Question on Heads

Tidybuoy · 07-16-2004, 02:36 PM

Hi,

I have a small problem. I stripped out a spark plug hole on my 1974 1.8 FI. The car already had a helicoil type fix (which I didn't know about) and when I was changing plugs, the old heli-coil came out with the plug.

I really didn't want to spend too much on this 1.8 since my ultimate goal will be to replace with a 2.0.

The only shop that I've been able to find to do a complete rebuild wants around $800 to rebuild - that seems high.

The engine is currently out of the car but I haven't removed the heads and so no inspection has taken place as of yet.

My question: since I haven't been able to find a good set of 1.8 heads, could I use 2.0 heads & would there be any pros/cons to going this way. I plan on keeping the stock FI so I need heads that have a temp sender spot & I also have to consider any changes to the engine tin.

Any advice would be great.

Also, I purchased a set of rebuilt 1.8 heads on E-bay about 6 months ago but it turned out that they were bus heads and had really small valves and no temp sender spot. Fortunately, I was able to re-sell on E-bay and recouped 99% of my investment.

Although I don't want to invest a fortune in my 1.8, I also don't want to sacrafice horse power either - the 1.8 is slow enough.

Thanks in advance.......................................Vern

Tidybuoy · 07-16-2004, 02:37 PM

One more thing: I have a fair amount of mechanical ability, but if I have to re-install new heli-coils I could use a little advice on this subject.

Thanks again...................................Vern

silver2.0 · silver2.0's Garage

First off, if you just want to get it going again, and all that is wrong is this spark plug hole, I would just fix the hole that has been damaged.
-To do this I would pull the motor and transmission- that will take about 2 hours or so, less when you get good.
-Next put the engine on a stand, and pull the head.
-Now just buy a heli coil kit, and run the tap down the hole. You will get almost nothing out in the way of shavings.
-Now clean the threads, and thread in the new heli-coil. make sure you break off the tab at the bottom, and make sure you thread in the insert slightly past flush with the outside of the head.
-Now, I would suggest pulling up your cylinders, and cleaning them very well, and seal them with ultra-greay permatex. (only at the base)
-Put everything back together, and you should have a good runner again.
This is the cheaper way, that takes some time.
Now if you want to you could just try to run a new insert in- with the engine and tin still in place. It might work. I would say it's worth a try anyhow.
If you really don' t like this motor, or it runs crappy, now might be a great time to upgrade to the 2.0. If you don't have a couple grand to lay down on a proper 2.0 conversion, I would suggest you take my first approach mentioned, and throw in a set of rings at the same time. (with a hone of course). Also if you tear it down, check out the valves.

Good luck.
Tony

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The 2.0 heads will fit onto the 1.8 cylinders, but I'm not sure what it would do to the compression ratio. Anyone happen to know the chamber volume of a stock 1.8 head? I think the stock 2.0 heads are in the 56-60 cc range. (Big range, I know!!)

You'll have to plug up the spark plug holes in the engine tin and cut new holes for the 2.0 plugs.

You'll have to drill a new hole in the 1.8 intake runner pipe flange for the center stud of the classic three-stud pattern on the 2.0 heads.

...I think the rest of it would work OK.

--DD

Tidybuoy · 07-16-2004, 05:19 PM

Thanks Guys!

The engine is already out of the car (and I'm proud to say, it took me about 1 hour & 15 min to do - with my friend's help).

I already purchased new rings, pushrod tubes, various gaskets, and clutch - I figured I'd do some basic maintenance well I've got the engine out.

I may check back with a few questions after I look closely at the heads. My primary concern is that the orig heli-coil pulled out & I wasn't sure if I would be able to get a new one to hold.

Vern

silver2.0 · silver2.0's Garage

don't worry about it, it happens ALL the time. It's the nature of heil coil. They tend to peel out, especially if they are not inserted slightly past being flush, and you try to start the plug a little crooked. Don't even worry about it. You can take a pair of pliers and yank out any heli coil like a big spring, and it won't do any noticable damage to the threads.

Tony

Jason Porter · 07-17-2004, 01:14 AM

It will definitely come out. I'm damn near an expert on this Heli-Coil deal by now. I've even developed a technique for tapping the over-sized hole for the Heli-Coil while the head is still on.

FYI - If the engine is out, I don't recommend doing this, since you have easy access to the head's removal already.

1. Turn cylinder you are working on to BDC, both valves closed, prior to compression stroke. This keeps the tap from destroying the piston, and although it's nearly impossible, keeps it from getting too close to the valves also.

2. Get yourself a can of CV greaseor Vaseline, worst case scenario use gear oil, and after cleaning your tap with some brake clean or alcohol, dunk the tap into the grease.

3. Most important, whether your head is on or off the engine, tap the hole straight, once you get a bite with the oversize tap, and are started, there's no turning back. And if you go in at the wrong angle, you will probably hit a valve seat, not to mention weakening the head.

4. Tap about a quarter of the way through or so, until resistance is building, and back the tap out. It will be covered in crap, mostly grease, but more importantly, any major aluminum particles from the tapping process. Clean this off with brake clean/alcohol.

5. Repeat steps 2-4 until hole is tapped.

Install your Heli-Coil, and fire her up. Don't worry about the micron(s) of crap that may have fallen in to the combustion chamber, because invariably, they're miniscule, and will blow out of the exhaust valve after the compression stroke. Anything small enough to stay in there will burn up in the next combustion cycle.

------

Granted, this isn't recommended, but if your in a pinch, it will work, and you shouldn't feel all that bad about doing it.

I did this recently, to my new 1911cc in my bug.

A. Because there's so much crap involved in taking the motor out, and,

B. Because I had to cross-thread the head putting in a plug in an emergency situation, and the plug later blew out of the head. But I fixed it as described above, and all is well. At 25,000 miles when I get my heads redone, It will be permanently fixed, but until then, I feel comfortable.

Good luck, and don't have too much fun.

silver2.0 · silver2.0's Garage

Jason's recommendation is ok for your engine, as it has already been tapped for the oversize helicoil. I would highly recommend against this though for anything else. The reason I say that is, as Jason stated, Most of the crap will get blown out through the exhaust, but you have a high potential for getting something stuck inbetween the seat and the valve, and ruining the seal. You have to put rings in anyway right?