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Discussion Starter · #1 ·
I got an email from a fellow Manta ITB racer that said SCCA has “corrected” the 9.0:1 compression for Mantas to 7.6:1 compression. (Read the Feb 2004 “Fas Track” at www.scca.org)

Last fall I got the rules “corrected” to 9.0:1 as it had been published for previous year versions (around 1995-1998) of the SCCA General Competition Rules (see the Aug 2003 “Fas Track”

I will be contacting the tech department at SCCA in the next coupe of days to “politely” get this corrected. So those of you who may be getting ready to send them a “nasty-gram”, let me see what I can do first. If that doesn’t work, then let the “nasty-grams” fly.
 

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I will hold the nasty gram then. I have been waiting until I was fully cooled down before writing a letter. I have a fresh 9:1 motor ready to install and do not want to start over.
 

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Were Manta's ever sold in the US with a 9:1 motor ?

I thought all Manta's had the 7.6:1 motor and only 69 & 70 GT's were 9:1, with 71, 72 & 73 GT's being 7.6:1

Bill D.
 

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Discussion Starter · #4 ·
A little background... The early 70's were the early days of smog regulations. Each state had different regulations with California the most stringent. Most manufacturers made different stuff intended to be sold in different places.

Opels solution to the smog regulations at the time was to lower the compression and make some timing adjustments. In general all of the cars that were to be sold in the U.S. were to be the same. However, there are known instances where "Euro" parts were put into U.S. cars so the assembly line wouldn't have to stop if they ran out of the U.S. parts. 1.9H heads are a well known example. Another example is the rear sway bar brackets on the GTs. (US cars didn't get sway bars so the differential housings didn't have the brackets but when they ran out they just stuffed the "Euro" differentials into the car and shipped them without sway bars... go figure)

In order to get IT rules changed you have to be able to document that something was available on cars for sale in the U.S. or a part was considered a substitute. (In this case, some dealers in states with less stringent smog rules may have been told to use 9.0:1 pistons or engines for replacements.)

In the mid 90's the SCCA rule book was changed to show 9.0:1 compression for the Manta. I was told at the time that someone had provided adequate documentation for the 9.0:1 compression. I don't know what the documentation was... and unfortunately I do not have any of the documentation that shows the 9.0:1 compression... we're talking about digging up documentation that is over 30 years old.

I didn't give it much thought at the time because I felt the GT was a better car for ITB.

Around 1999 or maybe 2000 the rule book changed back to 7.6:1 without any announcement. Again, I really didn't care. However, when the SCCA rules were changed in 2002 to allow modifications to fuel injection computers I began to think that a fuel injected Manta could be more advantegous than a GT. So last year I contacted SCCA tech folks and asked them to correct the rule book back to the way it had been... 9.0:1. At that time they said they would go back to the old rule books/documentation and investigate it.

Indeed, in August of this year... oops last year, 2003... they issued a tech bulitin and reinstated the 9.0:1 compression for the Manta. Based on this folks started building Mantas for ITB. Now they have issued another bullitin changing the rule to 7.6:1

With at least 2 people on this board and probably more buildimg ITB Mantas I hope that either SCCA has the documentation in their archives... or we can dig up the documentation.

I'm also going to call Gill at the Opel GT Source in the morning. Gill has all kinds of documentation... some of it in German... that he has aquired ofer the years. So I'm hoping that he will have something that shows a 9.0:1 available in the U.S or something like a service bulitin showing the 9.0:1 compression pistons for Mantas. (Please... Don't everyone call Gill and burry him with phone calls on this.) Hopefully Gill... or maybe someone else out there in "Opel-land" will have something. That will make getting this fixed a "slam dunk"
 

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1972 GT 9:1

I bought my 1972 GT from the original owner who purchased it new in Boston, Mass. then brought it with her to New Zealand.

When I took the head off it had flat-top 9:1 standard pistons in it when I was expecting 7.6:1 dishes. Contacted the original owner and she thinks that after owning the car a few months it was taken back to the seller because it was "too slow" and they "did something in the engine" to make it go better!

So it looks like the piston swap was something done then if the customer complained enough. They also fitted a Weber 32/36 carb at the same time.

NO documentation but if they did it I would not be surprised if there is a tech. buliten some where covering the upgrade.

