I have been reading (for years) about how the swirl port TBI heads will destroy TPI performance. Seems like everyone agrees that it's a mismatch of parts. While this is not something I set out to do, here is the story.

Have a friend (dave) that bought a 91 vert (305tbi/T-5). This car was originally owned by the older guy fron Horsepower TV. Not sure of his name but there was only two host. He was the one with grey hair. Dave bought the car with headers and an intake IIRC. This was actually done on HPTV.

Dave installed nitrous and ran about 13.1 @ 105. I think it ran 14.9 on the motor. Very good times for a stock 305 tbi! Then he decided to modify the engine. Ported heads, long tube headers, cam and a few other things. Half way through the porting, he changed his mind.

I ended up building a MPFI 406 sbc for the vert.

....that is a whole other story though. Dave felt bad and gave me the heads. I bought the stock 305 from him also. My T/A had about 180,000 miles on it at the time.

Used the TBI shortblock in my 86 t/a for about 100,000 miles. Ran stronger than the worn out original. Then it started to have massive blowby. I pulled it apart and found some cracked rings. One of the piston ringlands was broke too (between the 2nd and oil rings). Bearings still looked brand new.

Replaced one piston, rings, rod/main bearings. Other than the cam, it's still stock. The heads was ported and I also installed lt1 exhaust valves. Here is some more info on the final results.
https://www.thirdgen.org/forums/diy-...tml?highlight=

The bottom line is that my Trans Am runs very good with TBI heads. I have raced a bunch of cars and the 305 holds it own. Stock 350 TPI cars cannot keep up. 4.6l mustangs tend to lose alot. Gateway International Raceway will be open in a few months. Plan to have the nitrous setup by then. Hope some of you non-swirl port SBCs are out there. Maybe we can line em up!

 

Can this be moved to the TPI section...sorry...

 

I think the argument is that swirl port heads suck in general.

 

I have ported and planed swirl ports on my L98. It has tons of low end torque. It's hard to keep the tires from spinning. Pulls hard to 4K or so, then it pretty much runs out of wind. It's fine for my purposes with an auto. If it was a stick I wouldn't be as content with it.

 

where are you from? I tend to get around to GIR sometimes myself.

 

how exactly are you running such a big cam on those heads? i could be wrong but i didnt think those lt1's would handle the lift of the cam that youre running. and not to burst your bubble or anything but youre also comparing apples to oranges now. youre comparing stock 350tpi's vs a cammed 305.

also a stock LO3 your buddy had running 14.9 im not too into. unless the 5 speed makes a huge difference something in that car had to have been touched. i ran a 15.9 with a stock 305 TBI with headers, catback, gutted cat, no emissions, open element, 308 posi which that has i assume.

not trying to put you down because i too am going to be porting my 187 heads and camming my 305 and converting to tpi over winter, but i read your cam specs and unless you have special retainers or milled the guides down i dont see that working with 0.5-- lift.

 

Jefferson County, MO

 

Yeah, it's kind of not fair.....racing a stock 350 tpi car. The 350 car I raced was not exactly stock though. He had headers, vig converter, tuning and a couple of other small mods. My car has the stock converter AND 2.73's!

Dave might not of ran 14.9 . Maybe it was 15.3 or so. I can't remember exactly. Do know it ran LOW 13's on a 100 shot. Keep in mind that a manual can perform better at the track. Take the best tq converter made and I bet your car would of dropped a few 10ths, easy. The stick has the ability to "stall" at any speed...


The retainers are stock LT1. They was just milled down
.050" for clearance. The springs are less than ideal. Yet they work because I have reduced spring pressure just enough to prevent coil bind. Then engine will rev to 6k NO PROBLEM.
----------
..all stock heads suck, in general.

 

cool well you definately cleared that up i wasnt trying to be a **** i was just curious as to how you pulled it off. good job on the car. you should find a cammed LB9 and race him thatd be a great comparison.

