Hello... I looked at some of the old threads and found only Jibberish! Are there any concrete numbers for TPI with Swirl Port Heads? Not Vortec heads...

Some Dyno Numbers would be useful. Quarter Mile Times maybe?

I'm Finally mating my Aftermarket TPI Intake Setup with some Swirl Port Heads. The Engine was pulled from a 91 Silverado 1500. Removed the old TBI setup. The Snags...

1. Oil Pressure Sensor: The brass elbow that connects to the block on the TBI setup was too tall for the TPI Base. I'm assuming TPI uses a shorter elbow. Should I use some sealant on this elbow? Teflon? (I was able to have the nice guys at NAPA find me something I could use.)

2. Aftermarket Flat Black Edelbrock Racing Valve Covers are too tall, Maybe? Currently hitting Nitrous Port on Runners.

3. More to Come...

Not sure if you'll find numbers on your combo. If somebody is pairing a TPI intake with TBI heads it's kind of a Frankenstein- built from what was available laying around. Performance probably varies considerably from "What a pig!" to "I can't believe how fast it runs with those junk heads!" depending on the exact combo of parts and how close the tune is.

did you change th head gaskets to a thinner one or mill the heads down? because that engine will have low compression compaired to the tpi 350... hope you knew that already

Huh? I'm pretty sure the TBI 350s have the same rotating assembly as the TPI 350s, and as such I'm pretty sure they have the same or very close to the same compression ratio.

At any rate, I've been running L03 swirl ports and an F-body LT1 cam on a TPI 305 in my '91 TA for 2 years now. Do a search for my screen name and you'll find it. In the research I did, the swirl port heads made power power and torque than the regular 416 or 081 305 heads below 4500rpm. I was doing a low budget stock build on my TA, and the L03 heads were free so I did a valve job on them and put them on. I was assembling another complete long block for the car when the original started hammering, thats why I didnt re-use the stock heads. I was basically throwing all my spare parts together to build an engine so the car was down as little as possible.

I don't regret it at all. I've done all my own tuning, the car gets 26-27mpg on the highway, and my highway mode tune is still pretty conservative, I'm sure there's 28+mpg in it with more tuning. I basically just assembled the engine, I didnt port anything, I just bolted parts together because I'm not trying to make it a hotrod. I'm still running the terrible stock manifolds, Y pipe, and cat back on the TA but it still gets down to business. It has an S10 T5 with 2.73 posi and it will burn the the tires from a roll in 1st gear. I'd guess the car is mid to low 15s right now. This winter I'm putting larger L98 manifolds on it, custom y-pipe, and a 3" cat back. This spring I'll probably take it to the track and see what it will do.

I'd guess you'll have similar results using L05 heads on a 350 with TPI. Once tuned properly it should be a stump puller. You will need to do something with the tune to get the most out of it though. I didnt need to change my fueling much, but the ignition timing requirements for the swirl port heads is notably less than what the TPI heads need.

No, I didn't know that. Do we have the numbers for compression???

those 1500 heads im pretty sure are 76cc heads... the stock TPI 350 heads are 64cc.. and compression is 9.5.1 in stock form.

if you are using those truck heads, the compression is going to be in the mid 8 range.. either find some 081 TPI cast heads.. or mill those 76cc heads down if possible.

I just did a really quick google search and it looks like we're both right. from what I saw 87-90 L05s had something like 8.3:1, later ones had 9.3:1. I had no idea the early ones were lower compression...

The swirl port 350 heads are ALL 64-66cc in stock form. The difference is in the pistons. 12cc dished vs. 18cc dished. The one and two ton truck engines had a smaller cam and less compression.

I'm using the engine from a 1991 Silverado, would it be possible to have the Compression Numbers for that engine? Along with the Numbers from an L-98 with Iron, Aluminum Heads?? Maybe some one can enlighten me with with some Swirl Port Information?

a simple search here or a google search will give you the compression ratios for the engines you mention.

What swirl port information do you want? Fast355 is the authority on that topic, but we need to know what you want.

