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1970-GT
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Jeff, I'm building a 1969-70 GT head. It has a delta or triangle stamped on the side!?
I could check volume for you, not sure how to accurately check chamber cc's.
Will post a picture of it.
Lyle
 

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As far as I know, a 1.9 head is gonna have a combustion chamber volume of 52.1 to 52.6 ccs. This is quoting Bob in another thread. It's gonna vary a bit due to just how far the valves seats are cut in.
I know he had them all listed somewhere. Just can't find it...
The 1.9H is supposed to have a slightly smaller combustion chamber, as I recall it is not as small as the 1.5 or 1.6 but in my situation here I cannot legally run anything but a 1.9 head, or perhaps 1.9H head. The rules just say the head used must be for the block used. I think the H would qualify.
 

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1970-GT
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jeff denton said:
The 1.9H is supposed to have a slightly smaller combustion chamber, as I recall it is not as small as the 1.5 or 1.6 but in my situation here I cannot legally run anything but a 1.9 head, or perhaps 1.9H head. The rules just say the head used must be for the block used. I think the H would qualify.
Jeff, I have a set of steel stamps, with a 1 and a 9 in it! :D
The Opel has a power disadvantage to the Mustangs and Pinto's! I would build a 1.5 head. They won't care what you do, until you start kicking there butt's.:haha:
The tech guys don't know Opel engines, they won't cc the head, what would they compare it to?
They will just make you add weight to slow you down!!!
They want close racing, it sells tickets!
Lyle
 

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some people say that a 1.9 head flows better then a 1.5 (1.5 head with 1.9 valves)



you could take a 1.9 head and shave it like crazy to bump up the CR

probably the best thing you could do is petition the rules makers after all a 2.3 mustang or pinto is hardly fair. the only thing that can touch them is one of those 2.2 Dodge

maybe ask for any production head that can bolt up without modification be used. the reason being there are not many factory heads out there and you giving up so much in the displacement category to the 2.3 Ford

Almost every where you go those 2.3 Fords dominate since they managed to get the rules in their favor.

Davegt27
 

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Referring back to the "year" stamped in the head, I have a head stamped "70" and yet it has a 4 journal cam shaft (only 10 head bolts). Shouldn't the 70 only have a 3 bearing cam?
I don't want to start any porting or shrouding if this is a later model hardened head!:confused:
 

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Gordy,

I just looked at my extra heads, one is marked 70 and is a 4 brg, 10 bolt and the other is a 71, 4 brg, 10 bolt. Neither of these has the crack prone exhaust seats. I think only the 12 bolt heads are the issue.....
 

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Thanks Paul. I pulled the head off and the engine has the dished pistons, the lifters are hydralic but the head is a 10 bolt with the older timing cover (with the extra cork on the head gasket up front). I have one other head to check out (Ithink by taking the head side cover (spark plug side) I will be able to see how many cam bearing journals there are in the head.
 

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Referring back to the "year" stamped in the head, I have a head stamped "70" and yet it has a 4 journal cam shaft (only 10 head bolts). Shouldn't the 70 only have a 3 bearing cam?
I don't want to start any porting or shrouding if this is a later model hardened head!:confused:
Remember, the "1971" model year was started to be built in August 1970. So the heads were cast even earlier in 1970. My "October 1970 build date" 1971 GT had a four-bearing head, and low compression pistons
 

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Lately I've been reading some technical books.Makes me have some questions.I opened Your photo albums with Cih heads,Bob, to see some answers.
When it comes to combustion chamber modifications-is it importnat to open up the chamber wall for intake valve,where it is closest to the chamber wall?Sometimes called as the deadzone,where valve isn't fully efficient.

Ok,if it's done,then squish area will be reduced.But it's all about the compromise,golden middle.

I looked on standard 2.2Cih head,it has very small gap between chamber wall and intake wall.Then,remembered,that here You lot use even 1.94intakes and so on.So-no,with no gap?

Maybe that gap isn't that important in Cih heads?

Just learning :)
 

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Lately I've been reading some technical books.Makes me have some questions.I opened Your photo albums with Cih heads,Bob, to see some answers.
When it comes to combustion chamber modifications-is it importnat to open up the chamber wall for intake valve,where it is closest to the chamber wall?Sometimes called as the deadzone,where valve isn't fully efficient.
Lesis
I'm not even close to Bob's level.

I call that place a "pinch" point.
When using oversized valves open the pinch point all the way to the fire ring.
wall wetting_1.jpg
The cihs has a big problem with wall wetting. Plan on dealing with it.
wall wetting_2.jpg
You also might want to look here.
http://www.opelgt.com/forums/groups...fy-you-model-50-year-page36.html#gmessage2016
HTH
 

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That pinch point is marked as those tiny sockets left to the spark plug place?

And with wetting You ment that fuel sticks to the wall surface?

P.s.I never found that topic before,thanks,Wrench,there are some goodies written.
 

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When it comes to combustion chamber modifications-is it importnat to open up the chamber wall for intake valve,where it is closest to the chamber wall?
It is important if you want the head to flow at high valve lift. This is one reason why 'old time' Opel CIH tuners very seldom used more than .480"- .500" valve lift (12.2 -12.7 mm). Heads didn't flow well at that lift. Bigger valves only makes the problem worse! Flow improves, yes, but flow at high lift is even less than with smaller valves.

With this modified cylinder head for example (1970 casting, 1.9S head), I can have good flow even at 15.25 mm valve lift. A normal combustion chamber for a 1.9S (with 47 mm valves) will have maximum airflow at approximately 10.8-11 mm valve lift. After that, flow becomes worse, and very turbulent.



To improve quench, this head is fitted to a block machined to allow the pistons to extend .008" (.2 mm) above the deck.

There is more to be done to the head later as well, it involves grinding dimples into the combustion chamber wall and the short radius of the inlet ports. But for that I test on my flow bench and look for 'wet' flow patterns with spray dye. This helps to enhance boundary layer flow, and keeps the air/fuel atomized better.
 

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What do you think it's preferable to use with a 2.0E cilindre block: A 2.0E or a 2.2E cilindre head, both with 40/45mm valves?

Thanks
 

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What do you think it's preferable to use with a 2.0E cilindre block: A 2.0E or a 2.2E cilindre head, both with 40/45mm valves?

Thanks
It depends on the camshaft. But with less than 13 mm valve lift, I would use the 2.0 head. The 2.2 head only flows better at higher valve lift, but you will lose compression compared to the 2.0 head.
 
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