[opelgt73]

I just picked up my new car this weekend, it is a 69 GT with a rebuilt motor 2.0L, crane ignition, big valves, alpine stereo, and a DGAS Carb. It also has one of those neat little metal heater control plates. Mechanically it is perfect, but it does have one spot of rust that needs attention, and some spoilers that I am going to take off.
Anyway it came with a header just like this one
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1874394931
Is this worth my time in putting in? Or would a sprint manifold be better?

Also it came with some parts that I don't really need that I would like to sell to help offset the cost of painting or trade to get the parts that I need more. Here is a list:

NOS rear trim strip, one small dent
Three fenders cut out of a car, minimal rust.
Rear end from 70'gt, has mount for sway bars
Out of production NOS wheel bearing for early rear ends
Petals to convert from Auto to manual
LOW LOW mileage Solex, really clean, good for stock restoration.
Complete wiring harness out of car, supposedly uncut.
NOS VDO oil pressure sending unit

And some other random weird stuff that I have never seen before, I have some pictures that I can post if anyone is interested,
I would like to trade any or a combination of the items for an A/C setup and or a Sprint Manifold.

Thanks,
Chris

 

[opelbits]

Love to see some pics of the "weird" stuff. Might be interested in a rear fender (if you have one). Or the nos wheel bearings. I have a couple 'sprint' manifolds.

Tony P.
[email protected]

 

[opelgt73]

Here is the actual picture of it, I guess it is slightly different than the one in that Ebay auction. I know that the pipes had to be of equal length but I didn't know if this was "close enough"

 

[Paul]

Interesting.......

They do look close, but they aren't the same. One fits a GT and the other fits a Manta, I guess. Neither is a true "equal length" design. Even the collectors are different. The top picture has a better "merge" section but the collector length is too short. The one on bottom has, as Bob L. termed it, an Instantaneous Merge collector but it's longer, closer to the proper length.

I've had one of these same style headers on my 75 Manta since 1978. I had always "thought" there was some improvement over the stock exhaust. Always pulled much better up long mountain grades in the top of 3rd gear. But, now that I've read and re-read and re-read lots of posts by Bob L. and conversed at length with Rodney Davis at Headerdesign.com, I not sure what I'd put on the car short of a properly designed and constructed header. I know Bob L. has stated that the stock exhaust with the last two pipes lengthed about 10 inches (just before they merge into One) gives the best street performance, torque. But, I don't see how EITHER of them, unequal length header or cast manifold, are any good at ALL.

...Just my thoughts as I ponder the great mysteries of Gas Flow Dynamics, Wave Propagation, and Header Science.

Paul

 

[opelgt73]

I think what he is refering to reguarding the 10in dual pipe extension(and maybe he will correct me), is that by combining two compimenting cylindar's exhaust for a short run before they meet the others provides the propper back pressure.
The sprint is considered better than most all aftermarket headers because most headers are designed so poorly. And it is better than the stock because the stock one has the heat riser that creates an inpropper turbulance and backpressure that the smooth exhaust of the sprint doesn't.

 

[oldopelguy]

fi

For the sake of clarifiication, I can't tell much difference between my "sprint" manifold and my '75 efi manifold. They appear to be and function in much the same way. The efi manifolds are a little easier to find though.

 

[opelbits]

Here is the actual picture of it, I guess it is slightly different than the one in that Ebay auction. I know that the pipes had to be of equal length but I didn't know if this was "close enough"

I've had one of these hanging in my basement for years. Possibly one of the headers sold in JC Whitneys for $100 or so? It never looked like a good collector system on it. Although, what about cutting off the collector and converting it to a "4 into 2 into 1" (kind of like the stock system)? Seems like that might improve the flow and not be as heavy as the cast iron manifolds.

 

[RallyBob]

Re: Interesting.......

I know Bob L. has stated that the stock exhaust with the last two pipes lengthed about 10 inches (just before they merge into One) gives the best street performance, torque.
Paul

Paul, I was referring to using one of these 'short' headers, and extending all 4 of the pipes at least 10"......they're just too short to work at the rpms the Opel runs at and can benefit from. The header would still have unequal length primary tubes, but at least they'd be longer whee they can do some good. Better to be too long and imbalanced than short and equal! Better still to be long and balanced, but it's difficult to do in mass-production.

As far as merging two pairs of pipes into one, I don't like to do it. I prefer the power characteristics of a 4-into-1 header over that of a 4-into-2-into-1 header. At least a proper one. Better throttle response, better peak power, flatter power curve, and better plug readings.


Bob

 

[RallyBob]

Re: fi

For the sake of clarifiication, I can't tell much difference between my "sprint" manifold and my '75 efi manifold. They appear to be and function in much the same way. The efi manifolds are a little easier to find though.

Same thing!

