I plan on rebiuilding my motor soon, and plan on doing a few perfo mods. ANd i plan on keeping my tpi. Plan on buying an eagle rotating assembly, XFI cam with .510 lift, and 272 duration or so, and an edelbrock performer alum heads. so about 9.2-9.6 compression also headers roller rockers stuff like that. will a stock tpi be able to perform to these standards since in the end it will be putting out anywhere from 350-450 so will a stock tpi be able to hold up with a 52 mm BBK throttle body? Would spending the extra money to get an edelbrock tpi setup be better in the long run?

 

The TPI is highly restrictive. If you don't have the $$$ or know-how to make one flow very well (read the "quest for a better flowing TPI" thread in the sticky area) you are much better off going with something like the Holley Stealth Ram.

 

yea to allow the motor to reach its potential i figured i would definately need to change something

 

You're going to have to do some work to get above 300...

 

Right on advice, it depends on how strong your convictions are
for TPI. Personally, Id find a way to make it happen, like alot of
us here do. Then again, those people invest hordes or time/research
and money to have a balanced intake system that is still torquey
and street legal 100%

If your looking to bolt on instant success, maybe Super, Mini
or Stealthram is up your alley. And, it still keeps it TPI roots.

Also, FIRST injection is factory TPI on steroids.. Check them
out as well. If I had a full bank account.. I know I would!

 

yea i definitely don't have a deep pocket so...

 

The answer has to be based on two things. What will be the operating range of your engine and what do you want it to do.

If you are changing the cam to run over 5000 rpm, first your rear gear needs dropped to 3.55 to 3.73 and then you will need a different (then stock) intake as the TPI is limited above that RPM. That extra power will come at a cost of MPG, it really depends on what you are wanting.

 

plan on 3.23s, and its goona be a street car 99% of the time, with a few runs down the strip thrown in there. cam is goona be around the 1200-5200 range. maybe.

 

Edelbrock Performer heads 60759
CompCam XR258HR-10

This is what I run for a DD. With Flat tops it has 10:1 CR (190 psi) runs fine on 87 octane, 20 mpg highway. Motor is stronger then the 700R4. The stock intake is fine, normal 55 mph is 1700 rpm and it tops in third at 125 mph @ 5000 rpm.

Exhaust is more restrictive then the intake.

 

and you have a stock tpi and throttle body? no mods?

 

Very true. Be mindful of what the operating range of the cam is that you want to swap in. Especially if it is going to be a street car. For street applications something like the xr258hr from comp cams is a good choice, as has been pointed out. It will give you a good low end and mid range punch, plus it pulls hard to 5K with the stock TPI unit. Not to mention fuel economy.
If you want high end full out hp, you may consider a bigger cam and something like the HSR, where at the expense of some low end torque you will gain a lot of top end HP. You will also need higher gears than the 3.23 with that setup and fuel economy will be compromised.

 

y do you need to increase the gears in your rear if raising the cam rpm above 5000. and y does the tire size need to be specified?

 

By increasing the size of the cam, i.e. duration, you are shifting the power band of the engine up. You are gaining upper end hp at the expense of low end torque. Typically for every 10* increase in duration, you are shifting the torque peak of an engine up by about 500rpm. This affects the ability of your car to get off the line, since torque is what gets your wheels to spin. In order to allow the engine to get into its power band quicker and to overcome the loss in low end torque, you need to increase the gear ratios.
Tire size also in essence affects how quickly your engine spools up. Larger tires in the back have a larger diameter, resulting in a larger circumference. This in effect increases the distance a tire travels through a single revolution. The net effect is similar to having a lower gear ratio.

 

ok so technically you dont "have" to do anything like tires and gear ratios, but it is necessary to get all the performance you can out of your motor correct? also will 3.42s be enough? can you get away with 3.23s if its mainly used for street and seldom used for strip?

 

Yes, the TC is a 2000 rpm measured by data log. The only mod is 24# injectors (could use 30#), AFPR set at 50#, and dual exhaust (vettes come with stock tube shorty headers 1.5"). The next mod will be 1.75 shorty header this will raise the torque band 500 rpm or so. Also the tranny was setup by Probuilt, I am very happy with what Dana has done.

