1976 1800 Oil Pressure?

[jon8christine]

My '76 1800 has 105k miles on it and I'm still debating on rebuilding the engine with higher compression pistons and a mild cam upgrade etc. to improve the HP and 0-60. It's running mostly fine after upgrading to a 32/36 carb, though I still need to get a colortune or AF gauge to really get it tuned right. The tipping point would be if the engine needed rebuilt anyway due to being worn w/ 105,000 miles on it.

Once the engine is hot (fan comes on, generally runs between 180 and 190 deg F) oil pressure on my original dash gauge drops off from around 55psi cold to near 0 hot. The low pressure light on the oil pressure gauge never comes on, but the needle is close to zero. I installed a mechanical gauge on the engine, shown here

https://drive.google.com/file/d/1mwqmtM ... sp=sharing

and it verified what I was seeing. My oil pressure was as follows:

Cold Idle - 52 psi
Hot Idle (1,100 rpm) - 12 psi
Cold revved - ~70 psi
Hot Revved - ~60 psi

I've heard the low oil pressure light comes on at 7psi, but is my hot idle at 12 psi too low, indicating worn bearings that need to be changed before autocrossing next season?

[Nut124]

This is what I find in Guy Croft's book:

"as a general rule, under load from 3500rpm and up, approx 10psi/1000rpm is required. At idle, 15-25psi is observed depending on oil temp and crank clearances."

Yours would seem to satisfy the 10psi/1000rpm rule. Idling pressure is a bit low, certainly lower than my 1800.

What was your "revved" speed?

What oil are you running?

[18Fiatsandcounting]

My first thought as I was reading the original post was that the oil pressure sending unit was going bad, which is a very common occurrence as they age. But, I was glad to see the numbers with the external gauge.

My opinion: For casual driving, your oil pressure is fine. As Nut124 alluded to, you might need to simply move to a slightly heavier oil if that's possible. For example, using 10W-40 if you're using 10W-30 now. Do not use any of the "snake oil" oil additives that promise to fix all kinds of engine issues.

However, you mentioned autocrossing. That totally changes things so yes, if you are going to be driving the car aggressively, you really should first rebuild this engine with 105,000 miles on it.

-Bryan

[jon8christine]

I'm running 15w-50 conventional. RPM were about 3,500, but I was doing it myself, so glancing at the gauge after revving.

I was leaning toward rebuilding too after seeing the numbers and wanting to continue to autocross.

Thx

[18Fiatsandcounting]

Thanks for that info, and there's not much more you can do in terms of a heavier oil. Given your intention to autocross, I think rebuilding is the best path forward.

-Bryan

[SteinOnkel]

Send it and rebuild it when it breaks*? Most likely you will loose a ring and subsequently compression in one or more cylinders. Which is remedied by a hone job and new rings. Which you need anyways.

Ask me how I know all this...

*Although, right now is the perfect time to tackle big projects. Not like you're going to a music festival any time soon.

[Nut124]

Rebuilding is not cheap, particularly if you want more power.

Have you checked cylinder leakdown or cranking compression?

Unless your engine has a specific defect or problem I would be tempted to run it while preparing the plans for your rebuild. Putting together a parts list and cost can be eye opening.

[jon8christine]

So far my parts list is about $1000, doing the work myself except for making the heads flat and honing /boring the cylinders. Much cheaper than buying a boxster, which is my other convertible love that I'm still trying to talk myself out of if I can get a little more performance out of the Fiat.

[SteinOnkel]

Rebuilding is not cheap, particularly if you want more power.

Have you checked cylinder leakdown or cranking compression?

Unless your engine has a specific defect or problem I would be tempted to run it while preparing the plans for your rebuild. Putting together a parts list and cost can be eye opening.

Comparatively it is. I just spend $1000 on pistons alone for my other love. What does AR want for an engine rebuild kit? Like $500. That's free.

[SteinOnkel]

So far my parts list is about $1000, doing the work myself except for making the heads flat and honing /boring the cylinders. Much cheaper than buying a boxster, which is my other convertible love that I'm still trying to talk myself out of if I can get a little more performance out of the Fiat.

Ha, I had one before the Fiat. First oil change on that thing it was like panning for gold and I hit the motherlode. No more M96 cars for me, thanks.

[jon8christine]

Yeah I hear ya, I'm not interested in the older boxsters. I like the exterior and interior updates on the 981, 2013-2016 and after driving one... Wow.

[jon8christine]

So after a year of waiting on the machinist and parts I'm finally installing a new timing belt on my rebuilt engine. I have new 40-80 cams from Vicki's, adjustable cam gears set at zero and a new pointer (car didn't have one when I started on it). The issue is the belt teeth don't line up right when the cam gears are set to the pointers. Which cam should I move, or should I cheat them both? If both, then turn them in or out? Or does it all not really matter?

Thx


https://drive.google.com/file/d/14EwRUd ... p=drivesdk

https://drive.google.com/file/d/14PS_IO ... p=drivesdk

https://drive.google.com/file/d/14Ehb8b ... p=drivesdk

[Nut124]

Adjustable cam pulleys are for folks who precisely degree the cams and then set cam timing to a specific target, within a degree or so. This is an exercise that takes time, tooling and experience.

If you are not prepared to do all of this, then ditch the adjustable pulleys and use the factory pulleys. Once you see how the factory pulleys line up, we can debate which way to compromise.

[jon8christine]

The tools and time I have, experience is what I'm gaining as I build an engine for the first time this year thanks to all the helpful folks on this forum.

I threw the old cam gears on and they have the same timing belt alignment (maybe one of the gears advanced 1/16"). Vick Auto said to advance the intake by one. I assume in layman's terms he means rotate the intake cam CCW half a tooth until the belt is aligned, leaving the adjustable gears alone for now? This would increase the LSA and start with a more mild tune right?

Thoughts?

https://drive.google.com/file/d/16GiqgH ... p=drivesdk

[18Fiatsandcounting]

I'm sure Nut124 will arrive soon to give a better answer, but from your picture, I think you might be installing the timing belt in a "backwards" order.

Here's what I mean. Just focus on the intake cam and crankshaft to start with. Put the engine at TDC, then wrap the belt into position but not on the cam pulleys. Put the timing belt "behind" the exhaust cam pulley but not on the teeth. While keeping the engine at TDC, pull the timing belt to align with the teeth of the aux. shaft pulley, then pull tight and over the teeth of the intake cam. Don't worry about the exhaust cam pulley yet.

Once the belt is on the intake cam pulley (and the hole in the pulley lined up of course), turn your attention to the exhaust cam pulley. Line the pulley hole up with the mark, then with your left hand, depress the tensioner pulley. Then with your right hand, slide the belt from the back of the exhaust pulley onto the teeth.

Verify that everything is still lined up. If the teeth still don't line up, you either have something wrong, or the timing belt is the wrong one. There may be other possibilities.

Let us know if this helps at all. If not, I'll hand the mic over to Nut124!

-Bryan