Can I make 400tq out of a TBI 350?

a401cj wrote: you want to cam it so she's out of breath at 4000. a cam that will do that is a cam that will pull stumps

This^^^

You also have to consider Mike, the head/intake setup on the TBI's doesn't flow. Also, the TBI system can't stand large vacuum fluctuations or it goes crazy, so LSA's have to be kept at 112 or higher. And it's hydraulic flat tappet, not a roller like in the cars of that era. So, working with E36 M3ty heads, a E36 M3ty intake, and a E36 M3ty cam that can't have crazy ramp rates like roller cams do leads to these sort of combos.

I could upgrade to a roller cam, but that's another couple hundred extra bucks AND that's IF the block in my truck has the provisions for it (which it SHOULD, but you don't know until you pull the intake). Silly GM engineers/bean counters :(

Doesn't matter. 1.6 rocker won't make enough of a difference in ramp rate to cause a problem. Remember, I was building limited small blocks. 2 barrel rochester's with cast intake, and cast exhaust manifolds. I know about lousy flow. The increased lift really works on the exh. Sometimes on the intake.

I'll keep that in mind Mike, my father may have a set of 1.6 rockers lying around. Might have to try them on the exhaust side.

http://www.jegs.com/i/JEGS-Performance-Products/555/200102/10002/-1?parentProductId=1215318#moreDetails

For anyone following along, this kit is only $99.99 from Jegs. Seems to be the same stuff as the Melling kit I posted, but $30 cheaper. Says it's only good to 1985, but I don't know why it wouldn't work. I think what happens is everyone assumes the cam is going in a car, which after 85 SBC's went to roller cams but the trucks stayed flat tappet. Be wary though, there was a big issue with the "Summit Racing" brand of flat tappet cams and lifters, so much that tbichips.com dude removed them as recommended cams off his list.

http://www.carcraft.com/techarticles/116_0101_roller_rocker_ratio_test/viewall.html

This is what car craft has to say about roller rockers. 1.6's made an extra 20tq's at 3000rpm, so definitely something to look into! I love CarCraft, might need to renew my subscription...

Flat tappet should be fine, too bad today's automotive oils really aren't so great for the things, and new parts should probably be treated with kids gloves (extended break-in period, special oils or oil additives to replace missing ZDDP that was more concentrated in common oils from even five years ago). Too bad roller lifters are much more costly.

I typically run Rotella T6 (a group4 full true synthetic diesel oil with high zinc content) in all of my vehicles :D

I've never done a cam swap in my life (I race more than I wrench, and I wrench a lot!), but my father's done approximately 1 million, so the process of the swap and not flattening any lobes should go well cross fingers

slightly less than a junkyard 5.3..

Which doesnt make the number either. Which motor is cheaper to get to the 400 goal with? And then add the cost of the swap to the 5.3 number.

Ive driven a lot of 5.3 trucks and honestly i wouldnt swap one into.. another damn truck! It's not that great! The thing that makes 5.3 swaps worthwhile is swapping them into LIGHTER VEHICLES. Seems like i drive 5.3L customer trucks constantly and i cant ever remember ONCE thinking "this motor is worth the effort to swap into another equally heavy vehicle that already has similar displacement and wont be getting major mods".

Say you swap a 5.3 into an early 90s ext cab z71. Congratulations, you just made your 17 second truck a 16 second truck! Hoo-effing-ray.

The premise of this thread seems to be: OMG teh Tqs @ ~3000rpm or less!

Has anyone looked at a dyno of a 5.3 vs a TBI 5.7 instead of just going off peak numbers? The 5.3 vortec appears to be around 285 @ 3000rpm. Down 15 "torques" from the TBI... doesn't seem like a drastic difference.

That said, I'd probably keep the TBI. Swapping engines in something that isn't a performance car seems like a lot of hassle for not that much of a gain.

Sounds like a nice canoe to visit but i wouldnt want to live there.

