idk if this is the board for it but.... ive got an 88 camaro original 305 tbi, replaced 305 block with 350 (from an 89 Z71 pickup) with the 305 heads and everything else with no upgrades. ran a 15.2 in the 1/4. i just got it rebuilt bored .030 over, bumped up the cam slightly and new valves and springs in the heads. anyone have an idea of the power range im looking at for this, or how much my 1/4 mile time will improve?

 

Um get rid of those heads....they suck horrid...but times wise...

Need some details on the cam to prove anymore info but I don't think it will help much with those heads. See if you can get some L98 heads of some kind at least.

 

Dewey316 went 14.5 with "those heads", plus cam, intake manifold, and exh mods on a 305. Lo-tec, also a TGO member, went 13.6 using the bigger version of "those heads" plus cam, exhaust and intake mods on a 350. IIRC Lo-tec used a carb, so he side-stepped the issue of fuel delivery and tuning.

The 305 heads don't flow quite as well on the intake side as the 350 heads do, but these two examples show that you ought to be able to run quicker than 14.5 (because you have a 350) but not quite as quick as 13.6 (because you are using 305 heads on the 350, presumed unported). If you can get the tuning nailed, I think low 14s are reasonable, and maybe high 13s if you have no other weaknesses (traction, good trans etc).

The stock L98 iron heads are not going to provide a worthwhile performance improvement unless they are ported. Flowbench data shows that they aren't that much better than the 305 and 350 TBI heads.

Lo-tec's post:

https://www.thirdgen.org/techbb2/sho...hreadid=313766

Dewey's post:

https://www.thirdgen.org/techbb2/sho...hreadid=291790

 

Good ole swirlport arguement.

 

I did something similiar about 5 years ago to a 92. I used a 75 stock 350 from a truck, think it was a 78 z28 cam stock 305 tbi heads and flowtec headers. It went 9.4 in the 1/8 never got a 1/4 time

 

Yup. Proven by more than one person... now including vortecracing. 9.4 in the 1/8th is mid 14s in the quarter mile. I do believe in science (and experiments, even with cars) -- I don't believe in hearsay.

If you have evidence to the contrary, provide it.

 

thanks for the input, i am looking to upgrade the heads to some 350 style heads i need to get all the info from the engine builder first i do autobody work and leave all internal engine stuff to the pro's and do pretty much everything else tho. i dumped all my money into the engine and trans tho so im saving up over winter for heads, headers bigger tbi, dyno tuning, posi rear and some slicks. i hope with all that i get in the mid 13's. need to beat some stangs this next track season. last year i went once and my fastest time was against a 90 5.0 Rustang. i beat him with a 15.248. that was my first time at a track ever, so i was impressed. if anyone knows anyone with some heads for cheap let me know, or any of the other parts i said im saving for.

 

14s? dont you think a 14 with a 350 is limited? I am just saying just like TBI it has its limits and so do swirlports.

 

And for heads just look threw the websites classifieds area you will see them pass by there often. Also post in the wanted ads of what your looking for.

 

The TBI power limits from the factory are more from the exhaust and cam than they are from the swirlport (SP) heads. How is this known? Because the heads have been tested, in both stock (unported) and ported form and been shown -- by flowbench, dyno and track data -- to perform on-par with the iron TPI heads.

So the theory that TBI is weak because of the SP heads is false. The SP heads aren't performance heads (nor are TPI iron heads), but they are not the cause for slow TBI performance.

Have you read Lo-tec's post? He ran 13.6 with a (presumed) carb and unported SP heads. That's as quick as a number of TBI Vortec 3rdgens here have run. A 13.6 sec timeslip in a 3rdgen only requires stock LT1 -type power at the flywheel (approx 275 fwhp).... because an LT1 Fcar can run mid 13s.

Dewey ran 14.5 in a 305, also with unported SP heads. For both Lo-tec and Dewey, if their heads were that bad, then no cam swap and no exhaust modification would have made that much of a difference.... IF the heads were really the problem popularly claimed.

The peak flow from the 193 casting (Dyno Don's data) showed 178 cfm, which is good for approx 0.25*8*178 = 350 fwhp (D. Vizard's math for potential power based on peak head intake flow) with a large enough cam and with headers/intake. TPI iron heads flow slightly more on the intake side but less on the exhaust. Stock vs stock there is no large gain to be made in SP vs TPI iron head. Dewey and Lo-tec showed where the gains can be made: exhaust and cam for starters.

