What does your VE and timing curves look like for WOT ? I just tuned a L05 for power and wanted to compare since I'd never tuned an engine with the swirlports before. I expected it to need less timing than normal, and I expected the VE to drop off quickly at relatively low RPM, but the difference is a little more than I was expecting. This is with a completely stock 200,000 mile 350 TBI/auto with stock exhaust. My VE is 100% in the 2000 - 2800 range, trails off a little to 90 at 3200, then drops sharply to about 75 from 4000 and up. I have to keep the SA below 20* up to 2400 RPM, then slowly increasing to 26*. I just wanted to see if this is pretty typical for these swirlport heads. It will need an overhaul soon and I was planning on swapping to some 083 heads. I was planning on doing a power/mileage/tune comparison between the two heads. Anyway, if you can please post up your VE & spark curves for your swirlport headed engine. thnx

The swirl port heads are good for torque...low RPM... so that sounds about right..swirl port heads are done by 3500 RPM.. good for heavy trucks...

The HP curve holds flat well past 5,000 rpm with swirlies, it just stops pulling harder by 4,500 rpm.

From all the data i have read and dyno results i have read the swirly heads are done (depending on the cam) by around 3500. The heads were designed to work more on the torque side if i am correct...?

DynoDon, John Dewey, and I have done dyno/track testing that proves otherwise.

In my testing the stock swirlies were better than stock L31 vortecs at ALL points under 4,500 rpm on a stock TBI engine.

From what i have read they "wall up" around 4000 RPM and they were "dead" from that point on..

If stock swirlies walled up at 4,000 rpm, you better tell that to my stock 810s that were on my 350 crate. With the stock roller cam (peanut 305 roller), 1.6:1 full roller rockers, 8.75:1 compression ratio, edelbrock 3704 intake, ultimate TBI mods, Doug Thorley Tri-Ys, dual exhaust, and DIY tuning, it would pull hard to over 5,000. I ran stock 3.08 gears and the stock 1,600 rpm converter in the 700r4. Mine pulled hardest from 3,000-5,000 rpm!!

http://www.youtube.com/watch?v=koWaPeAu3hg

honestly the next TBI fbody I get it getting a set of ported 187's,my ported 3704 eddy intake and a 94 LT1 cam. Due to the fact I want it more for a driver than a racer. I think for the street they are a great head. I honestly think people obsess over high rpm power to much in a "street" vehicle. If the car barely see's over 4500-5000 rpms there's really no need for heads that can breathe to 6500.

Now that can totally relate ...How often doesn someone twist up iver 4000 RPM ? I thought that was the reason they used it in trucks for the torque factor...Sure you can get ore outta something but i know from what i am using my swilries for they are sooooo done at 3500 its almost funny...On the graph they almost fall dead straight down after 3400...sure it also has to do with cam selection but heads and cam go hand in hand...but i am sure fast355 has found wasy to make them do some cool stuff... =)

Honestly the 2 BIGGEST reasons the tbi motors fall so fast is the PUNY *** cam they put in these cars. 174/194 @.50 .350/.384 109 lsa. these cams were not meant for any kind of performance. I think the L03 should have came with a Ramjet style cam instead 191/196 @ .050, .431/.451 109 lsa, that would have been quite the improvement for the TBI motors.

200K mile 305 with wornout valvesprings laid down this with a 179/194 @ .050 cam, stock intake, and 1.5" primary headers. With a B-car LT1/Vortec roller cam, an edelbrock 3704, and ultimate TBI mods, it made over 220 RWHP.

Thats pretty good...I just was refering to what i was getting from D.D @ the flywheel on my L05 with vortec cam... I was very impressed .. something in the neighborhood of 400 LBS of torque if i rememeber correctly..And everything just seemed to die off around 3400RPM...(just wish i could get Fast355 to tune the burban for me =) lol

Its been a while since I tuned TBI, but I still dabble with the $0D code for my TPI Vortec 350/4L60E combination.

