This guide will help you modify and tune your FIAT TC engine for performance and efficiency. Head, Carbs, Exhaust, and Tuning issues will be discussed. This guide applies to FIAT 1600, 1800, and 2000 TC engines and for 3 types of modification profiles: Low, Medium, High.
With up to 9.0:1 CR go for Low modification profiles, with 9.0-10.0:1 CR go for Medium, and with higher that 10.0:1 CR go for High.
The expected horsepower at the crank in BHP +- 5 is as follows:
Low Medium High
1600 TC 120 135 150
1800 TC 135 150 170
2000 TC 150 170 190
The Head
It is the single most important element of an efficient high performing engine. Take your head of the car and take it to a good machine shop and ask them to do the following:
1. Fit new guides, seats and valves of your choice (see below), and shave the head.
2. Fully port the head shaping venturis related in diameter to the valve throat sizes.
3. Deshroud (smooth all edges between and around the valves) the combustion chamber, using dummy valves.
4. Port the inlet manifold so to match the head inlet ports
The valve sizes should be chosen as follows:
Low Medium High
in/ex in/ex in/ex
1600 TC 42/36 42/38 43.5/36
1800 TC 42/38 43.5/36 43.5/38
2000 TC 43.5/36 43.5/38 45/40
The 38mm ex valves may also be 37.5mm depending on what is available.
The camshaft selection is an important process particularly because of the variations in power/torque curves they have. In absolute power and torque figures the choices are pretty straightforward and that is as far as I will go into that subject. Make sure you chose a cam profile from an experienced cam manufacturer. Personaly I like Abarth (only copies of the famous 068 profile now available), Alquati (now from Pitatore), Piper, Kent, and Bariani & Colombo.
Chose the cam according to overlap (in degrees below) only, and forget max lift or tdc lift, unless you know what specific power/torque graph characteristics you require. Cam Overlap in degrees according to modification profile:
Low Medium High
1600 TC 70-80 80-90 90-100
1800 TC 70-80 80-90 90-100
2000 TC 70-80 80-90 90-up
The Carbs
FIAT TC engines work nicely with 40 IDF/DCOE/DCOM/DHLA, 44IDF, 45 DCOE/DHLA, and 48 IDF/DHLA carbs from Weber and Dellorto. Dellorto DRLA carbs can also be used, but some modifications are needed to fit them both on the manifold.
The single most important element of the carb is the venturi (or choke), and it is should be chosen taken into account all of the above discussed so far. Venturis can be bought, or they can be machined out from a smaller size up.
Choose venturi and carb size according to the modification profile chosen and shaped so far. Remember the carb is only a feeding device, and it’s mission in life is to feed the head. It’s the head type that determines how much it needs to be fed.
Chose venturi and carb size according to the chart bellow (venturi size in mm / carb size in mm):
Low Medium High
1600 TC 32/40 34/40 36/40,44,45
1800 TC 34/40 36/40,44,45 38/44,45
2000 TC 36/40,44,45 38/44,45 40/45,48
In cases where for a particular venturi size more carb sizes in the above chart appear available, larger carbs are preferred for quicker rpm raise and better overall throttle response. Everything else being equal a car with 45DCOE and 36mm venturis is a faster car than one with 40DCOE and 36mm venturis.
