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TBI 350 Power Upgrades

Apparently the L31 cam is 191/196 at .050", (.414/428 lift) so there is a bit more to that cam than the TBI one.

I think your results somewhat vindicate what's been said about the TBI heads...in the truck applications they actually flow (and perform) pretty well. The heads you have now will probably benefit more from other induction/exhaust improvements than the L05 heads would have.

Headersvsmanifolds.jpg


Edit: Personally I ignore the peak numbers when dealing with my truck, because that's not where I need power. Generally dyno tests are way off-idle, which doesn't give much of a picture for pulling power from a stop (particularly with a manual), but this testing shows a 30ft/lb improvement just past 3500RPM, and the smoother curves are going to result in better felt performance. Not to mention that looking at the 2500RPM numbers, the modifications are doing something even at lower RPM's. Not trying to push headers over everything, but this is the first time I've seen this "test", although it mirrors pretty much every other one I've ever seen...manifolds suck for performance, it doesn't matter which SBC manifolds you have, they cannot compete with headers. Unfortunately, the general tradeoff is the hassle headers often times provide. But if looking to eliminate hassle, then no mods should be attempted, because all of them result in some other complication, if they do anything worthwhile.
 
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From some of my research the exhaust ports on the vortec heads were more restrictive than the tbi heads, problem with this is there is little data or real flow data on those tbi heads to confirm this 100% I also read somewhere that ported the tbi head has some damn good potential..
 
My experience with tbi heads was a carbd 350 with a comp 260h. Compression was right at 9.5. This was a pretty hard running small block, and pulled hard to 5k..ish, don't remember for sure. Sure didn't feel like the heads were a restriction over 3k.
 
black dawg said:
My experience with tbi heads was a carbd 350 with a comp 260h. Compression was right at 9.5. This was a pretty hard running small block, and pulled hard to 5k..ish, don't remember for sure. Sure didn't feel like the heads were a restriction over 3k.
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That's the dogshit stock cam doing that..
 
Are the summit heads worth the cost? It doesn't seem like they gained the engine very much.
 
Would I be better off doing an intake, cam, and headers? I could do all that for way less money than a set of the Summit heads. And can I do a cam swap with the engine in the truck?
 
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I'd do that before I swapped heads, for your goals the swirlport heads are fine. The cam the main reason for the crap performance.
Heads can be added later if you so desire.
 
sreidmx said:
I'd do that before I swapped heads, for your goals the swirlport heads are fine. The cam the main reason for the crap performance.
Heads can be added later if you so desire.
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the ramp heads stifle flow* - so any intake, header, or cam swap would run into the brick wall of those ramps preventing any decent flow above about 3000 rpm. Ramp ports were the step before Vortec - someone in GM realized that if you spun the air/fuel mixture, you would get a more complete fill of the cylinder (take a hose, aim in directly into a coffee can, now take that same hose and hold the nozzle at 30* to the can). In a truck, low rpm and torque are where it's at and the design worked for that.... however, they are almost an absolute bar to performance because that same ramp impedes flow above a certain level (3000 rpm, actually it starts at 2800). Hydro-electric dams use ramps at the bottom of spillways to keep erosion from happening. That happens because the energy spins back against itself to slow the water down... that is exactly what happens with the ramp heads as well. You could easily see less power, less torque and worse fuel economy by putting performance parts on that motor with those heads. If you really want to save money, buy only the Vortec heads then upgrade as funds and time becomes available - but get rid of the ramps first.

*for those who have never seen - seriously, look inside the intake port on a ramp head, there is a little fuel/air ski jump cast into the port.
 
Wouldn't the added lift from a different cam improve flow through the heads?
 
aglinks said:
Wouldn't the added lift from a different cam improve flow through the heads?
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It allows the air a longer duration to enter the chamber, which if your exhaust is setup to scavenge will become part of the equation on the exhaust stroke if there is overlap in the intake and exhaust events.

The cam is so small in the tbi engine that there is no overlap, if it was me I'd be installing something around 200-210 deg and 450-480 on the lift. With a wide 114.3 to keep the ecu happy.
The duration could actually be greater than listed because the lobe seperation is so wide. Lift is good if you have good flowing heads and duration is required if your heads do not flow.

This is why an Ls or a vortec makes more power, the smaller cam duration and lift is able to accomplish more because the heads flow better.
The tbi heads are great truck heads, this has been proven that below 3000 rpm they smoke vortec heads but anything above they drop off in comparison.

I'll still stand by my method of intake, cam, headers before the heads because you will still get your boost in performance if the chip is setup and everything is working together. The vortec heads are great but if you dont want to spend more money this is the shortest path.

