Thorley Short Tube Header First Impressions

[parsky1]

I decided to install short tube headers on my VVT-I V8 with 200k miles. I bought new OEM manifolds from Toyota during a 25% off sale for about $700. I wanted new cats just given the amount of effort these take. My old cats were still ok. I also replaced the motor mounts at the time since you have to lift the engine a bit anyway. Can definitely feel how bad my old ones were after replacing them. Less vibration when it’s running and when it starts. I paid a mechanic for 17.5hrs of labor. 3 of that was fabrication. After it was all done he said he wouldn’t do the job again. It’s definitely not fun. The access to the studs on the short tube headers is about .001” away from impossible. You have to even cut down an open end wrench to have any chance to tighten one. Forget about using a torque wrench. I kept the factory y-pipe since my exhaust is still in good condition. New Denso upstream O2 sensors as well. We cut down new Toyita metal gaskets to fit vs using the Thorkey gaskets. New Toyota studs and nuts as well. All studs came out with no issues.

I will say mid band power is better. City gas mileage did not change really. Probably too much idling, acceleration and low rpm’s. Highway mpg went up about 1mpg. My 4Runner is basically all stock other than the headers. I feel like the 2-3mpg claims on the internet are overstated and I’m definitely not a lead foot. I did see 2-3mpg gains for the first 2 days but I think that had more to do with the ECU reset since the battery was disconnected for 3 days. It eventually settled out at same for city and plus one for highway after a couple fill-ups.

RRcats offered me $230 for my old cats.

 

[rdruss]

I decided to install short tube headers on my VVT-I V8 with 200k miles. I bought new OEM headers from Toyota during a 25% off sale for about $700. I wanted new cats just given the amount of effort these take. My old cats were still ok. I also replaced the motor mounts at the time since you have to lift the engine a bit anyway. Can definitely feel how bad my old ones were after replacing them. Less vibration when it’s running and when it starts. I paid a mechanic for 17.5hrs of labor. 3 of that was fabrication. After it was all done he said he wouldn’t do the job again. It’s definitely not fun. The access to the studs on the short tube headers is about .001” away from impossible. You have to even cut down an open end wrench to have any chance to tighten one. Forget about using a torque wrench. I kept the factory y-pipe since my exhaust is still in good condition. New Denso upstream O2 sensors as well. We cut down new Toyita metal gaskets to fit vs using the Thorkey gaskets. New Toyota studs and nuts as well. All studs came out with no issues.

I will say mid band power is better. City gas mileage did not change really. Probably too much idling, acceleration and low rpm’s. Highway mpg went up about 1mpg. My 4Runner is basically all stock other than the headers. I feel like the 2-3mpg claims on the internet are overstated and I’m definitely not a lead foot. I did see 2-3mpg gains for the first 2 days but I think that had more to do with the ECU reset since the battery was disconnected for 3 days. It eventually settled out at same for city and plus one for highway after a couple fill-ups.

RRcats offered me $230 for my old cats.

I a little confused, you say you "bought new OEM headers from Toyota" , but you installed Thorely headers? Does Toyota sell Thorley headers, or ...?

 

[parsky1]

Sorry, I bought new oem manifolds to steal new cats off of for the short tube headers. I wanted all new.

 

[LOSTR4]

That's wild! In my simple mind, I'd imagine with tuning, you could certainly gain the suggested 2-3mpg increase, but the sound should be better, too, right?! There's a set of DT long tubes available locally meant for the 4runner but the dude has a 1st gen tundra that be couldn't get to fit...blah, blah, blah...I'd love them if they are surely better. Good call on the motor mount swap while you're in there...I'd love to think I could tackle this but I'd rather not spend 17.5hours(professional)*4(personal factor) making it nearly a half month of work Thanks for the write up on your experience...I'd imagine after a month of driving you'll have better metrics to offer if you choose...at least, I'm hoping!

 

[SocalSam]

Interesting mod. If you have space, keep the old cats. I've done shorties on another V8 car and got about the same result as you did. Mid range was slightly better. Top end was better but on the street pretty much unusable. Low end torque suffered which made getting away from stop lights feel sluggish. Install was easier on an OHV motor. Aside from the very cool looks, the marginal performance gain was not worth the effort. In fact, the loss of street drive-ability (drivability?) was regrettable.

On an exhaust side note, I've often wondered if the y-pipe and single exhaust held our V6's and V8's back. Crown Victoria civilian cars gain 15 hp from dual exhaust swap with no motor mods and the same tune.

 

[rdruss]

Interesting mod. If you have space, keep the old cats. I've done shorties on another V8 car and got about the same result as you did. Mid range was slightly better. Top end was better but on the street pretty much unusable. Low end torque suffered which made getting away from stop lights feel sluggish. Install was easier on an OHV motor. Aside from the very cool looks, the marginal performance gain was not worth the effort. In fact, the loss of street drive-ability (drivability?) was regrettable.

On an exhaust side note, I've often wondered if the y-pipe and single exhaust held our V6's and V8's back. Crown Victoria civilian cars gain 15 hp from dual exhaust swap with no motor mods and the same tune.

Just watched an "Engine Masters" youtube yesterday: "S5E60 Single vs Dual Exhaust", pull it up if you can, you will be surprised at the outcome.

 

[4RunnerAquasport]

The factory Y pipe is so restrictive, installing only headers is really not going to gain much noticeable power or mileage.

 

[SocalSam]

Just watched an "Engine Masters" youtube yesterday: "S5E60 Single vs Dual Exhaust", pull it up if you can, you will be surprised at the outcome.

If a single 5 inch pipe can be fitted, OK then. Some practical considerations are getting over the rear axle which is easier with two smaller pipes and ground clearance and protection for off road.

 

[rdruss]

If a single 5 inch pipe can be fitted, OK then. Some practical considerations are getting over the rear axle which is easier with two smaller pipes and ground clearance and protection for off road.

3" and a straight thru muffler.

 

[parsky1]

The factory Y pipe is so restrictive, installing only headers is really not going to gain much noticeable power or mileage.

What part is so restrictive?

 

[parsky1]

Interesting mod. If you have space, keep the old cats. I've done shorties on another V8 car and got about the same result as you did. Mid range was slightly better. Top end was better but on the street pretty much unusable. Low end torque suffered which made getting away from stop lights feel sluggish. Install was easier on an OHV motor. Aside from the very cool looks, the marginal performance gain was not worth the effort. In fact, the loss of street drive-ability (drivability?) was regrettable.

On an exhaust side note, I've often wondered if the y-pipe and single exhaust held our V6's and V8's back. Crown Victoria civilian cars gain 15 hp from dual exhaust swap with no motor mods and the same tune.

I sold the old cats. New ones are exactly the same, just new. Given the expense of this, I wanted all new.

 

[rdruss]

What part is so restrictive?

Some people think where the exhaust joins together at the Cat on the V8 is a big restriction because it looks like it would be, but my guess is that's it's really minimal. After watching a dyno test where they took a hammer to the headers and beat the pipes down to less than half original diameter and it had almost no effect on power, I doubt that "y" in our exhaust is a big deal.

 

[Inv4drZm]

I forget exactly but I believe the factory Y pipe is in fact 'double walled' meaning what you see on the outside isn't the actual diameter the exhaust flows through, its much smaller.