The Exhaust
Exhausts are very important, but not as important as most people think. FIAT TC engines work well with custom 4-1 (equal primaries length) header systems and see-through single silencer only endpipes (absolutely no resonator or second silencer, unless you wanna cheat yourself or your wife’s ears are bass averse). Countless setups have been tried by tuners worldwide, but unless you look for particular power/torque curve characteristics, stick with the following three for your modification profile:
Setup 1: 1600 Low & Medium, 1800 Low: 38mm primaries + 55mm endpipe
Setup 2: 1600 High, 1800 Medium, 2000 Low: 40mm primaries + 58mm endpipe
Setup 3: 1800 High, 2000 Medium & High: 42mm primaries + 60mm endpipe
Tuning the FIAT TC Engine
First decide what kind of fuel you are going to use: medium octane or high octane. High octane is mandatory for the High modification profile. Low octane is out of the question for an efficient high performing engine. The following is for a FIAT stock points or stock electronic ignition systems:
Get an adjustable timing light and adjust your advance timing at 34-36 degrees at 5500 rpm if you run on medium octane fuel, and at 37-39 degrees at 5500 rpm if you run on high octane. This is a painful experience as it’s really hot in there… Now check what your static timing is at 1000 rpm and right it down for future reference so you don’t have to go through the max advance timing experience again next time. Static timing may be 5, 7, 11 or whatever, don’t trouble yourself with it anymore.
Next we balance the carbs. First turn in (closed position) all four air bleed screws. Have a synch meter (STE type preferably) handy, warm up the engine first and then turn the idle screw in until the engine reaches 3000 rpm. Now measure the flow in each barrel, and using the balance screw (not the air bleeds) balance the left and right carbs. Now get at idle and measure the flow in all four barrels. Write down the figure for the highest flowing barrel, don’t touch it, and then adjust the air bleed screws on the other three barrels so they flow the exact same figure as the highest flowing one that we didn’t touch. Then adjust the mixture screws ¼ of a turn out from the point where the engine’s rpm starts to drop when turning the screw in from wide out.
Now that you have nice set of balanced carbs it’s time to jet them properly. Take you car to a place where they have an Air/Fuel Gas Analyzer with a wide band sensor, or buy your own pocket type (LT-1, NGK, etc.). Invest in and take with you (in case of Webers) a set of F11 and a set of F2 emulsion tubes, sets of 160, 170, 180, 190 and 200 air correctors, sets of 55, 60, and 65 idle jets, and sets of main jets from 130 up to God knows what with 48s…
This is a two person procedure and it takes time. With the car fully warm get Air/Fuel Ratio readings from the sensor at 500 rpm increaments from 1000 to 7000 rpm or higher (much) for High modification profiles and write them down. First emphasize on the 3500 - 7000 rpm area and try various combinations of main jets and air correctors with the same emulsions to try and get Ratios ranging between 12.5 and 13.0 at every reading. Remember below 12.5 is rich and above 13.0 is lean. A Ratio of 12.0 is safe but uneconomical and underperforming, and a Ratio of 13.5 is safe and economical but underperforming. After you have worked that out, work the idle area and up playing with some idle jets, that should be easy by now. The right set of emulsion tube, air corrector, main and idle jet will give you Air/Fuel Ratio readings between 12.5 and 13.0 which means optimally tuned engine.
Drive home and enjoy.
FIAT TC Modification & Tuning Guide
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ventura ace
Vassilis,
Very clear concise info. You present it well. One question about Cam selection. Your table indicates an overlap recommendation for each case. Is this measured 1) at the standard of .050" clearance, 2) at the cam grinder's recommended valve clearance, 3) at zero clearance, 4) other? I suspect the answer is #2. Also, any guidlines on duration? This would have some bearing on the overal dynamic compression, based on how long the intake valves stay open into the compression stroke.
Thanks again for your guide.
alvon
Very clear concise info. You present it well. One question about Cam selection. Your table indicates an overlap recommendation for each case. Is this measured 1) at the standard of .050" clearance, 2) at the cam grinder's recommended valve clearance, 3) at zero clearance, 4) other? I suspect the answer is #2. Also, any guidlines on duration? This would have some bearing on the overal dynamic compression, based on how long the intake valves stay open into the compression stroke.
Thanks again for your guide.
alvon
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vcg
Max lift and tdc lifts are usually subject to confusion due to valve clearance selections. For ovelap I believe it is always at specification clerances, but of courses there ma be cases where this will vary. Cam discussion is a huge one.
