L31 Vortec 5.7 Heads/Cam advice for my 1999 K2500 Suburban

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JayMB

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Hi all,

I'm Jay. I'm new here. I bought a 1999 K2500 Suburban a while back and now I'd like to make it into a good towing/roadtrip rig for myself and my friends. I really like this generation of GM trucks. Prior to this I've only owned Squarebodies. I bought this one for EFI, Overdrive (4L80 - no 4L60's allowed here), lots of seats, and A/C. I'll do a build thread on it here when stuff gets serious but for now I just want to talk engine.

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I bought this truck for $1000 at an insurance auction. It's catalytic converters and drive shaft had been stolen, and it was listed as "possible engine damage" since it wouldn't start. I bought a parts truck for $400 and got a driveshaft, all the exhaust, and a new fuel tank + pump. Now it starts/runs/drives (fuel pump was shot).

The truck currently has a stock 5.7L L31 Vortec 350 with 260K KMs on it (162,500 Mi). It runs, clean oil, sounds fairly healthy (can't really tell if it ticks or anything because it has no exhaust at the moment).

I don't know the history of this truck, other than it was a fleet truck for a rural cable company for a large part of it's life. I feel like 255 HP / 330 TQ or whatever the Vortec 350's were rated for will be a little less than I want for it. I'd like to pull the engine out and get it redone as a 383. Here's what I got so far:

- stock 1999 5.7 Vortec L31
- 4.10 gears
- 4L80E being rebuilt with Jake's Performance B82 Billet converter (2200-2400 stall - basically an S10 converter)

I will be doing the 0411 swap and keeping the EFI. I have a marine intake that looks like a square-bore 4150 dual plane carb intake but has injector bungs in the runners. It's from a Mercruiser boat engine and it works with Vortec heads. I plan to use this with fuel rails and some 36-42 LB LS-engine-type injectors (either the 36LB supercharged 3800 V6 injectors that all the LS1 boys use, or the bigger 42LB ones found on 2010 or so 6.0L V8 truck engines with Flex Fuel). I'll get a pic of this intake shortly.

I want to use my fancy marine intake (pics to come later) and that leaves me with vortec heads. I hear that later Vortec heads (like, after 1998) are made in Mexico and have only 160CC runners, making them a bad choice. This, combined with the fact that these heads are well-known to crack - maybe I should get something else before I throw money at these making them support more lift and screw-in rocker studs. I like iron heads for truck motors. I'm thinking the EngineQuest EQ Vortec Head 350C. These can be had bare on ebay for $275 a side. My machinist will add springs and valves. They have revised water passages and thicker decks, plus screw-in studs from the factory. Anyone here use these?

What would you run for heads/cam on a L31 383?
I'm thinking iron heads and 9.3:1 compression.
4L80 & 4.10's put it just over 2000 RPM in 4th on the highway (65 MPH) with 33" tires.
Downshifting to 3rd to pass puts me at 2700 RPM.
Downshifting again to 2nd for towing heavy uphill takes me to 4000 RPM (roughly my peak power).
I would like max torque and decent fuel economy.

I'm thinking to go with the 395 HT383/Ramjet Cam from GM and basically build myself an HT383E.
GM advertises these as 323 HP @ 4200 and 444 TQ @ 3000.
Hotrod did an article where they got one up to 379 HP @ 4600 and 474 TQ @ 3700 with 1.6 rockers, an air-gap manifold and a bigger carb (not far off from my marine intake and throttle body).
https://www.hotrod.com/articles/gm-ht383-crate-small-block-tune-up/
Most importantly, they got the torque up to 450 LB/FT at 2500 RPM (roughly my converter stall speed).

I've been told that something like a Comp Cams Extreme 4x4 Cam might get me even more torque down low, but I'm not sure I want to thrash the valvetrain with super aggressive lobes on an engine that I want to tow across the country with. I'm happy to go full roller rockers and all that if it's a good idea. This engine was roller cam from the factory.

I need it to run on 87 octane and get decent fuel economy. I'm in Canada and our fuel options suck here. 91 octane is almost 20% more money than 87 so it doesn't really make sense for a truck.

I have EFI Live for tuning and I fear nothing electrical. I don't want to go LS engine because low-mile 6.0L truck engines (LQ4, etc) don't really exist here, and if they do - people want a fortune for them. Also I've always thought they don't quite have the torque down low that the old Vortecs did. I'd rather throw money at an all new forged 383 stroker and get more cubes than spend thousands on a stock engine I don't know the history on. It'll be 0411'ed anyways, so all an LS engine gets me is access to cheap aluminum heads - and I don't even like aluminum heads (for a truck).

