[jeff denton]

exhaust manifold?

Speedway GT came equipped with an exhaust manifold that looks like a "header." It is tubular, four tubes run into a collector. Yes. A header. Now, my buddy who thinks he knows it all says it is the original "exhaust manifold" that a 1970 GT came with.
I'll need some help with this, my friends...
Rules call for "stock exhaust manifold, no headers".
Well, you know how stock car racing goes...
To me, a stock exhaust manifold is a big heavy cast iron thing, but what do I know about German built imports?
Can anybody describe to me what their stock GT exhaust manifold looks like?
Thanks a million!


Mod Edit: Threads merged

 

[opelgt73]

NO that is definitely not the stock manifold.

The stock manifold IS cast iron, and attaches to the intake manifold to act as pre-heater to help your motor warm up faster.

HTH

 

[kwilford]

Stock Manifold

Here isa photo of a stock exhaust and intake manifold I just saw on ebay:

 

[jeff denton]

Thanks, guys. Now, who out there might have the stock manifold I need, and, who wants a perfectly good header?

 

[kwilford]

Stock Manifold

Here's the ebay one that I posted the picture of, and it comes with the supposedly "better" Bob Legere-recommended intake manifold, which would also probably work as a "stock" 1970 version (even though it is from a later model, 1973?)

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33627&item=1876624376

And Jeff, yes, we are almost neighbours. Kalispell is just a hop, skip and a jump from Calgary. I have skied at Big Mountain, Whitefish many times. Katheryn McCoy probably wants to know why you weren't at the Missoula meeting this summer with the Rocky Mountain Opel Club (look at the picture on the home page; it's Kat next to her car, just after the Solex caught fire. You can see the burned paint mark on her hood. And who says Solex's aren't a GREAT piece of fuel metering equipment?) Here is the RMOC site:

http://groups.yahoo.com/group/rockymountainopels/

Are you a member? There is a fellow Opeler in Missoula, Will Deschamps. I think he and Kat (from Leduc, Alberta) were the only Opel folks at that meet, but it sounds like they had a blast.

Back to exhaust manifolds, I suspect that you will find LOTS of them around, as they make great boat anchors. The preferable factory manifold is the "Sprint" version, which came on later and fuel injected engines. It has no "heat stove" to transfer heat to the manifold base, which is really only a "good thing" during one of our winters. Well, not this winter, with it so warm and all. But they flow very well. Would a Sprint manifold be allowed under the rules? They weren't stock in 1970, but they were factory supplied, and not even special order. Here's what one looks like:

 

[jeff denton]

Thanks again, Keith! I'm gonna say the Sprint is the one to have, in stock car racing the "rules" can be, ahem, "flexed" somewhat, if the Sprint was stock on any form of factory built GT then it just might be legal, if not, would anybody even notice?
So, where do I get one?
The whole Opel thing is new to me, the Speedway GT idea came to us in a brainstorming session as to what kind of car to enter this year in the Compact Class at our speedway. Something different, you know? Something that handles, even in "stock" form or modified within the "rules." Our team runs four other cars, Bomber, Hobby Stock, Limited Late Model and Late Model.
Speedway GT was located in Colorado, is in my shop now, becoming a full blown high bank asphalt race car.
I will be relying on (and greatly appreciating!) any tech help I can get regarding getting the most out of the 1.9L engine and am so glad to have found opelgt.com...

 

[kwilford]

I moved this thread to the "Racer's Forum, since it might get more appropriate readership there.

As for finding a Sprint exhaust manifold, i believe they are a bit rare, or at least much-coveted. But this is the group that can help you out.

 

[RallyBob]

The Opel GT does NOT have a good suspension for handling unless it is EXTREMELY modified. A Manta or Ascona is far more preferable....but I digress.

I have many years of experience fielding a two-car team of Opels (Mantas) in various forms of circle track racing, from 'stock' class right up to 'outlaw' mini-stocks which were faster than all the V8 classes except for the NASCAR Tour Modifieds on a 1/4 mile asphalt oval. I pretty much know what you can 'get away with' for engine mods on the stock class cars. If you have any specific questions, ask away.....