I wanna state one very important issue: one can get the same head flow from both a smaller valve setup timed with a wilder cam, and a larger valve setup timed with a milder cam. The first being appropriate for a high compression engine, and the later for a lower compression one. Reason is overlap of course.
Cheers,
I wanna state one very important issue: one can get the same head flow from both a smaller valve setup timed with a wilder cam, and a larger valve setup timed with a milder cam. The first being appropriate for a high compression engine, and the later for a lower compression one. Reason is overlap of course.
Cheers,
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vcg
I' ve come to the conclusion that duration itself at cams doesn't mean anything. I also believe that max lift itself doesn't mean anything. Both combined, however, mean almost everything for a cam. And this is overlap.
Max lift for a cam means something only if looked together with valve size.
Overlap and tdc lift, will tell you everything for a cam: fast road, hillclimb, rallye, race.
Max lift for a cam means something only if looked together with valve size.
Overlap and tdc lift, will tell you everything for a cam: fast road, hillclimb, rallye, race.
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Joe Clemente
- Posts: 151
- Joined: Wed Jan 25, 2006 1:35 am
- Location: Vancouver, B.C. CANADA
vcg wrote:Chose the cam according to overlap
Umm, no. No offence but overlap and tdc lift does not tell you everything. Timing of the valve events (opening and closing) is also an important component in cam selection and tuning. Especially on highly modified motors. Why would you not consider this? Personally, I want to know where in degrees of crank rotation that opening and closing will occur. Though not an unimportant consideration, overlap is just a component of that timing.vcg wrote:I' ve come to the conclusion that duration itself at cams doesn't mean anything. I also believe that max lift itself doesn't mean anything. Both combined, however, mean almost everything for a cam. And this is overlap.
Max lift for a cam means something only if looked together with valve size.
Overlap and tdc lift, will tell you everything for a cam: fast road, hillclimb, rallye, race.
I would suggest to you that if timing wasn't important then adjustable cam pulleys would be a waste of money. Last time I checked, that wasn't the case, not the least of reasons being that they will allow me to adjust my overlap whatever way I want by advancing or retarding the intake or exhaust cam.
One other question, just out of curiosity Vassilis. How long did it take you to experiment with all these different combinations to derive the information that you've provided? I am assuming you did all this yourself over some length of time. yes? My compliments on your dedication.
Regards,
Joe
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vcg
Joe,
You are so very wrong on that... The overlap is the most important figure describing a cam. It is deducted from in cam duration and in cam max lift position (lobe center) and ex cam duration and ex cam max lift position (ex lobe). Duration and max lift position give you overlap figure. You may have big duration cams with big or small overlaps, the former will be wild the latter mild. The overlap tells you how wild a cam is, and basically what kind of compression it needs to work. Tdc lift will give you further information and describe the flow. A high tdc lift cam is a high flow cam definitely, but a high duration cam is not necessarily a high flow one. All cam manufacturers sort their cams from mild to wild according to overlap. Check Gozzoli, Colombo, Piper, Kent, etc. sites.
The info on the guideline is accumulutaed knowledge from Hoermann, Abarth, and Alquati Cremona 70's brochures and catalogs. I am only a mechanical engineer and a weekeend tuner, not a full time one. But what I write is in this guideline is simple, basic, consice, and info that makes sense. It'san honest effor to gather stuf that makes sense.
I would rather have people add to the guideline something that they picked up from a serious source, than ask me ironic bullshit, and write nonsense on the importance of cam duration.
You are so very wrong on that... The overlap is the most important figure describing a cam. It is deducted from in cam duration and in cam max lift position (lobe center) and ex cam duration and ex cam max lift position (ex lobe). Duration and max lift position give you overlap figure. You may have big duration cams with big or small overlaps, the former will be wild the latter mild. The overlap tells you how wild a cam is, and basically what kind of compression it needs to work. Tdc lift will give you further information and describe the flow. A high tdc lift cam is a high flow cam definitely, but a high duration cam is not necessarily a high flow one. All cam manufacturers sort their cams from mild to wild according to overlap. Check Gozzoli, Colombo, Piper, Kent, etc. sites.