Anyway, old tbi 350s FEEL way stronger off the line than LS 5.3s do in equivalent versions of the same truck..

ProDarwin wrote: Has anyone looked at a dyno of a 5.3 vs a TBI 5.7 instead of just going off peak numbers?

That would be so cool if someone ran a bone stock TBI 350 half ton with similiar sized tires to a 5.3L equipped 1/2 ton, you should get me these non-existent dyno numbers done on the same day and same dyno. Oh, and had numbers starting at 2k rpm.

You know what's even cooler? Rather than having hearsay float around, I'm just going to end up dynoing a stock tbi 350 1/2 ton (277k kms), a stock 5.3L 1/2 ton with tq management removed (350k kms), and a stock 6.0L (abused, 160k kms) so I can have actual information and numbers to back things up.

How cool is that?!

I also don't care about torque at 3000rpm, I care about torque from off idle to around 2500rpm, typical truck towing rpm unless you are really hauling away from a stop. If your truck downshifts to 3rd and you are only doing 55mph up a hill, guess what RPM it's at? It ain't 3k! It's 2400rpm. So I STILL don't care what torque a motor makes at 3. Even 65mph in 3rd doesn't get me to 3000rpm, so there is literally no reason for me to care about torque at or above 3. We're not talking torque under the curve, we're talking torque at the bottom of the curve.

And THIS is why these conversations get funny. Common knowledge for building "power" goes out the window, and then people get frustrated when their suggestions get thrown back at them because they don't answer the original question.

so. the absolute best thing i ever did to get stump pulling torque to a 350 tbi truck was.....

put in a 472 cadillac. 500+ ft lbs almost off idle. that truck was amazing.

i mean - i'd do that before i did a 4.8/5.3 swap for a towing application. and i love me some 5.3 swap.

The big thing with the TBIs is that peak torque is in the 2400-2800 RPM range. Most of that is available off-idle...

Here are some good threads:

http://www.fullsizechevy.com/forum/general-discussion/performance/76859-tbi-mods.html
http://www.fullsizechevy.com/forum/general-discussion/performance/145234-tbi-airflow.html
http://www.fullsizechevy.com/forum/general-discussion/performance/68328-tbi-users-hp-information.html
http://www.fullsizechevy.com/forum/general-discussion/tech-articles/212879-common-performance-minded-faqs-about-88-98-obs-trucks.html

Enjoy!

HiTempguy wrote: I also don't care about torque at 3000rpm, I care about torque from off idle to around 2500rpm, typical truck towing rpm unless you are really hauling away from a stop. If your truck downshifts to 3rd and you are only doing 55mph up a hill, guess what RPM it's at? It ain't 3k! It's 2400rpm. So I STILL don't care what torque a motor makes at 3. Even 65mph in 3rd doesn't get me to 3000rpm, so there is literally no reason for me to care about torque at or above 3. And THIS is why these conversations get funny. Common knowledge for building "power" goes out the window, and then people get frustrated when their suggestions get thrown back at them because they don't answer the original question.

HiTempguy wrote: Because the truck is going to be lowered 3" all around, I'm thinking more like a 235/65R16. Not really any cheaper, but that would make the equivalent (or close to) of going to a 4.88 gear.

A 28" tire with a 1:1 3rd gear and 4.88s would be ~3500rpm at 60mph. What gearing does the truck have in it now?

Secondly, I agreed with your choice to stay with the TBI. I just found all of the discussion about how gutless the 5.3 is down low to be odd when it seems to still have respectable numbers down to at least 2500 (and I don't see any dynos below that).

patgizz wrote: so. the absolute best thing i ever did to get stump pulling torque to a 350 tbi truck was..... put in a 472 cadillac. 500+ ft lbs almost off idle. that truck was amazing. i mean - i'd do that before i did a 4.8/5.3 swap for a towing application. and i love me some 5.3 swap.

