91_5.7_TPI

iTrader: (2)

Were the L05 heads (TBI 5.7) swirl ports stock?

91_5.7_TPI

iTrader: (2)

He claims it is from a 9C1, but I thought those were Caprice and he got his from a blazer....

Fast355

iTrader: (2)

L05s came with Swirl port heads stock. From a Van, Truck, Suburban, 9C1, School Bus, it doesn't matter.

I have however seen a few late 1992 early 1993 trucks/vans/caprices equiped with 083 heads. That would fall in line with the end of the TPI 350.

I have also seen some L03s of the time with 081s on them.

kdrolt

ALL LO5s got them, which means the list above plus 89-93 Caprice, 91-93 Roadmaster, 91-92 Olds Custom Cruiser and 1993 Fleetwood.

I've also heard of the 191 casting, which was also supposed to be swirl port also, but I don't know what applications and years. I think it may have been the 350 swirl port head from before the TBI debut, because I did read a mid 80s C/K truck brochure online that indicated "fast burn heads" as used on a carburated Chevy sbc engine. That ad might have even used the term vortex to denote the swirl.

And consistent with the engine plant trying to use-up the TPI heads (081, 083), the swirl port heads were continued in use into the 1995 model year before the Vortec engines (well, heads) replaced them.

DM91RS

I wonder what changes the bins reflect in the tune from one head to the other from the factory. Have you had a look at any of those using these non swirl heads in the tbi applications?

91_5.7_TPI

iTrader: (2)

Well, this guy says he has the 9C1 L05 in his truck. Claims that a local somebody or another said it made 280 hp stock. And now that he has ported the factory (which he says aren't swirl ports) heads, add a cam with "a little more lift and duration" 65 lbs injectors and a off the shelf Hypertech II chip that he is making 340 hp at the wheels and that he has the dyno sheet to prove it. I am thinking that it was a desktop dyno set up for carbed engine. The thing is, he is a really smart guy, but at the moment, I am thinking dumba**. The vehicle is a 91 4x4 Silverado with a 5 speed with 4.10s and like 30 some inch mud tires.....

kdrolt

Not from the factory.



9C1 LO5 TBI was rated at 190 to 205 fwhp depending on model year, 1989-1993. So his claim is false.

The truck TBI 350s were factory-rated at 200-210 fwhp, and no more than 210 up to 1995.



There is a slim chance, based on what Fast355 said, that the heads are 083 (non SP) and not 193 (SP).... but it's a 91 truck, so it is possible that it got non-swirl heads. Porting swirl or non-swirl can result in flow on-par with stock Vortecs or better if the porter really knows what to do. A cam with a little more lift and duration than the stock truck cam would resemble the Bcar LT1 cam. The Bcar LT1 engine already has heads that are the equal of the iron Vortecs. With a upgraded exhaust, you can get 280 fwhp and approx 225-235 rwhp from the Bcar LT1 ..... IOW not close to 340 at the wheels. Even 245 rwhp wouldn't be close to 340 at the wheels.

The item that ices the B.S. conclusion is the use of the Hypertech II chip.



I don't know if it would over-estimate by nearly 100 rwhp. I doubt it.

I think your thinking is correct.

91_5.7_TPI

iTrader: (2)

He got the engine from a Blazer, then looked up the numbers and started saying it was a Intercepter.
Everytime I mentioned the facts, as in the SPs, he came up with something. The chip able to relearn becuase of the computer. I have the whole IM conversation saved. He started to get pissed when I called him at it, so I let him have it. I told him to run it at the local Dyno Day and at Bristol dragway. I'll get the high points from the convo and post them. Some funny stuff in there.

vorgath

Oh THOSE chips. They're real 'ol school. You plug in your headset, talk into it, and the chip will correct whatever you want.

I believe the Jamaican team was trying to put them in their bobsleigh, however the refs stopped them.

Fast355

iTrader: (2)

Don't make me have to go to Tennessee to BLOW this slow truck off the road with my stock port 187 headed 312. Because this guy is full of

Based on my old 1/8 mile times, DD2000, my Injector/Fuel requirements, I am making about 230 RWHP and 300-320 ft/lbs at the tires. I am running 10.80s @ 63 MPH, with stock 305 swirl ports cut for .550" lift.