The info on the guideline is accumulutaed knowledge from Hoermann, Abarth, and Alquati Cremona 70's brochures and catalogs. I am only a mechanical engineer and a weekeend tuner, not a full time one. But what I write is in this guideline is simple, basic, consice, and info that makes sense. It'san honest effor to gather stuf that makes sense.
I would rather have people add to the guideline something that they picked up from a serious source, than ask me ironic bullshit, and write nonsense on the importance of cam duration.
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vcg
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nickfury
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Joe Clemente
- Posts: 151
- Joined: Wed Jan 25, 2006 1:35 am
- Location: Vancouver, B.C. CANADA
WTF?
Obviously you've read my post the wrong way.
First of all, unlike what you've done, I wasn't second guessing your knowledge. Bravo.
I did not say that overlap was unimportant. I did not say it wasn't important to know your LATDC either. What I said was that cam timing is another important component in cam in selection. I'm not so sure what is ironic or bullshit or nonesensical about that. FWIW, I'll back up my "bullshit" as you call it. But don't take my "bullshit" word for it. You obviously don't. Go ask somebody you might have less contempt for, maybe Croft? Maybe speak to a cam manufacturer?
Regarding those cam suppliers, I have checked. I've got catalogs for that matter. Most of those cam suppliers you've mentioned do list their product from mild to wild but interstingly enough their listings don't include overlap info. Tell me if I've missed it, now. So that means the average non-mechanical engineer types, unlike you who can "deduce" the info, will read the given catalog info and then have to somehow figure it out using the "bulllshit" listed by the manufacturers. So, if they haven't got the cam timing specs, then they will somehow have to work it out using the lobe separation angles and the advertised duration... Yes, of course, how stupid of us not to see that... not too many engineers among us. Again, nothing wrong with knowing your overlap when selecting a cam. Particularly useful when taking into consideration the need for more or less compression and if you're force feeding. It's just not the only criteria, that was my original point.
A note on adjustable cam gears: For different lobe centers you said? Yeah ok.
How about this contribution to your guidelines. Hopefully it will help people figure out that which is so manifest in your opinion:
O = D - 2L (Call my bullshit whenever you feel like now...)
O = Overlap expressed in degrees on crank rotation
D = duration
L = lobe center
So, using adjustable cam pullies to change lobe centers as you've asserted will also affect (correct my bullshit if I'm wrong now) the overlap. Increasing or decreasing it? Make sense? Or am I still spewing "bullshit"? Significantly, what does the adjustment process involve? Altering the timing of the valve events. "Nonesense" though huh...?
Regarding the guideline info you supplied, again you seem to have read more into my post than was intended. I wasn't second guessing the info. I think it's great. I was just curious where it came from, that's all.
I won't presume to speculate what your insecurities might be but based on your little dig about "ironic bullshit" it seems you're a bit threatened with any form of disagreement. Sorry you feel that way. I really think you need to re-evaluate your take on this discussion.
I'd like to think we could conclude this thread politely Vassilis. I'll reiterate my position. It was not my intention to second guess your knowledge or impugn your motives or source of information. Hope you can appreciate this.
However, if you want to continue to be offensive I'm not so sure you'll get a pat on the back for that. Maybe you can email me directly and spare the forum the need to read about your contempt for "nonesense". I won't hide, it's veltro@telus.net
Peace
J.
Obviously you've read my post the wrong way.
First of all, unlike what you've done, I wasn't second guessing your knowledge. Bravo.
I did not say that overlap was unimportant. I did not say it wasn't important to know your LATDC either. What I said was that cam timing is another important component in cam in selection. I'm not so sure what is ironic or bullshit or nonesensical about that. FWIW, I'll back up my "bullshit" as you call it. But don't take my "bullshit" word for it. You obviously don't. Go ask somebody you might have less contempt for, maybe Croft? Maybe speak to a cam manufacturer?
