1300cc Yugo FI head on a Fiat SOHC 1500

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Joff
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Location: Tobyhanna, PA, USA

1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

Some years ago I put a stock head and intake manifold from a 1300cc fuel injected yugo on a Fiat 1500 short block. 10.6/1 CR. Used a megasquirt I to control fuel only. AL flywheel. It had great low end torque. I try to build cars that are fun but reliable and don’t waste a lot of fuel, as my job as a stiltwalking entertainer requires that I travel long distances economically. I don’t know if the light flywheel saved me any gas, because I had to raise the idle RPM a lot, as it was easy to stall. The top end was (at least comparatively) a bit weak. I suspect it was due to the smaller ports on the yugo head and the long intake runners that are 26mm diameter inside, that were restrictive.

It’s time for me to build another one of these for a Yugo convertible that has been sitting on my porch too long.. I’m planning on the following changes, yet very open to suggestions from anyone.

30/45/60 valve job, 30 degree back grind on the valve. The local machine shop doesn’t have the stone to do 30/45/70. I could buy one, but only if it can make a big difference, which may be doubtful considering that 26mm runner. What do ya think? Similarly I don’t see the need to open up the inlet port when it already matches the runner that feeds it. Unlike the Fiat version, the Yugo FI intake manifold is one piece, so I don't think the inside of the runners can be hogged out. Bringing the valve seat to the outer edge of the valve won’t shorten the life too much to use as a daily driver, will it?

Deshroud around the intake valve a mm or two.

Performance “stage 1” cam from Vick Autosports that I have sitting around.
Intake
valve open 36.8 BTDC
Lobe center 107.7 ATDC
Valve closure 70.8 ABDC
Duration 287.6
net lift 10.4
Exhaust
valve open 71.3 BBDC
Lobe center 108.2 BTDC
Valve closure 36.8 ATDC
Duration 287.6
Net lift 10.5mm
Are stock valve springs ok if I keep it under 6500 rpm with this cam? Don’t want to increase friction if I don’t have to.
I am hoping the cam will help out the top end without costing me too much in fuel economy @ 3000 – 3500 RPM. That’s my “highway in 5th gear” speed. I also have stock cams on hand, if that would be better for my purpose.

Being that fuel cost more in the UK and Europe , I suspect performance engine builders there have a greater understanding of how to build economy into a daily driver performance engine. In the US, it seems the people who can build engines don’t care about fuel economy. Thanks for any help! Jeff
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Abarthnorway - Remi L
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Abarthnorway - Remi L »

Hi!


I would put a lot of thought into cam selection if I was You - If You do not get a good one, the original is probably a better choice if You want tractability/economy.

My experience is not with the SOHC, but I have experienced issues twice with TC engines - both with american "performance cams" - I am sorry to say.


Remi Lovhoiden
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Joff
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

Hi, Remi, Thanks for the reply! My thinking is that if I want to help it breath at higher rpm and don't need all the low end I had on the other build, then this cam might be a way to help do that. I don't think it would be a good idea to put this cam on a stock carbed 1500 with it's 8.5/1 compression ratio, but with 10/1 and the ramming effect of those long intake runners it might have a chance. I know it's not good to be "over cammed" but it's a mild street cam and with those smaller ports it may help to open the valves sooner and hold them open longer. If I'm wrong, don't worry about offending me, I'm here to learn. It's not clear to me how, and at what rpm this cam would be wastefull. I don't mind wastiing a little bit, just not too much!
Thanks!
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Urbancamo
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Urbancamo »

Hi Jeff.

I'm just as newbie as you, but i can share some of my knowlegde.

Is that cam grinded from stock or billet? Or something else?

With that nearly 290 degree cam and common plenum setup, you might found your self pretty greatly reduced low end all-ready.

If you have throttle bodies or dual carbs, the this cam would be pretty spot-on. I might use little bit more compression ratio because this cam greatly reduces your dynamic compression ratio. Of course it depends greatly your engine components, like head work too.
I don't really know about US fuel quality.

You can read my topic of modifying Lada engine. My mission was similar than your's. Make a good, responsive engine which has more power than stock, but with reasonable fuel economy and good low- to high end torque.
I aimed pretty high dynamic compression ratio, over 8:1, which might be one of reasons for great torque and low fuel consumption. Couldn't be happier.


