7.4l vortec rebuild help

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Hey guys, how is everyone? So the trans is out on my 99 suburban k2500 so I’m going to rebuild the engine while I’ve got trans out because I think the rings are bad, it started using a lot of oil but not coming out as smoke from the tailpipe but my inside of the intake was coated in oil. Anyway, I’m wanting to do a pretty extensive rebuild but I’m unsure of which cam, valves, springs, pistons, etc.. I should get. I’m wanting to upgrade over OEM parts but not exactly strip worthy parts either. Lol. Should I have the block bored over? .030? .060? Bored over and add cylinder sleeves to get back OE specs? Should I get a new crankshaft? I love the slow low idle lope of a big block but is that attainable with the newer computer controlled engines? I would assume it depends on the cam intake/exhaust timing but is the pcm gonna go haywire if such a cam is installed? Also, it currently has no cats but before you bite my head off I bought it that way, lol, I would like to put cats back on it but with so many to choose from I’m also unsure of which of those is best. Along with no cats it also has the K&N intake and a 3” Flowmaster exhaust without headers though. 😕. I am however wanting to add headers but have been told that since it’s 4WD and the oil filter has been relocated to make room for that I won’t be able to install direct fit headers on it. Does anyone know of a direct fit that will work? Any and all help is appreciated, I want to Wake this beast up so part numbers or brand and model or as many details as humanly possible will be great. Thank you very much, if I’ve left out any pertinent information I apologize, I’m trying to type this quickly before I climb on my excavator for the day. Thanks again, hope everyone has an awesome day
 
I’m wondering if you might do better with a crate engine, ready to go. With that big part of the build done you could focus on the smaller parts of your project. A quick search found this:
https://www.summitracing.com/search/part-type/crate-engines/make/chevrolet/engine-size/7-4l-454

I realize this may not be what you want to do, but completely re-doing a big block can be a costly affair. Naturally, there are other sources for good crate engines but this is what I found pretty quick.

Now if your desire is to completely rebuild an engine yourself, you can find lots of proven “Engine combo kits” that have heads, intake, carb, etc that can really juice an engine. Edelbrock is one supplier:
http://www.edelbrock.com/automotive/mc/power-packages/.
Good luck, and have fun and let us know how it’s going!
 
You had a very typical intake gasket failure. They love to loose gaskets and then suck oil like crazy ...

Or, the PCV system failed. Sometimes the valve covers do not have the right baffle configuration to minimize oil loss, and they will act exactly like you describe - when the bottom end is fine ...

On your build - yeah a lopy idle is nice, except that it means a lot of extra fuel down the drain and may be hard to control idle and slow speed heat build-up ... I'd really shy away from trying that with a ECM controlled engine.

So the way to make this work best in a big Burb is to make a really fat mid-range torque engine. Lopers almost always move the power band to high for the street and any off-road work.

Start with the heads and the block. 0.030" over is all you need for a street engine. You want killer more TQ, then think about a stroker crank. But it ain't necessary ... Sleeves no necessary unless one cylinder is thin on one side. If the machine shop sees any core shift, they can sonic test and do what's needed.

Put a piece of steel across the top of the cylinder with a piston at TDC. Use feeler gauges to measure the piston crown (cleaned) down the bore. If it's less than 0.005", you have power coming right there. The goal is to get just about 0.050" total quench. Your gasket is likely 0.038" or so compressed. So if the piston is down the bore much, you have given up a lot ...

Get the heads done at a good local machine shop. Iron guides are fine. Really good 3-angle valve job minimum. Better is 4 or 5, if you can find the folks who will do the work well. Most won't and have not done enough to know how properly.

Spend some time with a die grinder taking out casting flash and guide boss material in a streamlined shape. Don't go crazy. Study up, do homework. Take a 0.020" pass across the face of the heads. Your CR is going to come from the pistons, not the head. Have them CC the heads and give you real numbers - no Inet look-ups. GM was all over the place on chamber sizes.

Now pick your pistons with decked block in mind. The block must be decked to the actual piston/rod combo. You are shooting for 9.1 static CR max for future unknown fuel. Dynamic CR will depend on cam and installed adv. Have the block decked to calculated piston crown -0.005" for safety ...

Me, I'd go Howard's Cam all the way with a matching lifter set because it has a 5 year guarantee if installed per instructions. Nothing crazy. The more cam, the less fuel economy. Most guys over cam an engine and then cry - don't. The CR and the tight quench do the job.

