89 gt cammed and 1/4 mile got slower

My friend has an 89 gt, i believe the only mods he has made to it are a mass air flow adapter, k&n filter and an f303 cam. prior to the cam upgrade his 1/4 mile time was about 13.7-13.9 now he runs 14.7s! i think he needs to upgrade everything from the cam up as well. he also gets a little knocking at aroung 6,000 where there wasnt before the f303 cam. Please help us make him faster again.

Need heads, intake and headers to make it breath, then you should be good to go.

thanks for the reply.I have a set of gt40's but there bare and i paid a pretty penny for them.hes on a tight budget right now, but well look into gt40's built and an intake. do you think he needs a throtle body also? or will it make any difference? it made a big difference on mine, but i have a v-2 supercharger. Also if we do heads and an intake i think well need more fuel and spark. What do you think?

If you can get the fuel pressure up to say 65lbs, 19lbs injector can flow enough for over 325hp. As for TB, they are pretty cheap, so I would go one size up.

As for GT40 heads, I had them on my S-Trim and they were horrid, but for N/A application they should be fine.

Spark is spark, I really think its over rated. The stock spark on the Stangs are very good:)

Thats good to hear, so we should be able to get this done pretty cheep. On another note thats why i dont have the gt40s on my 95 anymore. i have an s trim v-2 kit i didnt feel like they were performing like they have for me in the past. were going to the track this weekend ill video tape us both racing and try to figure out how to put them on here.

Thats good to hear, so we should be able to get this done pretty cheep. On another note thats why i dont have the gt40s on my 95 anymore. i have an s trim v-2 kit i didnt feel like they were performing like they have for me in the past. were going to the track this weekend ill video tape us both racing and try to figure out how to put them on here.

Cool! I would like to see that:grinyes:

The F-303 is not a radical cam by any means. In fact, it's a good blower and turbo cam.

Something is wrong if your bud slowed down a whole second just from a mild cam upgrade. You all need to check things over and make sure nothing was left unplugged or something. Run the codes and see if that turns anything up.

Also maybe try upping the fuel pressure one or two psi at a time to see if the pinging goes away or car goes faster.

We will definetly try that thanks. I just found out today that his car was factory automatic and he has a 5 speed. He did this swap at the same time as the cam. could the computer be looking for stuff thats not there? So you think adjustable FPR?

As long as he has a computer from an '87-93 Mustang 5.0, the ecu should not be the problem. Even if it is from some other 5.0 HO car, it's probably not an issue. Besides, your friend was cutting pretty good times before the cam swap.

Something else that came to mind are valve springs. The stock springs are fairly soft and should be upgraded with the cam.

It's hard to diagnose a problem over the internet with second-hand information, though.

Thats exactly what i told him! he needs to change the springs. i think were going to try springs tommarrow, and try to get better fuel delievery and see what that does.

wierd that he slowed down so much. especially after switching to a 5 speed. i'd check all the little stuff like fuel filters, air filter, timing, and possibly a clogged cat converter. does he have after market exhaust? If he is throwing codes that would be the ultimate place to start.

He takes his filter off when he runs. recently he put on a mac h pipe w/o cats timing is set to factory. we never get a mil light. Im stumped! im putting new springs in this weekend for him.

was it a really hot day?

yea its been hot everytime we went this year.

that will slow you down a little bit. tranny shifting ok?

He takes his filter off when he runs.

Wait a minute.... Is it a CAI or is the filter right on the air meter? Is the air meter bolted down like stock?

Yea the maf is bolted down like stock. the filter is a seperate unit from the meter.