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Discussion Starter · #1 ·
Well I'm going back in time a little LOL. I have a 95 Z71 with a stock TBI 305 and a chip. This engine has been awesome but I'm down to 60 PSI and it's still running. I'm going to pull it out bore it 30 over. I was thinking about drilling the provisions for a roller cam. Questions what was the difference in lift and duration from the hydraulic cam vs the roller cam 87-95? Why is roller cams so much more expensive than the hydraulic? Can someone point me in the direction of a good camshaft for Towing from 0-4000 etc in the roller and hydraulic that doesn't require modifications? I already have good exhaust etc? Thank you for any and all input.
 

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Discussion Starter · #2 · (Edited)
Well I'm going back in time a little LOL. I have a 95 Z71 with a stock TBI 305 and a chip. This engine has been awesome but I'm down to 60 PSI and it's still running. I'm going to pull it out bore it 30 over. I was thinking about drilling the provisions for a roller cam. Questions what was the difference in lift and duration from the hydraulic cam vs the roller cam 87-95? Why is roller cams so much more expensive than the hydraulic? Can someone point me in the direction of a good camshaft for Towing from 0-4000 etc in the roller and hydraulic that doesn't require modifications? I already have good exhaust etc? Thank you for any and all input.
 

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You can use a factory roller cam after drilling and tapping for the hold-down spider. Non-retrofit roller cam isn't that much more expensive. Part of what makes flat tappet cams so cheap is that they're cast iron. Most rollers are steel. Plus the roller lifters are a bit more complex.

I would have to look up the differences in duration and lift, but both are tiny. Like the early flat-tap cams were something like 181/187 duration. Later rollers weren't much bigger. Are you keeping the TBI? If so, you are incredibly limited with cams. Those computers can't tolerate much change at all. You'll have to find someone to burn you a chip, which can be kind of trial-and-error.

I also have to point out, for the cost of boring that 305 you can find a good running 350 and skip the complete rebuild cost. For $500 you can swap in a 350 from a TBI truck, and steal the ECM from the donor truck. Weekend swap gets you 80 more torques for $500 instead of weeks of rebuilding a tiny-bore 305 which will never see that much torque unless you open the really big wallet. 305s really kinda suck. The tiny bores limit breathing, the small displacement limits torque. I would use one to just get something moving under it's own power, but as soon as you spend $250 modifying a 305, you're better off just buying a $250 longblock 350.
 

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Does this block actually have roller cam provisions? As in the three bosses cast on top of the main oil galley and the ears to either side of the thrust face surrounding the cam bore. If so these can be brought up to usefulness by drilling and tapping.

Roller cams are made from a more expensive material. Factory production cams are mostly Compacted Graphitic Iron (CGI), this is a high grade structural casting material used a lot in high strength castings, it is more difficult to finish machine than the cast iron of flat tappet cams but less so than the type of billet alloy used in aftermarket cams. The reason for high grade material is the rollers of the lifters want to unwind the cam material’s surface. This is somewhat similar to shaping sheet on an English Wheel where the roller wants to curve back the surface it’s passing over.

The lifters are more expensive because once again real steel parts and extra assembly labor of the axle, bearing and wheel that a flat tappet isn’t using, And for factory lifters there is the guide flat machining. For aftermarket performance there is the added extensions yo the upper housing that attach the guide bars and the assembly into lifter pairs.

Actually the OEMs probably could have solved the flat tappet wear issues by making their cams from the CGI material used in their roller cams combined with a hard faced flat tappet, lifters. But the roller opened the way for faster lift rates and higher amounts you see in the Gen III and up engines which for street use are just not obtainable with flat tappet cams.

The TBI engines 305 and 350 (L03 and L05) use the same flat tappet cam which at .050 inch lift provide about 168 degrees of intake duration with less than .4 inch of lift. The 305 and 350 L30 and L31 engines in comparison have a roller cam that times the intake at 194 degrees and a bit more than .4 inch lift at the valve. While packing 26 more degrees and about .04 inch more lift than the cam you have, you will find the basic TBI program will pick this up on a fresh engine as the difference in breathing this picked up by the limited self learning that is there to compensate for normal aging wear of the engine, but this is close to the limit of the OBD-1 system on your truck, it will usually pick up both this cam and 1.6 rockers.