If your used springs were not good (sagged, etc.), I'd get Howard's springs too. If your springs are good - fine, unless you look at a cam that will lift higher than stock springs can handle (which you should not be doing on a real street engine ...). Call Howard's and get a recommended cam with your heads and pistons initially selected. Tell them it'll be a "Burb" ...

On a working street engine, I like steel roller tipped rockers. Those usually come from Comp. Crower is better, but way more expensive. OEM pushrods are OK if they are straight. If not, look at Crower.

Cloyes timing set. HV oil pump with low pressure relief spring. Drill the front two lifter gallery plugs 0.030" each. This will squirt oil on the back of the cam gear. That will over oil the cam chain. That will keep it all happy for many miles and reduce "chain stretch" which will keep your timing better longer.

Stock crank is fine. Nobody ever pushed a BBC crank out the bottom end unless they were stupid. Replacement H beam rods w/ ARP bolts are about the same price as fully re-cond OEM rods w/ ARP bolts, and may be lighter. Get it all balanced.

Change intake manifold for freer flowing unit. I like Wieand, but you can go wherever you want. Match the runner sizes to your heads. Wieand aluminum water pump. Now your motor is 50# lighter. Shorty Jet-Hot coated headers and you are another 40# lighter.

Even with a mild truck cam, this motor will spin 5,500 easy. One of the good "marine" cams will get you closer to 6,000. But you give up a bit of bottom end.

The bottom end grunt and mid-range will surprise a lot of folks. The tight quench means you can run more timing. So start looking at your distributor options. Rebuilt OEM is fine for these RPM ranges. But you may want to change the flyweights and the "scroll" to bring the timing in faster.

If you are rebuilding the tranny - I'd go with a Hughes Tow-Master converter. Same efficiency at cruise, but with more go off the line. You will be able to terrorize the tires with this build
laugh.gif


This all sounds straight forward, but this is a serious engine. It'll make the OEM unit seem pale in comparison, and the gas mileage will not suffer
laugh.gif
 
I was going to say I don't think it's the rings in this engine. I would think it's either PCV or Intake Gasket for sure.
 
Originally Posted By: BrocLuno
You had a very typical intake gasket failure. They love to loose gaskets and then suck oil like crazy ...

Or, the PCV system failed. Sometimes the valve covers do not have the right baffle configuration to minimize oil loss, and they will act exactly like you describe - when the bottom end is fine ...

On your build - yeah a lopy idle is nice, except that it means a lot of extra fuel down the drain and may be hard to control idle and slow speed heat build-up ... I'd really shy away from trying that with a ECM controlled engine.

So the way to make this work best in a big Burb is to make a really fat mid-range torque engine. Lopers almost always move the power band to high for the street and any off-road work.

Start with the heads and the block. 0.030" over is all you need for a street engine. You want killer more TQ, then think about a stroker crank. But it ain't necessary ... Sleeves no necessary unless one cylinder is thin on one side. If the machine shop sees any core shift, they can sonic test and do what's needed.

Put a piece of steel across the top of the cylinder with a piston at TDC. Use feeler gauges to measure the piston crown (cleaned) down the bore. If it's less than 0.005", you have power coming right there. The goal is to get just about 0.050" total quench. Your gasket is likely 0.038" or so compressed. So if the piston is down the bore much, you have given up a lot ...

Get the heads done at a good local machine shop. Iron guides are fine. Really good 3-angle valve job minimum. Better is 4 or 5, if you can find the folks who will do the work well. Most won't and have not done enough to know how properly.

Spend some time with a die grinder taking out casting flash and guide boss material in a streamlined shape. Don't go crazy. Study up, do homework. Take a 0.020" pass across the face of the heads. Your CR is going to come from the pistons, not the head. Have them CC the heads and give you real numbers - no Inet look-ups. GM was all over the place on chamber sizes.

Now pick your pistons with decked block in mind. The block must be decked to the actual piston/rod combo. You are shooting for 9.1 static CR max for future unknown fuel. Dynamic CR will depend on cam and installed adv. Have the block decked to calculated piston crown -0.005" for safety ...

Me, I'd go Howard's Cam all the way with a matching lifter set because it has a 5 year guarantee if installed per instructions. Nothing crazy. The more cam, the less fuel economy. Most guys over cam an engine and then cry - don't. The CR and the tight quench do the job.

If your used springs were not good (sagged, etc.), I'd get Howard's springs too. If your springs are good - fine, unless you look at a cam that will lift higher than stock springs can handle (which you should not be doing on a real street engine ...). Call Howard's and get a recommended cam with your heads and pistons initially selected. Tell them it'll be a "Burb" ...

