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Discussion Starter · #1 ·
RallyBob's Tricks For More CIH HP

Just looking at all the options to raise compression of my '73 1.9L motor. While plodding through some related Yahoo ClassicOpel keyword searches I came upon some info on using a 1.5L head on a late year engine to bump up compression. I think it was mentioned doing this could get close to the "earlier" high compression ratio engine.

Keeping the work to do this via just head work has it's merrits (like not starting an engine rebuild that I know will take 2X as long and 4X over budget...the story of my life) so I'm curious. My gut tells me I'm going to end up in the long run doing the engine rebuild with the proper piston swap, but I just need to ask about this 1.5L head deal. Questions abound like:

*Is this really as good as it sounds?

*If not, what's the catch?

*Where would one even find a 1.5L head?

*What would be the best guesstimate at the compression ratio doing this?

*Could the compression be bumped a bit more by milling the head? If so, how much milling will yield how many points?

*How will the 1.5L head flow compared to the 1.9L (assuming both are stock) just for a benchmark?

Just tossing some questions out there, any replies will be appreciated.
 

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searching

You need to do a bit of searching around this site, there are some great pictures somewhere. The head has much smaller valve "pockets" which yields a higher compression ratio. Unfortunatly, it also shrouds the valves a lot more, which would limit a lot of the gains you might get from the higher compression ratio. The real neat part, though, is that with the right port work you could end-up with a better head with a smaller chamber than stock, even with much larger valves.

There would probably be an issue with the extra 2 head bolts if you tried to use that new a block, as the 1.5 is the same as the earlier 1.9 motors.

As far as getting one of those heads, I just gave one to Mr. Legere, and I might have another I can get pretty easily. I'd have to do a bit of research, so don't hold me to it.
 

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Jimsky;
I sold the one I had to Eric pare of Orphan Motorsports in NC. But, the one I had, had a crack in it.
Gene
 

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*Is this really as good as it sounds?

It can be, it depends what you're striving for.

*If not, what's the catch?

Finding one. They were the middle option on 1968 Kadetts only. Base engine was 1.1, middle was 1.5, top was 1.9.

*Where would one even find a 1.5L head?

See above. Good luck!

*What would be the best guesstimate at the compression ratio doing this?

Low compression pistons were rated at 7.6:1 by Opel, but were closer to 7.1:1. A 1.5 head will bump that to about 8.8:1 or so, depending on how recessed the valves are in the seats.

*Could the compression be bumped a bit more by milling the head? If so, how much milling will yield how many points?

It again depends on the condition of the valve seats. But figure .025" will bump compression by around a half point.

*How will the 1.5L head flow compared to the 1.9L (assuming both are stock) just for a benchmark?

Since the 1.5 head has smaller valves than a 1.9 head, and has a more shrouded chamber, it does not flow as well as a 1.9. It DOES have the same sized ports, but you'd need to install bigger valves and unshroud the chamber to improve the flow to the same levels as a 1.9 head.

Keep in mind it is only a three bearing head too, as well as a 10-bolt attachment. Dont' expect miracles, if you bolt a stock 1.5 head to a 1.9 low compression block, you'll have more compression but less airflow. You'll gain mileage and throttle response, but not any power.


Bob
 
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is it worth it damn right it is

Go for it!

used to run a 1.5 head for 2 or 3 years

both with a 32/36 and later with 75 FI

the head cost $50 or $55 first head job cost $35 but when i but it on it leaked like crazy

so i took the head back off and said might as well put 1.9 valves in it so the second head job cost $90

the did a "performance valve job" they asked me what i wanted for seat press i shrugged my shoulders and said add 10 to the stock amount

if you can find one i say go for it

I still want to try my idea of using a 1.5 head with titanium valves and single valve springs.


good luck
Davegt27
 

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Discussion Starter · #6 ·
Well the main reason I'm looking into bumping up the compression is to get more "smile when you hit the go pedal" on local spirited drives. More power, more fun behind the wheel. To get my wife to stop complaining "your toy car goes too slow, can't you put a bigger engine in it?"

If working up a 1.5L head with the unshrouding and bigger valves is similar to a stock 1.9L head flow wise then this might warrant some more thought.

*Just how difficult will the unshrouding and valve work be? Easy, doable or "oh my god insane". More work and $ than the results obtained are worth? Or would this be close (power increase wise) to a 1.9L with flat top pistons and a stock head?

*Could a 1.5L head be worked up to flow better than a stock 1.9L head?

*Installing a OGTS torquer camshaft and 38 DGAS was in my "high compression" plans. How will these play in this mix?

