Engine build question(s)

[79X19]

I'm thinking of dropping my perfectly working but leaky 1500 FI engine with ?? confirmed miles on it (PO replaced the '81 motor with an '86) and rebuilding it but with some upgrades. So here's what I have:

• '86 1500 motor that's working well right now but needs leaks fixed and fuel rail rebuild (just to be safe)
• Euro Yugo cylinder head for increased compression. Bought from a member here and came off of a running car.
• 4 into 2 manifold

A few questions:
1. If the '86 motor has good compression can I just replace the current '86 head with the Yugo head?
2. Note in the picture that there are some differences with the Yugo head from the '86 head. What mods will I need to complete to make it work? Or can I jus swap it out and forgo some functionality? I'm never going to drive this in the cold or the rain if the mods required are for cold start??
3. In order to extract as much HP from this set up what sort of cam should i use?
4. I'm not interested in upgrading pistons if I don't have to.

I have upgraded the coolant system with a new water pump, ss expansion tank, new ss coolant pipes and new vics aluminum rad with dual fans so the coolant system is top notch if that matters in this discussion.

I've attached pics of what I have in terms of the head and exhaust for illustration purposes. The old cylinder head in the pictures is from the '81 motor and used just as a comparison. I believe the '86 motor would have the same set up.

Let me know what you think

 

[fiatfactory]

If the 86 engine you're upgrading has the extra 4 small M6 bolts at the front, (i.e. a 14 bolt head) then you have a compatibility issue with the 10 bolt head you wish to fit.

SteveC

 

[79X19]

Thanks SteveC. I have the original '81 block that I could use for the build. It would be compatible with the Yugo head yes? If that is the case what mods do I need to do to the Yugo head to make it work? Also what Cam should I get to give it a bit more get up and go. Mind you I don't need a race motor and not looking for K20 power by any means just looking for a bit more liveliness without needing to sink big money into it. I have rebuilt US muscle car motors in the past but have limited experience with this motor as you can see by my gaff with the 14 bolt vs 10 bolt.

 

[kmead]

Thanks SteveC. I have the original '81 block that I could use for the build. It would be compatible with the Yugo head yes? If that is the case what mods do I need to do to the Yugo head to make it work? Also what Cam should I get to give it a bit more get up and go. Mind you I don't need a race motor and not looking for K20 power by any means just looking for a bit more liveliness without needing to sink big money into it. I have rebuilt US muscle car motors in the past but have limited experience with this motor as you can see by my gaff with the 14 bolt vs 10 bolt.

Is the 81 block complete and in good condition? In all likelihood it was changed out due to an issue which requires rebuild. You can’t just swap the pistons from the late engine to the older, worn in a different way engine.

In regards to the head if you are looking to do a better cam then it should have some work done to it to maximize the new cam. There is also a value to adding the cut outs for the fuel injectors to ensure the spray pattern is maintained although people have successfully used the existing openings of a non FI head.

You are staring down the barrel of what happens to us all when contemplating engine work, once you change one thing you end up needing to change a variety of related things. Then there is the “while you are at it” issue of I don’t want to take this apart again so “I may as well” do this too. It is a slippery slope.

Dealing with the warm up system is another issue you will have to churn through with a different head. If you change to a different modern injection system this won’t be a problem as it would be dealt with by software and inputs from sensors. Using a different injection system would be able to accept a wilder cam which would allow the new injection system to perform better. But new pistons with more compression would allow even more power.

See what I mean?

 

[fiatfactory]

Thanks SteveC. I have the original '81 block that I could use for the build. It would be compatible with the Yugo head yes?

yes it is, both are 10 bolt configuration. You can fit a 14 bolt head to a 10 bolt block (once you plug the additonal four holes) but it doesn't work the other way around due to overlap of water / oilways

If that is the case what mods do I need to do to the Yugo head to make it work?

none, apart from those related to EFI differences, which have been covered by others on the forum

Also what Cam should I get to give it a bit more get up and go.

That's your personal choice, but bear in mind additional overlap will lower inlet manifold vacuum, and create fueling issues that the stock EFI wont manage with very well

Mind you I don't need a race motor and not looking for K20 power by any means just looking for a bit more liveliness without needing to sink big money into it. I have rebuilt US muscle car motors in the past but have limited experience with this motor as you can see by my gaff with the 14 bolt vs 10 bolt.

find a 14 bolt euro head from a carburetted car and modify it the same as you have done to the 1100 yugo head, that's gotta be easier / cheaper than rebuilding a bottom end just so you can use a yugo 1100 head.

As Karl says, it will become a case of "while I'm in there" and your time and funds budget will definitely blow out.

SteveC

 

[79X19]

Thanks all for the feedback.....I'll go get some therapy now. Not in the mood to rebuild a motor that's working perfectly besides the leaky tranny and oil pan for limited upside.

Looks like Ill need to be happy with exotic car styling, race car handling and riding lawn mower engine performance.