 

My 310 TPI runs strong, despite having 187 casting swirl port heads on it. Pulls hard all the way up to 5,000+ RPM with the Production LT4 cam and 1.6:1 rockers that it has.

 

Van, huh? COOL!

 

Yep, all 5,300 lbs of it with its 3.08 gears. I think the swirl port headed 305 does a GOOD job moving around the weight, despite the lack of proper mechanical advantage of lower gears.

For the poster doubting the 14.9, I have personally run a 15.1 from a stock automatic L03 car with nothing more than stickier tires, subframe connectors, and L.C.R.s. My brother and I got it down to a 14.35 @ 96 mph, on the STOCK longblock, prior to reducing the cars weight and opening up the long block. The 14.35 @ 96 mph run was made with the following mods.

L03 + L69 Dual snorkel air cleaner (Truck Lid & Filter), Long Tube Headers, 2 1/2" into single 3.5" exhaust, Late Model TBI PCM with Tuning, S10 stalled 4L60E trans, 3.42 gears, Drag Radial Tires, Lower Control Arm Relocation, Subframe connectors. Car handled and ran like a dream.

 

Double

 

fast355 my guess if that you have ported your 187s how much porting do you have into them?

 

The ones in my van had a little work to the intake swirl ramp and were heavily ported on the exhaust side.

The Camaro was stock heads.

 

Well I guess I cant really argue with that. lol. Point noted. Carry on.

 

I still think you're a magician. The 14.35 I can believe, but 15.1 from tires, SFCs, and LCRs (I'm guessing that means LCA relocation brackets?) is VERY difficult to believe. 90% of the TBI board that has cams, headers, exhaust, etc are running half a second slower than you are with your stock ride. There's something more than those three mods you're not telling us.

 

In the other thread, you mentioned 220 rwhp and (?) 280 rw ftlbs. At what engine rpm were these numbers reached? Your engine makes a good comparison to Dewey316's 305 (started with stock TBI heads; then swapped in ported 416s). I don't recall what cam he used though, and I don't know how optimally tuned his/your combos were.

I also agree with the comment on stock heads, for heads older than 1996+ Vortec-type heads.

 

Nope, that is basically it. The only other change was minor in the performance department, but were very benificial after more mods. The 700r4 had pucked and I put a 60E into it using the TBI truck PCM. The gear ratios in the 4L60E are identical to the 700r4, and I was running a very stock GM 305 Van tune.

 

...then explain a heavy TBI vert running 15.3-15.0, only had aftermarket intake and exhaust.

 

..that is why I used the qualifier "generally". Vortecs RULE!


My tune is not perfect. Cannot recall where the peaks was at, rpm wise. I do know the dyno correction factor was set to SAE. Many magazines and "tuners" will use STD. The standard numbers with less graph smoothing would be about 232hp/297tq. I can post the dyno sheet if you like...

 

I want to clarify this perfectly . I was the owner of that car . I ran 14.9 on street tires . The mods at the time were : Edelbrock shorty headers and cat-back . Edelbrock Pro Flow air cleaner , and a 3:27 9 bolt posi . Also had injector spacer . With 150 shot of nitrous I ran a 13.2 @ 105 . Still on street tires . Went to the track with drag radials and blew out the clutch . Never made it back . My brother now owns the car and it has a 406 MPFI . He has never taken it to the track .

 

fast 355 you have 356rwhp on that 310 now, correct? and its in the van,have you run it down the track yet?

