Another 1500 FI performance street build.

RyanG

RyanG

True Classic
I’m looking for some advice here as I’m not sure what the best path is. I’ve owned my ‘82 FI x1/9 for about 2 years. It’s essentially stock. The engine runs fairly well and when I first picked it up I went through and replaced hoses, gaskets, timing belt, etc. Like a lot of you I’d like a bit more power.

I’ve picked up what I believe to be a NOS Chinese big valve (Tipo?) head. I’d like to use this to take advantage of larger intake valves and higher compression.

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At this point I’d keep the stock FI system, add a performance cam (suggestions welcome, I’d like to find one that isn’t a regrind and doesn’t require milling the cam box), either header exhaust or a Fiat cast 4-2 exhaust manifold, and lighten the flywheel.

This all seems pretty standard stuff. However I have some questions.

1. The exhaust valves on the Chinese head are smaller than the stock FI head. Is it worth having the exhaust valve seats replaced with the larger (33mm?) size.
2. Will the stock FI system work ok with this modified head, higher compression, performance cam (within reason).
3. I also have a spare block that I considered boring to 87mm and getting higher compression pistons. Again- will this make much difference for power with the modifications to the head and will the stock FI system be able to cope?

I’ve toyed with the idea of a full build with itbs, microsquirt system and bored block but I’m afraid of going down a path where I will never reach the end. I appreciate any advice.
 
I've build a few similar engines.
Not sure what size exhaust valves are in the Chinese head; 32mm? PBS claimed the smaller exhaust valves didn't matter too much, but others may disagree.
Running the stock EFI has never been an issue for me.
I'd cc that head before considering higher compression pistons. I ran around 11:1 for many years before finally blowing the head gasket.
You can use reground cams with lash caps to avoid having to mill the cam box and the need for adjustable cam wheels. I like Elgin cams or MidWest's A400 for a nice street engine.
The IAS style header seems to work better than the cast iron 4-2-1, but I have to use the latter to pass CA smog...
I have PBS lightened flywheels in both my cars and would recommend it.
 
Mark said:
I've build a few similar engines.
Not sure what size exhaust valves are in the Chinese head; 32mm? PBS claimed the smaller exhaust valves didn't matter too much, but others may disagree.
Running the stock EFI has never been an issue for me.
I'd cc that head before considering higher compression pistons. I ran around 11:1 for many years before finally blowing the head gasket.
You can use reground cams with lash caps to avoid having to mill the cam box and the need for adjustable cam wheels. I like Elgin cams or MidWest's A400 for a nice street engine.
The IAS style header seems to work better than the cast iron 4-2-1, but I have to use the latter to pass CA smog...
I have PBS lightened flywheels in both my cars and would recommend it.
Click to expand...
Mark - thanks for the reply. Good to know that the stock FI should work. I probably need to do all the math to figure out CR with the head that I have and the block and pistons. Low 10:1 should give me a noticeable improvement? I don’t need anything crazy. Also good to know there are ways to compensate for a reground cam without messing with the cam box.
 
Jefco said:
Will a 14 bolt head work on a 10 bolt block?
Click to expand...
It’s my understanding that you can use the 14 bolt head with the 10 bolt block. I’ve compared the main head bolt openings on the stock head and the Chinese head and I believe they are the same.
 
RyanG said:
It’s my understanding that you can use the 14 bolt head with the 10 bolt block. I’ve compared the main head bolt openings on the stock head and the Chinese head and I believe they are the same.
Click to expand...
Should be fine, I am using a 10 bolt head on a 14 bolt block, the extra holes are 8mm bolts near the spark plugs.
 
GregS said:
Should be fine, I am using a 10 bolt head on a 14 bolt block, the extra holes are 8mm bolts near the spark plugs.
Click to expand...
Really?
I knew it works the other way, but was told that it doesn‘t work this way because of the coolant passages.
I laid a 10-bolt gasket on the 14-bolt block and didn‘t see how it could work.
But there may be different deck layouts on the 14-bolt.
 
Regarding valve sizes, you are not building a high-rpm screamer.
The head and valve sizes were designed by Fiat for a 1600 with over 100hp.
It can‘t be all bad.
Considering the cost of installing larger valve seats, I would stick with what you have.
You could optimize their flow per SteveC‘s instructions.
 
Regarding pistons, I would not buy expensive special pistons.
Shave the block to get the pistons to stick up a little and optimize squish at the same time.
Or optimize CR, squish and displacement by installing a 1600 crank.
I may still have one. 😉
 
RyanG said:
I probably need to do all the math to figure out CR with the head that I have and the block and pistons. Low 10:1 should give me a noticeable improvement?
Click to expand...
Unfortunately you're not going to get into the 10"s with just a head change, so it would be a good idea to break out the burette and measure some volumes to figure out what it will actually be...

the european version of the 1500 sohc uses similar/the same pistons with the large valve flycuts (like your US spec engine) and the combustion chamber for the european engine is the same/similar to the tipo one, so you're looking at 9.2:1 static or there abouts depending on head gasket choice / block skimming / valve head depths etc (the usual variables)

14 bolt head will go onto a 10 bolt block no problem simply by plugging the M6 holes in the head with some grub screws and sealant, but a 10 bolt head will not go onto a 14 bolt block though -not without some welding - as water and oil passages will intersect.