It may be that all they did was fit the Weber and the engine already had 9:1 pistons as its serial number has the prefix 19S
where as the USA models were known as 19US from what I have seen in books. What is the serial number perfix for engines over there? I know the Austalian Holden Torana engines were all 19S and 9:1 right through till 1979.
 

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Discussion Starter · #6 ·
A bit of an update but sorry, not much to report.

I tried to talk to SCCA today... after several calls (in which I only got put through to an answering machine) I left a message (early afternoon Pacific time) with a phone number and email address to contact me. I have not gotten a response yet.

On the documentation front I talked to the Opel GT Source (Gill) to see if they have any "official" documentation... the bottom line is unfortunately NO. However, he has a book with lots of article reprints some of which show 9.0:1 and some that show 7.6:1. He is sending me one of the books and I will see if SCCA will accept that. (By the way, this is one of the books that he sells, so after I get it, I will post a "book report".)

If anyone can contact Charles Goin... a Manta/1900 wizard... it is possible that he may have some "official" documentation

I will try to contact the tech person at SCCA again tomorrow morning and give another update tomorrow.
 

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Hey, where has Charles Goin gotten to? And I am NOT trying to make a pun! Seriously, he hasn't been around much (not that he hangs around this site at the best of time), although he has posted on the classicopels site. But his Goin' Manta site (http://www.opelmanta.com/) is "down" tonight. Any news?
 

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I guess it’s time to get your “nasty-grams” ready. I got an email from the SCCA club racing technical manager today. Here it is:

Robert,
The Club Racing Board was provided manuals that documented the change of compression ratio in 1971 and later models to 7.6:1. Based upon that information, a correction was made in the February Tech Bulletin.

Jeremy Thoennes
Technical Manager
SCCA Club Racing
PO Box 19400
Topeka KS 66619
(800) 770-2055
[email protected]

I also called and talked to Jeremy… nice guy but not really able to help much. He explained some. He said that the change last August was based essentially on my input. Following this it appears that someone sent the competition board (“Club Racing Board”) a “Mitchell” manual that shows 7.6:1 as the compression. (Jeremy didn’t say where the manual came from, but apparently a “Mitchell” manual is highly respected… more than Haynes and others… I’ve never heard of it.) Thus, based on the “Mitchell” manual the competition board issued the February Tech Bulletin (back to 7.6:1)

I tried to find out what would be needed to get the 9.0:1 back. As I already knew… documentation. Jeremy was very non-committal on what it would take. Rather, he said that we would have to submit it to the competition board. It would then be up to them. Another change would take 2 or 3 months.

Here’s my take. Unless there is something at least as definitive as the “Mitchell” manual it won’t get changed. Jeremy did say that magazine reprints would help, but I don’t think they would be enough. What is needed is at least one manual… preferably two that show 9.0:1 and the reprints. Anecdotal information won’t do any good.

The biggest problem we’re going to have is that SCCA will not make competition adjustments for the Improved Touring (IT) class. It has been a long-standing premise of the class that “SCCA will provide a place for a car to race, but will not guarantee that it will be competitive. So trying to justify the change based on competitive advantage (or disadvantage) won’t do any good. SCCA will correct specifications due to errors, but not change specifications for competition adjustments. More on this in a minute.

Options… none of them good.
First, come up with the documentation. If anyone has a manual for a 71-75 Manta, Ascona, or 1900 that shows 9.0:1 compression, then get in touch with me immediately. I’m not sure I have much confidence that anyone has such a manual.

Second, send in what is available for documentation (magazine re-prints) and hope that the Competition board is sympathetic.

Third, try and get the Manta reclassified into ITC (instead of ITB). I said earlier that SCCA won’t make competition adjustments to specifications. However there are numerous examples of SCCA reclassifying vehicles. (The Honda CRX and VW 1600 Rabbits/Sciroccos were changed from ITB to ITC a few years ago.) The case can be made that the Manta with a 7.6:1 compression, 76 HP engine should have never been classified in ITB with the 9.0:1, 104 HP Opel GT in the first place (along with the 100+ HP BMWs, etc.) The problem with reclassifying to ITC is that folks who have just built 9.0:1 compression engines are stuck “holding the bag”. (Our very own “IT Manta” comes to mind.)