 

[Jefco]

Your Fiat head in the pics does NOT have 14 bolt holes, you show a 10 bolt head.
There are differences in bolt diameters, newer heads (like my '86) have thinner bolts.
Your Yugo head already has scallops for the fuel injectors.
No one has mentioned the interference aspect, your valves may hit your pistons if out of timing (or if you break a belt).
Having smaller chambers will increase compression, without changing pistons.
The aux air regulator has a heater in it, but should be bolted to the engine for transmission of engine heat into it too.
Are the Yugo valves smaller? They look so in the pics.

 

[Dr.Jeff]

I did exactly what Karl described; had a excellent engine in perfect shape, decided to give it a look inside while it was out if the car, and ended up doing a complete rebuild/performance mods. It just snowballs. Honestly if your engine is currently in great shape and running well, then I wouldn't disturb it other than eliminating the oil leaks and servicing everything. The reality is unless you do major modifications you will not notice much difference in everyday driving. Possibly replacing the exhaust manifold with the dual outlet one is something to consider. But even that grows because it requires that the rest of the exhaust also be changed to fit it.

 

[fiatfactory]

Thanks all for the feedback.....I'll go get some therapy now. Not in the mood to rebuild a motor that's working perfectly besides the leaky tranny and oil pan for limited upside.

Looks like Ill need to be happy with exotic car styling, race car handling and riding lawn mower engine performance.

Fix the leaks and do the exhaust manifold and front pipe change, that will defintely net positive gains without opening the engine up at all.

I take it that you checked that your "86 engine" is indeed a 14 bolt engine? I can't see it, but an 86 should be a 14 bolt... are you absolutely sure you have an '86 year engine... I guess your just going on what the PO has told you?

Head bolt thru hole size doesn't matter, as the head locates on the head dowels... it's only an issue if you try to fit an M10 fastener head onto an M12 fastener block...and then you need to open them up/ drill them out... your going the other way around so there is no compatibility issiue there

1100/1300/1500 all use the same size inlet valve, but the seat throat inside diameter is larger on the 1500, so using an 1100 yugo head is actually a retrograde step for head flow. Due to the smaller combustion chamber it wll bump static compression, but it will not turn the engine into an "interference" engine, as that is due to the large flycuts in the piston crown, the actual valve seat depth into the head . i.e the distance from the valve head to the top of the block is identical in all engines (with the head unskimmed)

The 1100 head combustion chamber is also only 80mm approx across the chamber, so the inlet valve sits about 3mm closer to the chamber wall, this shrouds the valve and inhibits flow, so again a retrograde step. The 1100 head on an 86mm bore will bump static CR, but at the expense of flow, so it will have more punch down low, but run out of puff up high in the rev range

the exhaust valve is smaller in the 1300/1100, as is the exhaust valve seat throat.

all this is outlined in my "ultimate sohc" thread ...

SteveC

 

[79X19]

Steve,
The PO only told me he had replaced the original 1981 engine (Which I have complete) with a newer engine as he blew a head gasket. In looking at the shield that covers the fiat logo on the FI unit it shows in the upper right hand area of the emission sticker "1986 50 State". I assume that means the engine is from a 1986 X and that it has a 14 bolt head. Is that a correct assumption?

Also sounds like to get minor performance enhancements I could change the exhaust manifold, and maybe add a slightly better cam to the standard 1986 motor?.

 

[fiatfactory]

just look at the engine, below the spark plugs you'll see an additional four small 10mm head bolts ...if it's a 14 bolt ... they wont be there if it's a10 bolt engine.

dual out exhaust manifold will definitely yeild positive resuts with no downsides, the same may not be true of a cam change

SteveC

 

[79X19]

I looked below the spark plugs and only count 5 bolts.

 

[fiatfactory]

If the 86 engine you're upgrading has the extra 4 small M6 bolts at the front, (i.e. a 14 bolt head) then you have a compatibility issue with the 10 bolt head you wish to fit.

SteveC

Note the word IF is the first word of this sentence...

1986 should be a 14 bolt... so maybe the engine wasnt from an 86 afterall

SteveC

 

[johnph]

Thanks all for the feedback.....I'll go get some therapy now. Not in the mood to rebuild a motor that's working perfectly besides the leaky tranny and oil pan for limited upside.

Looks like Ill need to be happy with exotic car styling, race car handling and riding lawn mower engine performance.

True: Do not despair. A friend of mine installed a "Plus 50" nitrous system in his injected Bertone. It went like stink. So fast that he had to replace the brake pads. Get two bottles so when the first goes empty, you can change over and have more fun.

 

[EricH]

Also sounds like to get minor performance enhancements I could change the exhaust manifold, and maybe add a slightly better cam to the standard 1986 motor?.

If you're starting with a US-spec car, just bringing it up to the stock Euro specs will be a very noticeable improvement without compromising driveability at all. The hardest part (for an American) is getting a 1500 head from the other side of the Atlantic.