SteveC
 
Ulix said:
Regarding valve sizes,
The head and valve sizes were designed by Fiat for a 1600 with over 100hp.
Click to expand...
Actually the 1581 sohc is rated at about 90hp (it's the 16valve dohc version that's rated to 103hp)

While the Tipo 1600 inlet valve/valve seat and port will outflow the stock 1500 cylinder head valve/valve seat and port, the same inlet "choke point" will still remain - the inlet manifold. So while the larger valve / valve seat throat will benefit power and torque in the lower / mid range, the engine will still run out of puff / revs due to the inlet restriction, and the common plenum will limit your cam choice if you want anything resembling 900rpm idle speeds.

Definitely do something about the exhaust, as the 4 into 1 cast iron manifold is the single largest restriction to power production, going to the 4/2/1 manifold and matching dual front pipe is worth approx 8hp, so almost identical gains to those claimed by the maker of an aftermarket exhaust header.

SteveC
 
Steve said,
"14 bolt head will go onto a 10 bolt block no problem simply by plugging the M6 holes in the head with some grub screws and sealant, but a 10 bolt head will not go onto a 14 bolt block though -not without some welding - as water and oil passages will intersect."

I definitely have a 10 bolt head on my 14 bolt block, no welding, no plugged holes, 8 years and still going strong. I just had a look at my old gaskets, the only thing I changed was to open up some of the coolant holes in the gasket for better flow, but I did that on the 14 bolt one also.
 
I couldn't find a photo of the block, but I have photos of the 14 bolt head with 14 bolt and 10 bolt gaskets.
Original gasket, red points to oil feed, green to extra 4 small bolts.
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2 different used 10 bolt gaskets that have been used with the 10 bolt head. Photo shown sitting on the 14 bolt head
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The problem isn't with the oil feed passage and water passages, it's between the water passage / additional bolt hole/ oil drain passages at the front of the engine... there just isn't enough gasket sealing area to 100% guarantee that there will be no cooling system pressure loss at this point.... as the void presented by the (unfilled) threaded hole for the additional (small) head fastener bridges the gap

20221004_105202.jpg


the fact that you've replaced the head gasket several times tells me there must have been an issue....

the front of the head (around the oil return passages) is known for not sealing up well, hence during production several methods of "beading" the gasket around this area, reinforcement and bridging in the water jackets to attempt to stiffen the structure and finally the addition of the extra small head fasteners to cure the possibility of oil leaks.

for me the head fasteners are just too far away from this possible failure point to provide sufficient clamping force to absolutely guarantee the gasket seals

SteveC
 
Ulix said:
But there may be different deck layouts on the 14-bolt.
Click to expand...
There are, open deck and closed deck 14 bolt blocks ... as well as 80.5mm bore and 86.4mm standard bore 14 bolt blocks.

Your 1.9 build would have been an open deck block.

I have a closed deck 14 bolt 86mm bore block in my shed, if I get a chance tomorrow I'll lay a 10 bolt head gasket and dowels on top of it and take a picture, it's pretty obvious that the additional bolt holes in the block and the water jacket of the head intersect, and the distance from the additional bolt hole (which would be filled with coolant and pressure in this scenario) is far too close to the oil return passage to be considered "safe" with barely a couple of mm of gasket to do the sealing.

SteveC
 
I see your point, but I have not have had any failures at this point, maybe I have been lucky. The gasket width at the yellow pointer would be important, but there is no bolt hole in the 10 bolt head next to this point. And the bolt hole in the block is a threaded blind hole, which could have a stud to plug it if concerned.
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The only gasket failure was at a fire ring due to detonation.
 
Although this discussion has gone a bit off topic, I suppose the success of the 14 bolt head on a 10 bolt block may partly depend on the specific head gasket being used. I've found numerous different designs of gaskets from various manufacturers, as far as the holes and cutouts go, for the same engine application. So for any given gasket, the actual size/shape of the holes in that area may change the amount of gasket material left to cover the surface....with some offering more coverage than others. The quality of the gasket material - also highly variable - will also be a factor.
 
I have a different head “fit” question. The new head I have appears to be made for carburetors. The intake inlets are round
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Where on the FI head there is a relief in the inlet for what I assume is injector/injector spray clearance.
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Is it important to grind out a similar relief in the new head? It should be fairly easy to make a template that I can transfer the outline into the new head and duplicate that profile. Any potential pitfalls with doing this?
 
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