Thanks for reading and thanks for your input,
- Jay

P.S. I built a 243 headed LS1 with a buddy for a Camaro that goes like hell. LS engines are awesome.. for stuff like cars. Or if you stroke them with 4" cranks. Or Forced induction. Or with a high stall converter and no plans to tow. For whatever reason I've always felt like they don't get going until 3500 RPM. I come from diesels, so this drives me insane. Some of your LS rides will smoke me all day long - so don't take my LS jabs as a dis. They were born to rev. I am not. Thanks again!

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Christian Steffen

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Hi all,

I'm Jay. I'm new here. I bought a 1999 K2500 Suburban a while back and now I'd like to make it into a good towing/roadtrip rig for myself and my friends. I really like this generation of GM trucks. Prior to this I've only owned Squarebodies. I bought this one for EFI, Overdrive (4L80 - no 4L60's allowed here), lots of seats, and A/C. I'll do a build thread on it here when stuff gets serious but for now I just want to talk engine.

You must be registered for see images attach



I bought this truck for $1000 at an insurance auction. It's catalytic converters and drive shaft had been stolen, and it was listed as "possible engine damage" since it wouldn't start. I bought a parts truck for $400 and got a driveshaft, all the exhaust, and a new fuel tank + pump. Now it starts/runs/drives (fuel pump was shot).

The truck currently has a stock 5.7L L31 Vortec 350 with 260K KMs on it (162,500 Mi). It runs, clean oil, sounds fairly healthy (can't really tell if it ticks or anything because it has no exhaust at the moment).

I don't know the history of this truck, other than it was a fleet truck for a rural cable company for a large part of it's life. I feel like 255 HP / 330 TQ or whatever the Vortec 350's were rated for will be a little less than I want for it. I'd like to pull the engine out and get it redone as a 383. Here's what I got so far:

- stock 1999 5.7 Vortec L31
- 4.10 gears
- 4L80E being rebuilt with Jake's Performance B82 Billet converter (2200-2400 stall - basically an S10 converter)

I will be doing the 0411 swap and keeping the EFI. I have a marine intake that looks like a square-bore 4150 dual plane carb intake but has injector bungs in the runners. It's from a Mercruiser boat engine and it works with Vortec heads. I plan to use this with fuel rails and some 36-42 LB LS-engine-type injectors (either the 36LB supercharged 3800 V6 injectors that all the LS1 boys use, or the bigger 42LB ones found on 2010 or so 6.0L V8 truck engines with Flex Fuel). I'll get a pic of this intake shortly.

I want to use my fancy marine intake (pics to come later) and that leaves me with vortec heads. I hear that later Vortec heads (like, after 1998) are made in Mexico and have only 160CC runners, making them a bad choice. This, combined with the fact that these heads are well-known to crack - maybe I should get something else before I throw money at these making them support more lift and screw-in rocker studs. I like iron heads for truck motors. I'm thinking the EngineQuest EQ Vortec Head 350C. These can be had bare on ebay for $275 a side. My machinist will add springs and valves. They have revised water passages and thicker decks, plus screw-in studs from the factory. Anyone here use these?

What would you run for heads/cam on a L31 383?
I'm thinking iron heads and 9.3:1 compression.
4L80 & 4.10's put it just over 2000 RPM in 4th on the highway (65 MPH) with 33" tires.
Downshifting to 3rd to pass puts me at 2700 RPM.
Downshifting again to 2nd for towing heavy uphill takes me to 4000 RPM (roughly my peak power).
I would like max torque and decent fuel economy.

I'm thinking to go with the 395 HT383/Ramjet Cam from GM and basically build myself an HT383E.
GM advertises these as 323 HP @ 4200 and 444 TQ @ 3000.
Hotrod did an article where they got one up to 379 HP @ 4600 and 474 TQ @ 3700 with 1.6 rockers, an air-gap manifold and a bigger carb (not far off from my marine intake and throttle body).
https://www.hotrod.com/articles/gm-ht383-crate-small-block-tune-up/
Most importantly, they got the torque up to 450 LB/FT at 2500 RPM (roughly my converter stall speed).

I've been told that something like a Comp Cams Extreme 4x4 Cam might get me even more torque down low, but I'm not sure I want to thrash the valvetrain with super aggressive lobes on an engine that I want to tow across the country with. I'm happy to go full roller rockers and all that if it's a good idea. This engine was roller cam from the factory.

