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Discussion Starter · #1 ·
This winter I plan on taking out the engine of my 1973 Opel GT. I also am going to have a Getrag 5-speed so I'll put that in at the same time. I'm going to bore my engine out then port and polish the exhaust manifold. While all of that is going on hopefully I'll also install a Weber 32/36 carb. I need help on finding a good cam to go with all of these accessories. I was looking at the Opel GT source Torquer with .407 lift and 256 duration with hydraulic lifters. Or would it be okay for me to use the Combination with .430 lift and 268 duration? Which one would be better?
 

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Cam and piston choice is hard to make a good suggestion on without knowing what you want to have when your done. An economical daily driver or something you trailer to a track. Just an idea but you could do the S-10 clutch as well if your thinking of more power.
 

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swindler_57 said:
I'm going to bore my engine out then port and polish the exhaust manifold. While all of that is going on hopefully I'll also install a Weber 32/36 carb. I need help on finding a good cam to go with all of these accessories. I was looking at the Opel GT source Torquer with .407 lift and 256 duration with hydraulic lifters. Or would it be okay for me to use the Combination with .430 lift and 268 duration? Which one would be better?
As has been mentioned here a fair bit, the exhaust already flows quite well on a CIH, so you would be better off putting the effort into the intake manifold, inlet ports, head unshrouding and valves. Have a read around this forum, and especially RallyBob's article on porting the stock manifold.

As Grant mentioned, how much you do determines WHAT you should do. Are you going with stock 7.6:1 dished pistons, or 9.0:1 flat tops, or domed pistons to get you as much 11.0:1 (see "nobody's" current thread on his 2.0 conversion). If you are boring it out, are you going just a bit oversize (say .040"), and use the stock 1.9 head gasket? Or are you going to the 2.0 pistons (or the Chevy 265 c.i.) to get a bit more displacement? Or are you going to stoke it to 2.3 or 2.4 litres?
All that also determines what carb you get. If you are doing a mild overbore, flat tops and limited inlet porting, the 32/36 DGAV should be fine. More (and/or more cam), and you might want the 38 DGAS. More, and you will aspire to a SSD (Single Side Draft) and a 45 DCOE, or even dual SD's and dual 40 DCOE's. Or EFI, or...

OK, your real question is the cam. If you just want a docile street engine, with 0.040" over flat tops, and a bit of intake work, but no head or valve mods, the "Torquer" should be fine. The "Combination" should also work, but it will be a bit lame until you get the rpm up.

Since you are doing the work this winter, you have a bit of time to read the numerous articles, and ask a bunch of questions. Good luck!
 

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Cam Choice

Swindler_57

Rally Bob has listed his choice for best bang for the buck engine upgrades. He also listed a split profile from Cam Techniques. Use the Search feature and try key words "Cam Techniques". Even if you don't use that particular cam, I believe it was a solid lifter profile, you will be able to see how he developes a "package" of improvments. You should read and re-read his posts with the intention of understanding why he touts the benefits of a split profile cam. When you do, this info will drive your selection of engine mods.

I just don't want you to think that the only two cams available are the Isky Torquer and Combination.

Paul
 

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Discussion Starter · #5 ·
?

I don't want a whole ton of horsepower because this car will be my daily driver once I graduate next year. I want it to be streetable but have enough power to spank some of the honda's that linger around my small (9,000 pop.) town. I will read some more before this winter because after all I have to get all the money to pay for all of these mods. Luckily my dad's a mechanic and he's done this type of engine work before so he can help me too. I only want to put in the 32/36 DGAV carb, this is just personal preference and I really don't want anything that I have to dink around with all the time. I'm not quite sure yet about the bore though. If I bored my 1.9 out to a 2.0 I would have to get the 2.0L pistons and the 2.0L gasket set right? I don't want anything bigger than a 2.0L. Would it even be worthwhile for me to only bore my engine out 0.40? I'm probably only going to go with the flat topped pistons unless the dome ones will make that much of a difference. Thankyou all for all of your help. I'll read into some more of the posts that are already listed but if you have any more information to answer my questions please don't hesitate to post more replies. Thanks!
 

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2.0 Litre

One of the reasons that 1.9S are bored to 2.0L is that Chevy pistons are so much cheaper than oversize 1.9L pistons. If you can get some .040" (+ 1mm ...) pistons then that leaves you with further overbore options in the future. The 3.75" (95.25 mm) Chevy 265 CID V8 pistons are getting to the top limits of oversize and may give thin cylinder wall problems with 30 year old blocks with rust spots in the water jackets. So if you want to play safe and don't have a spare bock or two, then the + 1mm standard oversize flat tops are a viable option.
 

