bsherrin01

i have an 85 Z28 with a tpi 305. im going to put a 350 in the car but am trying to figure out if i should stick with the tpi or go with a carb. an engine builder said that i could only run certain types of cams for the tpi and that the cam couldnt be to big. is this true? i do want to run a cam in the car that will give it a pretty big lope. any help would be great. thanks.

Apeiron

Too big of a cam won't have enough vacuum at idle to keep the computer happy.

What are your intentions for the car, aside from having a lopey idle?

bsherrin01

its basically gonna be a street rod. something to drive and if someone wants to run then well go. i love the sound of the big lope. im probably going to try to get 350 horses out of it.

TA

iTrader: (1)

You can run pretty large lift cams in TPI cars especially if you go to a roller type, but you need to keep the duration moderate and the lobe centers tight to keep reversion to a minimum, or tuning is almost impossible. This also decreases the lope effect.

It's easier to pass emissions tests with the TPI, and you'll get better mileage. However, a carb will allow a lopey cam, and especially compared to a stockish TPI system, a decent sized carb will give you more power.

Good luck

TA

3rdgenZ

iTrader: (1)

one other thing you might need to know is that the 85 computer is different than the 86. so it limits your oppitions on tuning. not many people burn the chips for the 85. i made the swap and kept the tpi. its fun, but due to more technical difficalties than iam welling to deal withe. iam swaping to carb. the problem with tpi is that it cost so much for any after-market parts. ive put over 1k into keeping the tpi. but i just keep running into problems.
id love to keep it but it just doesnt make sence to keep it for me.

327_TPI_77_Maro

iTrader: (8)

You can easily upgrade the 85 to the '165 ECU. You can run a huge cam w/ TPI as long as you can tune it. Chip burning does not cost much to get into. If it is a street car, EFI is well worth the effort. They don't make carbed cars anymore for a reason. I run a 0.503/0.510" 224/230 roller cam with a '165 MAF tpi based system and it is cake to tune. I have run 108 LSA nasty idling flat tappet cams w/ TPI too. They are trickier to tune, but not anything that is out of the realm of the average computer user/car guy with a little time to play with. The MAF system is very forgiving. You can run a pretty nasty cam w/ MAF without having to tune much. SD is a whole 'nothing story, which is why I have never gotten into it.

lonman89

if you can keep the tpi i would,i wish i still could of used my tpi setup but when i bought my car the motor was so f'd i couldnt fix it so i swapped in a 350 thats carb'd,its true you can make sum killer power from a carb'd setup than fuel injection but its gonna empty the wallet quicker makin so many trips to the gas staion

85irocz355tpi

I have an 85 irocz that came with the tpi 305. I have since put in a mild 355 with a nice cam. My cam specs are 214 degrees of duration on int. 224 on exh. .470 lift int. with 1.5 rockers. .490 lift exh. The only thing I have done to the tpi and computer is put a hypertech thermomaster chip and took the screens out of the maf. It makes about 300 horse with the 305 injectors, stock tpi, and stock 305 tpi heads. Mild work has been done to the heads though. 85 is the only year for that particular computer, but the corvette used the same computer and you can swap proms. I have put almost 20,000 miles on this setup and have had no troubles. I get around 20mpg's, and it runs mid to high 13's. I say keep the tpi. If not send it to me I love them.