The motor is as follows:

EFI 300
204/214 @.050 cam
bowl and port work done on exhaust side, very minor bowl work on intake (dremel)
walker downpipe, 2.5" exhaust
19lb/hr injectors with adjustable reg


The truck- 1995 F-150 4x4
M5OD, 4.11 LSD rear, 4.09 aussie locked D44 front
33x10.5x15 BFG M/T 95% tread left
Long bed, reg cab


Graph is at the wheels on a roller dyno, on a rainy day.

A/F ratio on bottom. No chip or computer tuning. Speed Density system.






Anyone think headers will help?

SS, are your dyno results at the wheels?

 

Wow! I am a little surprised by those numbers. Mine are also at the wheels. You are running tires that are lots larger than mine, and a 4.10 gear is not as efficient as a 3.08, but I still would have expected better. You exhaust might be a little bit restrictive, but I doubt it is hurting you that much. My exhaust is designed to handle about 300 hp, which I will probably never get to. You might check your timing and make sure the throttle is opening all the way with the pedal on the floor.

 

thats what i said also SS, i know peak numbers arent mueaning much but the whole graph looks lacking...i dunno, i told him it looks low for what he did.

SS, do larger tires effect dyno numbers? and why are 4:10s less efficent than 3:08s?

 

What modifications did you have done to yours at the time of the 1.7 rocker dyno? Just headers, exhaust and rockers?

If you use 17% drivetrain loss, it comes out to about a 20ft-lb gain in peak torque, and a broader torque curve on the graph.

My head work was 90% focused on the exhaust side. All i did to the intakes was widen the bowls to the width of the valve seat and smooth any sharp edges. The exhaust ports needed a lot of work though.

I'm wishing i had stock size tires to put on there... What do you think it's good for, 5hp?

I'm sure if i turn up the fuel pressure a bit and get rid of that slight lean bump at around 2000rpm, i could get another 3-5ft-lbs.

I really doubt it, but a timing issue may be due to the ticking of the rockers, due to miscombobulated knock sensor readings. I don't know if the frequency would be similiar or not.

The truck feels to pull much harder than stock. It will actually suck you into the seat a bit in third gear now. Of course my mind was bias, so i took 3 friends for rides individually. They all started laughing hysterically because my truck has always been such a slow POS, and it was pulling them into the seat a bit. I'm not saying the truck is a rocket ship, its still a slow crappy pickup truck, but the increase in towing power and especially passing power is very noticable.

It would have been nice to do a dyno pull with the stock motor on the same dyno, but I did this pull in Rhode Island where i go to school. The only place close to me at my home in Connecticut charges $125/hour, 1 hour minimum. No thanks.

 

Larger, heavier tires do reduce the dyno numbers at the wheels. How much is a good question. The wheels and tires are the heaviest things between the flywheel and dyno rollers. They are also the largest diameter. Those two things combine to give them the largest moment of inertia by a very wide margin. I don't remember what my wheels and tires weigh, but I think they are around 45 lbs each. Those 33's are probably 60 lbs each and are a larger diameter. At least they turn at a slower speed than everything from the pinion gear forward. 4.10 are less efficient because the difference between the number of teeth on the gears is greater than on a 3.08. That makes it more difficult to cut the angles and curves on the gears such that they interact perfectly. They also have higher contact forces which increases friction between the gears even though they theoretically do not actually slide across each other. On the dyno the interaction of the gear ratio and tire inertia can be seen. This is probably where it's going to get wierd. I haven't tested any of this on my truck, but I have done it on a customers car several years ago so I'll use that car as an example. It was a 2000 Trans Am WS-6. It came stock with 3.42 gears and 17x9 wheels wrapped with 275-40-17 tires. It put down about 320 rwhp and about 340 rwtq through a 6 speed manual before chaning gears or tires. I swapped in a set of 4.10 gears (a 20% change) and the car gained about 1% more power and torque. I know that a minute ago I said 4.10's were less efficient, and they are. Here's why power was gained with 4.10's: The lower gear makes it easier for the engine to overcome the largest rotating mass in the car (the wheels/tires). After doing the gears we installed larger wheels and tires. The wheels and tires were basically copies of the 17x9's, but were 17x11 and wore 315-35-17 tires. That is an increase in tire width of roughly 20% which increases the moment of inertia by a corresponding amount. With these wheels and tires the power dropped by about 1.5%. That .5% is the difference that the less efficient gear cut had on power output. If you've been keeping score at home you know that we are talking about less than 5 hp total from most efficient combination to least efficient. That really isn't significant, but it is something. .5% on 140 hp is .7 hp. Not enough to worry about. I would guess the loss would be slightly higher between a 3.08 and a 4.10 than it was in this case of 3.42 vs 4.10, but still not that big a deal. The wheels and tires on this truck are another matter because they are much larger than what they are being compared against.

When I did the rocker swap I had already done the headers/exhaust, MSD, 19lb injectors, and AFPR. The last three didn't seem to do much if anything.

