Cam and Vortec Head swap

[spanky1205]

Sorry this is going to be long, I have read a ton of these threads and the first complaint from people who respond is they need more information, so I will just try to give it all in one shot. I own a 1987 4x4 that I plan to use as a daily driver until I give it to my son for his first vehicle. My goal is to have a good running truck, that I can go down to the local parts store and get what I need. I want to be able to pass a vehicle on a two lane road when I need to and sometimes pull a loaded 16' flat bed trailer, nothing extreme. The current engine is a SBC 350 with an unknown miles and cam, non matching smogger heads, flat top pistons with 4 valve reliefs, quadrajet carburetor, th700, np208, 3.08 gears, and 32x10.5 tires. I have good oil pressure so I have no reason to think much needs done with the bottom end and prefer to keep it that way unless something comes up. Once everything under the hood is working properly I plan to do something about the gears, for now they will stay. I did not build the engine so that is about all I can tell you, until I take it apart. I have had the valve covers off but I do not remember the numbers on the heads, I do remember reading they are both 76cc plain nothing special heads. The truck runs but, there is a vacuum leak that is caused from the intake not being bolted down tight to the heads. The previous owner stripped a bunch of the threads so now I can't tighten everything down properly. Rather than put money in those heads I would like to upgrade to vortec heads and serpentine belt system. The reason for wanting the new belt system is it will allow me to upgrade to the newer type of A/C compressor, I have read it works better with R134 refrigerant than the compressor that came stock on the truck, which needs replaced. I am also missing a few bolts/brackets and would really prefer to have everything on the front of the engine being held together correctly. I realize I will be going from 76cc to 64cc chambers and that will up my static compression to around 10:1. With all of that being said is there anyway I can use that combination of parts and still keep my power in the 800-5000ish rpm range by swapping out the cam? People on the internet say votecs can handle a little more compression with few problems, but I have no clue what "a little more compression" is and the only answer I can find is "it depends." I have also read I can run this combination with a 262 or 268 comp cam. I have looked up the cams and understand to a point what all of the numbers mean, but I do not fully understand what that will do to my truck. It seems like those cams push the power band too high. I realize I could get some aftermarket heads pretty easily but I am still left with the current configuration of belts with missing bolts / brackets. I realize to fully answer all of my questions you need to know a few more measurements to figure out the exact quench, static / dynamic compression ratio, and things that I have not even dreamed of yet. My goal is to have a basic plan and adjust as I get more information, is this realistic or should I be making a different better plan all together?

 

[Jrgunn5150]

Ok, so, Vortec heads are a good choice, with your pistons you will likely come in around 9.75:1 with a .040 thickness head gasket. More compression will make the truck feel snappier on take off, you will need to run premium fuel though.

The comp 262 has enough lift that it may not work with stock heads and retainers. Vortec heads, unmodified, can handle between .450 and .470 of lift. Increasing lift while keeping duration short is desirable for a "truck" engine, it will keep the power coming in early. This cam, or a similar one would be up to the safe limits of the stock springs, http://iskycams.com/cart/index.php?main_page=product_info&products_id=270

Vortec heads, a cam like the one above, a dual plain intake, your current carb should get you up around 300 hp easily.

 

[MikeB]

10:1 will be a bit much, even for the Vortec chambers. I’d sure look for heads with 70-72cc chambers. You do NOT want to run a thicker head gasket to reduce compression. All that will get you is less quench and more detonation.


You're right to be concerned about using a cam that's too big. Anything more than around 204 intake duration @ .050” will subtract from the bottom and add to the top. Heck I’ve even seen a relatively mild 204/214 cam cause a loss in torque under 2500 RPM vs. a stock 195/202 cam in a C10 pickup with 3.08 axle and 29” tires.


So you have to choose a cam that will make lots of torque across the RPM range where the engine spends most of its time. With 3.08 gears and 32” tires, I’d suspect that range is 1500-3000 RPM. So call it a cam with a 1500-4500 RPM powerband (in a 350), or maybe even 1000-4000. Remember, torque is king in truck, especially one that pulls trailers.


My thoughts on my Vortec heads:


http://www.gmsquarebody.com/threads/downside-to-vortec-heads.17707/

 

[MikeB]

Increasing lift while keeping duration short is desirable for a "truck" engine...

Exactly. I'd even say "very short duration" given your 3.08 axle and 32" tires. MUCH shorter than 214/214.

 

[4WDKC]

The vortec head is a version of the LT1 head from the 94-96 Impalas that ran 10:1 compression with fuel injection and 342 gears. If your 87 still has the stock EFI it can be tuned to work with the new cam and heads and still monitor for spark knock (is my plan for my 87 4x4 also). The 308s and 32s are putting unnecessary load on the 700 and they just arent very fun (mine was 342s and 33s, now 410s). With the 342s my truck hunted alot for the right gear on the interstate, instead of swapping gears I found axles and swapped them in it was cheaper than buying gears and paying someone to install them. 373 or 410s get my recommendation 70mph with 33s and 410s is around 2k rpm.

