Hey guys, hoping you can help me. I am looking for the torque/HP graphs for the speed density FI 5.8L. Been looking around the internet, and cant seem to find the graphs, just what people "Think" the engine makes. If you have some exact numbers for me that would be alot of help also, please just make sure you can site sources, im kinda tired of getting the "dunno where i heard it" from people I ask. Thanks for any help!

 

I doubt you'll find any "official" graphs because all stock these motors were a complete waste of graph paper.

 

Conanski, i had you in great steem, you were very knowledgeable and helpfull, but lately your sarcastic comments suck.

 

You picked the wrong topic to complain about sarcasm buddy. What he said was completely true, stock research aint worth the paper its printed on when it comes to these old engines. I fully understand that, and his comment was not out of line at all.
(kinda wished he could have posted some numbers up, but oh well )

 

I guess i understood something else, my apologies then.

 

Make your own graph at home!

Just plot the HP and TQ numbers here:

Engine_Specifications

(if the engine you are talking about is on there...)

Then calculate the torque that corresponds to the HP number, and plot that point.

Calculate the HP that corresponds to the torque number, and plot that.

Rotating Horsepower Calculators - Horsepower, Torque, Speed

So now you have a half-azzed "curve".

You can assume that it doesn't have any torque at 0 rpms, but has something at idle. You can assume it tapers off after the HP peak.

Close as I can get you.

 

If you want to know what the stock engine makes, look at the published spec.s for your
engine/year. They will be about as accurate as anything you could find. Conaski is also
right on in his comment because these engines in stock form leave a lot to be desired.
The camshafts are very mild grinds but the real problem is the extremely restictive
cylinder heads and exhaust system.

 

Believe me I have searched the web for graphs of these truck engines but came up empty handed, I have seen some 3rd party dyno mumbers on occasion.. like that diesel magazine article comparing a 351 to a diesel, but they used a chassis dyno of course so the numbers were even more pathetic. I can post up a dyno simulation of an all stock motor, but like I said there is a lot of blank graph paper on it.

 

If ya wouldnt mind doin that for me, that would be great. Im trying to do better at the local truck pulls, and im starting to play around w/ what rpm I should keep it at.

 

OK here's a simulation of an all stock 5.8EFI, it pretty much matches the popular peak HP and TQ specs found in service manuals at 200hp and 315tq. I believe the stock cam in an '89 is a little different than the F4TE cam, for starters it's a flat tappet with 0.416 lift and 260 duration, but I don't have complete specs on it so I can't accurately model it. In any event the outcome will be the same because we know what the peak numbers are so you can use these curves are a guide.

 

Thanks for the chart man!

Hmmm.... So every pull ive been in Ive kept things pretty close to redline for as long as I could, keeping the tach at around 5k rpms... But looking at this, that does not look like a good idea any more. Think things would perform better if i kept it in the 3000-3500 range?

 

Yep.. but then is your truck absolutely stock right down to the whisper quiet 2" exhaust system? If not then that graph changes.

 

lol i guess not. no whisper quiet exhaust for me, hooker comp LT headers, 2.5" true duals, and single chamber mufflers. Other than that shes still stock...

 

You have uncorked the exhaust and that is good. If you want more you will have to
uncork the cylinder heads and cam. The last to improve will be the intake to have a
very good performing engine.

 

Ive got a new cam, carb, and intake sittin in the storage shed right now. Just got a couple more things to buy and major upgrades will be on their way