Opel GT Forum banner

1 - 19 of 19 Posts

·
4ZUA787
Joined
·
665 Posts
all this talk of headers and exhaust manifolds i think is what led mine to crack its saying it wants an upgrade i think, well it all started when my exhaust started getting unusually loud after the car had warmed up and been driven so i took it over to my buddy who owns a muffler shop and we checked out the muffler no holes we checked the gasket to the head no leaks we checked the mainifold to the pipes no leak then he stuck his little hearing tool in the hole on the heat shield for the carb and bam thats were it was comin from, so i was like ok ill check it out some more when i get it home, well i get it back home and no worried about bruning a valve or something since its sucking all that hot air back in, so i was like ill be gone all next week dont need a car lets see what we got, pull the weber which is always fun as any one who has tackled that will tell yah, pulled the whole thermostat housing from the block since i felt i should replace those seals as well, then pulled up that heat shield and saw it right there the two center exhaust outlets had a crack all the way across, so i was like atleast i got an extra one i can throw on, i jus gotta get me the gasket for the block to the intake/exhaust and could anyone help me on what the seal for the heat riser thing is called???, jus gotta order those from ogts and maybe ill have it back toghter by next saturday to take it to the aug 14th meet.
 

·
4ZUA787
Joined
·
665 Posts
Discussion Starter · #3 ·
yah this ones a lill past the jb weld i mean it would hold but since ive already got the manifold off and have a good used one ready to put on just need intake/exhaust gasket from ogts, i tried every auto store in the area to find one on saturday and only one place said they could possibly order it for me and it would be a week, im jus gonna wait till monday and call ogts and have them send it to me in two days, hopefully itll be up for the omc on the 14th. and heres some pics of the crack right over #2 and #3 cylinder exhaust.
 

Attachments

·
Member
Joined
·
239 Posts
Whoa, nice crack!!

Your'e girl has a nice crack (pun intended)!!! Sorry we brought this on for ya talking about GT exhaust and all! I've got two parts cars, don't run and just bought a 1972 that does run off this site. The only negative about my new one is I haven't seen it other than photot's and I hear it's had the exhaust replaced and not original to the car and loud??? Won't know until The 11th of this month what I got there! I don't know why the stock exhaust has a heat riser for the GT and not for the Manta, maybe you need the het risers BS in Germany where they were made because of the extreme cold???Good time for you to upgrade to somehting else, but sems you've got another stock manifold.
 

·
4ZUA787
Joined
·
665 Posts
Discussion Starter · #6 ·
yah im thinking of getting something from ogts just havent checked on there stock of diffrent options will do that on monday, i believe the heat riser could be a emmisions item, and also to help are gts run better when cold, but the only bad part is once u get it up to temp ur jus heating ur gas up more, so im thinking of possibly modifing the manifold i have and make a makeshift sprint mainifold or jus by a header or such from ogts, well see in the next few days. wonder how long this header would last if i tried weldin it up, but dont really wanna see due to the pain it is to take that weber off. also if u ever have to pull ur exhaust mainifold pul the thermostat housing and raditor and fan and do ur front seal at the same time, kill two birds with one stone.
 

·
Registered
Joined
·
2,894 Posts
Wow,Talk about bananas coming in bunches, mine is cracked in the same area, although not as badly. I found it when I pulled the engine last week. If all else fails let me know, I have a few stock manifolds left. I'm upgrading to a sprint on the one that is cracked, Jarrell
 

·
Opeler
Joined
·
56 Posts
must be a weak/stress spot

that photo could be a picture of my manifold this spring :( . The crack looks just the same and about the same length. I drilled the ends and did a little grinding to fit the jb weld into the crack. At the time I told myself that I 'll be patient and pick up a replacement or even a header on ebay at a reasonable price. Hmmmm,,, still waiting... Has anyone else done a similar repair? Is it still holding?
 

·
Registered
Joined
·
6,344 Posts
I was going through the catalog I have from POR-15, and they show an exhaust manifold repair kit they have. I don't know if it works, but if it's like the rest of their stuff, I would be tempted to try it. JMTCW.
 

·
Member
Joined
·
239 Posts
Once again!

Once again, Opels Unlimited (who I never have delt with BTW) other than a phone call and email stated he has new Headers to fit GT that don't hang too low for $289 or used ones for $100? And Sprint depending on the bolts on the bottom for $100-$150 OGTS doesn't seem to stock any of these from what I've found so far!
 

·
4ZUA787
Joined
·
665 Posts
Discussion Starter · #11 ·
yah i have decided since i have my radiator out i have the exhaust and intake manifold out have the water pump off and now have the valve cover off i will do a head gasket because i no that if i replace the water pump and replace the header and gaskets that in a month or so my head gasket will start leaking even more, i have a few qustions, what is the compression ratio on a 72 GT 1.9 just thinking about if im gonna get it resurfaced or not if i should look into making the comprasion higher?, also ive read about how theres that o-ring u have to put in the head gasket, but are there any more tips like should i use rtv silicon or other type of adhesive for the head gasket, also whats the best way to deal with taking off the timming chain in order to get it re-alligned when i put it back toghter, i no how to remove it with the three bolts that hold it in just wonder what i should do to mark it befor removing it? thanks in advance.
 

·
Registered
Joined
·
2,894 Posts
Pvcar, the O ring comes in the head gasket kit and goes at the front of the engine above the Thermostat housing. Also check out this thread started by Otto And RallyeBob. It helped me greatly when I redid my head last week. Don't use RTV or any Silicone gasket material. If any comes loose, it can plug up the oil galleries. CopperCoat has always worked well for me.When I took my head off, I turned the crank pulley until the timing pointer was aligned with the ball that is embedded in the flywheel. This puts nos.1 and nos 4 cylinders at the top. If you have a FSM, it goes into greater detail. HTH, Jarrell
http://www.opelgt.com/forums/showthread.php?t=3296
 

·
Member
Joined
·
239 Posts
My manifold is cracked in the same spot!!!