 

[jeff denton]

Thanks, Bob. My first question would be, would you like to come and see Glacier National Park and oversee a 1.9 rebuild soon?
Thus far I have yet to hear anybody say a Pinto could ever outhandle a GT. That's all we have for competition, the track technical director knows something is up (we asked if we could run "something different like a 240Z") and he congratulated us for "thinking outside the box..."
Suspension mods are extremely limited, in fact, nil other than getting the right camber. But here again, who's gonna know the difference?
The compact class here is designed to be very low dollar fun, there's just no reason to build a complicated race car, we already have two of them... we think it would be neat to be the only team with an entry in every class!
But seriously, and specifically, what sort of easily obtainable (and reasonably priced) camshaft might you recommend? Rules call for maximum .425" lift, no duration limits. Sorry, no fancy valve work, either. No mechanical lifters, even! No porting, no unshrouding. No fancy pistons. .040 max overbore, .020 max decking or head milling.
See what I mean? It's just for fun, I guess.
Thanks!!

 

[RallyBob]

I know the perfect cam for you, I used to run it in 'lift-limited' classes. .405" lift, 250 duration @ .050"....pretty healthy. BTW, Opels cams stock with solid lifters from 1965-1970....so you have that point covered. Also, without a head thickness to measure by, you can mill the head a bit more than that, or run a 1.5 litre head with 1.9 valves.

Bob

 

[RallyBob]

I dug up some old specs for an engine I built many years ago for a circle track racer in New Hampshire. Same deal, 'stock' rules apply. But few know what comes stock on an Opel, so this is what I built for him:

>.040" shortblock, Total Seal gapless rings, flat-top pistons, block decked .010", new rod bolts
>1971 cylinder head, milled .050" (true compression was 9.6:1), 2.0 intake valves (stock Opel part), bowls blended and camouflaged, 3-angle valve job, bronze guides.
>.405" lift cam, 250 duration @ .050", 106 lobe separation, solid lifters, stock springs, shimmed for increased pressure.
>1975 (Sprint) exhaust manifold, custom downpipe made with 1.75" tubing, merged into 2.25" main exhaust pipe, exiting out in front of rear tire.
>1974 Manta intake manifold, short radius of plenum cleaned up, then sandblasted.
>32/36 DGEV Weber (track approved, since it is essentially the same as the carb the Fords run). I bored the secondary venturi out to 32 mm, streamlined the auxiliary venturis, and removed the choke.
>baffled oil pan (essential for cars turning left!)
>Reworked distributor, setup for 20 degrees initial timing, 36 degrees maximum timing. Replaced points with Pertronix, used MSD coil painted black (looks stock). Used NGK plugs.

Engine would idle at 1200-1300, revved to 8000+ regularly.

The car previously was a 6th-10th place car at best with stock engine. After the new engine, he was track champion for two seasons before he moved on to another class. He was torn down three times, every time the inspectors and onlookers found nothing out of the ordinary. Won 7 out of 8 races that he ran during his second season.

Bob

 

[Paul]

What are camouflaged bowls?

What did you do to camouflage the bowl work? And don't tell me you painted them green.....LOL. With these engine/cam specs, what was the power band?

Do you happen to know what kinda suspension tweeks this particular car had?

Very Interesting........
Paul

 

[RallyBob]

Re: What are camouflaged bowls?

What did you do to camouflage the bowl work? And don't tell me you painted them green.....LOL. With these engine/cam specs, what was the power band?

Do you happen to know what kinda suspension tweeks this particular car had?

Very Interesting........
Paul

Ha, ha, everyones's a comedian.....

What I meant by camouflaging the bowls is they were essentially modified to appear stock. I had my machinist mill down the valve guides approx. 1/4" to improve flow. I then blended the bowls into the valve seats with a carbide on a die grinder. I polish the bowls smooth after that, to 180 grit. Yes, typically you want it rough, but there's more to it than this. I then grind the port casting line or 'flash' line back into the bowl area, and scribe into this casting mark with a sharp tool. I follow up by having the ports sandblasted....not with a wimpy home unit, but by a monster commercial unit. It leaves an 'as cast' finish in the ports. The valve job is touched up at this point, and then all appears 'stock'.