One other option is a “nasty-gram” campaign… but I think that should be a last resort that I think has the least chance of working.

My recommendation…. keeping in mind that this is only one persons opinion… I won’t go forward without hearing from interested parties… is to go for the ITC option. There are some distinct advantages. The reality of the so-called 9.0:1 compression engine is that with flat-top pistons the compression really wasn’t 9.0:1. It was more like 8.6:1. So with allowed head shaving (0.025”) you only get back to near 9.0:1 In ITC, the flat top “replacement” pistons and no head shaving may indeed yield 8.1:1 compression. (I have never “cc’ed out an engine done this way, so I’m not sure). I also think there is a better than 50% chance the car would get reclassified.

Even if we got back the 9.0:1 in ITB, I think it is likely that the person who complained about it (and provided the manual) may well indeed complain again with more documentation supporting the 7.6:1 than can support the 9.0:1. Indeed we all know that the “majority” of Mantas (etc) that came to the U.S. had 7.6:1 compression and there’s plenty of documentation to support that… the 9.0:1 is the exception. So if the cars are reclassified to ITC, we’re “over it” forever.

For now, I’ll wait to hear from folks. Post here, email me here, or email me directly; [email protected]
 

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I scoured all of my books/documentation last week. I have nothing that supports the 9:1 ratio in a Manta. I would run ITC however I believe even with the low compression the car is a big overdog in that class seeing that we were running in the top ten in ITB with low compression. I am sure they will scour the results to see competetiveness.
 

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Discussion Starter · #11 ·
I agree, that can be a problem. If a particular driver... in a particular region, with an exceptionally well prepared (read cheater) Manta was running aginst poorly prepared cars, then the results will be skewed. But "straight up", there is no way a 2300+ lb Manta with 76+ HP can compete with 2300+ lb cars with 100+ HP. So the Manta (etc) is clearly misclassified.

That's the problem with "IT" cars in most regions. Many are "preped" to race... only the top "handfull" in each region are preped to win. In a lot of instances cars in 5th - 10th place are being lapped by cars in 1rst - 3rd place.

By the way, the Manta won't get "slam dunk" wins in ITC. The Honda CRXs and Rabbits that were moved from ITB to ITC will be the cars to beat. These cars consistantly ran in the top 5 (or better) when they were ITB. One Rabbit won the Pacific Coast "Runoffs in ITB around '93. A teardown was done on that car after that race and it was legal.

So, there is plenty of precident and justification for reclassifying the Manta (etc) in in ITC. That's why I think there's better than a 50% chance of getting it approved.

I'll take "IT Manta's" comments as a "go for ITC". I need to hear from others and to give a little time for potential documentation to come in.
 

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Thanks Bob

From what's been presented, I agree with reclassification to ITC, albeit I'd rather have the 9:1 compression and remain in ITB, but a case has been made for reclassification -- now, to sell the reclassification logic to SCCA.
I'd rather be in a slower class where I can "race" ... than be a "backmarker" in a faster class. I'm in the process of making a 1975 Manta slug (fat bumpers and FI) into an IT car ... and need all the help (rule and/or classification changes) I can get.

Ken
 

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I went to the main library today. They have a big selection of old repair manuals. All 71 and up 1.9 are listed as low comp. in the books I saw.

Looked at the old Car a Driver mags from 1971. Same thing, low comp....

Garry
 

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Discussion Starter · #14 ·
A long overdue update.

Nothing but bad news.

I had a long "sit down" talk with Jeremy Thoennes (Technical Manager SCCA Club Racing) at the "SnowBird Double National" (Phoenix International Raceway). Here's the "bottom line".

According to Jeremy, the SCCA "competition board" is considering allowing "competition adjustments" for improved touring classes. (My note: They have been considering this on and off for at least 10 years. At present, there are no competition adjustments). So until a decision is made on "competition adjustments" nothing will be done.

A also asked Jeremy about putting the Manta (with 7.6:1 compression) into "ITC". The essence of his answer is that while that may be "reasonable" no class changes would take effect until 2005. This would also be up to the "competition board".

My only answer is if you race in a part of the country where NASA races, they will welcome the 9.0:1 Manta with open arms.
http://www.nasaproracing.com/
 
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