Race Engine Forum UK

Hi, my name is Lucas, Im from Argentina, and I want to discuss with you how we can get more performance from this kind of engine/cylinder head.

Im owner of a 1971 Fiat 1600, a car that use all the mecanics implementantion from the Fiat 1500, even the same engine but with bore diferences, making 1625 displacement.

Originally has 8,8 RC.

Currently I have 3 cyinder heads and 2 or so of each manyfolds.... so I want to improve my car.
Here some pictures....





Thank you very much.

A nice looking head that I have not seen before.

Let's start with the top! Pick the best looking head, check it carefully for thread damage and especially cracks if you don't know its running history (if you are not sure get it pressure-tested), strip it down and let me have excellent closeup photos of combustion chamber, valves, valve seats, ports looking form combustion chamber outwards. Also let me see the outer port sections and a shot of the exit region of the inlet manifold and entry section of the inlet ports with their sizes (diameters if round).

Beware of severe water/detonation erosion/undercutting in the chambers near the valve seat inserts.

G

Thank you very much for yours quicks answers. I glad to tell you thats very exiting to me thinking I will share this proyect with you.

Here´s some pictures with dimension related details....
This one was the best looking cylinder head. I have to tell you I already use this one but I had to change it over again cause this one have a little water leak on one of the C. Head top cap (I already take the cylinder head today and this problem seems to be fixed, you can see the 2 brand news bronze caps...)


This cylinder head is coming from an 1969 ...Fiat 1500.... but I will use on a Fiat 1600 (1625 real cc´s)... When I try this one, comsuption drops a lot, but my car has less response too. I think the main differences are Valve diameters...later I will show you the numbers...


Here a picture from Cylinder head top....




---------Valve diameters.:----Port Diameter....:---...before valve seats (inside) diameter....:
Intake: -- 34,5 mm.-------28,5 mm.-----------------31 mm. (thats means no converge?)
Exhaust:- 31,10 mm.------29,5 mm.-------------I cannot get this number with my vernier caliper....



As you see, ports and tunnels are not aligned.... plus the spark plug go to one side of the combustion chamber....
I can see through the intake from the combustion camber to outside the cylinder head....but thats imposible to do with the exhaust tunnels...
exhaust valve and exhaust port planes are rotated at least 110 or 115 degrees... (a little bit softer curve line from exhaust valve to exhaust port or manyfold...i.e, I could be 90 degrees...but on this cylinder head are a little bit better than that (110 or 115 degrees)).



Valve guides are in very good conditions.. but the are made from iron.. no bronze...
Today I called a friend that work refurbishing cylinder head.. He told me.. "here.. on Argentina.. today, Its impossible to get a good quality bronze valve guides... so keep with the iron ones or put a bronze "little tube" inside of them...."

So I will expect your comments about this situation.





So thats all for today. I will be looking forwards from you...

Best Regards...

Lucas A. Bischof

If anything about information is missing. please let me know.

Thank you very much.

Dear Guy...

Actually I dont know how to start preparation on this cylinder head... but Im thinking that the inlet ports are too small... I will try to do a correct porting work with the manyfold.

Thank you very much.

Lucas

I'll get on this as soon as I am able!

Just for now - yes, do the manifold. Consider the relative sizes of the inlet port entry diameter and the entire section of the inlet manifold runners. If the runner is smaller than the port outer face it is going to generate an 'on-head loss' that we want to to try and minimise.

We can't get the loss the same on all 4 runners because their lengths are not the same and length governs viscous (drag) loss. But we'd want the runners to be all the same diameter and that should ideally be the same as that inlet port face if we can it without breaking thru. Which is often not possible but better to have the runner smaller than the the port rather than the other way round. Make sure the plenum region has good radii on all turns but don't be tempted to change the upper radius (assuming it has one) where the plenum (bit below the carb) runs into the runner roof - it may well be right already - they usually are.

On no account taper the inlet manifold in either direction, we want parallel runner sections.

G

Ok Guy... I will ask for your comments aftwer show you these pictures with the diameters comparis.

Here we have the manifold and the Cylinder Head....



Here a plenum detail.. please try to note about bad finished foundition on the top of the plenum.... I have to do something with that?
I have to fix it ?





More pictures....




Here the most important picture.... Note diameter differences..



Thank you very much dear Guy...

I will be waiting for your instructions.

Best Regards...

Lucas, from Argentina.

Great photos and I especially like the way you have taken time to annotate (mark up) the dimensions on the photos, it saves me so much time.

We have here a downstream mismatch of 4mm on diameter (32 vs 28mm) and the ratio of the mismatch is 4/28 which is 14% which is way too high. The higher the ratio the worse the intrusion into the airstream and turbulent losses. I would not want to see more than 4% which is 1mm on 28mm port entry dia.

But we will be enlarging the ports so before we decide exactly what to do give me the diameter of the runners too all the way to the plenum and the mininum diameter of the inlet ports - often they get smaller ie: taper towards the guide region.


You will need a calliper and vernier calliper to measure this.

GC

Dear Guy after trying hard to find a inner radius caliper (kwon as interiometro here)... I was able to get the dimensions on the manifold runners and cylinder head runners...

Here you have a picture with some indications... Please let me know if Im missing something...

By the way I had to tell you that on the manifold runners.. the runner section dimension keeps from plenum division trought the port... near 31 mm all the way.

On the cylinder head.. the runner start smaller and getting bigger on the way trought the valve seats....from 28mm to 32 mm...
Dimensions are very similar for all runners.... with minor diferences in order of about 0,4 o 0,6 milimeters..



Thank you very much again for your invaluable help.

Best Regards from Argentina..

Sincerely
Lucas A. Bischof

MODEL POST!

Excellent presentation of the layout, well done!

Nice to see an inlet manifold bigger than the ports for a change!

1. Remove casting 'flash' (bits sticking out) with burrs if needed and smooth the inlet manifold runners and plenum with carborundun rolls to 80 or even 120 grade. There won't be any difference in flow betw the two but 120 looks a whole lot nicer if that is what you want.
2. Using the inlet gasket mark out manifold face and the head face and 'true-up' the runners to 31mm true diameter inside the gasket as best you can, ie: place them on gasket centre as you can. If the gasket is too small I'd use it to mark out only and then later, during build either open it out or simply use silicon gasket and junk the gasket. The only problem with that is it can be very hard to get the manifold off! Enlarge the entry section of the head to 31mm dia (same as gasket) and open up the port to 30mm dia all the way thru to the valve guide region.

Keep away from the valve seat area and short side radius for now.

GC

Hi dear Guy... I want to tell you I´m still working on the manyfold and the Head. I will show you the pictures next week. Thank you very much for your help.

Best Regards..

Lucas

Great!

GC