Regarding those cam suppliers, I have checked. I've got catalogs for that matter. Most of those cam suppliers you've mentioned do list their product from mild to wild but interstingly enough their listings don't include overlap info. Tell me if I've missed it, now. So that means the average non-mechanical engineer types, unlike you who can "deduce" the info, will read the given catalog info and then have to somehow figure it out using the "bulllshit" listed by the manufacturers. So, if they haven't got the cam timing specs, then they will somehow have to work it out using the lobe separation angles and the advertised duration... Yes, of course, how stupid of us not to see that... not too many engineers among us. Again, nothing wrong with knowing your overlap when selecting a cam. Particularly useful when taking into consideration the need for more or less compression and if you're force feeding. It's just not the only criteria, that was my original point.
A note on adjustable cam gears: For different lobe centers you said? Yeah ok.
How about this contribution to your guidelines. Hopefully it will help people figure out that which is so manifest in your opinion:
O = D - 2L (Call my bullshit whenever you feel like now...)
O = Overlap expressed in degrees on crank rotation
D = duration
L = lobe center
So, using adjustable cam pullies to change lobe centers as you've asserted will also affect (correct my bullshit if I'm wrong now) the overlap. Increasing or decreasing it? Make sense? Or am I still spewing "bullshit"? Significantly, what does the adjustment process involve? Altering the timing of the valve events. "Nonesense" though huh...?
Regarding the guideline info you supplied, again you seem to have read more into my post than was intended. I wasn't second guessing the info. I think it's great. I was just curious where it came from, that's all.
I won't presume to speculate what your insecurities might be but based on your little dig about "ironic bullshit" it seems you're a bit threatened with any form of disagreement. Sorry you feel that way. I really think you need to re-evaluate your take on this discussion.
I'd like to think we could conclude this thread politely Vassilis. I'll reiterate my position. It was not my intention to second guess your knowledge or impugn your motives or source of information. Hope you can appreciate this.
However, if you want to continue to be offensive I'm not so sure you'll get a pat on the back for that. Maybe you can email me directly and spare the forum the need to read about your contempt for "nonesense". I won't hide, it's veltro@telus.net
Peace
J.
Last edited by Joe Clemente on Thu Aug 17, 2006 1:26 pm, edited 2 times in total.
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racydave
This is alot of good info, like all printed info, some of it is opinion, some fact. If I were to do a "full blown" setup, Id probably choose another venue, werent the Fiats weak on the botton end? I hope I am wrong, but in a few years we might be discussing how to make my engine run on ethanol? And for the tuners, head mods are the last thing to consider. Best I can summize is that if you are a modest tuner, dont confuse yourself, concentrate on getting the flow in and out. Do not get me wrong, the last two weekends I have been a spectator at race tracks, nothing better than hearing racing "midgets" on a paved high banked half mile doin 125 mph! There is nothing wrong with spectating, or with participating, I can be happy with my modest mods! I can appreciate the full blown discussions also, it makes me think, and gives me ideas. In the end, we all are driving in the same direction,it is easier to do it in a friendly manner. Thanks to the folks who take the time and exhibit the patience to educate the simple folks. Simply Dave
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Joe Clemente
- Posts: 151
- Joined: Wed Jan 25, 2006 1:35 am
- Location: Vancouver, B.C. CANADA
Dave,
The info that Vassislis has provided here is certainly a very useful guideline for anybody contemplating mods and discussion on this forum is always extremely informative. It is unfortunate though that some people feel threatened by disagreement. Makes things needlessly unfriendly.
Fiat bottom ends are pretty stout. Having said that, building one requires no different care and attention than would building most others. Force feeding is a different consideration though. Having gone the route of full out natural aspiration I liking the idea of turbo charging or supercharging more and more. I really like the process that this fellow in Australia has gone through. He's strapped on a vortech centrifugal blower. Totally cool, but requiring different considerations for reliability.