Bogie
e
 

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You will be a lot better off finding a rebuildable 350 like Curtis recommended, or buying a crate engine and adding injection. Your old throttle body is going to have air leaking around the throttle shafts and the injectors are probably near their end. See if you can get an adapter to your wiring harness from any of the aftermarket companies that offer stand alone injection and get one of their systems. Getting a chip reprogrammed correctly on the first try is difficult if you can even find someone to do it anymore.
 

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Discussion Starter · #7 ·
You can use a factory roller cam after drilling and tapping for the hold-down spider. Non-retrofit roller cam isn't that much more expensive. Part of what makes flat tappet cams so cheap is that they're cast iron. Most rollers are steel. Plus the roller lifters are a bit more complex.

I would have to look up the differences in duration and lift, but both are tiny. Like the early flat-tap cams were something like 181/187 duration. Later rollers weren't much bigger. Are you keeping the TBI? If so, you are incredibly limited with cams. Those computers can't tolerate much change at all. You'll have to find someone to burn you a chip, which can be kind of trial-and-error.

I also have to point out, for the cost of boring that 305 you can find a good running 350 and skip the complete rebuild cost. For $500 you can swap in a 350 from a TBI truck, and steal the ECM from the donor truck. Weekend swap gets you 80 more torques for $500 instead of weeks of rebuilding a tiny-bore 305 which will never see that much torque unless you open the really big wallet. 305s really kinda suck. The tiny bores limit breathing, the small displacement limits torque. I would use one to just get something moving under it's own power, but as soon as you spend $250 modifying a 305, you're better off just buying a $250 longblock 350.
Thank you Curtis. I'm going to keep the TBI and the fuel mileage with the 305 LOL. I just need a little bit more torque. I literally cannot believe this engine is running on 60 PSI. I have another question I'm more than likely going to use a roller cam. on the hydraulic cams they offer RV cams for low end torque but I can't seem to find one of these in a roller with just a little more lift than the original rollers that cam in the F bodies. I already have a chip installed but it's probably just to advance the timing. But I definitely do not want to get into burning chips.
 

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Discussion Starter · #8 ·
Does this block actually have roller cam provisions? As in the three bosses cast on top of the main oil galley and the ears to either side of the thrust face surrounding the cam bore. If so these can be brought up to usefulness by drilling and tapping.

Roller cams are made from a more expensive material. Factory production cams are mostly Compacted Graphitic Iron (CGI), this is a high grade structural casting material used a lot in high strength castings, it is more difficult to finish machine than the cast iron of flat tappet cams but less so than the type of billet alloy used in aftermarket cams. The reason for high grade material is the rollers of the lifters want to unwind the cam material’s surface. This is somewhat similar to shaping sheet on an English Wheel where the roller wants to curve back the surface it’s passing over.

The lifters are more expensive because once again real steel parts and extra assembly labor of the axle, bearing and wheel that a flat tappet isn’t using, And for factory lifters there is the guide flat machining. For aftermarket performance there is the added extensions yo the upper housing that attach the guide bars and the assembly into lifter pairs.

Actually the OEMs probably could have solved the flat tappet wear issues by making their cams from the CGI material used in their roller cams combined with a hard faced flat tappet, lifters. But the roller opened the way for faster lift rates and higher amounts you see in the Gen III and up engines which for street use are just not obtainable with flat tappet cams.

The TBI engines 305 and 350 (L03 and L05) use the same flat tappet cam which at .050 inch lift provide about 168 degrees of intake duration with less than .4 inch of lift. The 305 and 350 L30 and L31 engines in comparison have a roller cam that times the intake at 194 degrees and a bit more than .4 inch lift at the valve. While packing 26 more degrees and about .04 inch more lift than the cam you have, you will find the basic TBI program will pick this up on a fresh engine as the difference in breathing this picked up by the limited self learning that is there to compensate for normal aging wear of the engine, but this is close to the limit of the OBD-1 system on your truck, it will usually pick up both this cam and 1.6 rockers.

