My 427W on the dyno yesterday. Best way to de-tune this sucker?

[CptMorgan]

I have a nice-to-have problem.

My engine builder called yesterday. The 427 Windsor (Dart) they have built for me is making significantly more power than expected in early testing: 550hp @5800 RPM.

I don't have the specifics, nor am I an engine expert. I know we purposely picked a milder cam to calm the motor down and make it more drivable. Even with a 750 carb, it seems to be pulling well north of 500hp, past 6100 RPM.

I love the idea of a 427 monster under the hood of my new build, but I'd like to reduce the power a bit more.

Is there a smart way to reduce the (carb) throttle? Can I adjust the cable so the pedal hits the floor shy of wide open throttle? Other suggestions?


198273

[JohnK]

Not trying to be a smart-***, but what about just not stepping on the pedal all the way?

[Bill Elliott]

I am at 560hp and know that I will hardly ever get to experience , or put to the pavement, all those ponies. Just get used to feathering that throttle , you'll be fine.

[Jeff Kleiner]

Like John, not trying to be a wise a$$ but best thing to do is train your right foot and keep it connected to your brain. You can get into all kinds of trouble even with a 225 horsepower 302 if you forget that the pedal goes both ways---up and down ;)

Jeff

[Alec]

I was worried about this too during my build. I have a mk4 with a 427w that makes ~540hp and 525 lb-ft. We set ours up with a edelbrock EFI, and a mechanical linkage. The power comes only with significant depression of the pedal, which is to say, it does not feel touchy at all, and you can't accidently give it the beans. Now with 1500 miles on the finished car, I do not regret this motor in the slightest. It doesn't feel scary to drive. very very fun, yes, but not scary unless you are really irresponsible. Rule number one is to never utter the words 'watch this' when you are driving.

[toadster]

assuming the dyno doesn't have the side pipes installed, if you're going with a setup like Gas'N touring pipes, it will drop you 40-50HP

the headers you're going to use may make a difference as well

[Its Bruce]

What tires are you planning to use?

[Hoooper]

carb restrictor plate. You can even get an adjustable one

[J R Jones]

CptM, You brought her, you dance with her. Restraint is an acquired taste.
RWHP with the aforementioned exhaust system will net a lower, more relevant number.
jim

[Railroad]

You can change the ratio of pedal movement to the throttle opening rate. Not impossible with a cable, but probably much easier with a mechanical linkage. Note, your pedal will have a lot longer travel from idle to WOT, but the progression of the throttle will be easier to control.
You will get used to the normal throttle opening rate, just takes a little time.

[Jim1855]

My 427W was similar with a Vic Jr & 780 DP carb. 540 +/- at the crank, 440 at the wheels, Mustang Dyno. Had a mechanical throttle linkage system similar to Forte's that could be adjusted for pedal throw v. carb response. The more pedal throw the more modulation you have.

Easy to drive but had a split personality depending on how far and fast you pushed the gas pedal.

Don't mess with it. Drive it, learn it, love it. Trust me, you will.

Now the "Tim Taylor" in me says go for more, I'm planning too. But then I'm old and my sanity and common sense are failing.

Jim

[Fman]

I have a Dart 427 with similar power, have over 6k miles on the car now... it's easy to drive and only will be a problem if your right foot decides to make it one. You will learn throttle control the more you drive it. This is what you sign up for when you drop a 500+ HP engine in one of these cars. Personally I would leave it and just learn how to control the power, you might be surprised and like it!;)

[rich grsc]

Changing the peddle or throttle doesn't change the output. The simplest, and surest way is to pull some timing. Once installed you won't have the same HP, engines dyno doesn't have the water pump, alternator or power steering hooked up, all will pull more HP than you think

[Erik W. Treves]

As others have said - step on the gas like you are stepping on an egg... a couple things you can do is back off the timing a bit, but let me give you a little bit of a perspective, the HP isn't what will ultimately get you in trouble it's the Torque.. my bet is that you are going be north of 400 FT/LBS at 3500 RPM... this will cause the tires to likely start to go up in smoke.... You can gear down the rear gear- something in the 3:08 range and that will settle things down a bit - ultimately it is the a matter of grey matter connected to right foot... smooth application of the throttle....and short shift.... get some seat time... lots of seat time.... The throttle pedal design that comes with the kit isn't great and there are better solutions out there that give you more "feel" of the throttle.... I would highly recommended this upgrade.

https://breezeautomotive.com/shop/70810-gas-pedal-kit-breeze-ezemount-dogleg-with-wilwood-style-pedal-pad/

[GoDadGo]

When I learned how to drive and deal with my car I just kept bumping up the rev limiter by 500 RPM every two-three weeks.
Also, don't mash the gas, press into the throttle as you go from gear to gear.
You'll be fine and wonder what ever concerned you.