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swindler_57 said:
I only want to put in the 32/36 DGAV carb, this is just personal preference and I really don't want anything that I have to dink around with all the time. I'm not quite sure yet about the bore though. If I bored my 1.9 out to a 2.0 I would have to get the 2.0L pistons and the 2.0L gasket set right? I don't want anything bigger than a 2.0L. Would it even be worthwhile for me to only bore my engine out 0.40? I'm probably only going to go with the flat topped pistons unless the dome ones will make that much of a difference.
The 38 DGAS is the same basic carb as the 32/36 DGV, but has slightly larger throats, and both throttle plates open together, versus the "progressive" (first the Primary plate, then the secondary plate at about 3/4 throttle). Throttle response is NOTICEABLY better with the 38 DGAS.

The only reason to overbore by 20 or even 40 thou is to eliminate cylinder scoring, taper, or out of round. The increase in displacement is insignificant. But the increase in displacement to a 2.0 from a 1.9 is enough to add a few more HP, which is noticeable. And yes, the 265 or 2.0 pistons require a 2.0 head gasket

The flat top pistons (9.0:1 CR, which were standard until '71) gave at least 15 more horsepower alone than the dished pistons (7.6:1 CR, standard in North American Opels from '71 to '75). Domed pistons (such as nobody's 11.0:1 Venolia's) will add a few more HP as well, but you will probably have to use octane booster to eliminate detonation. But even 9.0:1 will require Premium gas.
 

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Camshafts

Swindler_57

You'll be hard pressed to find a camshaft that produces TOO MUCH horse power that has valve lifts within the limits of the stock valve springs. The max valve lift for the stock valve spring is .430".

All I'm saying is: if you are going to the trouble and cost of replacing the cam, you might as well get your money's worth. I'd go for: an economical over bore and a flat top pistons, unless something special drops in your lap, a split profile cam from Cam Techniques, a ported Intake manifold, and whichever carb you can afford the 32/36 or 38.

If you need major head work, then you should consider increasing the intake valve diameter. The first step is to go to the 42 mm valve from from the Opel 2.0.

These mods will give a very noticable improvement in HP and torque! The engine will appear completely stock. And... most importantly, will retain very good street driveability.

For even more fire power, you can lighten the flywheel to 17-18#, mill the head .050" and drop in the distributorless electronic ignition RallyBob documented the intall process a while ago, sorry forgot the name. You will for sure spank many of the ricers in your town then!

Check out RallyBob's suggestions for mods to do on a limited budget.
http://www.opelgt.com/forums/showthread.php?t=503&highlight=cam+techniques

Paul
 

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Discussion Starter · #9 ·
Paul

First of all thanks to all of you for all of the information that you've given me. It's really helped me out. Where would I find these cam technique camshafts? And which cam would be the best for my modifications? My motor runs just fine right now so I really don't need to do anything to it but since I have nothing to do this winter I was hoping to drop out the entire motor so that I could rebuild it and learn how all of it worked. And since it was out I might as well make it look nice with some paint and chrome too then I decided I should make my car go a little faster while I'm at it. I'm pretty sure that I'll go with the small bore of around say,.. 0.30 so that maybe I could use the 1.9L gasket and then use the flat-topped pistons. I can't really afford the 38 carb so I'm going with the 32/36. Well, any more help you might have to offer, thanks.
 

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swindler_57 said:
I can't really afford the 38 carb so I'm going with the 32/36.
I have bought two 38 DGAS's off eBay, one brand new never used, the other was like-new. Each cost just over $200 USD plus shipping, so before you drop $300 on a new DGAV, have a look around for a slightly used DGAS
 

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Cam Techniques

Swindler_57

You can find them at www.camtechniques.com. Their phone number is 941-727-5552. The owner's name is Dave.

RallyBob (on this list) would be the BEST person to make a recommendation on a complete cam specification if he knows your package of modifications. I can help you find cam specs and engine combinations used by others on this list who have listed their selections, as background information.

For example: I'll be using the following cam.....

Intake .438" lift 290* Adv. duration 222* @.050
Exhaust .426" lift 280* Adv duration 212* @ .050
112* lobe seperation angle.

engine specs......Stock 1975 FI, 1.9 +.030 bore w/flat top pistons; 1.72 Intake/1.50 Ext valves; New springs, retainers, etc; head milled .035"; combustion chamber de-shrouding and polishing, a fair amount bowl and port work. Intake flows 115 cfm at .500" lift and 10 inches of water. The exhaust flows 92. Since the proportion of ext to intake flow is still quite high, 80%, WE decided (at Bob's recommendation) to get this cam. Before we received the flow numbers we were going to use .426" lift 286* I / 280* E.

