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Discussion Starter · #1 · (Edited)
Re: 1.5L Head to Raise Compression?

*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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Discussion Starter · #2 · (Edited)
*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 pulled 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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Discussion Starter · #3 · (Edited)
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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Discussion Starter · #4 ·
OldOpelGuy is right in the respect that it's probably easier to remove the complete engine and swap it for an earlier engine.

Recently while in Califonia I helped Roger Wilson pull the stock engine from a customer's GT awaiting a 2.4 litre build-up. We got to his shop at 9:00, and the engine/tranny was sitting on the floor at 10:30. But it was already VERY hot out, and I worked at a leisurely pace (I was on vacation after all). Plus, I have never owned a GT, so it has been 17 years since I last pulled a GT engine out (back in '84-'86 I used to strip Opels for C & R). So I'd think that even with minimal experience, two guys could have a GT engine sitting on the floor in 2 hours.

The whole 1.5 head thing has been blown out of proportion I think. I don't care for them for racing use, but I feel that a prepped 1.5 head (valves and porting) makes an excellent hi-po street head for a 1.9 or 2.0 block with flat-top pistons. Depending on the amount of milling, unshrouding, and valve sizes, you can get 10.5:1-11.2:1 compression with a 1.5 head on a 2.0 block. And you can STILL run pump gas if you have a decent camshaft in the engine (bigger than the Torquer cam for sure). I have built quite few street engines with 2.0 pistons (forged 265 Chevy pistons in reality), and with big-valve 1.5 heads. Then run VERY well on the street. Depending on ancilliaries, you can get 125-160 hp out of this combo.

For a 2.2 block, a 1.5 head would be a bit much. Compression would be so high, you'd need racing gas. Besides, the best part about a 2.2 engine is the head, the ports flow SOOO much better than a 1.5, 1.9, 2.0 head.....

Bob
 

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2.0 with 1.5 head recipe

Here's a rundown of one of my favorite street engine combos.

This is assuming all 'normal' overhaul procedures are being done. By normal, I mean reconditioning connecting rods, replacing rod bolts, grinding/polishing crank to size, boring/honing block and decking head surface, new oil pump, timing chain, timing rails, etc. In other words, a complete overhaul.

SHORTBLOCK:
*1.9 block bored out to 2.0 litre displacement. There are two ways to go about doing this really, one is to use standard Opel 2.0 pistons, the other way is to use Chevy 265 pistons. I choose to do the latter, using Venolia forged pistons (flat-tops). The Venolia job number is 85681. Order them pin-fitted, but fitted for a .912" Ford pin, and have the Opel rods honed from .906" to .912". Either buy the pins from Venolia, or use 351 Windsor Ford pins. They're cheaper and lighter than Opel pins. Deck block surface flat. Double check all bolt holes for head bolts, lately I've seen some corrosion on the forward head bolt holes, and they can strip out. Heli-coils may be needed. I try to set the deck height so the pistons are at zero, i.e., flush with the deck.
*Reconditioned early forged Opel rods. Do not use the 'big' Opel rods as used in '74-'75, they're junk. Replace the rod bolts. Stock bolts are fine if you're gonna keep it below 7500 rpms...no reason to rev it higher.
*Balance rods end-to-end, and balance pistons.
*Rings....your choice, I use a moly top ring at least. I like Total Seal gapless secondary rings. Better ring seal over a longer period of time.
*Reground/polished and balance crankshaft. Don't forget, if you are using aftermarket bearings, the crankshaft thrust is often undersized as well, and will have to be reground.
*Felpro gasket set. One change...you'll need to use a Euro 2.0 litre head gasket. May have to change the front sealing area depending on the year of the timing cover.
*New timing chain, preferably with master link. New timing tensioners, new oil pump gears, new oil pump cover.
*Fully reconditioned timing cover...VERY CRITICAL...gotta get all the crap out of it.

