488 Rwhp - Stock Short Block.... Too Much?

[oz]

Greetings,
Long story short, I'm having my blown (Paxton 1220 SL) '91 5.0 (w/ 50k miles) dyno tuned and the tuner said that it made 488 rwhp.
From what I've read, that's too much for my stock bottom end.
I can have them pull timing and put a bigger pulley on the blower to reduce it.

That said, what's a safe HP number - assuming the mixture is never lean, etc?

Thanks!

 

[Noobz347]

It's not too much for the block to produce. What I mean is... it's ok for the combo to be able to produce it but NOT ok for you make it produce that kind of power every day. If you treat it nice and don't beat on it, it's perfectly acceptable. If you're a 20 something year old kid that thinks the gas pedal is an on/off switch, then I'd get it detuned.

I don't think that you're in that category so if it were me, and the car runs well... I'd leave it alone and keep in the back of my mind that this motor can eat itself if I go out and rip on it everyday. If you spend a lot of time at the track, I would still detune it.

Might want to consider slowly putting together a Dart block to transplant your internals.

 

[oz]

Nobz,
Thanks for the reply. I was kind of thinking the same thing... and I'm in my 40's so I don't beat on the car much and since it's a convertible without a roll bar, I have never taken it to the track. Not to mention the 16 year old tires on it that are rock hard and broke loose in the first 3 gears with 'only' 300 rwhp.... There is little to no reason to think that until I get tires that I can get that much power to the ground.

 

[Noobz347]

Nobz,
Thanks for the reply. I was kind of thinking the same thing... and I'm in my 40's so I don't beat on the car much and since it's a convertible without a roll bar, I have never taken it to the track. Not to mention the 16 old tires on it that are rock hard and broke loose in the first 3 gears with 'only' 300 rwhp.... There is little to no reason to think that until I get tires that I can get that much power to the ground.

Problem solved then. Your tires are likely the fuse that holding the rest of your drivetrain together. lol

Keep it on the "Whoa" and I think you'll be fine. Might still be a great time to begin planning your next block though. Take your time as $$ permits and do the swap when you're ready.

 

[wht93gtEd]

Problem is when that 16 year old kid next to you is acting like an idiot. And you think to yourself, "ppfffttt. look at that idiot....that's what gives us mustang drivers a bad name....I should smoke his ass" haha

I'm only that 30yr old idiot, but I've thought about it so many times.
Everyone hears the vortech and wants to go; I'm proud to say that I resisted all summer.

 

[oz]

Very true - but until I get new tires, it's a moot point.

I may very well start looking for a short block that can handle 500 hp or so and then build it up with my parts an not have to worry about it anymore.

 

[Noobz347]

Problem is when that 16 year old kid next to you is acting like an idiot. And you think to yourself, "ppfffttt. look at that idiot....that's what gives us mustang drivers a bad name....I should smoke his ass" haha

I'm only that 30yr old idiot, but I've thought about it so many times.
Everyone hears the vortech and wants to go; I'm proud to say that I resisted all summer.

Even in that scenario, I've not come across the 16 year old idiot that couldn't be desimated by smoothly rolling into the throttle. lol

It RARELY requires every ounce of available power to send Mom's honduh back to the garage.

 

[oz]

I was considering making them put the larger pulley (3.33") on the blower in place of the smaller one (2.9"?) that's on it now but they said that as long as I don't race it (don't plan to as it's a convertible) and keep my rev limiter at 5750 or lower, that it should be fine. It's a well known shop so I (almost) trust them...

 

[Noobz347]

I was considering making them put the larger pulley (3.33") on the blower in place of the smaller one (2.9"?) that's on it now but they said that as long as I don't race it (don't plan to as it's a convertible) and keep my rev limiter at 5750 or lower, that it should be fine. It's a well known shop so I (almost) trust them...

Yep... and I agree with them 100%. It's never been about how much power the motor is CAPABLE of making. It's about how much power you make it produce.

 

[oz]

I'm glad you put it that way.... I need to remember that fact. I have the power to keep it from going boom...

I may look at the dyno chart and adjust the rev limiter down such that I can't get to the top of the hp curve...

 

[Noobz347]

I'm glad you put it that way.... I need to remember that fact. I have the power to keep it from going boom...

I may look at the dyno chart and adjust the rev limiter down such that I can't get to the top of the hp curve...

I think your stock rev limiter is fine. Remember that you can hit that rev limiter making next to nothing to in HP. You start revving the whole assembly to 6000-7000 rpm then that's when you run the risk of making the crank walk. So reducing the limiter doesn't really change anything. What's more is that it sounds like your combo is capable of making block splitting power long before it hits peak rpm.

Changing the pulley and reducing the boost would be your best bet if you want a mechanical method of keeping power levels down. Your operation of the throttle is still the best though. It's not too uncommon for folks to split stock block while making a lot less power than what you're making.