The 112* of lobe seperation is needed to reduce the overlap due to the flap style MAF meter.

One thing you should keep in mind when you develop your plan, The CAMSHAFT will determine the perfromance level of your engine. All of the other mods you can do to the engine will only have a moderate impact unless you select a cam to complement/enhance.

HTH
Paul
 

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help me pick a cam

my cylinder head is in the shop.

my mechanic is port matching it this weekeed. he says he is going to do a street port for the head.Polish it all up too.

he wants me to find info on what you all recommend for a cam. he was not real fond of the "torquer cam" specs that I quoted.he thought we could do something more fun.

the cam is going on a just rebuilt 1.9- 20 over, 9/1 (new ogts pistons) engine.

what do i want? a better daily driver...not a race car..."my racing will be STAYING OUT OF THE WAY " of mothers on cell phones with screaming brats in the back seat as she does her eyeliner and drinks a moca frapaccino "...
if that susburban hits me I am toast.

I dont mind if I have to Fuss with it..I enjoy that.

so I need TORQUE..not top end.
 

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Discussion Starter · #13 ·
Paul

I went onto the camtechniques website and was going to request some info but I got confused so I kind of quit. I'm really not sure which cam I should get because my dad said that it was a very important thing (choosing which cam to install). If I have the wrong cam things just aren't going to work and my Opel will run worse than what I had started with. I think I'm going to need those specs from you if you could do that for me. I still want something mild but I do need whatever will work the best with my modifications. Bored .30, flat-topped pistons, 32/36 DGAV Weber, ported intake, 5-speed, and I think that is it. The paint color of my motor won't really make a difference so I won't list that ;) . Would a certain type of new ignition like an MSD make any difference with which cam I choose? Thanks again for the help.
 

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everything you say makes sense

I a working with the same engine/carb/trans as you.

I have printed off some info for my mechanic.
 

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piston valve interference

at what point does (lift/duration) does a 2.0 intake valve 42mm interfere the a flat top piston in a 9-1 1.9 engine?..or does this have to be worked out on site.
 

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Bucky,

I am not the cam selection expert. You must face East when you ask that question. Connecticut is East of you, I am South of you...LOL.

'Bout all I can do is tell you the answers I received, from the Opel Jedi Master, when I asked the same questions.

The max valve lift for the stock Opel springs is .430 inches. So first off, that restricts what cams are available to use. Cams with more lift will require NEW springs. From what I understand, Opel cams up to .430" would still be considered mild for the most part.

There two Isky cams that fall in this range. The Torquer with .407" lift and the Combination at .425" lift. I was running this one with flat tops, stock valves, 75 FI and a header. It idled normally and had better than stock power.

RallyBob listed a solid lifter cam with .405' lift in a split profile in the following post where he stated his recommendation with a limited budget. http://www.opelgt.com/forums/showthread.php?t=503&highlight=cam+techniques

I highly suggest you read the above linked post for yourself. His post is near the bottom of the page. All of my information has come from STUDYING his posts and his answers to my direct questions.

It has also been stated that the CIH engines like a 108 degree lobe separation angle. The stock cam was 110.5 degrees. You would need to ask someone other than me when to go to a cam w/108*.

He also had recommended a Cam Tech cam to me. Intake profile #H284-2 (.426", 218* @ .050) and Exhaust profile H284-1 (.426", [email protected] .050) when I was planning on using the 42mm intake valves from the Opel 2.0 head. But the local machine shop royally screwed up the head when fitting the 9mm valve stems, They were used to 11/32 or 3/8 valves stems.... My plan was to mill the head .050", along with the 42mm valves ... and I don't believe there would have been any piston to valve issues.

I've read and re-read enough of Bob's old posts that warned against enlarging the intake ports if using the stock valves. If upping to the 42mm valves, his instruction is blend the bowl and machine about 1/4" off of the valve guide protrusion on the Intake side ONLY. Blend the bowl on the exhaust side but make NO other flow improvements to the exhaust. The exhaust is efficient enough already. The SBC guys who want to work on the exhaust valve/port... DON"T Let them!!! With these valve sizes, anything other that light gasket matching is a waist of money. Do not polish the intake runner! Find and read Bobs posts where he describes adding roughness back to the intake short side radius.


Bucky and Swindler.... For a complete recommendation, I would suggest calling Dave at Cam Techniques and/or directly contacting RallyBob...

HTH
Paul
 
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