I need it to run on 87 octane and get decent fuel economy. I'm in Canada and our fuel options suck here. 91 octane is almost 20% more money than 87 so it doesn't really make sense for a truck.

I have EFI Live for tuning and I fear nothing electrical. I don't want to go LS engine because low-mile 6.0L truck engines (LQ4, etc) don't really exist here, and if they do - people want a fortune for them. Also I've always thought they don't quite have the torque down low that the old Vortecs did. I'd rather throw money at an all new forged 383 stroker and get more cubes than spend thousands on a stock engine I don't know the history on. It'll be 0411'ed anyways, so all an LS engine gets me is access to cheap aluminum heads - and I don't even like aluminum heads (for a truck).

Thanks for reading and thanks for your input,
- Jay

P.S. I built a 243 headed LS1 with a buddy for a Camaro that goes like hell. LS engines are awesome.. for stuff like cars. Or if you stroke them with 4" cranks. Or Forced induction. Or with a high stall converter and no plans to tow. For whatever reason I've always felt like they don't get going until 3500 RPM. I come from diesels, so this drives me insane. Some of your LS rides will smoke me all day long - so don't take my LS jabs as a dis. They were born to rev. I am not. Thanks again!

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Sounds like you are pretty well on track to me. I don't have a lot of input on the heads or cam choice, other than that you probably don't have to be afraid of the comp extreme energy cams in regards to valve-train wear, as long as everything is in good shape. I'd say if you're tuning it yourself find the cam that is going to perform the best, don't compromise based off of wear concerns, since you're looking for torque it won't be crazy high lift anyway.

The injectors are probably a bit large, something closer to 30 lbs @ 4 bar would be fine (good for 385 hp @ 80% DC roughly). I have the 36 lb injectors in my truck and rarely see 70% DC.

You shouldn't have too much of a problem getting it to run well with 87 octane at 9.3:1 cr, but I'm sure 91 would help a little.
 

Iowan

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This helped me, been looking to do some head and cam upgrades my self. Thanks! I will be opting for some 200cc heads and if money isn’t too much of an issue, Skip NKB-200-174s are my ideal head of choice.
 

L31MaxExpress

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I currently tow with a 5.7/4L85E combo. I had those Hecho en Mexico garbage 062 Vortec heads and one mild overheat cracked both of them. I built a pair of Assault Racing 200cc aluminum castings from Amazon. Looking at other heads on the market, I came to the conclusion the are knock off Dart Pro1 Platinums. I used a head improvement kit and guide plates from Competition products and 7/16 rocker studs from Comp cams. I chose to convert back to perimeter bolt valve covers and went with tall cast aluminum covers. I had to modify the a/c compressor bracket and built a 1/4 plate steel plate that bolts to the 4 forward bolts of the OEM bracket and provides the rear mounting points for the compressor via holes I drilled and tapped into it. I am running the L31 Marine crossram intake and Doug Thorley Tri-Ys. I had Comp Cams grind me a 215/224 @ .050 lift cam on a 110° LSA advanced 4° to a 106 ICL. I chose Magnum lobes rather than Xtreme anything for longer life. I also decided on Scropion 1.7 roller rockers. Used Comp Magnum push rods and GMPP LS7 lifters. I have it in a 1997 Express Conversion van that has a full 8 lug suspension setup and 5.13 geared 10.5 14-bolt under it. I have it on LT265/75R16s. I have a 4L85E with the stock GM B82 converter. It pulls the van around empty phenomanly well and has no issue pulling my 23' Jayco that weighs 6,000 lbs

I towed with a 3.73 gear and 30.5" tall tires and it was MISERABLE. You may not ever reach 4th gear on flat land much less have any pulling power in it. With the 5.13s and 31.5" tall tire I currently turn 2,850 in OD @ 70 mph. A long hill will put me in 3rd at 3,800. I have my Tow/Haul shift pattern set to hold it in 3rd gear down to 62 mph (3,400 rpm) at WOT. If it downshifts into 2nd at that point I would be at 4,800 rpm. MY WOT upshifts in Tow/Haul are 5,250 rpm. In Normal shift mode WOT shifts are set at 5,750 and the rev limiter is set at 6,000.
 
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slowburb

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Welcome to the site. Nice rig too. I'm partial to the longroofs, have one myself.