I figure your actual crank HP to be around the 560 range. 450-500 crank is the rule of thumb (not a hard fast rule). Crank driven power adders tend to reduce that rule of thumb even more because of the additional stresses on the crank and mains.

Then again... there are dudes out there that have run multiple seasons on an OEM block making over 500 RW down the quarter mile and had everything hold together.

Treatment and the quality of the tune are the biggest factors IMO. Additionally, like you said before... your traction isn't going to allow you generate a ton of cylinder pressure without you going down the road sideways. Your traction will give way long before you reach max potential in the combustion chambers.

 

[oz]

Thanks - I just need to think about it logically.
I guess missing a shift and hitting the rev limiter isn't going to really push it as the engine won't be making any power... and even if I do get new tires, I don't know if there are street tires that I could use that would give me enough traction to get anywhere near max power output.

I feel better now... Thanks again.

 

[JordanB21]

Nobz,
Thanks for the reply. I was kind of thinking the same thing... and I'm in my 40's so I don't beat on the car much and since it's a convertible without a roll bar, I have never taken it to the track. Not to mention the 16 year old tires on it that are rock hard and broke loose in the first 3 gears with 'only' 300 rwhp.... There is little to no reason to think that until I get tires that I can get that much power to the ground.

tires are suppose to be decommissioned after 10 years, how you still have them is a wonder, and how they're not cracked and still able to be driven on is a miracle

 

[Noobz347]

Thanks - I just need to think about it logically.
I guess missing a shift and hitting the rev limiter isn't going to really push it as the engine won't be making any power... and even if I do get new tires, I don't know if there are street tires that I could use that would give me enough traction to get anywhere near max power output.

I feel better now... Thanks again.

Yeppers... the OEM method of limiting rpm is the best option for forced induction IMO (exception: nitrous), because it completely cuts fuel to the cylinders. No BOOM. No backfire.

As far as the tires go... I would hazard to guess that you would encounter other drive-train issues first. That is unless your rear end etc. are already pretty built.

 

[oz]

Regarding the old tires, yea, I know - 10 years... The tires on my '69 were 23 years old when I took them off. I didn't understand why I couldn't get any traction and then I checked the date.... 1988...
I just had to change the tires on my motorhome - they are only supposed to be used for 6 years.... 6 tires at $300 each kind of sucks!

The rear end has a girdle but that's it at this point. I'm planning to reinforce the torque boxes and put braces between the rear end housing and the axle tubes to keep them from flexing. The transmission is stock so I'm thinking that I'm ony one hard clutch dump from turning it to junk.

 

[oz]

Oh yea, just curious - is cutting the fuel the best way to avoid a 'boom' or would cutting ignition be best? I thought the stock system cut off ignition... no?

Either way, my current ignition is the limiting factor as it's set to 5750 - so I'm pretty sure it's ignition that turns off. If it was fuel and not ignition, there would be an instant where the engine would go super lean.

 

[Noobz347]

Oh yea, just curious - is cutting the fuel the best way to avoid a 'boom' or would cutting ignition be best? I thought the stock system cut off ignition... no?

Either way, my current ignition is the limiting factor as it's set to 5750 - so I'm pretty sure it's ignition that turns off. If it was fuel and not ignition, there would be an instant where the engine would go super lean.

If you only have one rev limiter then cutting fuel (not reducing it) is arguably, the way to go. Like I mentioned above, the exception would be a nitrous system and particularly a wet nitrous system.

Limiting RPM with ignition needs to be done correctly (a 2 stage limiter for example). Doing it wrong can and has caused backfiring thorugh the intake tract.

Just plain ole cutting the fuel to every other cylinder on the other hand... It's like hitting an rpm wall. Those cylinders have no fuel and can't ignite.

It's really a question with no short answer and could be debated and made into a REALLY long thread. The only short answer I have for you is that for a combination like yours (and mine for that matter), the OEM fuel cut-off rev limiter is the best/simplest method of ensuring the safety of the motor. If you ever add silly gas... the equation changes dramatically.

 

[oz]

I think I'm going to try to avoid hitting the rev limiter so I don't have to find out exactly how it shuts down the engine and what the effects are.

Thanks!

 

[wht93gtEd]

Very true - but until I get new tires, it's a moot point.

I may very well start looking for a short block that can handle 500 hp or so and then build it up with my parts an not have to worry about it anymore.

Yeah, I'm pushing 11-12lbs of boost, but I still have tiny 245's and since I'm not racing at the track I dont need to worry about tires cutting loose shifting.

Even in that scenario, I've not come across the 16 year old idiot that couldn't be desimated by smoothly rolling into the throttle. lol

It RARELY requires every ounce of available power to send Mom's honduh back to the garage.

True; same here. Or they run away crying when I roll into the throttle and a little "tap" sends the tires spinning into oblivion.