That ramp was gm's attempt to swirl the fuel and air mixture. I don't know what physics @superbuickguy is subscribing too but I fail to see how increasing duration and adding some much needed lift to an air pump is going to be less of a gain? We're not applying a camshaft profile so big here that it creates less intake vacuum and makes the low end laggy.
The heads can be crap but the cam dictates the behavior of the engine, even if that means if completely mismatched for the combo, all that will happen is the engine will flatten out as the heads/intake/exhaust reach their maximum. But it will make power in the area of the curve the cam is dictating. So it will be biased one way or the other.
This has been proven again and again with stock smog headed sbc engines. Heck they even run them with stock heads up to 7-8k in circle track.. with dual plan intake manifolds sometimes.. and a two barrel.

If this is an L05 it should already have respectable compression, 9.2:1...
hope that helps.
 
I'll add this link to help you understand what I am talking about. Tbi heads while not the best are not far behind a vortec in terms of flow at least on the intake.. the exhaust side is far better, this thread shows a measureable gain with a small cam 206 set and porting.
https://www.thirdgen.org/forums/tbi/283217-garage-ported-193-s.html

Do some searching of the port flow measurements the guys are getting from these.. for note I have seen a stock Ls1 243 flow 240 cfm and if a ported tbi 193 can flow close to that you are doing damn good for potential and efficiency.

@bent72 has a tbi motor in his truck and from our conversations it is a serious serious engine that makes stupid low end.. and get awesome mpg to boot.
 
Did I miss something?

Stopped following this thread last week due to a lot of misinformation being given to the OP
 
sreidmx said:
It allows the air a longer duration to enter the chamber, which if your exhaust is setup to scavenge will become part of the equation on the exhaust stroke if there is overlap in the intake and exhaust events.

The cam is so small in the tbi engine that there is no overlap, if it was me I'd be installing something around 200-210 deg and 450-480 on the lift. With a wide 114.3 to keep the ecu happy.
The duration could actually be greater than listed because the lobe seperation is so wide. Lift is good if you have good flowing heads and duration is required if your heads do not flow.

This is why an Ls or a vortec makes more power, the smaller cam duration and lift is able to accomplish more because the heads flow better.
The tbi heads are great truck heads, this has been proven that below 3000 rpm they smoke vortec heads but anything above they drop off in comparison.

I'll still stand by my method of intake, cam, headers before the heads because you will still get your boost in performance if the chip is setup and everything is working together. The vortec heads are great but if you dont want to spend more money this is the shortest path.

That ramp was gm's attempt to swirl the fuel and air mixture. I don't know what physics @superbuickguy is subscribing too but I fail to see how increasing duration and adding some much needed lift to an air pump is going to be less of a gain? We're not applying a camshaft profile so big here that it creates less intake vacuum and makes the low end laggy.
The heads can be crap but the cam dictates the behavior of the engine, even if that means if completely mismatched for the combo, all that will happen is the engine will flatten out as the heads/intake/exhaust reach their maximum. But it will make power in the area of the curve the cam is dictating. So it will be biased one way or the other.
This has been proven again and again with stock smog headed sbc engines. Heck they even run them with stock heads up to 7-8k in circle track.. with dual plan intake manifolds sometimes.. and a two barrel.

If this is an L05 it should already have respectable compression, 9.2:1...
hope that helps.
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According to the codes in the glove box, it is an L05.
 
The cam I bought for my TBI engine is a COMP Cam/Computer Control cam. It has close to 30 degrees more duration, and about 20 thousands of an inch more lift than the stock cam. The cam is a single pattern cam, in order to keep down the vacuum fluctuation. Because of the single pattern, the cam is able to get away with 111 degrees of LSA, in order to give it more low end. I did not want to go crazy with a cam that had more lift because my stock swirl-port heads have press in rocker studs. If you go with a cam that has any bigger specs than mine, then you definitely need to go to a wider 112 LSA or more.

My GM Goodwrench TBI engine came with about 9:1 compression 64 CC heads. Different web sites listed different specs on compression for my engine, but it is safe to say that it is at least 9:1. Edelbrock makes a set of Swirl-Port aluminum 64 CC replacement heads that have bigger valves and slightly smaller ramp that give the intake runners a few more CC's of flow.
 
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sreidmx said:
I'll add this link to help you understand what I am talking about. Tbi heads while not the best are not far behind a vortec in terms of flow at least on the intake.. the exhaust side is far better, this thread shows a measureable gain with a small cam 206 set and porting.
https://www.thirdgen.org/forums/tbi/283217-garage-ported-193-s.html
Click to expand...

I'm seeing L05's at 178/146, and L31's at 239/160.

Peak numbers aren't all where it's at of course, but look at the RPM where the L31 in stock trim peaks, and where the L05 peaks.

Not real likely you are going to throw a larger cam in, and find that your low end torque increases, but you CAN spin the engine faster to keep it in the range a larger cam makes power.
 
I don't know if this is beneficial, but I just checked the VIN and it is a K code engine.
 
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