vortec heads

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Schurkey

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the rocker arms im wanting to get have 1.5 ratio 3/8 stud, i believe that is stock equivalent. Just a little unsure on valve springs
Make sure the rockers are self-aligning, like the originals.

I'd expect multiple sources have stock-equivalent valve springs and hardware.
 

Pro439

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I was just going to say in’96 gm went to self aligning rocker arms so if you want to use regular roller rockers you will have to use studs and guide plates. Being that this engine has almost 200k on it how often have you replaced the coolant. The extended life coolant becomes very acidic after 3 years or 300,000 and eats the head gaskets up. Vortec heads are known for cracking as they are as thin as you can go. I don’t recommend machining anything off of them. Yes these heads are great for what they are used for but trying to do anything will them is like throwing money into a pit. These engines are hard to do much to as the crank sensor limits going to a double roller timing chain. I have almost 260k on 1 of these and the head gaskets are just about done. If all you’re worried about is the engine being dirty I would just get a few cans of degreaser and let it soak and then hook the hose up to the hot water and wash the crap off. I have actual carbon in my coolant from the head gaskets going away. My water pump is leaking out of the mounting gasket which I have never had before in 42 years of driving and owning sbc. I’ve put 3 radiators in it since January it’s getting so it doesn’t hardly get outta its own way. I bought another truck which someone put dual exhaust on with glass packs and is so loud it’s waving a red flag for a ticket. The front steering is wooped and the p/s seat shorted so bad it melted the wiring all the way to the firewall and melted the floor under the seat. So dirty is an easy fix. Taking it apart to do stuff to it is entirely different. If you change the oil and filter and use good quality stuff you shouldn’t have any wear issues on anything and that’s the rule of thumb for everything. You also probably will end up breaking the exhaust manifold bolts off in the head or won’t be able to get the pipe off the manifold not that I’m trying to change your mind but these are different from earlier small blocks
 

L31MaxExpress

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I was just going to say in’96 gm went to self aligning rocker arms so if you want to use regular roller rockers you will have to use studs and guide plates. Being that this engine has almost 200k on it how often have you replaced the coolant. The extended life coolant becomes very acidic after 3 years or 300,000 and eats the head gaskets up. Vortec heads are known for cracking as they are as thin as you can go. I don’t recommend machining anything off of them. Yes these heads are great for what they are used for but trying to do anything will them is like throwing money into a pit. These engines are hard to do much to as the crank sensor limits going to a double roller timing chain. I have almost 260k on 1 of these and the head gaskets are just about done. If all you’re worried about is the engine being dirty I would just get a few cans of degreaser and let it soak and then hook the hose up to the hot water and wash the crap off. I have actual carbon in my coolant from the head gaskets going away. My water pump is leaking out of the mounting gasket which I have never had before in 42 years of driving and owning sbc. I’ve put 3 radiators in it since January it’s getting so it doesn’t hardly get outta its own way. I bought another truck which someone put dual exhaust on with glass packs and is so loud it’s waving a red flag for a ticket. The front steering is wooped and the p/s seat shorted so bad it melted the wiring all the way to the firewall and melted the floor under the seat. So dirty is an easy fix. Taking it apart to do stuff to it is entirely different. If you change the oil and filter and use good quality stuff you shouldn’t have any wear issues on anything and that’s the rule of thumb for everything. You also probably will end up breaking the exhaust manifold bolts off in the head or won’t be able to get the pipe off the manifold not that I’m trying to change your mind but these are different from earlier small blocks
GM went self aligning way before 96. Every TBI engine from 87 on has self aligning rockers.

Why would you ever want a junk double roller when single roller chains are better and stronger anyway with less slop.

The OP is in Texas, manifold bolts are not usually hard to remove here even on a 30+ year old engine.

No argument on the Vortec heads. I will not spend a penny on another set besides maybe installing LS beehives and Comp 787 retainers on a good set. The Etec170s blow them out of the water but then again so do the 200cc offshore castings for alot less $$ than the Etecs. My previous 350 in the van ran strongest with the 200cc jobs as they flowed considerably better than the Etecs. With the smallish cam I had in it, it loved the added head flow of the 200cc heads. The 200cc aluminum heads were literally stronger everywhere than the Vortecs or Etec170s. I milled down the Etec170s after warping them by overheating them a bit and put the on the L30 305 in the Tahoe. The Etec170s are awesome on a 305 vortec with a mild cam. Little 305 made close to 300 hp at the tires, torque curve was literally table top flat right at 300 ft/lbs at the tires from 2,500-5,200.

