Stock cam profile

[Fiat1980spyder]

1980 2L Does anyone know the gross valve lift, lobe Seperation, valve lift @tdc, degrees in std also combustion chamber cc

Stock engine

[vandor]

HM, I think lift is 9.1mm, but that's off the top of my head. Some of these specs are in the factory manual.

The combustion chamber volume I measured on a 2 liter was 53cc. Do not shave the head, or you'll end up cutting into the intake valve seats.

[RRoller123]

First order approximation using the factory data would make the total individual combustion chamber volume 61.6cc. (1996 swept volume divided by 4 cylinders and each divided by the 8.1:1 CR). So measuring about 53cc with plug and valve protrusion, carbon, etc. is probably pretty close.

This guy presents the most persnickety approach I have seen to calculating CR and measuring actual combustion chamber volume on his engine, and is very entertaining, not long winded or long worded..

https://www.youtube.com/watch?v=bWze92nt9OU

[FiatMac]

Here is the stock cam profile from measurements I have taken.

[Fiat1980spyder]

With the gross valve lift what would be the rocker ratio, if there is no rocker 0 or do they have another constant? Would Lobe lift be the same as gross valave lift if so accroding to the manual Lobe Lift(Without play) should be .3765in (9.564mm) Both. CC for 2L head was a average 53cc from what I found I will have mine done to verify. lobe seperation i can find, the rest i am at a standstill the engine is apart

[RRoller123]

I don't want to hijack this cam profile thread, but I have a question regarding the combustion chamber volume that was mentioned for the 1980 Spider 2L in this thread.

Given that the static CR being swept volume (SV) plus Combustion Chamber Volume (CCV) volume divided by CCV: (I had this wrong in my earlier post, obviously still learning)

Swept volume is about 499 per cylinder (1995 divided by 4)

a CR of 8.1 on the 2L yields a CCV of about 70cc
A CR of 9.1 on the 2L yields a CCV of about 62cc
A CR of 10.1 on the 2L yields a CCV of about 56cc

You would need a CR of 10.4 to yield the discussed CCV of 53cc, but the 1980 Spider has an 8.1:1 ratio.

So I am confused how we get to 53cc measured CCV What am I doing wrong in the calculations here.

Maybe it is the head gasket thickness that gives the extra ~17cc That seems like an awful lot though....

Pete

[fiatfactory]

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[RRoller123]

That is very helpful, thanks for sharing it! It now makes sense, because when one measures the volume of the head chamber, (by fluid fill or whatever) all those other factors remain unmeasured. Only the actual HEAD chamber is measured, not the gasket thickness, flycuts in the piston, etc. I am surprised that these other factors would have such a large effect; it gives one pause to think about the impact of Head Gasket Thickness when putting the engine together.

Pete

[fiatfactory]

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[RRoller123]

Yeah that makes sense, it clearly can be a significant volume. Now I have a follow up question: Shouldn't the Factory Specs - stated swept volume (or displacement) account for this, as the domes, cuts, etc move with the piston.

[fiatfactory]

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[RRoller123]

Excellent analysis!! Thanks.

Pete