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Discussion Starter #1
hey all I have my motor(10 bolt high compression 1.9) apart and the valves are not sealing well so it looks like I will be having larger valves put in. While it is at the machine shop I'm looking at doing the rallyBob port. My question is with those things done what else will I need to do with a stock lower end? I have a freshly rebuilt 32/36 carb for it. Do I need a new camshaft as well to work with the higher flow. Its the first time I've really dove into more than just surface modifications to a motor. Im not looking to make a full blown race motor (yet) just looking for a little extra juice.
Thanks for any input.
Dutch
 

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I personally would not do all the work and then use a stock cam. Definitely benefit from a bigger cam.
 

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The larger cam can be used with or without the larger valves, and vice versa. I ran for years in rallyign with a huge cam and stock 1.9L valves.The larger valves just makes the cam change more effective.

Do you for sure have the flat top pistons, or do you have the low compression pistons with the D-shaped dish in the top? Make sure of that, as it will interplay with your cam selection.

When you say you want more 'juice'. how do you drive this car? On the street? Is this a manual trans car?

As for the larger valves, I just did the 2.0L valves into a 1.9L head. I would not do it again, as the 9mm valve stems are archaic, and finding parts to go with them like stem locks and retainers is a big chore. (I only managed to find 1 source in the world for new 9 mm locks). I would convert to 11/32" stemmed valves, or something like that. There are plenty of discussions here about that.
 

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Many have run bigger valves with stock cams in the past, this will give your engine smooth idle characteristics

Though flat top pistons are a must!
 

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Discussion Starter #5
Yes it is a flat top piston, the car is a 4 speed, and will be driven as a sprited cruiser mostly but with occasional local autocross events. I just want to make sure since I'm into it this far and having the head done anyways I get the most out of it for the effort without redoing everything in the motor. I have a second motor that will be built up into a much higher performance motor after the car is on the road.
 

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Well, that is good and IMHO it makes sense to put in larger valves and go up only 1-2 steps in cam above stock the type of driving you plan. The flat tops help a ton on the compression ratio.... you will be at least in the mid-upper 8's for static CR. (No, the 9.4 is not the real CR.....)

You just don't want to overcam it and drop the low RPM torque any more for your intedned use. Since this is a middling build effort, then I would just stick with the standard Opel cams series offered by ISKY/OGTS. Just makes the spring setup and all that easier.

Again. IMHO. look at a more modern valve stem size than the 9mm stuff. Your shop will like you. My machine shop guy needed to make a tool for reaming the 9 mm guides... but he is old-school and can do that in a jiffy. Many of the new shop guys would be lost and have to charge you to BUY the tool.....

And IMHOx2, get the head skimmed on the surface for flatness, just to make sealing the head gasket go well. And new cam bearings....
 

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Call Gil @ opelgtsource.com and he'll set you up
 
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I see what you’re after & thought this might help. Here’s one of my favorite posts on the subject. See post #11


I really like the cam grind idea Bob came up with, it allows you to keep the vacuum advance on the distributor, and it’s easy to overdo it on the exhaust side as he mentioned. I went to the straight 2.0 L valves (Wished I’d stayed with the 1.9 exhaust valves) and have to say on my next cylinder head build I’ll be using the 11/32” stem 1.5”/1.72” valve combo instead, with thIs cam grind mentioned. As said there’s just a lot more of everything available. Keep in mind I have the 2” exhaust W/ Sprint manifold, I’m not sure how well this runs with a stock exhaust, you can always add the externals later. The Shorty header OGTS sells can get you headed in the right direction from what I’ve heard it may be a bit better than the Sprint.
 

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Discussion Starter #9
Well, that is good and IMHO it makes sense to put in larger valves and go up only 1-2 steps in cam above stock the type of driving you plan. The flat tops help a ton on the compression ratio.... you will be at least in the mid-upper 8's for static CR. (No, the 9.4 is not the real CR.....)