TOP END:
*1.5 head...magnaflux for cracks before you start anything else
*Valves: Here it can get funny. I prefer to use 1.85" intake valves, and 1.50" exhaust valves. In reality, the first few 1.5 heads I built had 1.72" intakes, and ran pretty well. I've also put 1.80" valves in 1.5 and 1.6 heads. So what do I recommend? I'd go with at least 1.80" intakes, but would rather have 1.85" intakes. Trouble is, the combustion chamber must be unshrouded appreciably to get the larger valves to flow. If you don't unshroud, the large valves actually flow worse than with the smaller 1.72" valves. I have a few photos posted of the chamber mods, and also have a template I use to open the chamber to a predetermined size. Lately, I use Manley undercut Race-Flo valves. The exhaust valves are available off the shelf as part number 11521 for about $10 each (standard length small block Chevy with 11/32" stems). For the intakes, I order them from Manley directly as #11522 (1.94"), but have them cut down to size (must specify size). This will cost a few bucks more, but they're cut to factory specs and it only takes about a week.
*Springs and retainers. I use Crower 86031 titanium retainers, they're 1.25" in diameter. For springs, I use 1.25" double springs, Crower #68106X208-8 - VALVE SPRINGS 1.245 TUNGSALLOY DUAL (Note: Edited as per Calvin's direction). They install at around 1.675". I also use Crower billet keepers, #86107. I use viton valve seals, V.S.I. brand, they're for a .341" stem and to fit a 1/2" valve guide. Part number is 45341 .
*Machine work: Install hardened exhaust seats. Cut the valve seats for the appropriate valves. Cut spring seats, intake side, to get proper spring heights (usually .050"-.055" must be removed). Mill head flat, install new bronze valve guides (Chevy type, usually .503" OD, and 2 3/8" long). I also remove all the rocker arm studs before any machine work is done, as well as all oil galley plugs in the head. I replace the rocker studs, matter-of-factly. They DO fail, especially old ones. I tap all oil galleys for thread-in plugs. Replace cam bearings.
*Porting work: Best left to a professional. Exhaust ports barely need to be touched, intakes require a lot of work. I have photos I can send you if needed.
*Camshaft: I used to run straight profile cams, that is, both intake and exhaust profiles are the same. But with a 1.9 head, and especially with the 1.5 head, there's power to be had by running a split-profile, with more intake lift and duration. My favorite streetable (solid lifter) profile is a Cam Techniques grind, with their F-306 for the intake profile (.459" intake lift, 246 intake duration @ .050") and their F-290 for exhaust profile (.435" lift with 242 exhaust duration @ .050"). I have the cam ground with 108 degree lobe separation for street use. You can either have the cam ground with some advance, or you can use an adjustable cam gear to correct the cam timing. I would run 3-4 degrees of cam advance. Idle is at 1100-1200, best power is 2500-6500 rpms.

ACCESSORIES:
*Intake manifold: Welded and ported to 'Hot Street' specs at least. Use a '73 or '74 core preferably. I also used a 3/4" carb spacer regularly, but this is tough to fit on a GT.
*Carburetor: 38 DGAS Weber. Will require a slight amount of rework, such as drilling bypass holes on the throttle plates, and modifying the power valve so it opens later. It will require rejetting. For more power, the venturis can be drilled oversized.
*Exhaust: I've had great luck by simply running a slightly ported Sprint exhaust manifold, with a full 2" exhaust from the collector point back to the rear axle, then using a 2.5" over-axle pipe. I recommend 2 free-flow perforated core mufflers, a single will be too loud.
*Ignition: You must run a recurved distributor with this combo, it won't run worth a damn otherwise. Baseline setup would be 18 degrees BTDC @ 1100 rpm idle, with a total timing of 36 degrees. If you have access to decent gas, you may be able to run as much as 22 degrees initial timing, but with the same total of 36 degrees. It will require some experimentation. For my money, I'd use the Compufire DIS-IX ignition system. It does everything you need it to do, for under $200.
*Clutch/Flywheel: I'd recommend a lightened flywheel. I always ran a 15.5 lb flywheel, the response was great. I used to run a Sachs heavy duty clutch, it lasted about 2 years. So I now run a custom setup from Action Clutch. Very reasonably priced. Alternatively, the S-10 Chevy clutch with aluminum flywheel costs a few bucks more, but it's basically bulletproof, and has the added benefit of a lighter pedal feel (more streetable).