Good Luck From The Dark Dart Side!

[CptMorgan]

Haha. I love the comments!

OKAY! Point taken. I'll live with it. Not a lot of sympathy for too much power in this group ;)

I'm old, wise, and experienced enough to control my right foot, at least most of the time.

I'm running the 15" Cooper Cobra Radials (235/295). They sure look cool for a car that will be period correct (ish), but I can't imagine they will hook up all that well. At some point, I'll get some stickier wheels and tires for running around the track days.

Yes, the side pipes, power steering, alternator, and water pump will drop some power. That is a really good point. I will need that 550hp to overcome those losses.

I know I'm going to love this little motor.

-Morgan

[GoDadGo]

Morgan,

You're Going To Love It!

Steve

[Pat Landymore]

There is another approach you can take to soften the throttle response…go to a spreadbore carb.

There are lots of good both factory and aftermarket options…and honestly…don’t overlook the good ol Quadrajet. The primaries are tiny, secondaries huge. The bigger ones (Cadillac?) were rated at 800 cfm. The tiny 1.375” primary throttle plates will tame the most extreme engine and the huge 2.25” secondaries will let her breathe when you want it.

I know I’m suggesting a highly unconventional choice!

That said I’ve had two that worked great: a 462 cid big block Chevy swapped 2nd gen Firebird and 1985 Foxbody 5.0 Mustang with a 150 NOS shot. In both cases, no regrets on my part and awesome fuel economy too.



Just a thought FWIW……

Cheers,
Pat

[FLPBFoot]

All good advice and one item I've not seen mentioned is air cleaner. As was mentioned, several front drive parts are not on the motor during dyno and most likely only a velocity stack was used on the carb. If you are using the large oval Cobra cleaner it restricts air like crazy. With it's standard filter it will only flow 525 cfm. My 427 with that filter only put out 380 hp at the wheels on the cars first run. Was WAY TOO rich too. Went down 6 jets sizes and to a K&N round with filter top and we ended up with a 50 hp increase to 410 hp at the wheels.

[CraigS]

Although I would love to have to live w/ >500hp, I will throw in another option. When I went from a 351W w/ a 650 carb to a 408W I found that I could buy just the main body for the carb to convert to a 750. It was about 40% price of a new carb. Perhaps you carb could be downgraded. OTOH, that might hurt just the top end HP but not affect low to mid range TQ so not help much. Railroad has the best idea, a nice smooth, longer travel linkage.

[Jeff Kleiner]

...I'm running the 15" Cooper Cobra Radials (235/295)... I can't imagine they will hook up all that well....



I've built 3 relatively low power (225-325) cars for customers using those and you are correct! ;) :D

Jeff

[Alan_C]

Easiest way to go is to add a gas pedal stop. If you can't go full wide open throttle you are golden. Make one that is adjustable, so that as you get comfortable with the car, you can dial out some of the stop. When you get to a power level you are comfortable with, leave it alone until you want more go power.

[Jetfuel]

There you go
Alan C got the answer

Jet

[ggunter]

You need a return spring on your right foot.

[StangRacer]

Moroso makes an adjustable throttle stop for Holley 4150 carbs... Part# 65042. I used one on my CMC Mustang as we were limited to a certain RWHP and torque... it worked great.

[boat737]

351W/427 Dart, Holly 750 carb, 520hp, 530 ft/lb torque. Pretty sure I've not gotten past 1/2 throttle. The few times I've tried, car got loose, I got scared. So the secondaries haven't been used, at least not much. In summary, the car is WAY more car than I am driver. I'm OK with that.

One more point. I don't think it's so much the horse power, but the torque. The amount of torque this engine has is unreal. Even small, but quick, throttle inputs will quickly get the car loose. As shooters say, slow is smooth, smooth is fast. And Clint says, "a man's got to know his limitations." I'm learning.

All that said, since I was building an old school car, I wanted an old school engine, and I wanted to have that "427" badge on the fender to mean what it says. If I were to build another, I would do it the same way again.