You're definitely on the right track with these proposed plans. That's a big heavy truck, so the added displacement will be a plus for torque. Same with the intake and induction setup; the vortec induction system is a real bottleneck. I'd like to ditch my 2 piece intake for one of those marine dual planes and TBI's one day. I really like small port heads for torque. That is how you maintain velocity and optimize cylinder filling and atomization. It doesn't sound like you plan to, but I would not deviate from the metallurgy & port/chamber design of the vortec heads for this kind of buildup.

I've also read (no first hand experience) that the EQ heads are heavier castings. Definitely buy them bare and install your own goodies. Using the '395 cam there is no need for screw in studs, but you'll want heavier springs than OEM vortec springs. Alexsparts dot com sells a nice drop in spring/retainer kit that works well for a '395 cam...running it myself. There is a lot of low lift flow improvement in a good valve job and a little backcut on the valves will add more flow also.
 

JayMB

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@Christian Steffen - Thanks for the kind words and advice. I was thinking more cubes = more fuel, and our 346 cube LS1 needed those 36 LB injectors (I don't like to cut it too close). But, you're right - that LS1 probably makes 425 HP and my 383 geared for torque probably won't be anywhere near there. Thanks for the reality check!

My deal with the 91 octane fuel is: Say it gets you 10% better fuel economy and a little more power, but it costs roughly 17% more here.. overall, you're traveling less distance for the money, and the performance penalty isn't large PROVIDED YOUR ENGINE IS BUILT FOR 87. I have a good friend who bought a 2008 1/2 ton with a 6.0L "vortec maxx" engine. These are 10:1 with flat tops vs the 9.4:1 6.0L in the 3/4 tons designed for towing. They say in the owners manual that one should use 91 octane "for best performance" but 87 will do in a pinch. He proceeded to jack it up on huge tires (~36") with 4.10's and use it for towing 6-8k LB campers all over the place.. while being too cheap for 91 octane fuel. He got maybe 6 MPG. Why? I bet you that thing was knocking, so the computer was pulling his timing all the time. The real stupid thing is that the Vortec Max engine makes something like a whopping 10 more HP/FT-LB than the normal, lower compression 6.0L, while needing 91 octane fuel. So the 3/4 ton truck would have been a better choice a bunch of different ways for my friend (don't get me started on that tiny 9.5"/10-bolt "Hybrid" rear axle and the inadequate 4L70E trans it had).

@Iowan - Thanks for posting those heads. I'm seeing $699 for 2 assembled heads that claim to beat Dart SHP's - seems too good to be true. Comes with hardware for a flat-tappet cam, so anyone running an L31 is probably going to want to buy them bare and "roll their own" for springs and stuff. I wonder if these are similar to what L31MaxExpress has below. I'd like to run a Vortec intake and I don't know anything about these, but if anyone has anything to chime in, please do.

@L31MaxExpress - I was hoping you would chime in here. From the small amount of lurking I've done here, you seem to be the local engine wizard.

I'm glad you can confirm that the Mexican Vortec heads are junk. I really like your steel A/C bracket idea. I have seen the clearance between the valve covers and that A/C bracket and could definitely see how that would be a problem with taller covers. I might move to taller covers in order to cram roller rockers under there.

Thanks for the input on Comp Cams Magnum lobes vs the XE's or whatever they are for the most part. I think this applies doubly to your engine in particular because that sucker is a screamer. I already have a set of GM LS7 lifters for mine, glad to hear those suit your needs.

As far as gearing and RPM on the highway: 3.73's and 30.5" tires put you at 2157 RPM in OD at 70 MPH in your original configuration. My combo with 4.10's and 33's puts me at 2192 RPM at 70 - so let's call that practically the same as your prior configuration. I'm a little saddened to hear that it wasn't a good setup for you.

With respect, I'd like to point out that I won't always be towing - while it sounds like your rig is a towing machine all the time. I would like to be able to attain somewhat better fuel economy and lower cabin noise when I'm not towing. I'm not trying to dispute that your setup is the best for you, I'd just like to show here that our setups should be about the same, except that mine has one higher gear and yours has one lower:

Your Gear: My Gear: RPM @ 70 (me/you):

--- 4th 2192/----
4th 3rd 2922/2864
3rd 2nd 4325/3818

From this lame chart, you can see that I should be roughly where you are as far as RPM to road speed on the highway. I have no doubts you will get up to speed much faster and have wayyy more power at low speeds.