Bogie
e
Thanks Bogie for your info. My 95 actually has OBD2 hookup but it's still the old technology. So are you saying a Vortec cam would work in this engine? I'm almost certain I have the provisions for the roller cam
 

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Yes the 96-2001 L30/L31 cam works well in L03 and L05 engines with Swirl Port head’s and TBI. You also need the install kit which is the dog bones, their retention spider, and the cam thrust plate with its retention bolts.

What do you mean your 95 has an OBD-2 hookup? The V8’s were OBD-1 which is a very different computer, software, fuel system, and wire bundles. Some 4.3’s came with either OBD-2 or OBD-1 in this time frame but I’m not aware that any V8’s were customer beta tested with OBD-2 before 1996.

I am in agreement with others that a 350 swap would serve you better than rehashing the 305. But that decision certainly is yours.

Bogie
 

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Regardless of which engine you decided to build or rebuild, (I agree 350 is better choice) my guess is you will be replacing pistons, you could go with flat top to bump the compression a little. Also if you by new piston make sure the compression height is 1.560 and not jobber 1.540 which many replacement kits contain.
 

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Thank you Curtis. I'm going to keep the TBI and the fuel mileage with the 305 LOL. I just need a little bit more torque. I literally cannot believe this engine is running on 60 PSI. I have another question I'm more than likely going to use a roller cam. on the hydraulic cams they offer RV cams for low end torque but I can't seem to find one of these in a roller with just a little more lift than the original rollers that cam in the F bodies. I already have a chip installed but it's probably just to advance the timing. But I definitely do not want to get into burning chips.
You may actually pick up some MPG with the 350 with the easier breathing and lower torque peak. Displacement has almost nothing to do with MPG. One of the best MPG engines I had in a truck was a Cadillac 500. Consistent 18 mpg empty with almost 600 lb-ft of torque and 3.08 gears/31" tires. Dropping in a TBI 350 is likely the same or better MPG with 80 more lb-ft for $500, or you can spend $2000 on getting an additional 30 lb-ft from rebuilding a 305. Your choice, but modifying a 305 is just folly.

Definitely use a roller cam. Way more area under the curve. Broader torque curve, higher peak torque, less risk of wiping a lobe.
 

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Discussion Starter · #12 ·
Yes the 96-2001 L30/L31 cam works well in L03 and L05 engines with Swirl Port head’s and TBI. You also need the install kit which is the dog bones, their retention spider, and the cam thrust plate with its retention bolts.

What do you mean your 95 has an OBD-2 hookup? The V8’s were OBD-1 which is a very different computer, software, fuel system, and wire bundles. Some 4.3’s came with either OBD-2 or OBD-1 in this time frame but I’m not aware that any V8’s were customer beta tested with OBD-2 before 1996.

I am in agreement with others that a 350 swap would serve you better than rehashing the 305. But that decision certainly is yours.

Bogie
I have nothing against 350 motors I have a couple of the early models built. But the fuel mileage in this truck has been awesome. But yes this 1995 has OBD2 hookup maybe it has something to do with the electronic 60LE trans. I will look into the L30 cams. I'm looking for low end torque for pulling trailers etc and rarely hit 4000 rpms. Anyways thanks for taking your time to help out👍
 

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Discussion Starter · #13 ·
You may actually pick up some MPG with the 350 with the easier breathing and lower torque peak. Displacement has almost nothing to do with MPG. One of the best MPG engines I had in a truck was a Cadillac 500. Consistent 18 mpg empty with almost 600 lb-ft of torque and 3.08 gears/31" tires. Dropping in a TBI 350 is likely the same or better MPG with 80 more lb-ft for $500, or you can spend $2000 on getting an additional 30 lb-ft from rebuilding a 305. Your choice, but modifying a 305 is just folly.

