Race Engine Forum UK

Hello Guy,

My winter project includes building an SVRA vintage racer using a 1972 Fiat 124 Spider. According to the rules, I will be limited to using the 1608 engine and would like to know a reasonable expectation of how much horsepower I can get and some ideas of which cams, piston dome height and any other information you could provide to help me reach my horsepower goal. Here are the allowed options from the SVRA rule book:

Internal engine parts are free
Accusump - wet sump must not be converted to dry sump
MSD type electronic ignition, must be triggered from distributor
An overbore of 1.2mm or .047" is permitted
Blocks and heads must be of the same material and design provided by
manufacturer and must be the of the original type, size and design as
originally fitted by manufacturer
All car should have a working chargin system unless they historically ran
historically ran without one
Flywheels and clutches free
Alternate period carbs are permitted. Dual IDFs bump a class
Intakes and exhaust manifolds free

Thank you for any insight you can give me.

Sure Denise, I'll give you willingly all the guidance u need.

But, Stateside, was that car not equipped with twin IDF as a production fitment and thus eligible in that class as-such?

If it was not tell me about the next class up where it would have to run on twin 40IDF carbs, I need to know (kind of) what you're racing against to set up a competitive spec.

GC

Guy, here are the cars that fall in my category. Does this help?

(3/EP) Vintage E-Production
*Alfa Romeo Giulia Veloce, Spider Duetto (1570)
*Alfa Romeo Giulia Sprint, Sprint Speciale
*Alpine-Renault (1600)
*Austin Healey 100/6 (2639)
*Elva Courier (1498 Ford) [single carb]
*Elva Courier (1500/1600 BMC) [twin SU]
*Fiat 124 Spider (1592, 1608) [dual Weber]
*Ginetta G-4 (997 Ford)
Fairthorpe Electron (1216 Climax/1296 Triumph)
GSM Delta (997 Ford)
*Lotus Seven (1100 Ford, 1098, 1216 Climax)
*MGA (1588 dohc) [twin SU]
*MGB/GT (1798)
*Morgan +4 (2138) [twin SU]
*Morgan 4/4 (1498 Ford) [dual Weber]
*Morgan 4/4 (1598 Ford x-flow) [single carb]
*Opel GT (1900)
*Porsche 356 (1600) [drum brakes]
*Porsche 912 (1582)
*SAAB Sonnet V4 (1698)
*Triumph TR3B (2138) [twin SU]
*Triumph GT6 (1998) [twin SU]
*Triumph Spitfire (1296) [dual Weber]
*Turner 1500 (1498 Ford) [single carb]
*TVR Grantura (1622 BMC) [twin SU]
*TVR Vixen (1598 Ford) [single carb]
*Volvo P-1800 (1780) [dual Weber]
*Volvo P1800 (1998) [SU]
WSM GT (1098)

Denise, hi

you'll have a real tussle on your hands in a straight line against most of the dual carb cars if yours has to run single carb. Is yours allowed in that class with twin IDF or would you have to move up a class?

If you want to run single carb in that class we'll have to go as ultimate on spec as we can. **

GC

** Yuh know, ditch any excess weight like gold plating etc...!

Guy Croft wrote: ** Yuh know, ditch any excess weight like gold plating etc...!

You're right about that, Guy. It wouldn't do to be flashy if I keep getting lapped!

This class is what I'd be running against with the dual IDFs already in place. Also, I might add there are no restrictions on venturi choke size on the carbs, which differs from current SCCA regulations that insist upon 28mm chokes.

OK - Race Fiat Spider 124 1608cc unit on 40 IDF, 28mm chokes. This is the 80mm bore x 80mm stroke unit.

Here is my recommendation.

Internal engine parts are free - race rods and pistons, StII cams only - or StIII inlet, StII ex - we don't want to overload the chokes, fully flowed, new valves, guides, race springs, 1" belt, 1" camwheels. The std crank should be fully spec'd GC style and balanced with fw/clutch. I have top-grade cast iron chill billet GC profiles with ex gear drive by the way.

Accusump - wet sump must not be converted to dry sump - OK - use race sump, oil cooler, full instrumentation.

MSD type electronic ignition, must be triggered from distributor - OK, to be honest the standard contact breaker setup will do fine.

An overbore of 1.2mm or .047" is permitted - go 81mm bore
Typo (memory) error!

Blocks and heads must be of the same material and design provided by
manufacturer and must be the of the original type, size and design as
originally fitted by manufacturer - OK

All car should have a working chargin system unless they historically ran without one - OK, we keep the alternator

Flywheels and clutches free - steel fw 7.25" clutch

Intakes and exhaust manifolds free - fully flowed IDF waffle manifold, GC spec 4-2-1 header and single race muffler.

In addition we'll need a race intake system for cold air, race rampipes, Facet pump, race head gasket and bolts, and definitely a high cap (pref alloy like Csaba's) radiator. That's all I can think of at present.

Properly dynoed I think we'll see 150 - ish bhp and 125lbf ft torque, peak power at 7600 or so, peak torque around 6000.

That's the brush strokes. The weak point is the gearbox - it will need top-bottom overhaul before use and make sure you have a spare trackside. have a read of Melvin's post (just put Melvin into search). He successfully races a 124 Coupe with an AC 1438 race unit on single carb and if you post on his thread he'll no doubt tell you loads about preping that car. You should maybe also consult with Don Tuscany on important aspects of safety and body prep.

GC

Guy Croft wrote:OK - Race Fiat Spider 124 1608cc unit on 40 IDF, 28mm chokes. This is the 80mm bore x 80mm stroke unit.

Here is my recommendation.

Internal engine parts are free - race rods and pistons, StII cams only - or StIII inlet, StII ex - we don't want to overload the choke.

GC

Thanks Guy. This is exactly the information I needed to get started. One item I confused you on is the carb chokes are free for Vintage, so would you recommend StIII inlet and exhaust cams in this configuration?

Oh, OK Denise, great. Go 34mm chokes and StIII cams, lift of 11mm or over 11mm inlet and say 10.5 ex.

GC

Thanks again, Guy. You'll receive my parts order a little later.