If you have any more questions, just ask.

Bob
 
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cool

Man, is it great to have Bob back. I may actually have to build another Opel motor after-all.

I do have a couple of questions for the master, while he is feeling generous:

-Is that too much cam for the stock EFI from a '75, and would it flow enough to work anyway? I was always under the impression that the EFI flowed pretty well, and that might be easier and cheaper even than the intake, carb and porting work. Perhaps with a Megasquirt or Haltech on the stock manifold?

-What kind of compression ratio would we be dealing with here? How much lower would it be with a 1.9 head and the same set-up?

-You didn't mention fly-cutting the pistons. Are the valves safe with that combo of piston and lift?

Thanks in advance Bob. I'm actually very excited about maybe not throwing away one of the motors in the garage now.
 

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Discussion Starter · #7 · (Edited)
-Is that too much cam for the stock EFI from a '75, and would it flow enough to work anyway? I was always under the impression that the EFI flowed pretty well, and that might be easier and cheaper even than the intake, carb and porting work. Perhaps with a Megasquirt or Haltech on the stock manifold?
Wayyyy too much cam for the stock FI to handle. But yes, with the FI's long runners, and better plenum, a stand-alone tunable ECU would work very well. But you need the money for an ECU, bigger injectors, fuel pump, regulator and high pressure lines (assuming it's not already a 1975 Opel), a laptop to tune it (unless it's SDS or Luminition which has its' own controller), and TIME to tune it. Preferably on a dyno. So there's a sizeable $$$ investment just for the induction system, probably $1500-$2k.

-What kind of compression ratio would we be dealing with here? How much lower would it be with a 1.9 head and the same set-up?
Depends on the valve sizes, head milling, unshrouding, but again, usually 10.5:1 to 11:2:1. A stock 1.9 head with 2.0 pistons gives 8.45:1 compression, with Chevy 1.72/1.50 valves an even 9.0:1 compression. With milling, you can approach 10.0:1, but then the valve notches need work.

-You didn't mention fly-cutting the pistons. Are the valves safe with that combo of piston and lift?
With the Venolias I mentioned, you have clearance (at least to 8400 rpms..that's as high as I've run that combo). Unless you mill the head appreciably, and then the intake notch of the pistons needs clearancing for diameter, rather than for depth.

Bob
 

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1.6 Head

Was there any difference in the head between the 1.6S and the 1.6N? Also I reciently heard that there were two different plugs used, one had shorter length than the other. Which one is preferred, or does it even matter?

Darrin
 

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Discussion Starter · #9 ·
I can't recall 'which is which', but there's no real difference in chamber volume between the two heads in 'as cast' condition.

The 'long plug' 1.6 head is identical in chamber shape to the 1.5 head. I prefer this one, as the 'plug area' of the chamber is tigher in shape, allowing for unshrouding yet retaining compression. The 'short plug' 1.6 head is more open near the plug area, so it is more shrouded at the valves. BUT, if you unshroud the 'short plug' head you will lose compression as compared to the 'long plug' head.

I have ported/flowed both types, and the variance in compression is the biggest difference after unshrouding. I personally also prefer the long-plug version as the plug electrode is closer to the center of the bore by 1/4". They tend to have decent combustion when used with a flat-top piston, at least for an archaic wedge-chamber design.....

Bob
 

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I have read a lot of threads on head types, setups and porting methods, but I have not noticed any data on chamber CC. Has anyone measured this for a big valve head? I've got 52cc's and going with domed Venolias in an attempt for 11:1. Any feedback appreciated.
 

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Discussion Starter · #11 ·
It depends. Depends on head milling, valve sizes, valve seat heights, how much unshrouding.....too many factors to generalize. Gotta take it on a case-by-case basis.

Stock 1.9 heads are about 52.1 to 52.6 cc's. But with time, as the valve seats recede, I've seen 1- 2 cc's increase.
 

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I just copied and edited an earlier thread that had a bunch of interesting suggestions by RallyBob on CIH performance. Bob, if you would like to edit this or add to it, please do. But I would appreciate it if other members would refrain from adding posts to this thread, so that it can more easily read. Thanks!
 

