IAP performance cams

[131lover]

Hi everyone!
I am new at this site, I have a question about IAPs performance cams!
I bought a pair of steel cams with duration 300 degrees 40,80/80,40 lift 10,35mm , for full spec see the link http://www.international-auto.com/file_ ... /index.cfm

Has anyone here used these cams? and are they ok to have in a daily driven street car,a Fiat 131 2000TC -83, with 2x40 IDF, 9,1:1 in comp, what are your spec in your engines?

I know i can put them in the engine and find out, but i just wanted some feedback on them!
Iam not a new to fiats but since I am from Sweden there arent many who have used these cams over here..
Regards
Alf Andersson
Sweden

[baltobernie]

I am using these with great success, in an engine similar to yours, except I have one large carburettor rather than two. It is important to make sure that the new cams are oriented ("indexed") correctly. You should invest in a set of adjustable cam wheels, and use a degree wheel to accurately set them to specs. Once set, they never need this attention again. Also be sure to set valve lash at 0.016" for both intake and exhaust, and make a note somewhere for future use, as this is not the spec for Fiat OE cams.

Don't discard your OE camshafts. After adjusting and tuning, if you find that these cams have cost you too dearly in the low-end of your driving RPM's, you can swap back the OE exhaust cam only. This will give you back some of your low-end performance, albeit at the expense of top-end power. (Do not try this with engines having a static CR of greater than 9.5:1, you need a lot of overlap in a high-CR engine.) BTW, you could then sell the IAP exhaust cam to another Fiat owner, who could use it without difficulty as his intake cam.

[sptcoupe]

Those cams are in hundreds of motors, and I have used them in 85% of the motors I have built. It will work fine with your set up, but a bit more compression and a decent header would be good mods.

[131lover]

Thank you for the feedback that's what i wanted to hear!

My plan for the future is to build on another 2l Tc block with Strada/Regatta Tc pistons ( 8mm dome) and head (43,5mm intake valve) lightly ported and refaced head seats, and a decent header, upgrade the Weber's to IDF 44!

I already have all these parts except for the adjustable cam wheels, that should work well with the IAP cams, or what do you think?

Regards
Alf

[lanciahf]

Alf
you might want to re-think Strada/Regatta Tc pistons ( 8mm dome) in a 2L. Compression ration is close to 12:1.

I have 4mm domes pistons with an IAP 40/80 cam on the intake side with a stock exhaust cam. Both cams are timed to 110 degrees overlap with millers mule adjustable pulleys.

Premium gas is a must with the 4mm domes and I hear horror stories of people shaving down 8mm pistons or buying extra thick head-gaskets in an attempt to lower the compression ratio to a more manageable level.

Carb is a single Weber 36 ADL from a Lancia Gamma 2L.

[djape1977]

with 8mm dome pistons, even with head gasket for volumex, my "mule" engine didn't last long.
on the other side, it did produce 8sec 0-100kph acceleration

[131lover]

Hi Lanciahf, Pedja, all!
lanciahf, your engine with the 4mm dome if they have the same height between piston crown and piston bolt in my mind should have a comp of 10,0:1 take or give some comp?

What i have read by Mr Croft, the 1800 Coupe European version had 9,8:1 in comp, and put them in a 2l these will get 10,2:1 and they have 5,2mm high dome, and he states that 8mm domed pistons in a 2l gets 10,8:1 , i know it can be some differences with different head gaskets!
Is Mr Croft wrong or I don't understand it?

I am no engine builder and no engineer, but it sounds strange to me that these 8mm domed pistons could give as high as 12,0:1 in comp?
I plan to use Marks multi layer gasket, the ,080" / 2mm thick..

I have heard of people here driving std races With 8mm dome pistons in a 2l and it had worked well, We do have premium fuel of 98 octane here, they say its good enough for higher comp engines!

Please do anyone have a clue whats right?
Regards Alf

[lanciahf]

The old/orginal Euro 9.8 pistons did not have 8mm domes. They were somehing like 2 or 4mm. The pistons you have are for the 1585cc Euro Ritmo, same bore as a 2L but with a much shorter stroke. These pistons fit the 84mm bore 2L but with the huge 2l stroke compared to a 1585 the compression ratio increases greatly. Someone that understands why this happens should chime in. now would be a good time....