 

what timing did u set set it on the heads

 

i put a tpi on my mild lo3 with a lt1 b-body cam and i need to know about what timing did u put urs on

 

what did u set the timing on ur set up on

 

what u set the timing on with that 305 tpi set up

 

here is what is odd using the swirl port 187 head specs with all my other specs the same aside from running the 081 head specs

in desktop dyno you get on a 9.3-1 compression 305 with l98 cam with 1.6 rockers

a max hp of 220@ 4500 and 311 tq @ 3000 with tbi heads
with 081 head you get a max of 207 hp @ 4000 and 304 tq @3000

i find that odd as when i had these same to engines in my car the tbi heads seemed to kill all power above 4000
but yet desktop dyno is telling me otherwise

its just funny as the 081s have a good intake port flow 195 but crappy exhaust 110
and the 187s have a crap intake port 165 but good exhaust 160

i made a dyno with the intake port of the 081s and exhaust port of the 187s and got 233 @ 4500 and 311 @ 3000

what is odd is the tq didnt change at all but you gain some hp from having the 081 intake

so can the 187s be ported to 190 ish intake flow and still keep some swirl ramp ?

or is desktop dyno just a crappy program ?

 

hello
say i like this post threads...
My 86 305 took a crap. so i went on craigslist here in the nw an bought this 83 305 for a only 200.00 bucks complete tbi to oil pan with wiring and org ECM,with a stock rebuild from chevy with 40 tho miles 1800.oo receipt for motor work.I took pics of it an went on line when i got home,, an found it to be a 83 LU 305 CROSSFIRE ...
so i put this block in with my 86 TPI on it, 58 throttle body,24 pound injectors.. behind the 305 is a 700r4 with shift kit, 3.73 gears.the motor is all stock. duel exsaust, no smog,stock chip, ....car weighs 2,935 pounds..do you guru's now any thing about the 83 LU305. this car has got *****... so any info would be great

Thanks

 

What are good performance heads, cam, headers, and intake manifold for 305 tbi? i cant seem to find anything about a 305 with specs or anything about people explaining things they've done. I dont know much about 305.

 

Check my thread out (LO3 rebuild HP estimates) is name of thread

 

305 vortech heads ignore what they all say they work just fine I have some on 400 tpi last vin on heads are 520 or 059 the the best heads for 305 and work we'll they don't have the full swirl ramp like tbi heads but bigger ports an cast bump in the chamber to induce swirl

 

L30 are what they were on hp increase over 305 tbi cans be had more l30 was very restricted

 

Plus all u would have to buy A vortec tbi intake swap everthing over

 

Are you positive the 305 vortecs have the ski jump in them? I always heard otherwise. I know they dont have the vortec heart shaped combustion chamber that's another big part of the reason 350 vortec heads work so well.

 

Hey guys, just a general question, I have a 357 sbc with swirl port heads and a L79 cam, 9.6/1 comp, headers, etc. It's a mild build but it makes plenty of torque to 5400 rpm, but I'm looking at bolting on a set of ported vortec heads and i was wondering what kind of increase to expect out of it. Anyone with any info would be appreciated. I know its hard to give exact numbers i'm just looking for ballpark figures so I know its worth the money.. If it isn't a may just wait and get a bolt on kit of some kind.

full setup now -64cc swirlport heads with 3 angle valve job, performer intake, 1.5 ratio rocker arms.

after heads- ported 64cc vortec heads, 2.02 valves, 1.6 roller rockers, performer RPM intake.

I'm sorry if this isn't the place to ask but it's the only article i could find really comparing the two things. If anyone knows of another thread please send a link.
Thanks!

 

Idk a link but ill tell u this ... find stock flow numbers for each head.... then remember this ... every 1 cfm of intake flow has the potential to make 1.8-2.2 HP !

91' firebird .. 305 TBI .030 over , balanced bottom end , speed pro hyper flattops , 10.6:1 CR , all ARP rod bolts and main studs , melling HV oil pump , trick flow super 23 175cc heads, Howards HR 214/218@.050 .488/.495 lift on 114 LSA , full roller 1.6 RR = .520/.528 lift , summit dual plane intake port matched , shorty headers into 2.5" Y w full 3" flow master system and 3" cutout in front of axle , msd billet dizzy, 620cfm TBI , custom CAI , tubular adjustabke LCA pan hard , umi torque arm wonder bar , BMR trans cross member , COMP engineering SFC's, disc rear w 4.10's, drilled an slotted rotors, EBL flash , VRFPR, WBO2,