The eprom has been changed a bunch and still needs more, it is a MAF ARAP.

The only suggestion I could make is, maybe a higher then 110 LSA would help with tunning. But the idle is smooth and the changes to MAF table 1 to flatten the BLM's was minimal.

Tires are 255/50 16

 

It really depends on how wild you want to go. If you stick with something like the xr258hr12, or even the xr264hr12, which are both good cam choices for TPI cars and are very streetable, 3.23 would be fine. If you start getting into more radical cams, then you will need to upgrade gears, stall in order to be able to drive the car on the street without too much trouble. A lot of power can be gained by putting in better heads, a mild cam, and a good tune with all relevant supporting mods, such as a full exhaust.
The cam should be the last thing that you need to select for your combo, such that it matches the rest of your parts. Considering that you want to keep your car as a street car most of the time, it seems excessive to want to push the motor far past 5K. What is even more relevent than peak power about a streat car, is average power, having a nice and wide power band. Perhaps, you should consider optimizing performance throughout let's say the 1-5k rpm range since this is where you will be most of the time you drive the car. In that case, achieving 450hp may not be necessary and the TPI unit may prove useful. Just some thoughts to consider.

 

well will upgrading the throttle body and porting be ideal for my app? when it comes to come choice i really justwant some thing within the 1000 to 5000 range and have a mean idle

 

to be specifc, if you're going to stay with TPI you'll get much more out of an aftermarket base/runner setup than a throttlebody.

 

the only problem with that is the edelbrock setup is 750 with only intake and runners. I wwas hoping that porting the intake and everything out will be able to support 350-425 well.

 

Power doesn't come cheep if you don't do the work yourself. You can buy the SLP runners and necessary gaskets and do the port work yourself. With a bit of work, patience, and research, you can do the work yourself and not brake the bank. You can also call a machine shop and see how much they would charge to do the porting and port matching. The stock TB will support up to 450 hp. That should be the least of your worries. If you want a cam that works between 1000 to 5000 rpm, think about the comp 08-500-8, which is the xr258hr12, or the comp 08-501-8, xr264hr12 - 1200-5200 rpm. As I had pointed out, both are good TPI cams. You will need better injectors and a good WB tune to make it all work right. A great deal of you power gain will be in you heads. Are you going to get into the bottom end of the motor? What CR ratio are you planning on running? Both of the cams above work fine with stock CRs and give good fuel economy. Idle is more aggressive than stock, a bit choppy, but still relatively smooth and fuel economy if fairly good. I get 23 - 24 mpg on the highway with the comp xr258hr12 in my LB9. With the stock 3.42:1 gear ratios and the stock T5, my revvs are at about 2300 and 70 mph.

 

The same cam with a 305 will have meaner idle then with a 383.

Also that mean idle is harder on your mpg and tuning.

Comp makes the "Mother Thumper" line of cams. They have the idle sound but are really tame, I think they are more for carbs. Gives the muscle car sound but are better mannered then a radical high RPM cam.

 

Which cam are you referring to? The comp xr258hr12 cam I have is in a 305, fully tuned and MPGs are very close to stock, within 0.5 to 1 mpg. It is not a carb cam. In fact, I put 10k miles on the car on the stock computer tune before I had the opportunity to get it tunned, which made a huge difference. Operating range is 1-5k. The comp xr264hr12 is just a little bit bigger. Still plenty of people have used it in 305TPI cars. I just decided to stay on the smaller side. You are correct that in a 350 or a 383 both of these cams will act like smaller cams compared to the 305, because with the increase in displacement comes an increase in the amount of air an engine needs to fill its cylinders. I think that as long as the LSA is kept around 112* tunning with either of these cams is not going to be an issue.

 

im looking for something with a good rough choppy idle. doesnt need to be extreme but i want it to be more on the choppy side then deep sound side. you understand what im looking for? Planned on a 30 over eagle internally balanced rotating assembly for 599, rated up to 500hp. then plan on somekind of 64cc heads(most likely). Any combo suggestions?

 

Call Comp Cams and see what they recommend, that will give you something to compare to.

 

ok, that seems like the best thing to do. thanks