I think for my needs I'd like to gear my engine more for low RPM use. Your cam/heads setup definitely suits your situation well though. <nod of respect>

Good choice on the 10.5" 14bolt Full Floater - I have one waiting for my rig too!
4.10's though, because apparently I'm cool with being a slowpoke.

Any chance you go by Fast355 on some other forums? Can't be too many '97 conversion van guys with tricked out L31's out there..

@slowburb - Thanks for the welcome. Longroof? I like that term for these trucks. I'll remember that. It's true, there's a ton of roof. I love this new (to me) truck.

I have to agree with you completely - I am leaning towards Iron heads with Vortec chambers and maybe 170-190 CC intake runners. Maybe 200 CC, but no bigger.

The EQ are supposed to be heavier castings. Revised water passages too, so that they don't crack where all the Vortecs do. Just so you know, the EQ Vortecs always come with screw-in studs. Just another nice little perk over rebuilding my heads or some non-mexican ones. They also come with high-end brand name inconel exhaust seats, which should survive the torture of pulling trailers up hills better than off-brand Chinese heads. I always buy bare heads and get them built-up, as I've found that even good heads tend to come with junk hardware, springs and valves. I have a great guy for head work. I hear that the EQ heads are slightly worse out of the box than the GOOD Vortecs, but better than the Mexican ones I have. A tiny bit of valve work is supposed to go a long way on them though - thanks for the reassurance and the backcut suggestion.

I was going to go with PAC Racing 1218 springs, because they were the original makers of the Comp 918 springs, before Comp cheaped-out, got a different supplier and had all sorts of QC issues with springs years ago. I have PAC 1518's (no longer made) on the Camaro with a large cam and they're awesome.

Thanks all for the help!

P.S. I see AlexParts mentioned here a fair bit here and I've never heard of him before - do you all order from this guy? Thanks!
 

JayMB

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Just to add a little bit of backstory so you all know where I'm coming from:

I live in Canada. It gets cold here. Most of our population is concentrated along the American boarder. If you leave the populated areas, the cellular service is poor or non-existent. Having a breakdown or getting stuck in the snow during the winter can be pretty bad if you're somewhere on a road where nobody goes.

To that end, I need a reliable truck that I can count on to not break down.

I drive all day for work. Currently we have a fleet of 2017 Ford F350's. They are all crew cab, long box. They always have about 3000 LBs of stuff in the box, and sometimes tow trailers in the 2-8K LB range.

They have 6.2 L V8 engines. Interestingly, these engines have a bore of 4.015" and a stroke of 3.74". Sound familiar? Yup, within 0.01" of your typical 383 Chev (4.030 x 3.75" for those who don't know). I like these Fords for work trucks. These engines are rated for 385 HP @ 5750 RPM and 430 LB-FT @ 3800 RPM, but they have a pretty flat torque curve and make an honest 400+ LB-FT pretty low in the rev range. We have 34.6" tires on these with 4.30 gears, and they really go pretty well. I RARELY have to rev mine past 3000 RPM to get up to speed merging on the highway (while loaded). They also get close to 14 MPG if driven politely (all highway).

We used to have 2014 dodges. 5.7 Hemi, CCLB, 3500 series. They were BRUTALLY UNDER-POWERED. They couldn't get moving to save their lives. They lived at 4000 RPM and got no miles per gallon at all. Prior to those we had GM 6.0L's. They were alright. Better than dodges but not as good as the fords (for power). When I joined, they were just being phased-out, so I don't remember them very well. We don't run diesels very much here since the emissions stuff makes them terrible on fuel and unreliable in cold weather.

I liked my ford a lot when I first got it. The powertrain was amazing. So much that I priced out how much it would cost for me to own one myself. About $65,000 CDN - or $10K in the first year. That's too much for a truck for me. Now that I've had it for a while, I remember why I don't like fords. It ticks A LOT at startup. One of ours just died out of nowhere - wouldn't start one morning and it disappeared back to the dealer for WEEKS. Sometimes when it's wet outside, mine seems to struggle to get started. The box, which is advertised to be aluminum is made out of beercan material - yes, it really is that thin. It also has places for dirt and grim to collect ALL OVER IT and aluminum actually does rust here. One of our trucks got rear-ended at low speed by a small car and the tin-foil bumper didn't protect the beercan box AT ALL. That truck is TRASHED.

But, they look nice and I don't pay to keep them going. If my truck dies at work, they continue to pay me while they find me another one - so it's fine. I'm looking into switching up where I work, which will have me traveling in rural areas far outside the major cities a fair bit more. I want a good truck for that.