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Unshrouding chamber of a 1.5

RallyBob said:
Here's a rundown of one of my favorite street engine combos.




TOP END:
Trouble is, the combustion chamber must be unshrouded appreciably to get the larger valves to flow. If you don't unshroud, the large valves actually flow worse than with the smaller 1.72" valves. I have a few photos posted of the chamber mods, and also have a template I use to open the chamber to a predetermined size. Bob
Bob Is this template available on this site or would you sell them??
 

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Discussion Starter · #14 ·
azopelnut said:
Bob Is this template available on this site or would you sell them??
It's a permanent steel template, I only have the one...
 

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Exhaust valve sizes

Bob,

I've got a 1.9L head at the shop now. I'm having the 42mm 2.0L intake valves installed. Should I take this opportunity to replace the exhaust valves with new ones? Planning to use Gregg's roller rockers if I ever get the 9mm tips for the Opel valves. Any other tips while the head is in for work. Just want to use it on the street and have it run well in traffic. Wouldn't mind hurting a Honda or two along the way though.

Thanks,
 

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Discussion Starter · #16 ·
David McCollam said:
Bob,

I've got a 1.9L head at the shop now. I'm having the 42mm 2.0L intake valves installed. Should I take this opportunity to replace the exhaust valves with new ones?

Any other tips while the head is in for work.
Unless the old exhaust valves are very tired (high mileage) or bent, they should be fine.

Nothing extraordinary to do other than the things I've already mentioned. Rocker studs should be removed at least and passages cleaned. Oil galley plugs should also be removed and passages cleaned, and preferably replaced with thread-in plugs. Inspect cam bearings, mill the head if you want a bit more compression. You can safely clean up the ports a bit, you don't need to enlarge them at all, just trim the valve guide protrusions a little and blend the bowl areas. No use in making the ports themselves bigger unless you have 'big' valves, the ports are already plenty big for the size valves they have and the rpms the engines operate at. If you mill the head be sure to deburr the edges of the combustion chamber to fight off detonation. That's all that comes to mind offhand.

Bob
 

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Thanks.

Hi Bob,


Your suggestions are always welcomed. I'll get the word to the machinist to thread the galley plugs.

I'm going to run solid lifters on a new camshaft that I'm having ground. The profile will be similar to the 19E profile for the European GT/E to be used in conjunction with the roller rockers from Gregg. I'll also be using a falt-top 1.00 mm oversized pistons with the older style rods. That precipitated my question about distinguishing from the new rod.

I've also acquired the diesel oil pump for the CIH. This is supposed to supply higher pressure at startup and prevent scoring of the bearings. Is this true or "hype"?

Thanks again.
 

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David McCollam said:
I've also acquired the diesel oil pump for the CIH. This is supposed to supply higher pressure at startup and prevent scoring of the bearings. Is this true or "hype"?
Sort of....

The diesel pump covers are cast iron, not aluminum. They are more consistent and stable plus the regulators don't have the crappy plastic 'bullet' style seat. Running pressures are a bit higher though.

As far as idle pressure....the only thing that affects that is the engine's condition (bearing condition, clearances, timing cover/pump gear wear). Raising the pressure via the regulator does not affect the idle pressure.

Bob
 

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Oil Pressure

Bob,

Well, sounds like it's a better setup than the aluminum cover. I have several of the aluminum covers that are new so I suppose those would be okay, too. I've only had on occassion where the pressure fell off or registered low with the aluminum cover. That was before I knew about resurfacing the cover. I replaced the cover not knowing any better.

Thanks for your advice.
 

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Plate!

On Rover V8 oil pump covers ( oil pump very similar set up to the Opel on the front cover) I have made up a plate out of O1A ground gauge plate with the correct holes made in it that can be clamped betweenthe original alloy cover and the pump body. This is much harder wearing and esily replacable.
The bypass oil from the relief valve can also be rerouted int the pick up passage too, instead of just across the gears to improve gear rotation stability and thus reduce pressure surges and air entrainment....
 
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