The amount of power consumed by the drivetrain is debatable. For a manual trans people think anywhere between 10 and 20%, for an auto 15-25%; it just depends on who you ask. On a 4X4 with stock size tires I think 17% is reasonable. Who knows how much the larger tires will hurt. If you can weigh them I could do a calculation and tell you how much they would theoretically change it, but it would only be a rough estimate. Just to take a guess I would say that 5hp is on the low side of what the tires are costing you.

I wouldn't worry too much about you air/fuel ratio. Yes, it's a bit lean, but it isn't showing much of anything on the power chart. The most it will do is take that little dip out of it. For most of the run you are right around 12.5-13:1 which is pretty good. At 2000 rpm the ratio isn't killing you.

I don't think the rockers are causing you a problem with timing. I noticed on my truck that it quit making power once I got it past about 14 degrees. At 18 degrees it was costing me 10 hp on the top end. I usually run it at 12.

One interesting thing I see in your chart is that the power peaks at 3500 rpm. Mine peaks at about 3100 where the chart shows that it is starving for more air. That means your setup is balanced pretty well. I really wouldn't worry about it if you can feel the difference. Another of my customers roadraced a 73 Vette with a stout SBC in it. We figured it made about 500 hp and he was about to get 12.20's out of it at the drag strip on the roadrace rubber. On the dyno it showed something like 250 hp at the wheels. He was physically ill. If we raced dynos he would have had problems, but we don't. I found 17 rwhp for him in his carb and distributor that day, but he was still disappointed in the numbers. It doesn't matter what the dyno numbers are as long as you see a gain from what you had previously. That Vette could spin the tires the length of every straight but one on our track, so the fact that the dyno didn't give him good numbers didn't matter.

 

I understand what you mean by not worrying about the numbers. The power difference is awesome from stock, and i am very pleased with it, regardless of what the dyno says. I guess it would be easy to get hooked on the dyno though, even after trying just once. I could see myself experimenting again with dyno, going beyond a social stage, into a physical dependency and eventually being a craven lunatic junky, abandoning all my friends and selling all my belongings just to get some more dyno.

I guess the dyno is more of a tuning aid than it is an ultimate measuring device. It shows my torque curve, which i am pleased with. The work i did seems to have caused the drastic loss of torque to turn to a much slower decline. If you look at dynos of stock 300s, they do well down low, then it looks as if someone threw a brick straight into it's face.

Thanks for the long and thoughtful reply SS. I have to go, my neck itches real bad and my eyes are all bloodshot.

Do you guys know where i can score some dyno around here?

 

I think tires are hurting you on that.

I dont think headers will help you. Headers are for WOT enviroments, not driving around town. Your economy would suffer as well.

 

a few of my friends have tried the dyno and they said it wasnt that bad, but im worrid ill get hooked. should i try it?

opus, the header on a 300 seems to really compliment the already good torque curve while adding a generous boost in overall torque from idle to redline...look at SilverStreaks dyno for proof.

 

Thinking a little more about it. I am assuming they arent big tubes like in a V8. So long as it continues to keep good back pressure, it just might be a good thing. But then you need to decide if the money you are investing in headers, manifold, and new carb, are going to be worth it.

 

the headers will better scavenge the cylinder regardless of throttle position. The exhaust is not regulated or metered.

headers will improve low end but i'm not sure if its worth the longevity issue. I dont like rusty old tubes hanging off the motor.

 

ppsssttt ceramic coating ;-)

 

That is 100% false. The only reason better exhaust components hurt fuel economy is because people want to hear what they spent their money on and can't keep their foot out of it. Anything you do to make the engine a more efficient air pump will help your mileage as long as the rpm range is not changed a ton. Even then the mileage typically doesn't start to suffer until you add a cam with a bunch of overlap.

Is this national backpressure awareness week or what? Good backpressure means zero backpressure.

I have serious doubts about it being possible to install a header tube that's too big on a 300. Most engines with 50 cubic inch cylinders love 1.75-1.875 inch tubes minimum. It would be pretty tough to get a tube that big stuffed into the 300's architecture. The tubes available for the 300 are all very small considering the size of the cylinders.

You guys should all be jealous of me, dyno time is $45 for 3 pulls here.

My heades have been on for 7 years in a month or two and I haven't had any problems with them. I wish I had coated them before I put them on. They would look nicer and the intake manifold would probably run a bit cooler as well. My next set will definitely be coated.

 

Looks like we'll have to agree to disagree then.

 

Alright i am jelous, and i hate you.

Its 75 for me. And thats the GOOD price.

Headers have interested me, maybe my recent turn off from them is due to the fact that i have no money and my financial future is looking grim.

I will continue to slowly modify and post results for the forums though. I think maybe i'll make a webpage or something to detail the modifications and the results. It would probably be very useful.

 

rhetor

P.M. me, lets discuss what you can or can not afford for a Header or otherwise.
I've some things I need to get rid of.