*I haven't pull the head yet, so I don't appreciate the 10 bolt comment. Will a 1.5L head fit on a stock '73 1.9L block?

*Will I have to make a deal with the devil to find a head gasket for this? Just which head gasket would I use?

Gotta love this site, type questions and magically answer appear. Thanks again.
 

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Depending on your ability and workspace, it may be possible to do the high compression piston swap now. 1.5 head or piston swap both require the head to be removed. If you then check the pistons, bores, and rod bearings for size and wear, it may be easier and cheaper to find a set of used 69-70 pistons (I'm sure somebody on here might have a set they are not using since they already have enough door-stops) the same size (stock or over bored), install new rings and bearings and put them in the engine while it is still in the car. Obviously, this is not 'ideal', but you acheive your goal, get to decide if 9.0-1 pistons are what you really want when you do the full rebuild, with what maybe the same amount of work and maybe less money compared to finding, buying, and reworking a kind of rare head.

If the 1.5 head is compatible with the h.c. pistons, then it would make sense as a 'step by step' project. If the head is not compatible, swap pistons now, why spend money on a head you'll have to replace when you do swap the pistons?
 

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*Just how difficult will the unshrouding and valve work be? Easy, doable or "oh my god insane". More work and $ than the results obtained are worth? Or would this be close (power increase wise) to a 1.9L with flat top pistons and a stock head?

Any machine shop could install the 1.9 valves into a 1.5 head. Better yet would be to use 2.0 intake valves, but those would likely have to be ordered new from OGTS. You could also put
Chevy valves into the head, but that requires new guides, new valves, new springs, new retainers, and a lot more machine work. Unshrouding for the 1.9 or even 2.0 intake valves is easilly accomplished by the machinist, but if you step up to larger valves than that, then hand grinder work is required.


*Could a 1.5L head be worked up to flow better than a stock 1.9L head?

Absolutely. I have a 1.5 head that flows 119 cfm on the intake ports. A stock 1.9 head flows 88 cfm. But it has much larger intake valves and extensive porting.

*Installing a OGTS torquer camshaft and 38 DGAS was in my "high compression" plans. How will these play in this mix?

It's all good. Better if you port the intake too with the DGAS, in fact it's more important than the DGAS itself.

*I haven't pull the head yet, so I don't appreciate the 10 bolt comment. Will a 1.5L head fit on a stock '73 1.9L block?

Yes. But be aware that the 1965-to-late 1972 shortblocks had one type of timing cover, and newer shortblocks have another type of timing cover, the latter with two extra holes for 8 mm bolts (naturally the later heads have the two extra bolt holes as well). Helps to reduce oil leaks. But, when Opel did this they changed the height of the timing covers too relative to the block, so you MUST use the same year head gasket as the year of the timing cover/block.

*Will I have to make a deal with the devil to find a head gasket for this? Just which head gasket would I use?

Use a 1973-1975 Felpro gasket.

As oldopelguy mentioned, he recently gave me a 1.5 Opel head (complete engine actually). BTW, thanks again Stephen! Now, I just got a call from my European contact and he just came across a 1.6 head. A 1.6 head is nearly identical to a 1.5 head, but as it's a later casting it has 4 cam bearings instead of 3 like a 1.5's. So if I can get that head from Europe, I would be freed up from needing the 1.5 head I recently aquired. We'll find out soon.


Photo: 1.5 head with Chevy valves, 1.85" intake and 1.50" exhaust, and extensive unshrouding.
 

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Bob's pictures always make me smile! Kinda like the Twizzlers add.

I'm with Opelbits on this issue, though. The 1.5, and wow 1.6, heads are such a pain to get, the block work might be easier first. I wouldn't be surprised if it wasn't easier to pull the whole motor anyway and do a swap than it would be to try to pull the head with the motor still in the car.

In fact, my recomendation would be to get an extra 1.9 head and intake to practice your porting skills on first. There are lots of write-ups out there about porting the heads, mostly by RallyBob, (and I wouldn't be surprised to find out that Mr. Wilford has a copy of all of them.) Spend some quality time on the intake and head, get some larger valves put in the head, and slap it on. Your potential output might not be quite as high, but if you ruin the head you, and the rest of us, would be out a lot less, and you would still end-up with a much better motor. If you cover shipping or want to go for a day drive, I'll even give you a head, or 2, or 3, and intake to work on! I'd even be game for meeting halfway.

Any head is going to need some work to reach it's true potential, and I'm sure even RallyBob has a few heads piled-up somewhere that were destroyed by an over-zealous 1/4" grinder. It's part of the learning curve. With some time and not a lot of cash you could spend this winter making a great performing 1.9 head to wake the car up next spring.
 