Tommi
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Joff
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

Nice! We don’t have many Ladas here in the US. I see a few of the 4 wheel drive Lada Nivas that individuals import one at a time on an internet auction site, once in a while. I’d buy one like yours! Yugo is the only communist made, Fiat copy, I can obtain around here.
I like that it's sort of an anti-status symbol.
”Is that cam grinded from stock or billet? Or something else? “
They start with a stock cam and build up the lobes with a cobalt welding process, then regrind. Base circle is close, but a little smaller than stock. Should fit with the valve job that sets the valves a little deeper.

“With that nearly 290 degree cam and common plenum setup, you might found your self pretty greatly reduced low end all-ready.”
I’m no expert on cams but I’ve used this type of manifold before and think with it’s long runners, it gives good velocity and wave action at a lower rpm than a twin carb setup. I got my worst fuel economy ever with twin weber DCNF 40s. Good up top, too touchy when those big butterfly valves start to open. I spent a lot of time and money trying to get them right and I don’t think they can ever provide the performance with economy that programmable fuel injection can. I was very surprised that Guy has not quite embraced the new tech in the new book.

Although it’s preferable to get it right the first time, it would not be too hard for me to swap cams if I choose the wrong one. I'm hoping someone will explain the details of how it will waste fuel.
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Joff
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

Just wanted to add a picture of the manifold I am talking about. Photo is of a different project of mine, but it uses the same type manifold.
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Abarthnorway - Remi L
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Abarthnorway - Remi L »

Hi!


Cam selection is really hard to do - and I do not have any firm advice for Your setup as I have never done a cam change in a FI engine. In my experience it really comes down to trying it out to see what works - or not - to achieve the desired effect. A certain cam can give many different caracteristics depending on the setup as a whole. Inlet tract lenght and exhaust setup alone can make massive differences - I have experienced that between a 124 Spider and a 130TC with identical engine internals. Only differences were Carbs, inlet manifold and exhaust. I really do not understand why - but the engines had very different characteristics.

To measure a cam out of degrees and lift alone can is not enough to determine its effects. I have seen and tried out several cams of approx 300` and 10mm+ (TC engine)lift and they are not at all the same when fitted to an engine. Timing, lift at TDC and lift rate is also very important. I have only made one SOHC - a 1300 with 284`billet cam with high lift and quite some lift at TDC. Together with Twin carbs and a tubular manifold it easily pulled 8000+ but didn"t pull any good below 4500. On the other hand a 290` cam with 10+ mm lift in Your setup might prove perfectly right:-)

Regarding twin carb setups being less responsive at lower revs I totally disagree. Tuned correctly the just purr around town with ease, and give a fantastic low to mid range torque - with the right cam/chokes that is:-)

I am not trying to put You off - but be sure to always expect the unexpected.

Install the cam and see what happens!:-)
Keep us posted

Good luck!!!


Best regards

Remi Lovhoiden
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Joff
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

Ye said:
”I have experienced that between a 124 Spider and a 130TC with identical engine internals. Only differences were Carbs, inlet manifold and exhaust. I really do not understand why - but the engines had very different characteristics.” Seems to me the wave action in different pipes, both intake and exhaust, would be a good explanation.

On your 1300 – imagine if you increased its stroke to that of a 1500. With a given amount of cylinder pressure, it is now going to make more torque due to the increased leverage, so more power down low. Also it’s pulling in more air per stroke, so that would help too. At high RPM you would overwhelm your intakes (unchanged) ability to provide air, at a lower RPM, thus your peak power would be at a lower RPM than with it’s original shorter stroke. That ‘s a good explanation of my reasoning on my engine, anyway.

“be sure to always expect the unexpected” That’s what I live for, and why I try to make every build different! My last one, and current daily driver is a supercharged Yugo –not because it was a sensible thing to do, but because no one had done it!
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Joff
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Re: 1300cc Yugo FI head on a Fiat SOHC 1500

Post by Joff »

I have the head at a machine shop getting the 30/45/60 valve job after doing a little porting and deshrouding. I decided the sensible thing to do about the cam is to ask the folks who have been making and selling them for years.
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