[davedino23]

i have a 85 gt ford mustang carb and when i take off she pretty good but once she hits 3000 rpm she takes right off what would cause this? and what is better for power carb or fuel injection? and how would i find out how big the carb is on her also what would be the best carb for her? thanks..

 

[MustangBradley]

With a car as old as yours, the first thing to do is a compression test. If you are weak on one or two cylinders, the best carb in the world won't help.

As for which makes more power, either can be used to achieve obscene levels of power. Since yours is carb already, better to stick with that.

Power was probably item #9 on the list of priorities when your engine was spec'd out. Your cam is pedestrian at best, along with a restrictive intake and exhaust. You can change all of this relatively easy with a fat check book.

There are many articles on-line that describe cam-head-intake-exhaust combinations for the 302. Most of these are designed for hi rpm performance, (nothing sells magazines like huge HP figures) others for the mid range you desire. I'd call a reputable builder and tell them what you want and let them detail the parts you need to achieve it.

 

[davedino23]

the engine is all redone with the new exhust right through her she is now spose to be a 306 so im told when she was done.. i would just like to know why she is slacking when starting off and when she hits the 3000 rpm she starts to go like shes nuts or something i had a 89 mustang a few years ago and she was nuts right from bottom end to top and she was stock.. the 85 i have now with a carb should have more power then the 89 but idk.. i would like her to be like she is at 3000 rpm all the time just cant figure out what is causeing this..

 

[MustangBradley]

What you are experiencing is a phenomenon known as "getting on the cam". This is when all of the stars align, and your motor is at its most efficient at producing power. Engineers and hot-rodders have been chasing the "low end OR high end" problem for a 100 years. Basically, you can't have your cake and eat it too. You can mask this fact with adding power, but it is still a balancing act.

If you want low end grunt, which is best for street driving, you need an intake with long runners. This promotes a bulge in the torque curve low in the rev range. The side effect of this is once you pass about 5000 rpms, you can't flow enough air to make big power, so your hi rpm performance suffers. Picture running down to the mailbox, then trying to breathe through a straw. You can't get enough air.

On the flip side, if you use short runners, these flow a lot of air, and make great hi rpm power, but they trade that low end grunt for this ability to just run off and leave everyone once they pass 3000 rpms.

My examples are trite and leave out many of the finer points, but they work in a nutshell.

You mention the 89 (which I had as well. I miss that car!) which had the long intake runners. If you recall, the stock motor had 300 fl/lbs of torque while only putting out 225 hp. That motor was tuned for torque, which gave it ability to just GO from a standstill.

You can compensate for a weak low end by putting in some steeper rear gears, but you end up paying for that each time you fill your tank.

I recently read an article about a turbo kit for the 5.0 series of engines. They used a stock 5.0 with those long runners. They were able to get 520 ftlbs of torque at just 3500 rpms. This is PRIME street torque. At 2500 rpms, they still had 473 ftlbs, so this curve is more flat than curve. They went on to a boost level of 15 psi and got 631 ftlbs but this is way beyond the stock blocks limits.

Do some research on different cam profiles along with intakes, and look for the combinations that start their main power production at 1500 rpms instead of 3000.

 

[davedino23]

thank`s alot your a big help idk i prob stick with what`s in her its not a big deal if she don`t take it till she hits 3000 rpm. i was meaning to ask aswell you would`nt know where to get a cowl hood would you i just got a strut tower brace and it don`t fit it sits right on top of the fliter on the carb and the hood won`t close would a cowl hood slove this for me or? thank`s again..

 

[MustangBradley]

Is your brace built for your year car? If it is, and it hits, you probably installed it wrong. I remember back in the day, installing one on my 1989 and it came real close to the hood, but it cleared.

If you don't need the big hood, why spend the money?