On a working street engine, I like steel roller tipped rockers. Those usually come from Comp. Crower is better, but way more expensive. OEM pushrods are OK if they are straight. If not, look at Crower.

Cloyes timing set. HV oil pump with low pressure relief spring. Drill the front two lifter gallery plugs 0.030" each. This will squirt oil on the back of the cam gear. That will over oil the cam chain. That will keep it all happy for many miles and reduce "chain stretch" which will keep your timing better longer.

Stock crank is fine. Nobody ever pushed a BBC crank out the bottom end unless they were stupid. Replacement H beam rods w/ ARP bolts are about the same price as fully re-cond OEM rods w/ ARP bolts, and may be lighter. Get it all balanced.

Change intake manifold for freer flowing unit. I like Wieand, but you can go wherever you want. Match the runner sizes to your heads. Wieand aluminum water pump. Now your motor is 50# lighter. Shorty Jet-Hot coated headers and you are another 40# lighter.

Even with a mild truck cam, this motor will spin 5,500 easy. One of the good "marine" cams will get you closer to 6,000. But you give up a bit of bottom end.

The bottom end grunt and mid-range will surprise a lot of folks. The tight quench means you can run more timing. So start looking at your distributor options. Rebuilt OEM is fine for these RPM ranges. But you may want to change the flyweights and the "scroll" to bring the timing in faster.

If you are rebuilding the tranny - I'd go with a Hughes Tow-Master converter. Same efficiency at cruise, but with more go off the line. You will be able to terrorize the tires with this build
laugh.gif


This all sounds straight forward, but this is a serious engine. It'll make the OEM unit seem pale in comparison, and the gas mileage will not suffer
laugh.gif








Make sure you speak with a tuner regarding what can actually be done with the stock ECM. From what I remember the 99-00 OBS has a modern ecm that is the same or similar to the later ones used on the NBS trucks with LS motors. This ECM lends itself to be tuned more than the earlier ones but you should check on fullsizechevy.com. You could always go stand alone like megasquirt but idk how far you want to go.

If you're going to build a 454 I would personally be looking at an LS swap. Even a stock 6.0 is going to vastly out perform a stock 454 and you already have the ECM that can run it. I know you probably want the big block torque but for a daily driver I think you will save a lot on gas. If you're willing to blueprint a 454, then you have to at least consider a 6.0 swap with a cam and a tune. Or you could be my hero and perform a cummins, OM series diesel or other small diesel swap.

The OBS is my favorite truck, my fam had a 95 burb 2500 4x4 350 TBI. My dad traded it in during the height of gas prices in 2005 for an 04 sierra z71. Wish we still had that heap, it had every option that a 2500 could have and was mega BA when my mom would pick me up from school where everyone else had mini vans and cars and we had a 2500 HD burb!

OBS burbs hold a special place in my heart, I would love a 6.5. Good job keeping that thing on the road, you have awesome taste in cars!

EDIT: I just wanted to add that you could do the intake gaskets/replace the PCV and then save up or do more research for a swap. I'm not a pro mechanic, but removing and rebuilding both a motor and trans and then putting them back together again seems like a troubleshooting nightmare waiting to happen. This would also allow you to put more time and money into the transmission, and give it a shakedown to see if it works properly after it is built. It would be awful to try to track down drivability issues when you have a freshly rebuilt trans and a freshly rebuilt upgraded mill installed at the same time. With automotive projects I have learned to take things slowly and methodically, as they can really bite you and cause you to loose interest in wrenching on cars period, which has happened to me in the past.

What are you doing to the trans? If you are planning to build the motor, I would be beefing that trans up to the max and getting a big cooler and a mag-hytec pan.
 
Last edited:
Originally Posted By: StevieC
I was going to say I don't think it's the rings in this engine. I would think it's either PCV or Intake Gasket for sure.


^^ Correct ^^.

And you won't need to bore it - have a PROPER engine machine shop do a "glaze breaking" cylinder hone only, and then new rings.

....or just replace the intake gaskets!!!!!!!!!!
 