Hey guys just got my new 1972 GT home from buying her in Texas! When looking her over I noticed there was no heat sheild under the Solex and there is a One inch crack on the middle stack, talked to Gil at OGTS says it's common. Guess I'll be installing that new Pacesetter Manta header sooner than I thought. Also Gil told be the compression should be about 136, Mine is a bit low 120/90/94/114 The car now has 58,800 on her, obviously it's 158,800 and time for a rebuild. But the car is as clean as a whistle No rust
except the battery box, has air/cond that works and an automatic trans which makes her a rare GT worth the $2,500 I paid for her!!! So a rebuild, new header and Weber are in her future.
 

·
OPEL-LESS!!!
Joined
·
2,116 Posts
if any of you guys need stock manifolds, i have them for 15 each, or i have just one header in good shape for 100
 

·
4ZUA787
Joined
·
665 Posts
Discussion Starter · #15 ·
rangerrick
i purchased my gt same as urs basiclly got her in cali thought had auto trans has working a/c system and only had a few lill body rust spots which most gts get any ways, i got her for a really good deal $200 , and this was purchased from the origanal owner as well. and if u need an extra tranny or tranny parts for that auto trans email me i have most of the auto tranny left jus sitin around, one good way to tell if the car would have 158,000 is look and see if its drippin a ton of tranny fluid. good luck.
 

·
Member
Joined
·
239 Posts
It was, fixed it!

The tranny was very low on fluid when I got her barely read on the stick and slipped when I went into a turn. Looked under and saw the pan gasket was soaked. Took it to a shop and had the pan gasket & filter replaced and the rear shaft seal, they also said the vacuum modulator was bad but they couldn't find one. I got one from OGTS and have to install it yet. So even though the car is extremely clean interior as well it's got to be 158,800 and it used used 2 1/2 quarts of oil in 2,300 miles but still averaged 20-23 mpg.
Amazingly the plugs were very clean when I took them out and found my compression to be on the low side.
 

·
Old Opeler
Joined
·
5,564 Posts
Cracking!

Several things contribute to exhaust manifold cracking - in no particular order:

1) Overheating due to retarded ignition timing and/or incorrect fuel mixture. Both these faults tend to have fuel still burning in the exhaust manifold which will glow red-hot in sympathy! Even when everything is correct long hi-speed runs heat things up real hot - this can be helped by the "two extra holes in the head gasket" which lowers the exhaust gass temperature coming out the centre ports (but increases the heat load on the cooling system so that needs to be in top notch condition too)

2) Unsupported exhaust system, which thrashes about putting load on the area that cracks - especially if a larger, heavier muffler is used and the rear resonator is removed to be replaced by exhaust tips that do not have the same suspension system as the original item.

In my experience, cracked cast iron remains cracked despite the best efforts to repair it. Drilling the ends of the crack, heating the whole kit and caboodle red-hot in a furnace and gas welding with compatible eutectic type rods has some chance of success. However the "JB Weld" no-heat option is worth exploring too - but the ends of the crack still need to be drilled with a small drill to remove the stress points at the ends of the crack.

Whatever repair is attempted ( BTW: brazing it up just goes "hot-short" at the temps reached and makes the real cast iron welding option nigh-on impossible after that) it is time to find another undamaged exhaust manifold or a header - you will need it sooner or later.
 

·
Super Moderator
Joined
·
5,922 Posts
lgladdis said:
that photo could be a picture of my manifold this spring :( . The crack looks just the same and about the same length. I drilled the ends and did a little grinding to fit the jb weld into the crack. At the time I told myself that I 'll be patient and pick up a replacement or even a header on ebay at a reasonable price. Hmmmm,,, still waiting... Has anyone else done a similar repair? Is it still holding?
As pvcar noted in a different thread, you can weld cast iron fairly successfully, with proper pre-heat and the correct rod. And to differ with GTJIM, you can also braze exhaust manifolds quite successfully. I once broke an exhaust manifold on a 2.6 V6 Capri (mechanical break, due to a pot hole, rather than a heat-stress induced break), and managed to repair in place. It lasted at least three years, and about 30,000 hard miles before I sold it. Although he is correct about it making future welding problematic (but NOT impossible).
Lonnie, if you need a manifold, let me know. I bought a Sprint, which is in being surfaced and sand blasted for my GT. If it passes inspection, I have a very nice spare stock manifold, which has already been surfaced, ported, SS heli-coils installed, and treated to a high-temp coating. And I believe John Warga has a spare Kadett manifold (after he converted his GT manifold to a home-built Sprint, by cutting off the heat stove and welding a plate on).
 

·
Old Opeler
Joined
·
5,564 Posts
Temporary!

Granted, exhaust manifolds can be temporarily repaired by brazing. Cupro-nickel ("Seelbraze") rather than Cupro-tin ("bronze") being more successful. However I have been the poor mug who has been involved with the new owners this sort of "quick fix" has been palmed off on to and had to set about to repair the "repair". Pehaps I have a jaundiced view in that here repairs are expected to last the life of the car - which used to be 200,000 miles or more - but now the country is flooded with 2nd hand Japanese Imports and repairs are becoming a thing of the past. Just junk it and get another 2nd hand cheapie is now the order of the day!
 
1 - 19 of 19 Posts
Top