[131lover]

Hi !
I know for sure that the 124 Coupe europe version has 5,2mm high dome and 9,8:1 in comp, the regular european 1800 had a 2,0mm high dome and 8,9:1 in comp,
I have had a few of these engines that i took apart so i have been measuring these pistons to this values, I also have a few Strada/Ragatta engines that i have been taken apart, they have the 8mm dome.
At Vicks Autoparts they sell the 8mm domed pistons and state that it should give 10,2:1 in comp in a 2l engine, i think thats far to low!

Yes I know that the stroke is longer in a 2l, I dont understand why Mr Croft state that it will give 10,8:1 in a 2l then?
Anyone who have been measuring the comp for these pistons?

Alf

[131]

I've recently put a 2 litre block together with a set of 84.6mm pistons from an 1800 Fiat 132, they have a dome a little under 3mm. The block was decked, 0.7mm removed, the head is from an 1800, with smaller combustion chambers than the 2 litre head. After measuring everything and crunching the numbers I've got a static compression ratio of a little under 11:1. Assuming a particular dome will give you a certain CR without measuring other variables is guesswork.

[divace73]

hey Mick , have you used bigger valves at all?

[131]

hey Mick , have you used bigger valves at all?

Yep, stainless from Csaba at autoricambi.

[LIQUIDLOUNGE]

The old/orginal Euro 9.8 pistons did not have 8mm domes. They were somehing like 2 or 4mm. The pistons you have are for the 1585cc Euro Ritmo, same bore as a 2L but with a much shorter stroke. These pistons fit the 84mm bore 2L but with the huge 2l stroke compared to a 1585 the compression ratio increases greatly. Someone that understands why this happens should chime in. now would be a good time....

The stroke has nothing to do with the compression ratio. Chamber size, piston dome/shape,headgasket are the major determiners of compression ratio. Even increasing the bore can make for a very slight increase in CR, but not stroke. Maybe in a very old motor where the cylinder was part of the combustion chamber this could be true.

[maytag]

The stroke has nothing to do with the compression ratio. Chamber size, piston dome/shape, headgasket are the major determiners of compression ratio. Even increasing the bore can make for a very slight increase in CR, but not stroke. Maybe in a very old motor where the cylinder was part of the combustion chamber this could be true.

ok, I'll bite: How is this true?
A compression ratio is a value that compares the volume of the cylinder (including chamber in the head, etc) at its greatest capacity to that of its smallest capacity. Greatest capacity occurs at the bottom of the stroke, and smallest capacity occurs at top of the stroke.
So if you shorten a stroke, then you decrease the greatest capacity, and increase the smallest capacity, thereby lowering your compression ratio.

How can we therefore say that "stroke has nothing to do with the compression ratio"? You CANNOOT EVEN CALCULATE A Compression Ratio without knowing the stroke.

Headgasket is certainly NOT a "Major determiner" of compression ratio, as you state. Yes, it can be used to fine-tune a CR in small increments, but the thickness of your headgasket, multiplied by the diameter of the bore, is an addition to your cylinder volume. And a relatively small addition.

Piston shape has very little to do with it either, except in considering the volume of the dome, flycuts, etc. and "size" or "volume" would be a better term than shape. Shape is incorrect.


I'm open to being wrong here, but this is my understanding. Help me see what you meant by your statement.

[maytag]

The old/orginal Euro 9.8 pistons did not have 8mm domes. They were somehing like 2 or 4mm. The pistons you have are for the 1585cc Euro Ritmo, same bore as a 2L but with a much shorter stroke. These pistons fit the 84mm bore 2L but with the huge 2l stroke compared to a 1585 the compression ratio increases greatly. Someone that understands why this happens should chime in. now would be a good time....

is this the original question that prompted the statements below?

if so, I think the description offered in my last post should cover it. But as a clarification: if all else remains the same, increasing the stroke of the motor will increase compression ratio. This is because the pistons travels farther DOWN the bore (increasing the bore's largest capacity) and then travels farther UP the bore (increasing the bore's smallest capacity).
Nothing can impact a CR more effectively than this.

Does that help?