Bob

 

[opelbits]

Rallye Bob-
I bow to your knowledge/experience on this. Just a theory I had as all the Mustang crowd (I had a couple, which, by the way, there seems to be some sort of connection between people with Opel GTs and 70 Mustangs. I've met quite a few that have had both.) likes the 'Tri-Y' headers.
Still seems like a good starting point for the lengthening you are suggesting. Relatively cheap, too.

 

[RallyBob]

Since my old posting from the beginning of the year lost its photos when this forum changed programs, I figured I'd post this photo again.

This is an equal length (within 1/4") header for a racing Opel engine of mine in a Manta. Primary tubes are 1.625" diameter, and the collector is 2.75". Primary lengths are 36" long. This is for a 2.2 litre engine capable of 8500 rpms and making over 220 hp, so it's way too big for a normal street-driven 1.9 litre. But it shows the work involved in making it fit the car. It took me about 8 hours to build.

Bob

 

[oldopelguy]

Wow

I love that picture.

I read once that, while equal length is the best way to go, you could sort-of cheat with equal volume for each leg on a header with good results. That is, if the leg absolutely couldn't get longer, if you could adjust the diameter larger to make the volume of the pipe the same as the rest it would still work OK.

Does this actually work?

 

[RallyBob]

It sounds like in theory it would. However by simply increasing the pipe diameter, you may lose velocity. And that's bad no matter what. Guess it depends on 'how much'.

Bob

 

[Paul]

Pipe Extensions

Bob, Yes I remember and still have a copy of your post about lenghting the primary tubes of the "Poor " header. What I was refering to and maybe incorrectly refered to you as the suggestion provider for this modification, was a picture of someones picture in the vault (I think) of Classic Opels, where someone had lenghtened the last two legs of the "Stock" Tri-Y type exhaust. The post to go along with it seemed to indicate an increase in Torque.

I'm glad to hear that you think lengthing these primaries are worth doing. I'd love to find a better collector and at the same time replace it. From all indications, it needs to be about 2.25" OD and 12" to 14" long.

Great topic and thanks for all the useful info

Paul

 

[opelgt73]

Bob,
so could I cut the collector off and add say 12 in to the inside pipes and 10 to the outside ones?(or whatever the difference is between them. Maybe have them bend out a little and then come back in so that I could get the propper length?

also since you are the one to ask, would it be benifical to do this Over say a stock sprint manifold?
My motor is a 2.0L with the C&R big valve kit, and a DGAS.
right now it has the stock cam but I also have the C&R "Autocross" cam.
would it make a noticible difference?
The reason that I ask is because if i used a sprint I wouldent have to get a whole new exhaust(and as it is the exhaust is brand new), so I don't want to switch to a totally new one unless it will be a big difference.
Thanks,
Chris

 

[RallyBob]

Re: Pipe Extensions

I'd love to find a better collector and at the same time replace it.

www.headersbyed.com

Not the cheapest, but the stuff's nice (I buy all mine from there) and talking to the owner is like getting a PHD in header technology.

Bob

 

[RallyBob]

Bob,
so could I cut the collector off and add say 12 in to the inside pipes and 10 to the outside ones?(or whatever the difference is between them. Maybe have them bend out a little and then come back in so that I could get the propper length?

also since you are the one to ask, would it be benifical to do this Over say a stock sprint manifold?
My motor is a 2.0L with the C&R big valve kit, and a DGAS.
right now it has the stock cam but I also have the C&R "Autocross" cam.
would it make a noticible difference?
The reason that I ask is because if i used a sprint I wouldent have to get a whole new exhaust(and as it is the exhaust is brand new), so I don't want to switch to a totally new one unless it will be a big difference.
Thanks,
Chris

It would be better to rework the header like you suggested rather than use the Sprint manifold. I assume you weren't going to use a stock exhaust pipe anyway? The stock GT pipe is only 1 5/8" diameter, your engine would benefit from a 2" pipe diameter anyway. Combined (reworked header and larger pipe), there will be a big difference over the Sprint manifold/stock pipe diameter.
I'd also install the autocross cam, it will make a noticeable difference, and will compliment the exhaust upgrades very nicely. This should give you about 125 hp. If the distributor is reworked, and the carb tuned correctly, the car will have a very nice power spread (2000-6500) and a decent idle at about 1000 rpms.

Bob

 

[opelgt73]

When you say distributor reworked......what do you mean.
I have some of the old C&R catalogs and they refer a few times to "reworking the distributor" and I didn't know what they were talking about.

 

[George]

header

I have one of the headers that J.C.whitney sold for the opel gt that I bought in 1974 or 75 and never put on.would it be worth the time and effort to install it?I never put it on because the head flange is thinner than the stock intake.

 

[Gary]

When you say distributor reworked......what do you mean.
I have some of the old C&R catalogs and they refer a few times to "reworking the distributor" and I didn't know what they were talking about.

Here's a start: http://www.opelgt.com/forums/showthread.php?s=&threadid=224

Do a site search for "Distributor" it has been mentioned in a couple of threads.

Gary