If I knew then what I know now it was the PCM and torque management holding it flat at 300 ft/lbs by retarding the timing to keep the engine at an artificially limited estimated torque value. The PCM uses air charge from the MAF/VE tables, air/fuel ratio, current spark advance and a MBT advance table as well as a engine torque loss and accessory torque loss table to derive an estimated torque production value. If the PCM is capped for say 300 ft/lbs and the predicted output torque is estimated at say 330 ft/lbs it will reduce the output torque by retarding the spark advance using the torque loss programmed spark retard values.
 
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L31MaxExpress

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SIngle roller chain with a 3 way adjustable crank sprocket. Like $50 at full price and fits behind the reluctor wheel. These are dead reliable to 6,500 rpm with as much valve spring pressure as you dare on hydraulic roller lifters and do not stretch for hundreds of thousands of miles. I have literally pulled one of these engines apart with 3/4 of a million miles that was untouched and the chain was like new. The single roller with the added oiling/air bleed holes GM put in the lifter gallery end plugs just plain work.

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caw_86

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SIngle roller chain with a 3 way adjustable crank sprocket. Like $50 at full price and fits behind the reluctor wheel. These are dead reliable to 6,500 rpm with as much valve spring pressure as you dare on hydraulic roller lifters and do not stretch for hundreds of thousands of miles. I have literally pulled one of these engines apart with 3/4 of a million miles that was untouched and the chain was like new. The single roller with the added oiling/air bleed holes GM put in the lifter gallery end plugs just plain work.

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On my shopping list already.
 

L31MaxExpress

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Just further improving my point, the L31 I went through for the 87 G20 van has the OEM GM single roller timing set with ~115K on it and it is as good as a new one. Zero concerns re-using it with a bigger cam, more valve spring pressure and a big block oil pump. When I was degreeing the cam and rotating it forwards and backwards it moved virtually instantly with maybe 1-2* of crank movement before the cam changed directions.

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L31MaxExpress

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On my shopping list already.
One word of advice on install, they have so little slack in them, you will likely have to rock the crankshaft to get the cam sprocket lined up with the bolt holes. Do not try to force it on by trying to thread in a bolt, it can mangle things if you do. Rock the crank back and forth until the cam alignment dowl and bolt holes line up and the sprocket slides on the cam with light hand pressure.
 

tayto

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GM went self aligning way before 96. Every TBI engine from 87 on has self aligning rockers.
not trying to start an argument here, but I pulled a TBI 350 from a low mile '87 R2500 about 5 years ago. It had '191 TBI heads and had non-self aligning rockers. This was a really WEIRD block. it had provisions for roller cam, but the spider bosses were not milled or tapped. I actually rebuilt this engine for my squarebody and tapped the bosses myself to run a roller cam. after getting the engine installed it started getting really low oil pressure . ended up tearing the block down and found it had this REALLY weird counter bore machined into the lifter bores. worked fine on flat tappet but for roller lifters the oil band would go into this counter bore and bleed off the oil pressure into the lifter valley. 2 machine shops missed this and i even had the engine broken in on the dyno! i found some obscure information that apparently with thesee blocks I could have run 3.1 Lumina roller rockers with this weird lifter bore. the machine shop ended up getting me a different block.
 

L31MaxExpress

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not trying to start an argument here, but I pulled a TBI 350 from a low mile '87 R2500 about 5 years ago. It had '191 TBI heads and had non-self aligning rockers. This was a really WEIRD block. it had provisions for roller cam, but the spider bosses were not milled or tapped. I actually rebuilt this engine for my squarebody and tapped the bosses myself to run a roller cam. after getting the engine installed it started getting really low oil pressure . ended up tearing the block down and found it had this REALLY weird counter bore machined into the lifter bores. worked fine on flat tappet but for roller lifters the oil band would go into this counter bore and bleed off the oil pressure into the lifter valley. 2 machine shops missed this and i even had the engine broken in on the dyno! i found some obscure information that apparently with thesee blocks I could have run 3.1 Lumina roller rockers with this weird lifter bore. the machine shop ended up getting me a different block.
I have seen some weird stuff in 87 as well. The 87 G20 I have was a very early build. The stock TBI 305 had 187 heads with the port walls milled between intake ports like the 4.3 heads with stainless steel clips pressed over them. Some of those clips had actually broken and the ends were missing on them, I am assuming the engine injested them although it ran fine.

I also discovered despite having a catalytic converter, it was an open loop TBI system with no provision for an 02 sensor and no EGR valve. The intake manifold was cast shut where the EGR went. It also had an OE roller cam and torx bit valve cover bolts.

That being said almost every TBI engine I have been into had self-aligning factory rocker arms.

My parents 1980 C10s 305 had the lifter bore machining messed up from the factory. Several of the lifter bores were factory sleeved. When that engine got up over 100K the sleeves pushed out and the oil pressure dropped. Our mechanic at the time, shoved them back into place and tack welded them to the block. That repair worked a good number of years until dad had a low mileage 350 swapped into the truck.
 
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