472/500 Caddy is still one of the best kept secrets there is. It weighs more than an iron SBC but surprisingly quite a bit less than a BBC.

ProDarwin wrote: A 28" tire with a 1:1 3rd gear and 4.88s would be ~3500rpm at 60mph. What gearing does the truck have in it now? Secondly, I agreed with your choice to stay with the TBI. I just found all of the discussion about how gutless the 5.3 is down low to be odd when it seems to still have respectable numbers down to at least 2500 (and I don't see any dynos below that).

I'm really just bustin' your balls. I completely agree with what you are saying.

As for the rpm thing, the Z71 (and most modern day 4x4's) run tires at least 31" tall with 4.10's. My truck specifically has 265/75R16's (31.6") with (ASSumption on my part as the truck is 30kms away and stupid me didn't check the RPO in the glovebox) 4.10's. That's what my calcs were based on, so 65mph in 3rd is around 2900rpm. I expect to make lots of torques there regardless of what I do with the truck, just like the 5.3 makes lots of torques there. Great for when you drop down to 3rd pulling that hill with 7k pounds of trailer, but considering you just upped the torque multiplication by dropping down to 3rd, it better freakin' hold that hill even with only ~300tqs!

Vigo wrote:

slightly less than a junkyard 5.3..

Which doesnt make the number either. Which motor is cheaper to get to the 400 goal with? And then add the cost of the swap to the 5.3 number. Ive driven a lot of 5.3 trucks and honestly i wouldnt swap one into.. another damn truck! It's not that great! The thing that makes 5.3 swaps worthwhile is swapping them into LIGHTER VEHICLES. Seems like i drive 5.3L customer trucks constantly and i cant ever remember ONCE thinking "this motor is worth the effort to swap into another equally heavy vehicle that already has similar displacement and wont be getting major mods". Say you swap a 5.3 into an early 90s ext cab z71. Congratulations, you just made your 17 second truck a 16 second truck! Hoo-effing-ray.

have you ever towed with a TBI 350 powered truck and a similarly equipped 5.3 powered truck?

i don't care what the power ratings say or which one would win a drag race- the 5.3 is just a flat out better engine for towing. towing is just so much more effortless with that engine.. and why does everyone get hung up on the "400 torques" thing? it's just a number, and numbers don't get work done.

Have you ever towed with a 5.7L vortec vs a 5.3L? And which would you say is better? I have and know which one is. And why it is better is explained quite easily by the torque curve. And it gets better mpg loaded or unloaded.

Anyways, as an update, I've been collecting some more info and playing around with cam/dyno software (the ULTIMATE in bench racing).

From my understanding, I can cross the Edelbrock TBI intake off my list of mods. Even with everything else I plan on doing, the $300 is a waste of money, it basically gives you a couple extra horses and a couple extra tq's (both in theory, and via people's reviews).

So really, what it comes down to to make torque out of the motor is a cam with low duration, a LSA of 112 or higher, high lift (well, high for a hydraulic flat tappet), and long tubes.

Since originally (as I laid out in a previous post) I could cobble together my own cam swap "kit" for around $200cdn, but now I have an extra $300 on the table, I've decided to definitely support a well known cam manufacturer who got back to me right away about my cam request. I'll be using the CompCams K12-249-4 complete kit, which comes with:

It is a really, really good deal to have all brand new parts, plus that double roller chain kit is icing on the cake. You realistically should replace 200k mile valve springs anyways and it is basically a requirement as the stock TBI springs are garbage.

The dyno/cam software shows 460ftlb's at 1500rpm LOL! I'm thinking NOT, but I wouldn't mind the torque peak being around 2000rpm as that's what I desire.

Holy wow. Can't believe the legs on this thread.

TBI: Two not-so-big throttle bores blocked by two large sloppy shower injectors. Those injectors are just plain in the way. There are good reasons why the OE evolved away from TBI technology. Torqs or whatever, air is not getting into the engine. Just pretend you're an air molecule hanging out on the highway, waiting to get sucked into an engine. See the air molecule. Be the air molecule.

