Race Engine Forum UK

This is my first forum posting!!!

I purchased online an unused bare head with bronze value guides. It is a 1592cc twin cam head with an ID of: F.F. 1X / 132AB.1A.0 S62 / 4238527 C. My research tells me it was originally for a 1973 Fiat 124 Sport Coupe 1600. The website I found said that the head has a compression ratio of 9.8:1. Or it may be for a 1970 Fiat 124 Special T 1592cc with a compression ratio of 8.9:1. If not where does it come from and what is the compression ratio?

I plan on the following modifications: Intake and exhaust port modification, combustion chamber modification, heavy duty value springs, oversize-diameter intake & exhaust valves - 43mm intake, 37.5mm exhaust.

My question is will the head accept the oversized values? Will the compression ratio increase to 10.3:1 on an 1800cc block w/flat pistons? Will using a 93octane w/10% ethanol work on a 10.3:1 engine?

I will be using dual 40IDF Weber carbs, header w/ 2 ¼” free flow exhaust and 3.9 rear. I have not decided on cams yet. It is for my 1976 Fiat 124 and will be doing a lot of highway driving at65mph/105klmh

mccamie

Please post a photo of the combustion chamber!

GC

GC

Per your request I have posted photos of the 1592cc head chamber and plate info.

mccamie

I can't ID the head from the number - I don't have it in the list.

But the cc volume will be about the same as the one attached.

See my next post..

G

For starters the compression ratios were all achieved by use of various styles of domed piston.

Not your fault but you are going entirely the wrong way with your project so I guess I could say you have come to the right place for advice before you start!

I have input some figures into an Excel download table to show you how CR is calculated, you won't get anywhere near the CR you want with flat top pistons, indeed if you execute a big valve conversion on your head it will a) need extensive deshrouding to get any benefit and b) go way bigger than the one I have illustrated. The head in the photo above for Graham Waller likely started at about 49cc (when NEW and I emphasise new...)

You need domed pistons and I can tell you with well-prepped head the cc volume will go easily over 53cc and with the small swept volume of the 1800 you need an intruder of very large volume to get a decent CR. On an ex works 1800 for member Mick Wood -even tho the unit was a big-bore (86mm) and even tho the final chamber volume of the 45/40 big valve head was a miraculously low 55cc my forged piston design had to have a dome of nearly 18cc volume even just to get 10.1/CR....

the truth is this - you can make the chamber quite a bit bigger and not add a huge amount to the volume, but the only way to get high CR is an appropriately sized dome on the piston..

GC

G
Thanks for the information. I plan on sending head out to a good Fiat engine builder to get the work done.
mccamie

I plan on sending head out to a good Fiat engine builder to get the work done.

You're currently talking to one...

regards
Tom

Nice try Tom!!!


G

(perils of running a free forum, well, 'free' as in 'paid for by GC....!..'

"A good Fiat engine builder"
LOL
That's the funniest thing I've ever heard.
What is Guy Croft supposed to be?! A belly-dancer??

N

I am sure no slight was intended by Camie!


G

Forgive me if I offended anyone regarding my comment. I live in Bethany Beach, Delaware, USA not the UK. So sending it overseas to get work done would be a bit expensive. Thank you G for your response.
Camie

No worries Camie!

You are an accredited member here same as everyone!

G

Hi Camie,

No offence meant, and certainly none taken. It just looked a bit funny to me so I suggested our host here might actually be the Guy you're looking for. (Yes, pun intended.)
Are those shipping rates really that steep compared to your rebuild? I regularly buy stuff from all over Europe (on Oboy) and that comes through UPS and the likes at reasonable cost.
Anyway, it is of course your engine and your wallet.

regards
Tom

Tom

I checked online USPS rates to Lincoln UK and got a cost of $101.00/£62.75. I thought it best that I get it done here in the US. I will let you know how it turns out.

Proverb: Money is not everything but it is way ahead of number two. What is number two? Anything you want if you have the money!

Thanks
Camie

Just my .02 worth. I own a machine shop and specialize in cylinder heads, if I were you I would spend the money to ship your head to guy any day. The wealth of experience that you are getting for the cost of shipping cannot be compared. You will spend 50.00 driving all around the country side trying to get your head done. Half of the people you talk to will just laugh at you as they only work on domestic engines for performance upgrades. None of them has the quantitive experience that guy has in this particular model. All of the power is made in the head; the bottom end is merely an air compressor. Do not skimp on you head or you will have future regret.