You just don't want to overcam it and drop the low RPM torque any more for your intedned use. Since this is a middling build effort, then I would just stick with the standard Opel cams series offered by ISKY/OGTS. Just makes the spring setup and all that easier.

Again. IMHO. look at a more modern valve stem size than the 9mm stuff. Your shop will like you. My machine shop guy needed to make a tool for reaming the 9 mm guides... but he is old-school and can do that in a jiffy. Many of the new shop guys would be lost and have to charge you to BUY the tool.....

And IMHOx2, get the head skimmed on the surface for flatness, just to make sealing the head gasket go well. And new cam bearings....
thank you very much I've been reading as many threads as I can try try and glean info however lots of it is much more technically written than I am currently familiar with so it gets confusing.
 

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Discussion Starter #10
I see what you’re after & thought this might help. Here’s one of my favorite posts on the subject. See post #11


I really like the cam grind idea Bob came up with, it allows you to keep the vacuum advance on the distributor, and it’s easy to overdo it on the exhaust side as he mentioned. I went to the straight 2.0 L valves (Wished I’d stayed with the 1.9 exhaust valves) and have to say on my next cylinder head build I’ll be using the 11/32” stem 1.5”/1.72” valve combo instead, with thIs cam grind mentioned. As said there’s just a lot more of everything available. Keep in mind I have the 2” exhaust W/ Sprint manifold, I’m not sure how well this runs with a stock exhaust, you can always add the externals later. The Shorty header OGTS sells can get you headed in the right direction from what I’ve heard it may be a bit better than the Sprint.
I guess I should have posted this already: I have the OGTS short header Pertronix ignition and coil, 32/36 carb, will be getting the flywheel lightened. so all the bolt on stuff ive been following but the internal stuff I'm not familiar with is where im getting confused/ info overload. Thanks for the info !
 

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You will find out that all performance upgrades warrant the same almost across the board. They all work in concert and usually improve economy as well. Does very little to just bolt on a few expensive parts. Cam grinds in particular have a huge impact based on compression ratio, flow, overall vehicle weight, tire circumference, final drive ratio, and driving style.
 

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I see what you’re after & thought this might help. Here’s one of my favorite posts on the subject. See post #11
I really like the cam grind idea Bob came up with, it allows you to keep the vacuum advance on the distributor, and it’s easy to overdo it on the exhaust side as he mentioned. I went to the straight 2.0 L valves (Wished I’d stayed with the 1.9 exhaust valves) and have to say on my next cylinder head build I’ll be using the 11/32” stem 1.5”/1.72” valve combo instead, with thIs cam grind mentioned. As said there’s just a lot more of everything available. Keep in mind I have the 2” exhaust W/ Sprint manifold, I’m not sure how well this runs with a stock exhaust, you can always add the externals later. The Shorty header OGTS sells can get you headed in the right direction from what I’ve heard it may be a bit better than the Sprint.
I knew I had generally followed a lot of RallyBob's suggestions during the rebuild to my GT engine, but until I re-read his post mentioned above, I didn't realize just how closely. Keep in mind that Bob posted this back in 2003, seventeen (17!!!) years ago...

Here are his suggestions, matched to my actions:

38 DGAS Weber carb. It will work on a mild engine, even a bone-stock engine, but must be rejetted accordingly.
Yes to the 38DGAS, and it has taken five or six distinct jetting steps to get it right, greatly aided by installing a wide-band Air-Fuel-Ratio (AFR) sensor and gauge. Also removed the fuel sock in the tank, installed a Carter low pressure rotary fuel pump at the tank outlet with an inlet filter, re-routed the fuel line to the front of and below the radiator, up to the outer fender wall, then installed an outboard nipple on the DGAS. No hot fuel to THIS engine!

Ported intake manifold, preferably '73-'74 smog-style. Easiest to port and get good results.
I used a 1971 intake, as that is what I had, with the bottom milled off and replaced with a full vee-floor tent (which I would now modify to have a blunter tip), corners and exhaust bolt holes TIG'd up and fully blended to straighten the flow. Looks beautiful, sad to have it hidden by the carb and heat shield.