The last TBI I tuned was a 92 G20 Conversion van with 240K miles on it. It had the 4L60 non E in it (aka 700r4) and we (brother and I) set it up with the EBL. Stock 350 TBI (K vin with 210 HP @ 4,000 and 300 ft/lbs @ 2,800) engine down to the stock exhaust manifolds and air cleaner assembly. It had a highflow catalytic converter and Dynomax RV muffler, single 3" exhaust. (Bought it for $350 with a slagged converter, not running) I was able to get it to run 0-60 in 10.1 seconds with the stock 3.42 gears, stock 1,600 rpm converter, and P255/70/R15 tires. With the stock 299 ECM and AWLD chip, it would run 0-60 in 13.5 seconds. It is my guess if this run had stayed WOT through the whole 1/4 mile, it would have broken into the 16s on a STOCK engine. Thats GREAT for a 5,500 lbs tank. With nothing more than a tune-up, and fluid changes, we put 50,000 miles on it in about 7 months. I sold it with about 290K on it, still running great, 17-18 mpg all day long. I tweaked the 299 ECM before selling it.

I didn't mean to get so off topic with this one...

I wouldn't waste my time with the 083s, unless they were ported and you are running a cam of more than 215* @ .050 on the intake and more than .450" of lift.

I know my VE tables do not directly cross over, because of my 18 psi fuel pressure I was running, but I included them. Even at 18 PSI on a stock engine I was needing over 90% VE from 1,600 to 6,000 rpm. At 6,000 rpm, I was at 80% DC on the injectors and 12.4:1 a/f ratio.

Am I to understand that the VE & spark that you posted is for a completely stock engine/head/exhaust combo? Mine has untouched heads and stock exhaust manifolds, and it seems to want to die off much quicker than yours. I'm running a 747 ECM with $42 mask.

I haven't completely decided on the head swap, but it will probably be 083's or the stock 193's. In either case they would be ported. I recondition cylinder heads so I have a lot of options there.

Gentlemen please remember that your valvesprings ,ASSuming you still have the original stockers, are probably tired and are floating your valves. You might see this as a sudden enrichment in the fueling during a tuning pull and you might even be convinced to pull fuel. Changing to a stiffer pushrod and upgrading a valvespring on a stock engine will extend the usable rpm band of the current cam/valvetrain setup. My 350 (lo5)in one of my other 91's got upgraded to a "drop in" lt1 spring from howards cams, it woke that dude up! I was able to lean the tune out and add some timing after 3500 and it was much more crisp up to 5400 where i upshift.

Chris

Honestly I'd have to say that I don't really think the springs are causing it. I have worked with cylinder heads for quite some time now, and I just don't see the particular characteristics of valve float in this case. There is no audible loss of control and it isn't showing up as fluctuations in the WBO2 output. It is turning up to 4500 RPM before the shift, which is about where I'd expect to see the first signs of valve float, but the characteristics I'm seeing are starting more than 1000 RPM earlier, and are quite smoothe in effect. It's much what I'd expect to see with factory restricted heads, cam, and exhaust.

With that being said, I think you do have a great point that's worth checking out. These are original springs with 200,000 miles. I'll check in my shop for a set of springs that will drop in there. I may be able to get some lightweight retainers on there in the process. It would show pretty decisively if valve control was/is a problem with this project.

My engine was the stock medium duty truck GM crate 350 TBI in a van. The engine had stock exhaust manifolds and exhaust on it. A highflow cat and single in/dual out muffler like stock. The exhaust on a Van flows MUCH better than a thirdgen though. My engine had an Edelbrock 3704 TBI performer and a ultimate TBI moded TBI. The air cleaner assembly and intake ducting in a Van is much less restrictive than a thirdgen too. I had a Hypertech powerbowl in place of the stock spacer ring.. The engine had 1.6:1 full roller rockers on it too. I made 191 RWHP @ 4,200 and 278 RWTQ @ 2,600 with a STOCK longblock.

I was considering some 1.6 Rockers when I redo my heads.. (Valve seals, and a bad lifter eeek) Does it make a large difference on these heads? It feels like it still pulls passed 4 grand, and I see why it would make sense to change the springs... 3 angle valve grind wouldn't hurt, either...

I haven't pulled the springs yet, but I have a line on some slightly used 187 heads.

Has anyone here put the 187's (305 swirlports) on a 350 engine before?
It seems like it should work out really well. If they are like most stock GM heads, then the ports are identical to the 193 casting, but just using slightly smaller valves and having smaller combustion chambers. The compression and the amount of quench area will be increased.

As a reminder, this is a fuel mileage project.