I see you're in Missouri. Call this guy with all your questions:

Will's Automotive Machine Shop
630 Park Ave, Poplar Bluff, MO 63901
Phone: (573) 686-4404
 
Originally Posted By: 99Burb454
Hey guys, how is everyone? So the trans is out on my 99 suburban k2500 so I’m going to rebuild the engine while I’ve got trans out because I think the rings are bad, it started using a lot of oil but not coming out as smoke from the tailpipe but my inside of the intake was coated in oil. Anyway, I’m wanting to do a pretty extensive rebuild but I’m unsure of which cam, valves, springs, pistons, etc.. I should get. I’m wanting to upgrade over OEM parts but not exactly strip worthy parts either. Lol. Should I have the block bored over? .030? .060? Bored over and add cylinder sleeves to get back OE specs? Should I get a new crankshaft? I love the slow low idle lope of a big block but is that attainable with the newer computer controlled engines? I would assume it depends on the cam intake/exhaust timing but is the pcm gonna go haywire if such a cam is installed? Also, it currently has no cats but before you bite my head off I bought it that way, lol, I would like to put cats back on it but with so many to choose from I’m also unsure of which of those is best. Along with no cats it also has the K&N intake and a 3” Flowmaster exhaust without headers though. 😕. I am however wanting to add headers but have been told that since it’s 4WD and the oil filter has been relocated to make room for that I won’t be able to install direct fit headers on it. Does anyone know of a direct fit that will work? Any and all help is appreciated, I want to Wake this beast up so part numbers or brand and model or as many details as humanly possible will be great. Thank you very much, if I’ve left out any pertinent information I apologize, I’m trying to type this quickly before I climb on my excavator for the day. Thanks again, hope everyone has an awesome day


You haven't done a compression or leakdown test? If you just want to rebuild it then fine but the oil burning is likely a blown intake gasket which is common on these motors.

For the cats, look on Mandrel bend solutions website, they offer some round body cats which are the spun insides vs the catacombs, you can get them 100 or 200 cells per sq inch vs the 5-600 stock ones have, they flow way better and you can be perfectly legal for the weight of your vehicle if you select 2 of the proper body size. I have the 5" body 200 CPI ones on my truck (2 total) and pass emissions checks every year with them.
 
Waste your money on a rebuild if you like, but a Vortec 454 makes a lot of power to begin with and oil in the intake without exhaust smoke is indicative of everything but worn bottom end.
 
IF this engine ends up needing a rebuild, don't get all crazy with boring for the sake of boring and throwing speed parts at it. It's a truck after all.
You want to bore a block the minimum amount to get straight, round bores. .030 is probably fine. Recon your rods and add nice ARP bolts, cut the crank .010. Good quality flat top pistons with the decks milled to get a perfect .030 deck height.
I'd most likely use Edelbrock heads and a cam with lots of low end torque to move that truck around.
Even if the short block is sound and you still want headers, check out Sanderson. They make a wide variety of cast iron header type manifolds. I'd run that on a driver long before tube headers.

I also agree with Maxdust above about the 6.0 swap. I have a Suburban with a 5.3 and like it way better than the 350 I had in my '98.
 
Originally Posted By: 99Burb454
Hey guys, how is everyone? So the trans is out on my 99 suburban k2500 so I’m going to rebuild the engine while I’ve got trans out because I think the rings are bad, it started using a lot of oil but not coming out as smoke from the tailpipe but my inside of the intake was coated in oil. Anyway, I’m wanting to do a pretty extensive rebuild but I’m unsure of which cam, valves, springs, pistons, etc.. I should get. I’m wanting to upgrade over OEM parts but not exactly strip worthy parts either. Lol. Should I have the block bored over? .030? .060? Bored over and add cylinder sleeves to get back OE specs? Should I get a new crankshaft? I love the slow low idle lope of a big block but is that attainable with the newer computer controlled engines? I would assume it depends on the cam intake/exhaust timing but is the pcm gonna go haywire if such a cam is installed? Also, it currently has no cats but before you bite my head off I bought it that way, lol, I would like to put cats back on it but with so many to choose from I’m also unsure of which of those is best. Along with no cats it also has the K&N intake and a 3” Flowmaster exhaust without headers though. 😕. I am however wanting to add headers but have been told that since it’s 4WD and the oil filter has been relocated to make room for that I won’t be able to install direct fit headers on it. Does anyone know of a direct fit that will work? Any and all help is appreciated, I want to Wake this beast up so part numbers or brand and model or as many details as humanly possible will be great. Thank you very much, if I’ve left out any pertinent information I apologize, I’m trying to type this quickly before I climb on my excavator for the day. Thanks again, hope everyone has an awesome day


If you are loosing oil , first thing I would do is a compression test , " wet " & "dry " . I would not go off the deep end with this , until I knew more .

