I have an EFI 302 in my 92 F150. My pass side exhaust manifold has a crack in it. I was thinking about getting a set of shorty headers. Is there any noticeable gain in power with shorties? Or do I have to go long tubes to feel any difference?

 

You will get substantial gains... particularly in the midrange.. with the shorties if...... you knew there was an "if" didn't you...

If.. you also remove the stock Y-pipe and cats and replace them with something that actually allows air through.

 

Ski,

Are the shorties more effective on the SBF than they are on the Modular Motors? On the mod motors, everything I've read says that they add very little. This may very well be indicating that the mod motor manifolds flow better than the SBF manifolds.

On my Galaxie, I can't get any long tube headers for a small motor. The left side exit is difficult due to the clutch linkage, BUT I think I could find shorties that I could make fit. If they are considerably effective I would go for that.

In the Desktop Dyno, are shorties the equivalent of HP Manifolds? Would stock manifolds, duals and glass packs be the equivalent of HP Manifolds in Desktop Dyno.

BTW, I made the dual plot thing in Desktop Dyno work just as you described.

Thanks very much for sharing your experience.

 

Ford trucks have always been super quiet from the factory compared to the competition, the whole exhaust system is restrictive.. every single part, and that continues to this day. As stated the shorties will make little to no difference at all on these trucks if the stock cats are retained, but even unequal length shorties are a vast improvement over the logs with a high flow cat behind them.
A friend of mine has put shorties on 4.6 and 5.4 trucks and he reports gains in power and milage on both when the catback is also upgraded and a tuner employed to raise shift points. On the newer trucks you will also find a restriction in the air intake plumbing where it goes into the fender, it reduces down to about 2" from 3" between the TB and MAF meter, again probably done to reduce noise. The Mustangs always got better factory exhaust systems than the tucks so you can't really compare shorty performance on the car.

In DesktopDyno I think you would have to use HP manifolds to get something that would compare to shorties, and even then shorties will work better than the manifold in the real world due to better scavenging. The mustang dyno results I have seen usually show shorties and longtubes producing similar results as long as the plumbing behind them is similar, the shorties make more midrange HP but the longtubes make more low rpm TQ and high rpm HP. Even then the difference is only about 5%.

 

Well if I need to get rid of the y pipe and cats (which I had in the back of my mind), any suggestions what to do with the O2 sensor? It's right in the butt crack of the y pipe.

 

Yeah.. the better headers will have a boss welded into the collector for the O2 sensor, if they don't pick one up and have a muffler shop weld it in.. assuming you don't have your own welder.

 

Thanks for the reply.

Do you think that manifolds, duals and glass packs with no cat(s) would come up similar to HP manifolds in Desktop Dyno?

 

No.. the Ford manifolds are really small compared to the Chev versions and that's what DesktopDyno calculations are based on. If anything actual numbers would be even lower than what DD reports for stock manifolds and dual exhaust.

 

Thanks. I'm not really concerned about the exact numbers. I just want to compare the different combinations and component interaction.

From what you say, there would be even a LARGER gain from stock manifolds to small tube headers.

 

And for that the dyno sims are fine, they are just a calculated guess after all.

Yes. As an example the 5.0 in my truck now makes 280 peak HP with nothing but small tube headers and a cam, dyno info found around the web will also show this is typical for a 5.0 with sufficient cam, intake and exhaust flow... be it carbed or EFI. This exposes just how restrictive the stock truck exhaust really is IMO. DesktopDyno predicted this combo would only make about 250hp, so that shows that the simulation is only as good as the input data. I suspect the head flow numbers I used are a bit low.. I have found several places showing flow numbers for E7 heads and they vary quite a bit.

 

If I'm going to redo the Y pipe and cats anyway should I go with long tubes instead? Will long tubes put the collectors too far back to go back to the passenger side and into one? I need it to go back down to one for the O2 sensor and because I dont have room for exhaust on my driver's side with the transfer case and front driveshaft.

Also, my truck has only one O2 Sensor. So doesn't its new location have to be after the exhaust goes back into one? But still before the cat(s).

 

It's not necessary for the O2 sensor read off of both side for the engine to run well. They may be some slightly off readings, but nothing major provided your engine is in good condition. Also you can route the drivers side exhaust between the tranny and front driveline over the cross member the under the tranny to the passenger side and Y pipe. Check this out, New Exhaust - a set on Flickr, it's some really good pics of pauls exhaust routing:

 

That's right, the EFI system in these trucks treats all injectors the same so as long as you don't have a bad injector the motor will run fine with the O2 sensor seeing only 1 side of the motor. My 5.8 ran for years like this and passed our emissions sniffer tests.

 

wow... thats cool... wonder what size pipe and muffler.. and where he got the colector (Y) pipe from???

 

looking at the pics again... are those long tube headers or shorties?? look like long tube ones.............