1972 124 Sport Spider

[mdburchette]

Hello everyone! First, I¢ž¢d like to comment on your new forum, Guy. It is a wealth of information that has further fed my passion for Fiats. Even though the discussions on your site are over my head, I feel any questions I have will be answered informatively and without ridicule. Hats off to you for a well behaved site!
My name is Denise Burchette, from North Carolina, USA. I am a housewife with 3 beautiful girls and a brand new grandson. My love for Fiats started when I was a teen, back in the late 70¢ž¢s with a 1968 124 Spider. It was sold years later to accommodate a growing family, but it was never forgotten. In 1994, I was able to buy a worn down 1972 Spider and have worked off and on for 11 years to restore it, with the help of my husband, Ron.
Being a female in a male world can be a bit intimidating, but my motto is …œyou don¢ž¢t know until you try‚. It¢ž¢s very satisfying to be able to work on my own little car, even if it takes me three times longer than normal.
As I stated earlier, my car is a 1972 Fiat Spider with a 1608 engine and dual 40 IDFs. It was completely stripped down, sand blasted, refinished, with new interior. We gave the engine a rebuild with custom .0040 over pistons, moving the ring groove up .0030 and elongating the rods for less weight. The block was decked and I port matched and polished the head . It¢ž¢s running original valves with Guy Croft springs, a PBS intake with 40 idfs and ported and ceramic coated 4-2-1 exhaust manifold. Everything was balanced and the crank polished. It sports a 6ALN MSD module and Blaster II coil, with a Fiat electronic distributor. I had a three disc racing clutch specially made and modified a flex plate from an Fiat automatic transmission. Not only did this shed quite a few pounds from the rotating mass, but it was a blast to drive. I either squalled tires from a stoplight or stalled the engine. After deciding my clutch leg was getting bigger than the other and realizing this was not a good setup for grocery shopping, I had another racing clutch made that was more well behaved. I was still able to take 10 lbs off the original Fiat setup. Even though my 1608 is at a modest 9.78:1 compression ratio, it is quick off the line and is still pulling at 7200 rpms. My next project is building an X19 race car. Am I too old to start racing? Wish me luck!


New pistons:


Racing clutch:


Engine compartment:

[Guy Croft]

Hi Denise!

I am very pleased to see you here and read your post. A nice informative article, especially re the light clutch flywheel assembly. It is the first time I have read what actually happens on a road car if you go super light, thanks!
Now, taking a break from more usual GC tech blurb - I am dying to know how you gold plated those carbs!
BTW those restrictive gauze lids on the rampipes, they have to go! Get yourself some K&N filters.

Regards,

GC

[mdburchette]

Hello Guy! I have been lurking for some time and have enjoyed your site. I may even accidently learn something if I keep it up.
I have taken your suggestion about the K&N air filter to heart and will be changing my setup this winter. Thanks again for looking out for me.
As for the gold carbs, I bought a set of 13/15s, sat at the dining room table, completely dismantled them and sent the housings to New England Chrome Plating: http://www.newenglandchrome.com/
They did a beautiful job of plating the carbs with 24k gold and I was surprised to find all the ports, nooks and crannies were free from debris. I thoroughly cleaned, then reassembled them, including new sealed bearings for the shafts. The intake got a good polishing, then once on the car, I tuned them and took it for a test drive. I was impressed by the top end performance I received, but even though there is no stumbling and I enjoy quick response on the lower end, I realize the dual carbs are a bit more tame than the Holley 350 I pulled off.
My reasoning for gold plating the carbs was the bling factor. First place at the east coast Fiat show against professionally restored trailer queens had eluded me until this year. Now I have a trophy to show for all my troubles.

[Guy Croft]

Crikey!

24carat gold! I was confident you'd tell me it was anodising!
I hope the gearbox have an inspection port so you can show them the beautiful purple clutch too!

Anyhow, joking apart, the Holley is not a unit I'm familiar with at all, tell us more when you get time, photo appreciated if you have, save me looking it up my Summit Racing catalogue. How did you achieve accurate jetting and what manifold was it mounted on?

Many thanks,

GC

[mdburchette]

Unbelievably, there was a joint venture between Holley and Weber in the Holley 5200 carb. I believe this carb was also called a 32/36 downdraft Weber, being made by Holley and licensed by Weber. Mine, though, is a 350 cfm 2bbl racing Holley.

Ron had modified a single port 1800 manifold and made a mounting plate to accomodate the carb. He also had to build the throttle linkage setup to work with the early style Fiat throttle rod:





The main thing I liked about the Holley was the very quick response. The car could spin tires in 4 gears without blinking an eye. I understand the small clutch had a lot to do with this, but the power was instant with this setup. The one thing I didn't like was the idling. In order to maintain an idle without being rough, it had to be set at 1500 rpms. This is not a problem with a race car but since this car is basically my fun car, I didn't like the fact of feathering the gas pedal at stoplights.
Once I had the car dynoed, I realized the 350 cfms were not enough for the 1608 engine. Ron misjudged how effectively the crossflow head design sucked in air and he quickly realized rejetting would not be sufficient. A 500 cfm carb would be more suitable, but I opted for the 40 idfs at this point.
It still gives me a chuckle to think back on this. Ron is a Holley man and was quite sure the 350 would be a bit too much, since that's the same carb he runs on his 350 V8 race car. To find out it wasn't enough for a little Fiat 4 cylinder was a humbling experience for him. Of course, he had the last laugh. When I decided on the Idf's, he promptly told me I'd have to set them up and tune them because all he works on is Holleys.