Unless you are just looking for a reason / excuse to dump a boat load of money into it . If so , have fun ! :)
 
Holy Toledo! You got a phone number BrocLuno? Lol. That's exactly the kind of information I was hoping for and honestly didn't think I'd get but once again, Bobistheoilguy forum has paid dividends. I asked about rebuilding a tranny last winter and got more than hoped for there too from Clinebarger. I've still to rebuild that tranny however because I got lazy riding around on the used one I slapped in there that's now bad as well. Ugh.
I suspected the intake gasket to be bad causing my oil consumption, I had to remove the intake to get to the distributor to change the rotor and upon inspection of the intake I found it soaked it in brand new oil. He reason for the rotor change and new plugs and wires was a direct result of the oil leakage at the intake fouling the plugs, causing a bad misfire. I had changed the plugs and wires when I bought the truck 20,000 miles earlier. Smh. I also changed the PCV valve and cleaned the MAP sensor spigot as best I could without spraying any cleaner on it.
Anyway, I have searched for an aftermarket intake for the vortec 7400 but have had zero results, the search always pulls up an intake for the 5.7, which has the throttle body out the front, my 7.4 has the throttle body out the side near the rear of the housing.
Once again, thank you very much for this information, I may call on you again for advice if that would be ok.
And my machinist has been around for a long time, everyone, and I do mean everyone takes their stuff to him. He's about 70 years old and knows everything about everything when it comes to hunks of mechanical iron. So I'm thinking I'm in good hands with him. He won't have any of the newfangled computer gadgetry though so it might take a bit longer to get things figured out but I don't like computers anyway. Lol. Have a great day
 
Maxdustington, thank you for the information!
The reason for the rebuild is mostly for performance, I'm just wanting to fix the oil consumption issue while my beloved old girl is down yet again. I've looked at crate motors but I've not looked at an LS swap. The crate motors are running about $3500 bare bones and I'm not wanting to sink that much into something I'm just going to change anyway. So a rebuild is my best option I think, plus I would like to keep my Burb original as far as powertrain is concerned.
A Cummins swap would kick some major hind end but I do love the thunder of a big block over the roar of a cummins. A good friend of mine has done exactly that though, in an 84 Chevy 1 ton short bed Silverado. I forget the particulars and I don't have any pictures anymore but I'll try to get a few and post for you if you'd like. He's a Cummins freak, he's also got a 98 dodge 2500 long bed crew cab with every bell and whistle a person could think of motorwise. That thing will flat get up and go I'm here to tell ya!!
Since you're a fan of the late 90's Burbs as well I was going to post a pic of mine for you but I don't have any pics on my iPad because I've cleared all of the memory out to make room for music storage since I primarily only use my iPad for music in my Burb....which is broke down.....again. Lol. I'll post one or two for ya though from my phone in a bit. Have a good one!
 
NYEngineer, correct. I wasn't going to bore it for the sake of boring it. The reason for possibly boring it was because of another common issue with these motors. That being cylinder knock because of the pistons and cylinder walls not all being the same diameter. I've read numerous articles about this and it coupled with the oil pump not being sufficient causing severe cold start cylinder knock I was worried that the cylinder walls may be damaged and causing at least some of my oil consumption. I don't know if smoke coming from the oil fill tube when the cap is removed is due all or in part to bad rings but I've always thought it was from the rings. Ive got a small amount of smoke when I remove the filler cap after running the truck for a while. It could be that I'm getting this smoke from the intake leak as well but I'm no mechanic, I'm just a wrench turner. I've always been a poor boy and have had to work on things myself to get them fixed so I know just enough to be dangerous. Lol. Hence the reason for my post.
And there's no way on Gods green earth that I'm swapping out that 454 for anything. Not in this truck. Now, if I ever get my dream car, a 63 Impala SS convertible, I want to put a 572 crate motor in that. But this Burb is gonna stay the way she is, she's my beloved old girl, cranky and cantankerous as all get out but my girl just the same. Lol. I want to eventually have that truck looking brand spanking new again, albeit with several modifications, but new nonetheless.
Thank you for your input, hope to trade messages again sometime. Have a good day
 
WyrTwister, yeah, I'm looking to dump a boat load of money into her. Lol. She's my "show" truck. I'm on an SPL stereo team so her appearance and the way she sounds is very important to me when I pull up at a show/event/competition. Plus I love the sound and the feeling in your stomach of a properly built and tuned GM big block.
 
Good lookin' Suburban. I love those.
I see what you're saying. I'd do a nice big block with torque for days.
 
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