Read these threads and have a look at these pics:
http://turbo124.com/forum/viewtopic.php ... sc&start=0
The info that Vassislis has provided here is certainly a very useful guideline for anybody contemplating mods and discussion on this forum is always extremely informative. It is unfortunate though that some people feel threatened by disagreement. Makes things needlessly unfriendly.
Fiat bottom ends are pretty stout. Having said that, building one requires no different care and attention than would building most others. Force feeding is a different consideration though. Having gone the route of full out natural aspiration I liking the idea of turbo charging or supercharging more and more. I really like the process that this fellow in Australia has gone through. He's strapped on a vortech centrifugal blower. Totally cool, but requiring different considerations for reliability.
Read these threads and have a look at these pics:
http://turbo124.com/forum/viewtopic.php ... sc&start=0
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racydave
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vcg
It's getting nowhere Joe. I am extremely dissapointed with the way you handled me from your first reply to your last.
There is no way I can make you not to be ironic and ask me bullshit like how meany heads did I try to come up with that, etc.
And ther is no way I can make you write and admit that every single internet site of a cam manufacturer sorts cams by overlap.
You were offensive from your first reply with no reason, and you continue to behave like a racer - tuner king of the forum, king of knowledge, and all that. You may agree with some of the guidelines you may disagree with others - that's fine. Write it down, lets build on it. It's not my property what I wrote: I read it, put thought in it, part of it I tried it and I share it. That's all.
I would rather discussing with you and the rest of the guys, FIAT TC block characters, long stroke - short stroke, revvy - torquey, and head matchups with torquey big inlet valve ones or revvy with big ex valves. Or discussing the low max lift - high tdc lift tendency in cam design (Kent FT11, etc) to save volume from combustion chamber digging to fit the valves deeper and avoid piston flycuts.
Or I would rather be discussing carb jetting with wide band air/fuel ratio analyzers, the only way that I know of to achieve near perfect jectting.
There is no way I can make you not to be ironic and ask me bullshit like how meany heads did I try to come up with that, etc.
And ther is no way I can make you write and admit that every single internet site of a cam manufacturer sorts cams by overlap.
You were offensive from your first reply with no reason, and you continue to behave like a racer - tuner king of the forum, king of knowledge, and all that. You may agree with some of the guidelines you may disagree with others - that's fine. Write it down, lets build on it. It's not my property what I wrote: I read it, put thought in it, part of it I tried it and I share it. That's all.
I would rather discussing with you and the rest of the guys, FIAT TC block characters, long stroke - short stroke, revvy - torquey, and head matchups with torquey big inlet valve ones or revvy with big ex valves. Or discussing the low max lift - high tdc lift tendency in cam design (Kent FT11, etc) to save volume from combustion chamber digging to fit the valves deeper and avoid piston flycuts.
Or I would rather be discussing carb jetting with wide band air/fuel ratio analyzers, the only way that I know of to achieve near perfect jectting.
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Joe Clemente
- Posts: 151
- Joined: Wed Jan 25, 2006 1:35 am
- Location: Vancouver, B.C. CANADA
I luv it! "tuner king of the forum" ...vcg wrote: You were offensive from your first reply with no reason, and you continue to behave like a racer - tuner king of the forum, king of knowledge, and all that.
yeah ok... whatever you say... 
Seriously, the only one behaving like that here is you Vassilis. I don't profess to be any of those things quoted above and I was not trying to be offensive to you. I simply disagreed with you and you summarily dismissed my views. I personally don't have a problem with somebody telling me they think I'm wrong. But that's all you did and you were particularly rude about it.
Like I said to you before, you've read way more into my posts than was intended and you seriously need to re-evaluate your take on this.
Grow up and get a grip on yourself Vassilis, really. And if you need to continue with these indignant jabs, do it off the forum. You know where to find me. I'll be more than happy to listen.
Hugs and kisses.