Definitely use a roller cam. Way more area under the curve. Broader torque curve, higher peak torque, less risk of wiping a lobe.
Why they put a 305 in a 4×4 extended cab is beyond me lol.
 

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Much of the fuel mileage you get on your 305 is the miserly cam GM put in those engines. You will find that the L30/L31 Vortec roller cam without L31 Vortec head’s (I left out L30 vortec head’s as they are simpler and less efficient) and the the Multipoint fuel injection system the fuel mileage of a Swirl Port, TBI engine will measurably drop. The Vortec cam has a lot more duration and lift and in the TBI engine with less efficient head’s and injection system you will see tge decrease, this is from first hand experience with these swaps.

These modern engines are point designed to hit legal emissions and mileage standards. To that end each configuration and generation contain specific design elements that when used piecemeal across the configurations and generations do not produce the same overall result.

We hot rodders had a blast of serendipity with the L31 Vortec head as it as a stand-alone item makes fantastic power no matter what it gets bolted on. This, however, does not carry across the configurational divide with better fuel mileage without the sequential multi port fuel injection system and the supporting cast members of its somewhat weird computer controlled distributor and ignition system and the cam.

The cam alone will give you a little power improvement but it will cost some fuel doing it. With the L30 and L31 it‘s the better combustion characteristics of the Vortec chamber and the more precise injection that held the line on fuel burn with more power.

Bogie
 

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Lets put it in context. You will spend a lot of money to just rebuild the 305 and it would cost you no more (other than an initial core purchase $200/$400 for a 350. Then you resell your core for $150 and you are out $50 to $250 for 45 additional cubic inches. Without changing the cam you will have more low end torque than you will get with a cammed 305. 45 cubic inches is a lot.

No matter which way you go, your current chip will most likely not match your engine and you will need to deal with that.
Much better off adapting an aftermarket injection that self tunes and you probably will increase gas mileage because it doen't have to deal with factory emissions garbage and you can run a lower temp thermostat.

The concensus here seems to be that a 350 is the best choice and that a 305 isn't worth the effort. When you are done with the 305 you will be lucky if you gain 20 HP and it will never have the torque and midrange of a 350.

If you do a little research, you can locate a 350 from a similar year Chevy that is a 350 and comes with a computer and harness that would simply plug into your existing harness.

"The low-compression version of the 1995 Chevrolet 350 was used in four vehicles: Suburban, G30 van, C/K3500 and C/K2500. "

Rebuild that and maybe get pistons with a little higher compression.
 

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Discussion Starter · #16 ·
Regardless of which engine you decided to build or rebuild, (I agree 350 is better choice) my guess is you will be replacing pistons, you could go with flat top to bump the compression a little. Also if you by new piston make sure the compression height is 1.560 and not jobber 1.540 which many replacement kits contain.
I have been searching for a 30 over 1.560 everyone states it's for a 84-87. What's the deal with that? Isn't all the blocks basically the same?
 

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My guess is that the ring thinkness is different after 1987, but I would call the piston manufacturer and review with them.

I have a feeling you will be buying pistons for an 87 engine and have no problems.

a quick google search pulls these up.


 

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I have been searching for a 30 over 1.560 everyone states it's for a 84-87. What's the deal with that? Isn't all the blocks basically the same?
No all 350 blocks are not the same. One or two piece rear seals and flat tappet to roller cams notwithstanding The other big change came with powder forged rods and hypereutectic pistons the length of of the cylinder extension into the crankcase was shortened as was the piston skirt. As you get into this transition period you find some odd ball match ups as a result. This isn’t to critical but there part mixes that can get you into situations that should be rebalanced.

Bogie
 

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Are you sure your 1995 305 doesn't have a roller cam? Beginning around 1986, most 1/2 ton trucks got roller cams. And even if they didn't there's a good chance the block was drilled to accept a roller cam retainer plate and "spiders" to hold down the roller lifters. At least that was the case with 86-up 350 blocks.

As for a flat tappet cam, this one from Crane is a bit unusual, but from first hand experience I can tell you it will make lots of torque in the 1500-3500 RPM range.
 
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