The way I look at it is, I could spend $10k building my truck the way I want it (GM, good parts, no-nonsense) and be into it for just the first years worth of payments on that ford I currently drive at work. I could buy brand new, and get a warranty - but like I tell my co-workers: That roadside assistance warranty package stuff isn't gonna help you when you're out of cell service range and your crappy brand new truck died in a blizzard. We have a guy with a 2016 EcoBoost 2.7 in an F150. It died at 29,000 KM. It got a new engine and he traded it.

Another guy I know has a 2014+ Chev truck.. Yeah, I wouldn't buy one. Electric power steering.. ABS box is under the cab in the salt spray zone, traction control won't let you spin the tires AT ALL even with it turned off (his claim, I haven't driven it) and the frame is made of high strength tin foil. It's been in something like 11 times for brakes, airbags and seatbelt recalls. 5.3 direct injection engine that's still underpowered and costs 6000X as much for injectors and stuff WHEN they die. I wonder why the old port-fuel-injected 6.0L is still being used in the 3/4 tons and better? Partly it's the emissions rules, and the other half is that the direct injection engines can't take the kind of sustained beating a towing truck engine does and still survive the warranty period.

I tell my buddies that if someone built a truck that never ever broke down and got 10 MPG, I'd buy two. My dream truck is a 1986 K30 CCLB with a 12-valve cummins or a DT466, and NV4500, NP205 and D60/14FF. I don't have $30K to do that right yet though. Maybe my next truck.

So far I'm into my "new" truck for:

$1000 - 1999 Suburban in decent shape with no driveshaft, fuel pump or exhaust
$400 - parts truck to remedy the above failings, plus a rust free door to replace the one rusty one
$2000 - 4L80E done right
$700 - AAM1050 aka 14FF with disc brakes and 4.10 gears that's about 2-3" wider than my current 14sf so that the back wheels don't look so "tucked-under". My old axle had 4.10's but no limited slip. This one has a G80 "locker" - which is basically a requirement even on a 4x4 where I live. It also had 57,000 KM on it so I couldn't say no.

That leaves me roughly $6k for an engine, injectors, all associated parts, exhaust, etc. Plus I want to paint it underneath, build some steel bumpers for it..

After that, and a rebuild on the NP241 and front AAM925 I should have a brand new powertrain (almost).

What do you think? Am I out to lunch?
 

Christian Steffen

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@Christian Steffen - Thanks for the kind words and advice. I was thinking more cubes = more fuel, and our 346 cube LS1 needed those 36 LB injectors (I don't like to cut it too close). But, you're right - that LS1 probably makes 425 HP and my 383 geared for torque probably won't be anywhere near there. Thanks for the reality check!

My deal with the 91 octane fuel is: Say it gets you 10% better fuel economy and a little more power, but it costs roughly 17% more here.. overall, you're traveling less distance for the money, and the performance penalty isn't large PROVIDED YOUR ENGINE IS BUILT FOR 87. I have a good friend who bought a 2008 1/2 ton with a 6.0L "vortec maxx" engine. These are 10:1 with flat tops vs the 9.4:1 6.0L in the 3/4 tons designed for towing. They say in the owners manual that one should use 91 octane "for best performance" but 87 will do in a pinch. He proceeded to jack it up on huge tires (~36") with 4.10's and use it for towing 6-8k LB campers all over the place.. while being too cheap for 91 octane fuel. He got maybe 6 MPG. Why? I bet you that thing was knocking, so the computer was pulling his timing all the time. The real stupid thing is that the Vortec Max engine makes something like a whopping 10 more HP/FT-LB than the normal, lower compression 6.0L, while needing 91 octane fuel. So the 3/4 ton truck would have been a better choice a bunch of different ways for my friend (don't get me started on that tiny 9.5"/10-bolt "Hybrid" rear axle and the inadequate 4L70E trans it had).

Just google "fuel injector calculator" any play around with the power numbers to get an idea of what you'll need. Most people try to size them so the DC doesn't go much over 80%.

That doesn't surprise me about the vortec max, pulling a bunch of timing is a great way to kill mileage. Either way 36" tires on 4.10s and towing was a bad idea.
 

slowburb

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I wouldn't recommend skip white parts to anyone.

OP, if you're going to run anything but vortec or EQ...or anything with a runner volume larger than 170ish, get AFR's or get nothing. Period.
 
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