So Lo-tec's engine wasn't being overly taxed by a lack of airflow through the heads because 275 fwhp (to get a mid 13 timeslip) is a lot less than the 350 hp the engine could make with a large(r) cam.

I don't expect robbyho21 (the original thread starter) to run that fast because he is using heads with a smaller intake valve and because he is using TBI (and not a carb). That's why I said 14s with his combination and with his unknown tuning ability. IF he optimized the tuning (giving optimum fuel delivery), he should be able to run under 14 because Lo-tec already did it.

IOW he should run quicker than Dewey (because Dewey had a 305) but I don't expect him to run as fast as Lo-tec because of the smaller valve heads.

robbyho21: read the garage ported thread started by Fast355. Flow data on many relevant heads is summarized within it. You'll have to weigh the cost of new performance heads vs the need for porting and machine work by a shop. If you are doing this cheaply, I advocate DIY porting and there are a number of factory heads proven in the thread to flow really well after porting, SP and TPI iron among others. If you are blowing real dollars, then you better also consider what you'll need for an intake, fuel (carb or TBI/TPI etc), and tuning (if you stay with injection). You don't need to break the bank to beat up on Mustangs. FWIW.

 

Yes the swirlports will go 14's, it's been done plenty of times, and not to discredit anyone's work, but keep in mind that 14's are still slow.

 

None of you'll are running enough cam, stall, gears, or enough fuel to make the power. I am using ported 081s which really aren't flowing any better than my old 193 swirl ports. The swirl ports were actually better on the exhaust. These 081s were just a Quickly done set to get me back on the road again. They are only flowing 220/180. Slow, yah but put it into perspective. A more aerodynamic 6.0 AWD Express with better traction, a 300 HP 6.0, and 4.10 gears runs over a full second slower in the 1/4.

My latest times are in this post.

Mods

Here are the times. Keep in mind this is in an aerodynamic brick that weighs 5,300 lbs and spinning the tires through 1st.

I cut a horrid .931 R/T (I must have been asleep)
60' =2.42s (No traction)
330'=6.57s @ 57.4
660'=9.96s @ 73.9
1320'=15.5 @ 88.7

I still beat the Mustang GT in the next lane. Man was he ticked!

Edit- Here are the simulated numbers for my combo. These were generated by Engine Analyzer and CarTest v4.5. No alterations to the numbers in any way! The specs of the engine are right on and are about what I am seeing on the dyno after you consider driveline losses.

60'=2.54s @ 28.5
330'=6.75s @ 54.2
660'=10.15 @ 74.1
1320'=15.74 @ 88.5

Really not that far off if you ask me. Once again the simulator showed lots of WHEELSPIN, just like my experience at the track.

Top Speed=140 MPH
EPA Combined Mileage=17.3
0-60=7.3 Seconds

Engine Analyzer dyno numbers!

RPM---------HP------TQ
500----------8-------84
1,000-------38------199
1,500-------85------298
2,000------123-----322
2,500------159-----334
3,000------194-----339
3,500------238-----358
4,000------283-----372
4,500------326-----381
5,000------359-----377
5,500------380-----363
6,000------386-----337

 

I did some computer modeling with my engine in a 1992 Camaro RS that weighs 3590 lbs, with my 312 engine, a 700r4, 2,800 stall, 3.08 gears, and P245/50/R16s. The thing just spins and spins and spins.

60'=2.15s @ 27.5 MPH
330'=5.75s @ 63.1 MPH
660'=8.70s @ 82.3 MPH
1320'=13.39s @ 107.5 MPH
Top Speed=171 MPH
0-60=4.9s
EPA Combined Fuel mileage=19.3 MPG

The launch was made at 700 RPM which is OFF-IDLE, same as the G20 and shifts were made at 5,800. The 1-2 shift at 38 MPH anihalated the tires.

If someone was willing to give me a decent tire size for these cars, I would plug that in too. I want realistic. I have found it is about 2-3 MPH and 1-2 tenths off actual in my van. It under-estimates fuel mileage to some degree.