The four is a good street engine, but when you start asking it to go racing, its a grenade.


I think it is important to find out WHAT KIND of "racing" the OP is interested in.
I was actually really interested until I read the last paragraph.

The type IV is the cheapest engine in my vintage racing group.
I cant think of an engine that is as fast as the 914-4 that costs less.

You can DEFINITELY make more HP with a type-IV than a 914-6 motor for the same money.
HP costs MORE with a 6 than with a 4 - period.

For what it would cost to rebuild a 6 to stock specs, I could build a type-IV from the ground up and get 130 hp.

Here's mine (vintage rules, so ~stock displacement):
Stock 2.0L crank & rods
Stock 2.0 Heads cut ~.020 for 10.5:1 CR (mine are single spring, would do double next time for higher RPM)
Keith Black 96mm pistons w/ hasting rings
Webcam 86b w/ new lifters
Deck ~.030
Mallory Unilte w/ optical pickup
MSD-6AL
Weber 40 IDFs
Kerry Hunter header (would do Tangerine but $$)

In my race group there is a 2.0L type-IV 4-cyl that consistently beats ALL of the other small bore cars INCLUDING a 914-6.
ChrisFoley
QUOTE(stugray @ Dec 17 2015, 03:53 PM) *

...
Here's mine (vintage rules, so ~stock displacement):
...
Keith Black 96mm pistons ...

I thought Vintage Production cars are limited to 1.4mm overbore.
stugray
QUOTE(Racer Chris @ Dec 18 2015, 06:53 AM) *

QUOTE(stugray @ Dec 17 2015, 03:53 PM) *

...
Here's mine (vintage rules, so ~stock displacement):
...
Keith Black 96mm pistons ...

I thought Vintage Production cars are limited to 1.4mm overbore.


Unknown to me when I built my first engine.
I will fix that on the next build, but as a rookie, they did not penalize me (yet).
I am in 81 D-prod. with a 71 2.0L.


Brett W
http://www.svra.com/race-groups/

The reality is no one in Vintage racing really cares about what you do inside the engine for the most part. Especially with a Porsche motor. Gentleman's racing really doesn't involve tear downs. Build something that will be reliable and reasonably competitive. You won't win much of anything in HSR/SVRA with a four cylinder 914. They just never seem to be competitive. They are mid to back of the pack type cars.

In HSR, the 2.0 litre Challenge class is dominated by 2.0 six cylinders. The four cylinder engines don't even come into the game. The six cylinders were making 230+hp. You will never get close with a 2.0 Type 4, nor will you have the durability of the six.

Guess it depends on the goal of the OP. But 130hp will have him sitting in the back being passed by many an MGB and everything else. One of my MGB customers is making 170+ in Vintage trim. That is Group 2 for HSR and Group 3 for SVRA. He races against the 356s and other older British stuff, those cars aren't 130hp slow either.
stugray
I guess it depends on the club then.

If you check race times for rocky mountian vintage racing rmvr.com you would see that Jason Cobb is consistently the fastest car in the small bore run group and it is a 4-cyl.

http://www.mylaps.com/en/events/1141246#_g...7206.1450490374

RMVR SPRING RACE GRAND PRIX, GROUP 3 SMALL BORE PRODUCTION

jdahl
Brett,

Thanks for the initial feedback. I probably should have called the first option "off-the-shelf". The real issue seems to be the lack of high compression "off-the-shelf" pistons for the type 4. I believe your comment about rod length was directed at the second proposal, not the first. Is that correct?

As far as the 96mm pistons, trying to build the engine legal.

SVRA Group 3 rules
http://www.svra.com/wp-content/uploads/201...roup_3_1213.pdf

"Engines: Must be standard or optional series, bore and stroke as provided by the manufacturer for make and model Bore may be increased by .047ยด (1.2mm)."

Carbs are restricted to 40's.

I did reach out to Len on the heads, his quote was reasonable for what he offers (new not rebuilt), but outside the current budget.

Tangerine exhaust, I'd love to have one, but again outside the current budget.

As for building a stroker motor; again, playing by the rules. If the Datsun guys want to run cheater motors, that's their call.

Stugray,

Are you running flat top pistons? You compression seems higher than I would expect.

My car will also be running DP.

Brett W
You guys should head east next April for the Walter Mitty Historics at RD Atlanta next spring. You will have a blast running with those guys.
stugray
QUOTE(jdahl @ Dec 18 2015, 07:50 PM) *

Stugray,

Are you running flat top pistons? You compression seems higher than I would expect.

My car will also be running DP.


Flat top Keith Blacks.
Heads were flycut ~.020 (IIRC)
No head gaskets
Minimum deck height (~.030)

I'll see if I can find my notes from the calcs.
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