88īTransAM

Hello.

I can get two cylinderheads from a 305 tpi engine. Are they good for more power for my 305 ci L03 TBI-engine ??

Thanks.

Fast355

iTrader: (2)

Stock for stock they are not. I know of one car in particular that slowed down in the 1/4 mile going from stock swirl ports to stock TPI heads, with no other changes.

88īTransAM

No, sorry, I didnīt say it. I donīt want to change only the heads. In winter, I want to build in:

- 264 duration intake, exhaust camshaft
- the chip for this cam
- Edelbrock 3704 intake manifold
- z28 valve springs
- edelbrock timing chain

At the moment, I have:

- headers
- empty catalysator
- 2,5" pipe
- Flowmaster muffler 80s series

Now, I readed, that the TBI-heads are very bad and now, I can get TPI-heads. Iīm not sure. Should I buy this parts ???

Thanks from germany.

Fast355

iTrader: (2)

TBI heads are not all that bad. It really depends on what you are wanting to do with them. I know that Dewey316s ported 081s (TPI heads) did not make signifigant power on the 187 swirl ports until 4,500 rpm. I also know tht the 187 swirl ports made MORE torque than the 081s did up to 4,200 rpm, despite running very lean at lower RPMs. Ported the swirl ports would have out-torqued and made more hp than the ported TPI heads. In essence Dewey316 gave up 10-15 ft/lbs of torque from idle-4,200 rpm to gain 10-20 HP from 4,500-5,500. To me that trade-off is not acceptable for a daily driver. Low-midrange torque makes the car responsive, quick, and makes for better fuel economy. Ported swirl ports will out-power TPI heads to around 5,000 rpm.

I don't know what kind of smog laws you have there in Germany, but I would be looking for either the latest ZZ4 aluminum corvette head or the 059 casting 305 vortec head. The ZZ4 head would probably be the best for what you want to do. The 305 vortecs will require a vortec specific intake manifold.

91RS5spd

how about this then, Im wanting to put in a LT4 hot cam, will I need to ditch the swirl port heads of my TBI to a at least a 081 TPI head to use this cam? Or can I retain my TBI heads for the LT4 cam?

Kevin91Z

iTrader: (1)

LT4 HOT cam is *WAY* too big for a stock 305 TBI engine. FIrst the lift is too big for the stock heads, second, the TBI cmputer will not be happy at all with it. You need to stick with roller camshafts that are less than 210 degrees duration, less than .460 lift, and 112 or higher LSA. The stock LT1 or stock LT4 camshafts are good ones. Check out the other threads in this forum for how to put a camshaft in a TBI engine.

91RS5spd

Ive been hearing different Kevin from the 305 TPI guys. It's agreed that it's a big cam but not so big that it is removed from the realm of cam choices for us 305ers. Also it's common for 305 owners with this cam to keep there rocker ratio to a 1.5 to keep the lift of the cam down below the .500 mark. I belive the actual lift is like .492 for both the intake and exhaust.

Anyways im sure im not telling you anything you don't already know. so back to the point shall we Im unclear as to if there is a difference between the TBI and TPI heads as to how much cam they can support..... so all I was wanting to know is if the Hotcam could be ran with the TBI heads or if id need to swap to the TPI heads (which id evenutally do anyways)

Kevin91Z

iTrader: (1)

LT4 HOT cam will not work on any thirdgen engine, carb, TBI, or TPI without adjusting the fuel and the spark. For TBI/TPI, that means a custom chip. For the stock TBI computer, its a little more difficult to tune unless you swap to one of the better TBI computers out there. I'm not saying its a bad cam for a 305, I'm just saying its not a good cam for a 305 TBI.

BMmonteSS

You really can't run much more than .460 lift on any stock chevy head either. You'll have to cut down the guides at the least and install screw in studs if you don't want any problems.

On top of that the hot cam would probably be pushing around a 6200 rpm at peak power. You'll need to shift at 6500 plus to get the full potential out of it. Running a stock SB at 6500 opens up a whole bunch of issues, like rod strength, valve float, and the factory balance not being all that great.

Like Kevin said, Big cams are doable on the stock ECM, but it's much easier to tune on the new PCM's or the EBL.

Thanks for the informative non-biased post Kevin.