1975 'Sprint' exhaust manifold from fuel injected Opel. You'll have to grind the triangular nub off the center pipes to clearance the intake manifold.
Yes to the Sprint exhaust manifold, and port-matched it to the downcomer pipe flange, and also heat-tape wrapped both

Custom 2" exhaust pipe. GT's only have a 1 5/8" pipe, while Manta's come stock with a 1 7/8" pipe, yet they're rated at the same power (? I never understood this...). Even a stock engine will benefit from this mod, you will not lose torque, and it will help the entire power band. Use a perforated-core, straight-thru design muffler up front. For a GT, use resonated rear tips, and a custom 2.5" over-axle pipe splitting into two 1.75" pipes out back. Nice sound, not too loud, and looks good. A Manta can use a second straight-thru muffler (round body) and it will emulate a resonator nicely.
Replaced all the 1 5/8" pipe with 2" pipe, starting at the downcomer where the two pipes come together as 2", and removed the reducer. Also added a 6" flex joint just past the downcomer. Kept the stock Bosal muffler and resonator, but cut the inlets and outlets very short to minimize the length of diameter that is less than 2". Is somewhat louder than I expected from a stock muffler/resonator, but has a proper throaty tone, especially when on the throttle

Electronic ignition. At least a Pertronix unit, with an upgraded coil. Another upgrade would be a Crane XR-700, but for a few bucks more a Crane XR-3000 is a lot nicer, and you can eliminate the resistor wire in the ignition with this system. Use a Crane PS-91 coil with this, it works well. Lastly, another option for the ultimate in 'trick' bolt-on ignitions, the Compufire DIS-IX 'distributorless' system kicks butt.
Went with the Pertonix II 91847V, which is more robust than the Pertronix I, and also provides variable dwell. Still have the FlameThrower coil with 3 ohms (had originally planned for the Pertronix I), but seems to have LOTS of spark.

Did not go distributor-less (yet), but modified the '75 distributor by removing the retard pot, installed limiting set screws on the mechanical advance. Currently set at 16 degrees BTDC at a 1000 rpm idle, 35 degrees max at 3500 rpm

Electric fan.....much quieter, and adds a few hp in the upper rpm range.
Yep, removed the mechanical fan and installed a 14" 2000 CFM pusher fan, controlled by radiator outlet temperature to come on at 180 F, runs until rad cools below 170 F

Tuning! Having the parts is one thing, but getting it setup right is another. Most cars are not getting nearly 100% of their part's capabilities, so setup is crucial. Consider having it dynoed on a chassis dyno. These days, $75-$100 will get you about 6 pulls on a dyno, and tell you more about your setup than a month's worth of driving on the street. If you can get 6-8 hp from tuning, then you just got more power than a 38 DGAS is worth, and for a lot less money. Not to mention, you will get better gas mileage, and save $$$ in the long run. Well worth it.
Someday....

Bore block .020" over, install flat-top pistons. A small increase in power from the displacement, another small increase from the compression, and yet another increase from the 'newness' factor. It's no longer a 30-year old engine. Use Total Seal gapless rings on the second compression ring. Relatively modest investment but the engine holds compression nicer.
Forged 0.020" over flat top pistons, block decked 0.010" which makes the pistons "proud" by 0.005", milled the head 0.005". Didn't go to Total Seal rings

Lighten flywheel. No power increase, but acceleration is improved. Stock flywheels weigh 22.5 to 23.25 lbs on average. You can very safely lighten to 17-18 lbs.
Lightened flywheel from 23.6 lbs to 19.6 lbs. Stayed with the stock 8" clutch, for now....