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Discussion Starter · #10 ·
Very encouraging. Thanks for the photo Bob. Sounds like this might be a viable option. Finding a uasble 1.5L head is the major gating factor. Assuming one can be found, I need to figure out the involvement and $ for this route versus flat top pistons. Then make the best choice on which way to go.

1.5L HEAD
*I already have a ported intake manifold, it was last winters project. Do I have a fighting chance doing the unshrouding work myself, or is this not is the same realm of porting an intake manifold? If not, any ballpark what this might cost?

*Using 2.0L intake valves from OGTS, good suggestion. A new complete valve set is about $120. The springs (assuming they are OK) that comes off the 1.5L will play with the new valves? A new set of OGTS valve keepers are $10, cheap.

I guess then it getting the actual head re-done, that I can price out locally. OK now the flat top piston route.

FLAT TOP PISTONS
*OGTS sells the 1.9L flat top set for $380. I'm assuming this is with rings and pins, correct?

*Can I really pull the old pistons and install the new ones WITHOUT taking the engine out of the car? That's the rub for me. My single car garage (that also houses 2 motorcycles) has an 8' sheetrocked ceiling and I've got no lifting or hoisting gear.


Just trying to figure out which way to go here. Thanks for all the inputs.
 

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1.5L HEAD
*I already have a ported intake manifold, it was last winters project. Do I have a fighting chance doing the unshrouding work myself, or is this not is the same realm of porting an intake manifold? If not, any ballpark what this might cost?

It'll be very similar to porting the intake, but will take a bit longer as it's cast iron.

*Using 2.0L intake valves from OGTS, good suggestion. A new complete valve set is about $120. The springs (assuming they are OK) that comes off the 1.5L will play with the new valves? A new set of OGTS valve keepers are $10, cheap.

Use later model springs, such as the ones off your 1973 head. The early springs (solid lifter) are actually weaker than the later springs for hydraulics.

Bob
 

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sounds like you just about talked your self out of it


for a street car i would go one or two directions

cheap way 1.5 or 1.6 head if you can find one
2.0 valves are nice but only if you have some already laying around

if you want to spend money on Valves go on Ebay and buy some titanium valves and have them cut down ha ha just kidding

just get your 1.9 valves put in. put a limit say $300 if its going to cost more the that its probably not worth it

the second direction is jump right up to a 2.2 yep 2.2
call OGTS up and ask how much for a used 2.2 i got one for $800 way back when

ask people on this forum about all the details of a 2.2
but for the street 2.2 is where its at.
you will probably have to put your 1.9 head on it but big deal

if you do any porting hey that's great but unless you are a pro like Bob don't expect any miricles

a good book to get is How to build Modify & Power Tune Cylinder Heads by Peter Burgess and David Gollan.

have fun
Davegt27
 

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Discussion Starter · #13 ·
OK, last question:

*Can pistons really be swapped in a GT with the engine left in the car? Doable, or so difficult that you'd wish you would have pulled the engine?

Comments please.
 

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How about the affects of swapping the cam when going to a 1.5 or 1.5 head? Or is that assumed when talk of larger valves are mentioned?

Always seemed to me that simple route is to swap to 1.5 head and use 1.9 cam to help fill the cylinders.
 

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Ok, let's try this again. I wrote this out twice already and through no fault of the forum found it to be an exercise in frustration. But I am all better now.......

A couple of things to watch out for when swapping pistons with the engine in the car:

- the oil pan. Even though you are not removing the engine, you do need to remove the engine support crossmember so you can remove the oil pan and have clear access to the rod bolts. Also, see following post about supporting motor.

-the cam gear. The cam gear stays with the engine, chain included. You may need to rotate the crank to get at all the rod bolts, so be careful with the cam timing. Stick a screw driver or ratchet extension through the cam gear, keep tension on the chain while rotating the crank. The cam gear will spin on the screwdriver. If you mess up the timing, I don't know what to tell you.

-#4 piston. You may have to lower the front of the motor a little to get clearance between the block and firewall overhang to get the piston and rod out of the block. Shouldn't be much, though.

-oversized pistons and undersize crank journals. There is always the chance (unless you have been in the motor before) that you have oversized pistons or an undersize crank from a previous owners rebuild efforts. Even factory motors or service (replacement) motors can have these. You won't know what you need to find until you open up the motor. You can reuse the rod bearings in your motor, but I would recommend replacing them and the main bearings (front and rear mains may not be do-able 'in the car'), if possible, for reasons of the extra stress on the motor and decent oil control. Also, look for bad or broken piston rings.

