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Stock exhaust manifold v headers

opfor2

opfor2

1/2 ton status
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Oct 28, 2002
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Ventura County, CA
Today while working on my 90 Blazer I noticed that the passenger exhaust manifold was cracked back towards the firewall. So, what should I do? Replace it with an OEM manifold or get a set of shorty headers? (I live in the Peoples Republic of California so I need to stick with smog legal headers) I have a hi-flow cat and a cat back flow maser exhaust already. Would headers really help me on power and MPG or should I stay stock.

Thanks

Dan..
 
Headers are a help especially since you already have a larger free flowing exhaust system. I ran a set of shorty Gibson headers from an 88 chevy truck on my blazer and had to slightly modify the driver side frame rail for them to fit but was VERY happy with them and am planning on that again for this blazer. The ones i bought were stainless and excellent quality but not cheap.
 
I got a pair of non-air headers from summit for 87.50 for my 89. It was probably the best deal I have seen on them. Like 4x4HIGH said, you already have the rest of the exhaust done, so it will make a pretty noticable difference.

Erik
 
I'm keeping the stock manifolds, because I am cheap, and I won't have to worry about making them fit. If I build a more performance oriented engine in the future, I will probably try to get ahold of some Doug Thorleys. :D
James
 
The only problems I had with the install was removing the metal powersteering bracket that was attached to the aluminum bracket. I got a puller from advance and tried to remove the pulley, but it would not budge, so I got out the sawzall and removed the bracket that way. I also had to remove the bumpstop for the front diff. from the passenger side. Over all it wasn't that bad. Just make sure that you remove your plugs before you do it. I ended up breaking two of mine off because I thought that I could squeeze it in there without breaking any of them. Wrong.

Erik
 
Edelbrock TEMS Headers

Any body got pictures of thsese header installed. I'm concerened with the Y pipe and the front drive shaft clearance.

Thanks Ed
 
i got a set of thorley headers, and hi flow magnaflow cat/muffler. i didnt really see a difference in power. my feeling is you need a higher HP motor to take advantage of the increase in flow. stock motor is fine with stock exhaust. you start seeing gains when you build up the motor and its being held back by a restrictive exhaust.
headers also resinate heat into the engine compartment. i had alot of problems trying to get the headers sealed up. i kept having exhaust leaks at different gaskets. never had a problem with manifolds. reason i went to headers was causs my manifold cracked. if i could do it over again, i'd probly just get a replacement manifold.
 
Jonny-K5 said:
i got a set of thorley headers, and hi flow magnaflow cat/muffler. i didnt really see a difference in power. my feeling is you need a higher HP motor to take advantage of the increase in flow. stock motor is fine with stock exhaust. you start seeing gains when you build up the motor and its being held back by a restrictive exhaust.
headers also resinate heat into the engine compartment. i had alot of problems trying to get the headers sealed up. i kept having exhaust leaks at different gaskets. never had a problem with manifolds. reason i went to headers was causs my manifold cracked. if i could do it over again, i'd probly just get a replacement manifold.
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Exactly... that and, when I was installing some cheap flowtech :doah: headers on my old '66 c-10, I sat there shaking with bloody knuckles and high blood pressure and swore I would never fool with headers again...... If I ever build something nice, like a 383 stroker, then I'll probably get a good set, but until then, I'll just settle for stock horsepower..... because contrary to spike TV commercials, there is no "magical" horsepower bolt on.. :wink1:
James
 
I checked my LMC catalog today and they want 299.99 for ONE replacement manifold. Wow that's a lot of $$$$$$
 
Typical gains from back to back dyno tests with long tubes are 20-40hp on bone stock chev 350's.

That is nowhere near a slight gain for the relative ease of install, or compared with the complexity of figuring out a better engine component combination.
 
dyeager535 said:
Typical gains from back to back dyno tests with long tubes are 20-40hp on bone stock chev 350's.

That is nowhere near a slight gain for the relative ease of install, or compared with the complexity of figuring out a better engine component combination.
Click to expand...

what type of bone stock 350 are we talking about? a 180horse smog dog? or a stock non emissions 350 w/ a healthy carb. i cant see squeezing 20 horse out of a anemic late70-80's engine.

these gains were probly produced at or above 5000 rpm. the stock cam in my 89' quits @4k. i bet the dyno results would be very close @ 3500rpm and under ,which is where most of our truck engines live. torque numbers are probly very close in that range too, and thats what you feel in the seat of your pants on the street.
 
I have Edelbrock TES/headers on my 89 I like them. Have had them for bout 6 years now and have never had a leak. I bought then for the same reason as you . Cracked manifold. Great upgrade. More power better MPG
If you get headers be sure to get headers with the 02 bung or weld one in. Gotta have the 02 sensor with TBI
 
Thunder said:
I have Edelbrock TES/headers on my 89 I like them. Have had them for bout 6 years now and have never had a leak. I bought then for the same reason as you . Cracked manifold. Great upgrade. More power better MPG
If you get headers be sure to get headers with the 02 bung or weld one in. Gotta have the 02 sensor with TBI
Click to expand...

Thanks for the relpy. Did you have any problems with the install ?

Dan..
 
No. Simple install They bolt right in with no cutting or welding. Hook right up to the stock exhaust at the cat. If you have to keep the cat convertor you should install a new high flow convertor while you have everything apart. The stock cat is pretty restrictive. No clearance problems with my 2" lift. But I have heard if you have over 4" lift the front drive line may hit the Y pipe.
Smog legal in Calif too.
 
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