The entire rotating assembly was balanced (static then dynamic) to 1/10 of a gram. Seems like overkill, bu this is the smoothest CIH I have ever built

Recondition the head, install hardened exhaust seats, larger 2.0 litre intake valves, and mill .050" off the head. This will increase compression a bit, to about 9.5:1 true compression. Still workable with pump gas. Don't worry about cam timing, I'll get to that in a moment. The head's ports can be cleaned up a bit. Don't enlarge the actual port area, just blend the bowl areas, and have the machinist mill about 1/4" off the intake valve guides and 1/8" off the exhaust guides where they protrude into the port. Blend the edges of the guides slightly.
There, you just improved airflow by about 10-12 cfm per intake runner, and 8-10 cfm per exhaust runner with minimal effort. If you do any more to the head, then you'd better know what you're doing, or you may do more bad than good! After the head is milled, make sure to deburr the edges of the combustion chamber to reduce the chances of hot-spots.
Hardened exhaust seats installed, stock valves, very slight bowl, guide and port blending, only 0.005" off the head. I will do a more significant head re-work if/when I take the engine to the next step (stroked crank and 95+ mm pistons, would like to build it as a 2.2).

If/when I did that, I would upgrade to a MegaSquirt EFI controlling a distributor-less ignition. Already have the wide-band AFR

Performance cam. Nothing crazy, if you are using stock valve springs (you should be), then you are limited to .425"-.430" max valve lift anyway. I usually keep it to .420"-.425" max, but that's just me. If you are not gonna rev it hard, use hydraulic cam/lifters. Less maintenance. Shoot for a custom profile, with split intake/exhaust duration. This helps the Opel's notoriously weak intake flow (note the trend? Most modifications are aimed at intake flow). For a truly mild driveable cam, I'd go with around 212-214 degrees of intake duration @ .050", and around 6-8 degrees less on the exhaust lobes. Grind at 110 degree lobe separation for a smoother idle and broad power band. Now, to correct for the milled head, have the cam guy grind the cam with 4-5 degrees of advance. This will correct the retarded cam timing, and give a touch of advance for better torque. Stock Opel cams are ground 1 degree retarded for comparison.
Went with the OGTS Combo hydraulic lifter cam, 0.420 lift, milled guides to take proper umbrella seals for both intake and exhaust, RennSport PolyLock rocker nuts

If you decide to put a bigger cam into the engine, expect to have to modify the distributor to get good throttle response. This mild cam I've recommended would run well with 3-4 degrees more initial ignition advance than stock, but can use a stock distributor. I'd use a later distributor too, a 72-74 model.
Modified the cam gear to take a Comp Cams SBC off-set bushing and slotted the holes, currently set at 4 degrees cam advance (can go as much as 8 degrees), modified the end cap for an adjustable cam thrust bolt, installed a cam oil dam (1/4"x 3/8 copper plumbing fitting, 1/2" oil lift).

I installed a Getrag 240 5-speed, lowered 1" (OGTS front leaf, cut-down Kadett Wagon coils), 15x7 alloy rims w/ 195/55-15 tires, Big Brakes and Big master cylinder and 9" booster. This is now the nicest GT I have ever driven.

But there is always more to do...
 

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Discussion Starter #13
Well my memory did not serve me well from when I was Looking at the motor last. unfortunately they are dished pistons so It looks like I will have to replace those as well
 

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Well my memory did not serve me well from when I was Looking at the motor last. unfortunately they are dished pistons so It looks like I will have to replace those as well
You could always try to find a 1,5 liter head to use as a basis if the short block is still good.
 

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Well my memory did not serve me well from when I was Looking at the motor last. unfortunately they are dished pistons so It looks like I will have to replace those as well
Then a full tear down and inspection of your short block is in order. Not a bad thing considering at this point you don't know the condition of your crank, main, and connecting rod bearings...
 
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Discussion Starter #18
Then a full tear down and inspection of your short block is in order. Not a bad thing considering at this point you don't know the condition of your crank, main, and connecting rod bearings...
I just dropped the head and manifold off at the machine shop and will be checking into bottom end now.
 

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Discussion Starter #19
Good news is that the owner/ machinist seems to be pretty sharp and excited to try something on the different side. Where as most places around us wouldn't touch it. The shop has a very good reputation so we shall see how it turns out
 

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Discussion Starter #20
Now I just need to track down the photos of where everyone removed material to lighten their stock flywheels
 
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