[FMO]

Hi.

I am so impressed about your car and Your knowledge about Spiders :-).
I hope I someday would achived the same level :-)) I have had mine Spider for only 11 months.
I will try to install a pair of Solex 40 PII-6 carburattors during the winter. But I have to find out what I have to do with the throttle linkage!!!!

Regards
FMO

[Guy Croft]

hi Denise

I am going to 'stick my neck out' here, because I have never even held a Holley carb in my hand!

I want to make some observations for you and Ron to consider. The most airflow one inlet port will flow on an TC head with valves in the 41.8 -42.7mm diameter is about, say (just for argument sake, save looking it up) 110 cfm, less with a downdraft manifold fitted, way less.

A production carb for a 2 liter engine, like the 34ADF (let's just suppose it was fitted to your engine) has choke sizes of 24mm diameter. That's a combined area on full throttle, equivalent - factoring in the throttle plate intrusion - to a 33mm orifice. A radiused 33mm orifice flows 102cfm at 10" depression. You can maybe see where I'm going here.

That 34ADF carb is likely to 'under-flow' a well prepped head by the time the loss on a 4 branch inlet manifold is factored in. Especially on cylinders 1 & 4 with the longest runner and curve. I'm not going to get hung on exact bhp predictions because it doesn't matter overmuch in this context. The main point is you'd have to go bigger on the chokes to capitalise on the head flow potential and get really strong top-end bhp. The bottom-end torque might be fine - but the small chokes are going to strangle the airflow. You'd want your carb-manifold combo flowing at least the same as the port and preferably 20% more.

So, trying to interpret this right, you've got a Holley that flows 300cfm, feeding one 100-110 cfm port at a time - and the power is down and it won't idle? That begins to look to me much more like a carb air velocity and maybe also a carb fuel signal problem. Low velocity thru the carb can be really bad news.

Check it out, come back to me, this interests me, partly because I never used Holleys because I figured they were way too big for the small Fiat TC unit. I know how catastrophic the torque loss can be if the carb is too big, I learned that with 48DCOE on a big valve 2 liter Fiat years ago. And they won't pick up and give useable torque to pull away from from idle either.

Maybe I'm way off the mark here, in which case I am very ready to learn more.

GC

[mdburchette]

FMO, thank you for the compliment, but I'm afraid I'm just muddling through life trying to learn.

Guy,
I understand where you are coming from and will get more technical information from the people that know Holleys. My comment basically came from a conversation I had with the guys at the BMW race shop that dynoed the car. The dyno showed the engine becoming very lean on acceleration and I was told the carb was not sufficient. Armed with the dyno sheet, Ron called the shop that prepared the carburetor and was told a bigger carb would be better.
This all peaks my curiosity. Do you know the cfms of the 40 idfs for each port?

[Testament]

What pressure differential are the holley carbs rated at though? it might be better to just compared the throttle bore or venturi size to the webers rather than flow ratings.

[Andy007]

Hello MDburchette,

i have also a Pininfarina Spider with 2.0 Engine ( see readers cars, the dark green one ) I am interested to install HC Pistons on my engine.
The picture of your pistons are very nice, can you tell me something about compression hight, dome hight, weight ?

Where do you have these pistons from, do you have an adress for me ?

Greets Andy007

[Andy007]

Hello MDburchette,

i have also a Pininfarina Spider with 2.0 Engine ( see readers cars, the dark green one ) I am interested to install HC Pistons on my engine.
The picture of your pistons are very nice, can you tell me something about compression hight, dome hight, weight ?

Where do you have these pistons from, do you have an adress for me ?

Greets Andy007

[mdburchette]

Andy,

Your car is beautiful with special attention to detail. I like it very much!
As for my pistons, they were made by JE pistons and have the same dome as stock and weigh 4 ounces less than stock. The compression ratio of 9.78:1 was achieved by decking the block. It is very expensive to have pistons custom made. Had I known about Guy Croft and his experience with these TC engines, I would have ordered them from him. I would suggest you email him with what you want from your engine, such as driveability and performance and he will be able to set you up with what you need. He has taken all the guesswork out of trying to figure out what to do.

Denise

[roko]

Nice Ride. And not Red. This has the all my favorite Fiat nuances :The 1608 with IDFs,in Gold to Boot! Looks great and with 10 # off the rotating mass it must scream" where is my risotto" in low,showering the few followers in burnt rubber dust.
thank you Roko
Waiting for the X/19 racer!!!