I just read this thread https://www.thirdgen.org/forums/tpi/...signs-1-a.html


I haven't laughed that much while reading a thread on here, in ages...

Good Stuff! ( I came across this thread when I did a search for 1MeanZ) I didn't find the article on the 305 with l03 heads though...

What is the difference between the l03 and l05 heads? What applications did they come in? Maybe you can show me the website where they show the different Compression Ratio's for early and late model applications?

Can Killjoy or Someone post the numbers for the L98? Along with the different combinations offered and thier specifications? I just would like to see a solid base of where I could of been and where I am know. Thanks for your support.

when i converted my tbi rs to tpi stock peanut cam and heads with tpi and 3.23 gears 15.7 @ 86 .
adding headers and 1.6 full roller rockers took me to 15.3@90 but had bad tires and no traction but my lb9 with 98 cam did 14.5@99 with the same setup and tires a month later thats the best i can compare the 2 engines

when the car was bone stock with k@n in the factory air cleaner and 2.73 gears best the car could do was 16.7 @81 but had one wheel peel and would burn the one tire like crazy off the line.
with open element and 3.23 gears i got it down to 16.1 @85 . and would chirp the tires hitting 2nd every time i wot

after blowing up that engine i put in a 91 lb9 ie l98 cam and tpi heads with my above mods ran 14.5@ 99 with bad tires
new tires ran 14.3@98 hooked
mind you i never ran this engine with stock manifolds or rockers

adding dual cat exhaust and flowmaster catback 14.1 @ 99 but now the engine is starting to knock


from a seat of the pants differance the tbi felt better on the freeway and would chirp the tires hitting 2nd bad tires
where tpi would wheel spin hitting 2nd and kick out a bit with the same tires

mods went like this no clue if this helps you but

stock - tbi open element fpr mod 3.23 gears alloy drive shaft stock exhaust
car was better then stock but slow at the track chirped tires hitting 2nd
converted to tpi same setup as above but car was alot faster spun hitting 2nd
then added headers and 1.6 rr buy this time the engine was getting tired and was adding mods to apperently make up for broke piston ring that turned into spining a rod bearing

next swaped in a stock 91 lb9 with l98 cam differance was very apperent no traction would kick out badly wot hitting 2nd car was faster every where
im thinking the cam is the differance

a freind of mine that built his car pretty much the same as my old setup tbi 305 tpi on top hooker headers full exhaust 3.42 gears and he never stood a chance after my lb9 swap



all the 87-92 305s had 9.3.1 compression and dished pistons with valve reliefs the truck tbi 350s had 8.7.1 low compression option 73cc head for the hd trucks there was also a 9.5.1? for caprice tbis i believe or it was the same as the tpi 350 9.7.1 lest me 91 camaro service manual says so


the tpi oil pressure sensor is down near the oil filter you will need elbow off an 85 86 tpi to clear the intake

Just for the record, Swirl Port Heads aren't made for performance.

"THIS HIGH SWIRL HEAD CYLINDER HEAD IS NOT A PERFORMANCE ORIENTED CYLINDER HEAD. IT IS INTENDED FOR GOOD BOTTOM END TORQUE AND FUEL ECONOMY. THE INTAKE RUNNER IS RESTRICTIVE BECAUSE IT HAS A RAMP CAST INTO THE BOTTOM OF THE BOWL TO PROMOTE HIGH SWIRL." -GM Performance Parts.

Those heads are just stock 350 TBI Heads, whether car or truck.

A simple match formula, or compression calculator could have told you:

Bore: 4.00 Inches
Stroke: 3.48 Inches
Head Gasket: 0.039 *Stock(Possible to obtain in thicker or thinner. Thinner = Higher Compression)
Cylinders: 8
Cylinder Head Volume: 65.33 cc (Assuming it is a 14102193)

That equates to a 9.76:1 Compression Ratio

As for numbers, it's all depending on mods and tune. Nothing will be identical.

Rauch... Has given me my answer!

I have gone with AFR 180CC STREET PORT heads.

Thank You..