Poor little air molecule, which grille do you pick?

460lb/ft of torque at 1500 RPM... what software gave you that number and what are you assumptions? Are the specific heads you have now modeled in as well or is it somewhat generic? Are you going to do anything to the heads besides springs? I ask because these motors liked to wear the guides and you could get a bit of an improvement with a three face valve job, polishing the backside of the valve, maybe play with shaving the decks for a little more compression (which opens up other required activities so if not I wouldn't blame you).

pres589 wrote: 460lb/ft of torque at 1500 RPM... what software gave you that number and what are you assumptions?

Like I said, definitely a farce (comp cams engine dyno). I did everything as CRAPPY as possible, 300cfm throttle body (the TBI unit with the ultimate mods flows ~490cfm, BUT that also has to include the space fuel is taking up), stock iron crappy heads, basically made everything as terrible as possible.

As for airflow, why does it matter? Yes, I would agree with you... above 4000rpm. But the amount of airflow required below 3000rpm is nothing like above, so (as many have suggested), the "airflow" issue really isn't an issue for the rpm I'm operating at. At least, that's how I see it

since the 5.3 swap is totally ruled out..

people have claimed noticably more torques and better throttle response and gas mileage just from adding a fuel injector spacer that raises the injectors up 1/4" farther out of the throttle bores. i don't know that i've ever seen any dyno charts on that.. i can tell from personal experience that getting rid of the stock air cleaner spacer on a TBI engine does wonders for the low rpm toque- you can keep the stock air cleaner housing or you can put a regular 14" open element drop base air cleaner with a 4" element right in it's place by relocating the MAP sensor down and out of the way. if you have a TBI unit with 2 air cleaner studs, you need to get a single stud from the junkyard and screw it into the throttle body. this really woke up the 92 Caprice TBI 350 that i had swapped into an 88 S10, but i was never able to get a title and register that truck so i can't say what kind of real world difference it made since it was just something i used to jump thru snowdrifts in my back yard...

Thanks for the tips Derrik, I'll keep 'em in mind.

Thought I'd share a picture of the truck with everyone.

You are all totally jealous of that bitchin' topper. It's so tall I can almost stand in it, I love it :D

Edit- And I also found out it has the G80 rear end (locker, I'd have liked a posi with clutches but oh well) and the GU4 (or GT4, I forget) rear axle ratio code = 3.73's. That calculates out to 65mph at 1800rpm in OD. Might have to fiddle around with tire sizes to get things right depending on how much tq's I end up making.

Also, in hoping to gain mpg I was going to lower the truck. Do you guys think 3" front 2" rear is too much?

They're already slightly nose down, I'd drop it level.

My first thought is that 3" is a drop in the bucket.. im not sure it will do anything.

I mean, on a car where lowering 3" reduces your clearance by 80%, im guessing it's fairly effective.

Im just not sure about the practicality of trying to limit the air under the vehicle in your application.

I guess i would build E36 M3ty airdam first and if it does something, build a better one, lower the truck, or do both.

I always felt like torque should be 50 lb @ 1 ft instead of 50 lb*ft, which can easily be interpreted as work.

i agree with vigo on the lowering. i'd try an air dam first to test the effectiveness of lowering.

one must remember with trucks - you are pushing a brick through the wind. the best thing i've ever found to increase my mpg with a truck is to ride in the draft of semis as much as possible like on mythbusters.

oh yeah - not cool that you got an extended cab z71 for free even if it does need a trans rebuild.

doesn't look nose down to me, looks a tad nose up just like my burb, the leaves are probably sagged a tad from being used as a truck for the last 18 years.

summit racing has some drop knuckles on their clearance table at the original store in ohio - i saw them and got sad because i wanted to go the other way an inch or so