10% o.d.

TinManSC92

Registered User
i think i blew my head gaskets last saturday. changed my H.B. with the hbj and all the underdrives and tensioner springs that bill sells at scp. he recomended the 10% j/s as well so i went for it. - with shipping it was over 1400.00 so thought i'd get my moneys worth. - i gotta say it's a big difference in pull. so i wonder if it's the U.D. pulley that was responsible or we're they going anyways. why i think that is because when i shut my engie off there was a gurrgling sound for a few minutes afterwards. so i changed the water pump - there was a trace of coolant on top of it anyway- and thought it was fixed. sound to you like that was the beginning of H.G. failure beforehand? i heard it again after i shut down the engine with it's big cloud of whte smoke.
 
if you have a big cloud of white smoke coming out of the exhaust, a burning antifreeze smell, milky oil on the dipstick, rough idle/stalling or liquid coming out of the tailpipe while the car is running. then i'd say your head gaskets MIGHT be blown... but seriously, im in the middle of a head gasket replacement right now... it sucks... i feel for you...

a 10% could definately be a reason for the gaskets to blow, ive heard that 5% is safer but still risky. check when you shut the car off for bubbles coming up into the coolant resevoir, and also check your coolant level.
 
Bubbles are definately a sign but not a definate sign of hg failure. Could also just be getting rid of airlock. For me, the engine working like crap suddenly along with the bubbles was pretty clear.
 
The bubbles on top of the water pump are a leaky water neck. They suck, I have taken mine off at least 10 times, sanded it and it still leaks. But I don't care, as long as I don't run over the fluid and lose traction...cant see it from the drivers seat.
 
Go to napa or carquest and get a combustion check kit. You take a sample of coolant and it'll detect if combustion gases are in it.

If those gaskets where original you where probably heading there anyway. I can't remember if you had modded your exhaust or not? If not, then 10% was way too much.

Fraser
 
I have a 10% on my stock XR7. I guess I'm an idiot, huh? :confused::D:rolleyes:

so you would recommend running 10% on a car with a totally stock exhaust system meaning no exit porting, the stock cats, the stock resonator and so on on a car with original HG's with about 150k on it?

Mine let go with no OD on it at 90k, no resonator and I wasn't even pushing the car hard like I do now.

Fraser
 
I didn't recommend anything, just posted up my experience like everyone else does. :p

I ran a 10% on my XR7 for many years before anyone ever told me that it would be a problem. That was when I lived in Texas and used to thrash on the car in the 100 deg heat all the time. Never knew any better. Car blew headgaskets sitting in my driveway here in Ohio with 140K on the clock because the fan was uh, non functional. Ugh.

The XR7 I have now is bone stock down to the air filter and I run a 10% on it because I'm too lazy to change the pulley. Of course I also run 89 octane in it half the time too. Motor isn't original though so I guess I'm cheating. :eek:

BTW, blown headgaskets generally have very little to do with your exhaust system.
 
I have a 10% on my stock XR7. I guess I'm an idiot, huh? :confused::D:rolleyes:

I must be one as well, only three times as bad.....:rolleyes:

My 89 SC is 10% OD along with my 91 5 speed and 90 SC auto and all three are stock....

I know enough not to beat on them all that much until I can get around to having them tuned......

However, 2 weeks ago, my bone stock 90 XR-7 blew her head gaskets sitting in the drive way less than a minute after starting her up......:mad:
 
Ok guys, I apologize for calling you idiots which was not my intent. I was just going by my experience as well as others who have posted here over the years.

Fraser
 
so you would recommend running 10% on a car with a totally stock exhaust system meaning no exit porting, the stock cats, the stock resonator and so on on a car with original HG's with about 150k on it?

Mine let go with no OD on it at 90k, no resonator and I wasn't even pushing the car hard like I do now.

Fraser


Circa: 2005
while it has been considered the gospel here that freeing up the exhaust is the headgasket saviour, I didn't blow headgaskets until many years later when I seriously overheated the car. I've never believed the notion about exhaust and headgaskets. I still don't.
 
More boost and heat in from 10% OD on stock blowers and stock IC's with stock exhaust. This sounds like a recipe for failure :confused:

Then again the GTP guys do OD on stock exhaust. Are the motors that much stronger? Iron heads? Better factory tune?

I thought the stock tune was rich enough to compensate this so it must be boost pressure that is lifting the heads? Or is that the increase in ACT's are causing detonation and killing the head gaskets?

So many different causes that may kill head gaskets, and each case is different, but I personally would upgrade the exhaust as my first mod besides the air silencer removal (which now i hear may be unneccessary). :D
 
I wasn't suggesting that adding boost doesn't increase the likelihood of blowing a gasket, but often times cause and effect are not linked by "common sense". Most people who blow headgaskets after a pulley change were 95% blown before the pulley change.

Putting a 10% pulley on a motor that already has junk head gaskets is irresponsible and not recommended regardless of what exhaust you have. If you buy an SC with 150K miles on it and think that you are going to improve performance through any variety of mods without blowing the head gaskets, well good luck.

But putting a 10% pulley on an otherwise stock motor with good headgaskets hasn't been proven to blow the gaskets significantly faster than they would otherwise. With my stock XR7 the 10% overdriven stock blower (no belt slip) only makes about 13psi anyway so there's not much threat there. Now if you have an MPII with coated rotors, that would be an entirely different story.....(the same car made 17psi so equipped) :cool:
 
yah, i'm going to go with the guy that says that was irresponsible of me to do. none the less i think they we're going anyways so they needed to be replaced. but i got to say again that it was such a blast having it on there for the few days i did. what really surprised me wasn't the big pull in first gear as much as the ginormous thrust when i shifted to second. second gear has some serious lift and down right stupid. :eek: probably not worth the 2200.00 bucks it costs to fix though. but i'm not convinced enough to take it off. i think they were just plain worn out. will see.
 
I dunno what the deal with my 93 SC is....
I'm running 10% Blower Pulley, IC Fan, Stock Fan override and K&N Drop-in with silencer removed. It will boost 12 PSI no problem, and I still have stock exhaust setup. :eek:

My SC runs great has 150K is a daily driver and I only feed it 87 octane (talk about playing with fire) :eek:
 
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