-the cylinder ridge. Wear/corrosion/deposits can create a ridge at the top of the cylinder that will prevent the piston from coming out. This can be removed with a ridge reamer from a goood auto parts store.

-cylinder honing. Running a drill mounted wire hone through the cylinders would be a good idea (not sure if you can even get into #4), especially if you buy new pistons. Personally, I would not spend the money on new pistons if I am not able to clean or hone the cylinders. used /worn cylinders=used pistons.

You must understand, this is a half assed way of getting more power by using your time and labor instead of money (you want to save that for the real rebuild). This is not a rebuild, or even an overhaul. It is merely a piston swap and motor inspection (you may find something that tells you your motor cannot be rebuilt and the search for a suitable candidate would follow). The idea is to do this as cheap as possible because the purpose is to get you more power until the time comes to rebuild, why do things twice? Or spend money twice?

I can't think of anything else off-hand. Except that you will need a ring compressor. Makes it easier to get them back in the block.....
 

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Discussion Starter · #16 ·
Thanks for the details, gives me some things to think about. This is a winter project, so I've got time.

The problem with doing things half-assed is...they're done half assed and you get all the unanticipated stuff that goes with it.

Just feeling things out, with what I've learned here there's a good chance I'll just bite the bullet and commit to a real overhaul and piston swap done the right way.

"Quality is remembered long after price is forgotten" That saying has a lot of truth to it.
 

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Supporting The Engine:

Preferred: Engine Hoist

Depending on how much you do with your cars (or friends cars), there are a couple options here. The first is renting one. A good choice if you think you will never need on again. But the problem is that the rental hoists are almost too big for GT work. The second is buying one. I bought mine at Sam's Club for about $250. It is a folding unit that is actually more than enough for the Opel motor. I have seen even cheaper models at Autozone or even Big Lots ($150, but only for four cylinders, or 429 heads/manifolds, but I wouldn't use it for a complete V8). The beauty of this choice is that you will always have it when you need it. Or convince a friend to go halves. Or just sell it when you are done (buy it for $250, then sell it for $150. It will be worth the $100 loss to have it around for the duration). These options are easy but require spending money. (See also: Harbor Freight, Northern Tools)

Next Best: Chain Hoist

If you have exposed rafters, you can hang a chain hoist very easily. But it is a good idea to sandwich some 2x4s and make some vertical posts to go on either side of the car. Then run angled braces from the rafters to the posts. They will take the weight of the motor and the rafters pretty much just control fore and aft movement.
In the case of sheetrock or drywall ceilings, make another beam by sandwiching 2x4s to use in place of the rafter. Find the rafters in the ceiling and bolt the beam to them. Don't cut the sheetrock, just bolt through it, but make sure it is solid and stable. In the photo below, you can see a similiar set up on the far right. It is narrow because I use it just for lifting motors high enough to put on an engine stand. This was before I got an engine hoist. As you can see, I have a drywall ceiling. And it is right about 7'. A 6' person will bump their head into the garage door opener in the middle. The beauty of this is that the GT motor comes out the bottom.Even using the engine hoist, I have no problems with the ceiling.


Stupid (but it worked) Choice:

I had the motor in place under the car and the car on the ground. Had a friend stop by after work, attached a couple chains to the front of the motor and lifted it up until the crank pulley caught on the front cross member, braced it with 2x4s, jacked up the trans end and bolted it to the chassis. Then moved the jack up and lifted the motor so I could put the engine crossmember in place.
 

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Detritus Maximus
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"You get what you pay for"

The benefit of trying the piston swap, is that you will get an idea of what the flat top pistons are like. If they are not enough power, then build up a head/cam combo. Still not enough? Get a 2.0 or 2.2 shortblock (or talk to Calvin about his adventure) since you already have the head prepared.
If you do it this way, you get to the combo you really want. If you rebuild it with the 1.9 flat tops, you might decide it's not enough and then have to buy and build another motor. Nothing quite like spending a bunch of money and not getting what you hoped for.
 

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Don't want to sound negative, but if you're gonna do all of that, you might as well yank it. Rebuild/replace it and you won't have to worry about for a long time. I tried to do things "in" the eng. compartment and it seems like it's more trouble than removal.
My 2-cents.
 

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You will not get rid of all the honing grit and metal if you hone the block in the car. The proper way to do this is to remove the engine from the car. At this point you can evaulate your options, whether it's a stock rebuild, 2.0 upgrade, 2.2, or whatever.

Food for thought.

Bob
 
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