[Alan_C]

I've built 3 relatively low power (225-325) cars for customers using those and you are correct! ;) :D

Jeff

Yes sir, not sure if the intro in the MK4 assembly manual still says about 300 HP is the sweet spot, none the less I agree with it. I did a donor build using a 2004 Mach 1 as my donor, it was only 7 years old at the time. Everything that I could use from the donor was used except the radiator which was toast courtesy of the prior owner.
The second owner of the car had it dyno'd, produced 299 HP and 320 TQ at the rear wheels. This was the 4.6L DOHC engine that was the predecessor to the Coyote. All aluminum block and heads plus dual OHC. Redlined at 7200 rpm and would get there in a hurry in the lower gears. It was a fun but not too intimidating ride. The second owner is preparing to to swap in a 1st Gen Coyote with some upgrades that will product 2nd Gen Coyote performance, maybe better.
Today, I would suggest the sweet spot is a Coyote with about 400 rear wheel HP and TQ. More is really unnecessary and tough to hook up anyway.

[Ted G]

Keep what you got! I'm similar with my 427w and love it!!!

[RRussellTx]

the HP isn't what will ultimately get you in trouble it's the Torque.. my bet is that you are going be north of 400 FT/LBS at 3500 RPM... this will cause the tires to likely start to go up in smoke.... You can gear down the rear gear- something in the 3:08 range and that will settle things down a bit /[/url]

X2 on this.
I have a 427W with the 3.31 IRS and I wish I had more torque at lower RPM's.
My tuner built a spreadsheet showing me the difference the rear gear makes with different ratios and the difference in wheel torque is not trivial.

[Ford & Jeep Fan]

Put some Slack in the throttle cable. that way when you shove pedal fully to firewall its only about 70% throttle opening.

[GoDadGo]

Since I was building an old school car, I wanted an old school engine, and I wanted to have that "427" badge on the fender to mean what it says. If I were to build another, I would do it the same way again.

Boat737's comment hit the spot for me.

You can always run a smaller carb, take timing out, put in a throttle stop, install a rev-limiter, add a restrictor plate, etc, etc, etc.

Can you make too much power, of course you can but not having enough would really stink.

I tried to split the difference between the power of the 427 and the finesse of the 289 cars but like Boat737 I wanted my fender badges to mean something and they do so my 383 emblems represents what is truly under the hood.

Though my engine has made 505 HP at 6,500 RPM, I've got the rev limiter set 500 RPM below that peak rating so it only puts out 465-HP (6,000 RPM) and 465-TQ (5,200 RPM) and it works just fine. In addition, I played around with timing and rev-limiter until I found the sweet spot for me and my abilities.

I know you'll find what you are looking for with a little tuning or de-tuning, but in the interim just be careful:

Here's A Short Ride In The Redbone Roadster:
https://youtu.be/GpqvBPwIbzI


Good Luck!

[MB750]

I'm not sure you've made your mind up yet, but perhaps tweaking the secondaries on the carb to not open as much, or not at all, will mute the performance a bit. I've got an Edelbrock AVS2 and it looks pretty easy to tune the secondaries to come on as easy or hard as I want.

[J R Jones]

As power and performance increases, (street) utilization is inversely proportional.
The more you have the less you can use it.
With professional and consumer experience in motorcycles I am very wary of the hazards of road driving. I did road race and acquired experience approaching and exceeding 10/10ths.
In either street or track, situational awareness leads to confidence and avoidance of dangerous circumstance. I am not upset when that shi+ happens.
It is the unforeseen that upsets me requiring emergency countermeasures; muscle memory helps.
When the weather, road conditions and other drivers are not hazardous, modulating a volatile vehicle can be routine. When something goes wrong (like gravel, sand or wet spot) you will be tested.
jim

[CNIdog]

Only driveablity issue my neighbor had with a similar power capacity, was easy to fix. He added a small extension at the carb end of the throttle linkage lever, making it a little longer. The extra length ensured a smooth transition through the gas pedal movement. Initially the gas pedal put too much throttle movement early in the initial pedal travel which made it very jerky off the line and when shifting. I'll see if he can put a pic in here.

[Busamike]

A very wise man once said, "Theres no such thing as too much horsepower, just too little traction".

[Avalanche325]

Like everyone says, use the throttle carefully. On AND lifting off. Don't hit the gas coming around a corner. Point and shoot.

I deleted a whole paragraph. Instead, I'll just say PLEASE put better tires on your car.

I always recommend autocross before you do track days. Lower speed, no walls to hit (usually), and you actually get to drive harder. At autocross, you will slide, spin out, lock the brakes, and generally go past the limit. You will have a BLAST doing it and learn a lot. Those are things you don't really want to do on a track with walls and other cars.

After a few track days, you will be wishing you had 600hp.

[GTM_Vet]

That on a engine dyno? If so that's flywheel HP which will decrease once you get it mated to the rest of the drive train. Right?