Head gasket failure - next steps

[njspider]

Midwest Bayless does excellent work.

[davefrancisco]

Continuing the dialog and questions.

So head is getting redone, stock rebuild on a 1.8 Litre head. Also carb is getting rebuilt as well. 32 ADFA with single plane manifold.

In addition, my brother has a 2L block that he is willing to donate. Likely some beer will need to be provided during exchange, but still a good deal. So here are the questions

1. If i just mate my stock rebuilt head to his stock 2L block is there any things I need to worry about? Valve clearances is one thought.
2. If I add high compression pistons are there other adjustments needed?
3. if I do high compression pistons plus new performance CAMs what are the things I need to consider?
4. If I do 2 or 3 are there other things I should do to get the biggest bang for my buck? Bigger valves come to mind.

My big concern is valves hitting pistons. And will there be any differences in setting up the mechanical timing?

If you had this situation and some budget what would you do?

Thanks as always for the feedback

Dave

[18Fiatsandcounting]

My understanding is that a 1.8L head on a 2L is a good swap since the 1.8L head has a better combustion chamber and inlet port designs. With the stock 2L pistons, piston-to-valve issues would not be a problem as the 2L pistons are flat.

What sort of compression increase are you thinking? The stock 2L was abysmally low, so almost anything is an upgrade. Once you go much over 9:1, you might need to start looking for premium gas. You can go over 10:1, but I'd shy away from this unless you know someone who really knows what they're doing.

Cams are another option, but like everything in life, there are trade-offs. Performance cams just shift the torque curve around so that it comes at higher rpms, and since you're at higher rpms, that equals more HP. The stock Fiat cams were actually pretty good for all-around driving, but if you spend most of your day at 5000 rpm and above, you can look into better cams.

If you go with domed pistons, higher lift cams, longer duration cams, etc., you would need to check piston-to-valve clearance. No differences in valve timing unless you want to experiment with adjustable cam pulleys.

Also, while a 2L will feel "torque-ier" at low rpms, the 1800 will rev easier. It all depends whether you want your power at low rpms, across a wide range, or at high rpms. Tradeoffs...

-Bryan

[TheBender]

Bryan pretty much summed up everything I’ve learned/been told from experts I trust. To rebuild the block and do the pistons is where you’d get the most power out of updates. But (at least for me since I would be paying for it to be done) it’s also very pricey. I am not sure if you mentioned what year, but from the sound of it you have a 78. If you’re looking for a nice cost effective gain, take a look at putting a 79 exhaust manifold on it. 78 exhaust manifold is quite restrictive as it goes 4 to 1 tube. The 79 goes 4:2:1 and is much more free flowing. I was quite shocked how much difference I felt from that simple update.

[davefrancisco]

Sorry for the delay here. Just returned from vacation.

After the head is reconditioned to stock spec's, my plan is to mate the 1.8 head to a stock 2L block. I will check the compression on the 2L motor and decide if I need to replace compression rings. I'll check on oil consumption as well and pull oil pan and do a visual on the bottom half of the motor. Good to have a living donor motor.

My hope is not to have to do any repairs on the bottom half of the motor.

I will look at a replacement exhaust manifold as well. So Thanks Bender for the add to Bryans very informative post.

Thanks

Dave

[davefrancisco]

Bryan,

I don't have a target compression ratio, but my thought/hope is that it will increase with just the addition of the 1.8L head.

Let me know if my thoughts are correct, and if you know what the compression ratio would be with this combo.

I missed this point in my last post.

Thanks

Dave

[18Fiatsandcounting]

I think the CR will increase with the 1.8L head, and here's why. I have a few spare heads in my garage, and the 1.8L heads seem to have a combustion chamber volume of around 45 cc. The 2L heads are more like 50 cc. So in VERY rough numbers, that would be about a 10% increase in compression, so for example from 8:1 to close to 8.8:1 just by going with the 1800 head. Again, VERY rough numbers.

Here's a slightly better calculation. Each cylinder of the 2L block is very close to 500 cc. (1.998L divided by 4) Figure about another 5 cc for the head gasket and 15 cc for the valve cutouts in the piston, and with the 2L block and head, the stock CR would be (500+5+15+50) / (5+15+50) or around 8.1:1. Put the 1.8L head on it, and that calculation becomes (500+5+15+45) / (5+15+45) or around 8.7.

By the way, this is a calculation of static compression, but dynamic compression ratios could be different as this depends on your intake system, your cams, and rpm. Dynamic compression is what a (running) engine cares about, and it can be extremely difficult to measure as it's the ratio of the volume of air and fuel pulled into the cylinder compared to how much that volume is compressed at whatever rpm.

If you really want to increase your CR even further, that requires domed pistons.

-Bryan

[davefrancisco]

Thanks Bryan.. Appreciate the math and logic behind this. I'm not looking to go any higher than the 1.8L head will provide. The increase in torque I should feel with 2L block and somewhat higher compression should make the car a bit more fun to drive.

Carb is being rebuilt and will also be looking at a better exhaust manifold as suggested by thebender. These 2 things will add a bit more.

Thanks

Dave

[18Fiatsandcounting]

Forgot to mention: I put a 2L block in my '69 spider but kept the original 1438cc head (long story, variety of reasons). When rebuilt, the engine pulled very well from 40 to over 100 mph. And beyond, but I didn't want to over-rev the newly rebuilt 2L engine. And see the next paragraph.

The downside of this is that the 1438 head doesn't have big enough intake ports for good flow at higher rpms, so the engine runs out of steam at around 5500 rpm. It will pull past this, but just not as forcefully. Your 1800 head has better ports and so it shouldn't have this issue.

Bottom line: An 1800 head on a 2L block with a good carb and intake manifold is hard to beat without spending a lot of money.

-Bryan

[RichA]

On a related note ... I need to get the head off my 1975 CS1 1800 so I can get the valves reconditioned.

I've got a workshop manual but it basically says 'take the head off' !!

I've not been able to find anything on YouTube etc and would be a lot more comfortable doing it with some step by step instructions.

Has anybody got some instructions/guidance of what need to be done?

cheers

Rich

[18Fiatsandcounting]

Happy to guide you through the process, and it might be easier by phone, so if you want to send me your phone number by Private Message, and a good time to call, we can go that route. If you don't want to do that, let me know and I'll start typing a reply on this forum. Just takes longer.

-Bryan