Not sure of all the mods his car had, I gave him suggestions, but don't know what he did or did not do. For a stock class such as this, there's not much you CAN do. But, I told him to rotate the right front sway bar bushing 90 degrees, this induces a bind in the sway bar under cornering, effectively making the bar stiffer while retaining the stock bar. I also told him to use stiffer shocks, and to remove the rear sway bar. Another thing, which I know he did, was switch the panhard bar around, to work better for left turns. Normally, the Manta has the bar attached to the axle on the right side, and to the body on the left. This was reversed, the way a GT has it. He MAY have installed stiffer front springs too, based on my suggestions.

Bob

 

[jeff denton]

Awesome! Thanks a bunch, Bob. 8000 rpm? Wow.
What kind of balancing work is needed to do that?
You say my 70 1.9 has solid lifters? Rules forbid that.
I think I should give it a go with a very legal engine at first.
One neat thing about running an Opel is that who around here would know stock from "camouflage" but how would I prove it is stock if I had to? Maybe I better collect a few engines...
The "camo" trick is ultra sneaky. Who thought that one up?

 

[RallyBob]

The "camo" trick is ultra sneaky. Who thought that one up?

NASCAR pretty much invented it 50 years ago. Penske Racing perfected it in the late '60's. Heck, there are even companies that specialize in just this sort of work!

8000 rpm's? A stock Opel shortblock can handle it. Nothing special for balancing, costs me $130 to have the rotating assembly (crank. front pulley, flywheel) balanced locally. I do the pistons/rods myself.

Bob

 

[RallyBob]

Originally quoted by Jeff Denton on L.S.R. Opel GT thread:

Bob, over the winter I need to pick your brain some about our new rule changes in the compact class and how to apply them to Speedway GT. One is there will be no camshaft rule. Run ANY cam, and a ruling on my car is if it came factory stock with solid lifters I can use them. Also the stock exhaust manifold rule changed to allowing use of a tubular steel header with primary tubes not running further aft of the bellhousing.
I think only you would know what cam to use...
Sorry to have strayed a bit from your topic but I know your gears are always turning and I respect your wisdom here...

Jeff, I started a new thread so as to keep the L.S.R. GT thread on-topic. You'll have to refresh my memory, but I seem to recall your class allowed for almost no modifications, correct?

That said, it makes little sense to go with a monster cam with stock valves, etc. And you'll need different retainers, the stockers begin to fail (split in half) at around 7800-8000 rpms continuous useage.

I've built a lot of engines for restricted-rules Opels in circle track, mostly here in the New England states and also in the Nashville area. Most of the rules allowed for a max lift of .430", and no limit on duration, so I tended to use a particular cam with .405" lift and 250 degrees of duration @ .050". Lobe separation depended on track length....

If you run down some of your specifics again, I can get a better idea of what to recommend for you.

Bob

 

[davegt27]

i have a 2.0 sprint manifold looks just like 75 sprint except the head pipe mounting flange is bigger (not sure it will fit a GT)

and it says GM on it but its cast iron

also have some performance cams also

Love to get rid of some stuff.

[email protected]

David Ligon

 

[jeff denton]

Thanks, Bob, I always print your replies and file them in the Speedway Gt file. The new cam rule is great, the header rule is awesome, and the radiator change was needed by everybody.
The cat is out of the bag, the compact class knows there is an opel coming, those who have seen it have spread the word that it's build outclasses all others... This is gonna be fun...
Thanks for all your help!

 

[baz]

jeff
you had better hope none of the pinto runners ever hear of this site or you will be in deep deep du du

 

[jeff denton]

well, porting the heads and knife edging the crank and trick stuff like that are illegal, as are mixing head/block combos, the rules are written to outlaw certain tricks that can happen among the Fords...
Horsepower does not rule at tracks like ours. It's all about the tires and getting them to work. A lot of rpm is helpful.
I will build a very blueprinted stock engine with good oil and windage control. After that, it's just cam selection and header tuning. The carb will be Holley two barrel just like everybody else's. The compact class cars run full throttle except for an instant between turns 1-2 and 3-4. Brakes are used only in true Maalox moments, which we tend to try to avoid...
My mentor in this sport has always been Smokey Yunick, pehaps you recognize his fame in NASCAR. He was a genius at reading and re-reading the rules and inventing a way to get an advantage figured out around them. And in the compact class here it looks like everybody's just copying each other, not doing anything very scientifically. I think my GT was born with better genes than any Pinto and has inherently better potential for success... If not, you just do like everybody else and dabble in bold outright cheating and see if you can get away with it.