1.5L Head to Raise Compression?

[opelbits]

RallyBob is right, I forgot about the grit and cleaning. Scartch that one, it's a bad idea.

Old Hippie-
The idea of doing this in the car is definitely not ideal. But it can be done. A creative person can get by without a hoist, but they have to be very careful about safety.
While it may seem easier to just pull the motor and rebuild/replace it, the money, time, or resources to do that may not be there. Or may not be the goal. Jimsky's original idea of using the 1.5 head to increase power was a 'stop gap' measure until he was ready to rebuild. My opinion is that the work needed to redo the 1.5 would take more effort and money than swapping in a set of used flat tops. I've had my GT engine layed open like this. Not for this reason, but I had the head and oilpan off and the engine support out of the car. It was much easier than pulling all of it out of the car. In the time it would take just to get the motor ready to drop, I was already working inside the engine.

My question in all of this, since I didn't think of it before, is this- would the modified 1.5 head be useable on a 2.0 or 2.2? Or would the effort be better spent to do a 1.9 head the same way if a 2.0/2.2 might be the final set up?

It really depends on what the theoretical final goal is. A nice rebuilt stock (more or less) 1.9 with about 100hp? Or a search for 125hp+ for extra fun factor?

[oldopelguy]

Since there really is no such thing as a numbers matching Opel anyway, and the car runs fine now, and I have 4 or 5 extra engines in the garage I need to get rid of anyway, wouldn't it be easier to but the time and effort into another motor and then swap? The Opel motor in the GT can easily be swapped in an afternoon, and the car would only be out of commission for that period of time. If you tried to work on the motor in the car, the car and the garage would be useless for anything else for who knows how long?

That's too much like the kind of project that gets started, drags on too long, jades the owner as he forgets how fun the car is and his wife demands the garage back, and rings the death knell for another Opel. Half of us got our cars from just this kind of situation, and we've all seen it go wrong.

With another motor entirely, if the project gets abandoned in the middle, you're only out money, but with the motor in the car you're out a car too.

Soap box now set aside, this started with a simple head swap, which is pretty straight-forward and might yield good results if one could be found. If a servicable one could be found, this might be a good afternoon project. If not, and more is required, go with the motor swap!

My $.02.

[opelbits]

Ah! The beauty of collecting parts and never throwing anything out.....'cause you might need it some day!

I have one friend that has too many cars and parts (project supplies), but hasn't really started, much less finished them. Never gets rid of anything and he gets more stuff to not do anything.....

Then I have another friend that gets rid of anything not attached to the car. If he has spares, they are given away, sold, or thrown away. If he later needs something, he will buy it again.


Can't fathom either one, myself...

[namba209 (R.I.P.)]

Pull the engine/tranny assembly. A couple more hours of work make it worth it after you crawl under the car, work over the top of the engine, crawl back under the car, etc. It is easier to work on the engine bolted to an engine stand and spin/rotate the engine than work under/over the car, and you can see everything you are doing. You've got to do over half the work to remove the engine just to work on the engine in the car. Just My $.02.

Ron

[davegt27]

boy are you guys hitting me where it hurts

haven't driven a street GT of my own since 97 haven't driven a race GT in 3 years

it took a year to get the race motor done

that's why i like the 1.5 idea it takes my back when i was doing something besides collecting parts

RallyBob mentioned something about 1.5 on the Phone and i was off and running

some time its better if you don't know to much and just go for it

at the time all i knew was the 1.5 would bolt right up and that it would raise CR and it was some what of a closed chambered head

Later RallyBob mention something about the intake being the most restrictive item in the intake track that info along with the video Gil sent me which showed some guy installing FI i was off again

ah the fun days before the race car

i say if you can get your hands on 1.5/1.6 go for it if you cant get a kent/piper adj. cam sprocket and build up a 1.9 Head

Get it shaved all that stuff maybe a little porting you can do your self but don't expect any miracles.

And later when it comes time for a motor you still have the Head.

call OGTS some times he has just a 2.2 crank

later
Davegt27

[RallyBob]

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

[opelbits]

Ok, if the 1.5 head can be used with any 1.9-2.0 bottom, then it makes sense to build one. My concern was that if the 1.5 head was incompatible with anything more than a 1.9 and if Jimsky wanted more power through a bigger bore, then he would have to build another head. At that point doing a 1.9 head straight off the bat would make more sense financially.

Since Jimsky's idea was to use a 1.5 head to get an inexpensive performance increase until he was ready to do a full rebuild, and in light of the work/money (what would the head and reworking cost, anyway?) apparently required to effectively acheive that goal, I felt my piston swap suggestion was a viable one. Obviously pulling the engine and doing a rebuild or swapping the existing engine for another would be the best choices. But they do not fit the requirements of easy, cheap, and do-able by one person (but a creative one!) with no hoist or engine stand.

But nevermind all that, now I'm interested in 1.5/2.0 125-160 hp engine......I have a couple low-comp Manta motors to play with...

[RallyBob]

Originally posted by opelbits
But nevermind all that, now I'm interested in 1.5/2.0 125-160 hp engine......I have a couple low-comp Manta motors to play with...

I can give you pretty accurate specs on how to build a single-carb 140-150 hp engine with the 2.0 block/1.5 head. This is probably my favorite street setup, short of a 2.2 engine.

Bob

[jimsky]

*how to build a single-carb 140-150 hp engine with the 2.0 block/1.5 head. *

Now that I'd be very interested to hear about. I'm all ears....

[RallyBob]

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 #68106/208. 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

[oldopelguy]

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.

[RallyBob]

-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

[Old Hippie]

That sounds like great stuff but the cost would kill me and make alot longer the rebuild job as the money came in. I can see me getting the bore done w/ chevy pistons, but not the expensive add-ins. I am cheap, after all. Course, if my block is in good shape shape (or needs min. boring) as is the crank, I go standard. I don't need to "hit the speed" so to speak. I'm for showing off the car and cruisen AND gas mileage. Let's face it, I'm 50 and I'm not out to impress the highschool/collage girls .

[rallye73]

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

[RallyBob]

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

[Propmark]

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.

[RallyBob]

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.

[davegt27]

if you get engine dyno on computer you can ply around with CR and it will give you different CC numbers for the combustion chamber

or you can get the Auto math book and figure it out

i know the engine dyno programs are not that good but your not looking for exact numbers just something to point you in the right direction


davegt27

[jmbinjax]

I am trying to purchase the Venolia pistons Bob references in comment #30. I contacted Venolia but was told the job number is too old and they don't have the specs for that job.

By chance does anyone have the exact specs I need to order these pistons from Venolia? Maybe someone has purchased them more recently?

You guys are great and any help would be appreciated!

[Propmark]

Venolia part number 10790 for 3.750" Bore (11:1). I stroked my crank to 3.005". Were purchased around 9/18/03 for $264.60 set.

Pins Venolia part number 4340-827 floater with spirolocks. $60.60 Set.

Fit pins to piston, $13.00.