i am going to put a cam in my 1991 305TPI. i have full access to a shop and air tools so it will only take about a day. i know its not a 350, and its "pointless" but i dont care.

my mods are headers, 3 inch catback, 3.73's, K&N. everything else is stock: automatic 305TPI, stock ECM. im looking for a cam that wont require a retune of the PROM. i would also like to avoid upgrading the injectors, but i will consider it if i have to. im just looking for something that will work with my factory PROM and be driveable. im getting lifters too. This car already makes pretty decent torque, and is quick off the line with the 3.73's. im not a cam expert so im not sure what to go with here.

thanks

 

I'd suggest one about like this...

http://store.summitracing.com/partde...2D08%2D501%2D8

I have no clue why it's shown on Summit as "not computer compatible". Here's the Comp catalog pages that show it. Go down to page 144 (about pg 15 or so of this file) where it's listed in the "computer controlled" section as "best in 305 or 350 Tuned Port Injected engines with no modifications".

http://www.compcams.com/Technical/Cu...ML/128-169.asp

I personally don't think it's "pointless" to put a cam in a 305; rebuilding the short block would be, but a reasonable cam upgrade is certainly worthwhile.

 

now what about lifters...and also do i have to get new rocker arms? summit suggests 3 brands of new rocker arms with that cam, but does not suggest lifters. i may just call comp cams and ask them what lifters i need. how much engine power do u think i could gain with this cam? my car currently makes 205 wheel horse power which isnt too bad for what it is... 86k miles btw

 

You have to be very careful when changing a cam on a 90-92 TPI car. They use a MAP sensor so any time you increase air flow in to the engine you have to re program the chip. 85-89 TPI car use MAF sensor and can compensate for some increase in air flow because it measure the amount of air going in to the engine. I would try to buy a cam and chip combo or check with a chip company and see what cam they recomend for their chip.

 

i know a guy who put a pretty radical cam in his 1991 305 TPI formula, a non-roller too, and it ran fine....stock ECM and everything

 

anyone have more advice?

 

I'll like to see that car running. I bet that if he took the car to the track is going to be slower. Any time you change a cam you have to re-do the computer chip on those 90-92 cars, if you want them to make more power that is. It is just like re-jeting a Carb. The MAP sensor can't read any increase in air flow coming in to the engine because a MAP sensor does not measure air flow it just measure Vaccume so your car is going to run very lean.

 

As long as your stock lifters are in good shape, you can reuse them.

Not necessary, but if you replace them, go with roller tip at least. Comp Magnums are pretty good, Pro Magnums are probably as good as you can get.

 

will i really have to program the PROM? more airflow = less vacuum...correct?

i figure i will replace the lifters just because if i do something to this car, i usually go all out and do it right.

maybe i could get away with an AFPR...increased fuel pressure will allow more fuel to leave the injector, compenstating for the higher performance cam. am i right?

 

well you might want the AFPR later on but it wont really help you out at the moment

 

They ain't cheap. And, there's typically nothing wrong with them if the engine isn't full of no-oil-changes crud. I'm running unknown mileage used LB9 lifters, not a hint of a problem with them in almost 2 years of daily driving and summer racing.

No, you are wrong. Speed density doesn't work that way.

On the other hand, that isn't that big of a step up in cam, so you may get away with doing nothing.

 

then whats the point of an AFPR? how much of an increase in hp would i get with that cam?

 

AFPR is just one piece of the tuning. You can't do all the tuning by changing the timing, either. You've got to get it all working together.

You can find more details on the TPI and DIY PROM forums.

 

well should i get the cam?

 

If you do, you should also get a new timing set, and the valve springs that are recommended for the cam, along with their correct hardware, and tools to set them up correctly. NO aftermarket cam will work like it's supposed to with already worn-out stock springs and chinesium/plastic cam sprocket.

No reason to waste $$$ on the lifters, if they're not bad somehow; which is unlikely. Not the wisest use of your $$$.

 

Just get yourself a used LT1 cam, throw it in with a new timing chain set and and some roller tip rockers. (1.5 ratio)
It won't be perfect but will function fine.
I have done this several times.

 

how do i know what valve springs to get? arent the stock rockers 1.5:1?

 

Stock rockers are 1.5:1. Rarely does much good to go 1.6:1. The "1.52" that Comp quotes is their way of saying their rockers are more accurate than stock stamped steel rockers.

The Comp link Sofa posted has the recommended springs to the right of the cam listing. 986-16 or 987-16.

 

I used the xe258 on my '91 305 tpi.
I didn't re-program the chip.

Without nitrous, I was about 14.1-14.3 in the 1/4

 

You can get a used 1988-89 350 cam (207/213 int/exh duration @.050 and .415/.430 lift) with 1.5 ratio rockers. If you use a set of 1.6 rockers you'll get .445/.460 lift and about 2 more degres of duration at .050. Your total dur. will stay the same. This cam is bigger than yours and will not change your vaccum much, but it will make more power.