 

[Jrgunn5150]

My thoughts on my Vortec heads:


http://www.gmsquarebody.com/threads/downside-to-vortec-heads.17707/

My thoughts are similar, unless you already have a set, or are getting them for nearly free, it doesn't make alot of sense to go with Vortecs vs say, a Skip White head.

 

[MikeB]

If your engine is a 1987 it might have a roller cam block, even if it has a flat tappet cam. Here are some roller cam block casting IDs:

14102058
14088526
14011148

I've also seen several 10243880 blocks, which may have been used for service replacements.

If your block can be fitted with an OE-style roller cam and lifters, here's a GM cam that would work pretty well with your current gears and tires: https://www.summitracing.com/parts/...vbPvo5cORNQgU8F916g3SBhv9xa_PJPBoCmZQQAvD_BwE

I'm running one in my 9.3:1 355 with Vortec heads, TH350, 2.73 axle(!) and 29" tires. It's not rocket ship, but moves away from a stoplight pretty well. And when cruising at 2000 RPM, it's only a downshift away from more power.

 

[shiftpro]

The vortec head is a version of the LT1 head from the 94-96 Impalas that ran 10:1 compression with fuel injection and 342 gears. If your 87 still has the stock EFI it can be tuned to work with the new cam and heads and still monitor for spark knock (is my plan for my 87 4x4 also). The 308s and 32s are putting unnecessary load on the 700 and they just arent very fun (mine was 342s and 33s, now 410s). With the 342s my truck hunted alot for the right gear on the interstate, instead of swapping gears I found axles and swapped them in it was cheaper than buying gears and paying someone to install them. 373 or 410s get my recommendation 70mph with 33s and 410s is around 2k rpm.

Excellent point on the gear ratio/700r4.
Read this post over a few times, it's important.

 

[shiftpro]

10:1 will be a bit much, even for the Vortec chambers. I’d sure look for heads with 70-72cc chambers. You do NOT want to run a thicker head gasket to reduce compression. All that will get you is less quench and more detonation.


You're right to be concerned about using a cam that's too big. Anything more than around 204 intake duration @ .050” will subtract from the bottom and add to the top. Heck I’ve even seen a relatively mild 204/214 cam cause a loss in torque under 2500 RPM vs. a stock 195/202 cam in a C10 pickup with 3.08 axle and 29” tires.


So you have to choose a cam that will make lots of torque across the RPM range where the engine spends most of its time. With 3.08 gears and 32” tires, I’d suspect that range is 1500-3000 RPM. So call it a cam with a 1500-4500 RPM powerband (in a 350), or maybe even 1000-4000. Remember, torque is king in truck, especially one that pulls trailers.


My thoughts on my Vortec heads:


http://www.gmsquarebody.com/threads/downside-to-vortec-heads.17707/

As I'm sure you already know, one can't accurately determine the compression ratio without more data, such as how far down the hole the piston tops out at. I've become a maniac decking blocks to get the piston up to where it should be. Even prefer to see it sticking proud maybe .010. Need to know which head gasket is being used and the compressed thickness to determine what the squish zone actually is.
But I realize this is too much detail for many 'normal' human beings.
Yes this requires getting all the machining done on the block, and assembling the crank and at least one piston/rod to determine it's relationship with the deck/valves/squish zone. Then pull it apart and toss block back on the decking machine. And... cleaning everything up again. Whew. No wonder it takes me years to finish a project... I a little crazy please forgive.

 

[spanky1205]

The vortec head is a version of the LT1 head from the 94-96 Impalas that ran 10:1 compression with fuel injection and 342 gears. If your 87 still has the stock EFI it can be tuned to work with the new cam and heads and still monitor for spark knock (is my plan for my 87 4x4 also). The 308s and 32s are putting unnecessary load on the 700 and they just arent very fun (mine was 342s and 33s, now 410s). With the 342s my truck hunted alot for the right gear on the interstate, instead of swapping gears I found axles and swapped them in it was cheaper than buying gears and paying someone to install them. 373 or 410s get my recommendation 70mph with 33s and 410s is around 2k rpm.

Sorry, I should have said axles rather than gears, I was trying to make a long post as short as possible and missed that. Different axles are on my list, just further down for right now.

If your engine is a 1987 it might have a roller cam block, even if it has a flat tappet cam. Here are some roller cam block casting IDs:

14102058
14088526
14011148

I've also seen several 10243880 blocks, which may have been used for service replacements.

If your block can be fitted with an OE-style roller cam and lifters, here's a GM cam that would work pretty well with your current gears and tires: https://www.summitracing.com/parts/...vbPvo5cORNQgU8F916g3SBhv9xa_PJPBoCmZQQAvD_BwE

I'm running one in my 9.3:1 355 with Vortec heads, TH350, 2.73 axle(!) and 29" tires. It's not rocket ship, but moves away from a stoplight pretty well. And when cruising at 2000 RPM, it's only a downshift away from more power.

The original block was swapped out for an older 4 bolt main block circa 1978. like a fool I did not write all of the casting numbers down and now I regret it. Next time around I will not make the same mistake. Regardless the original TBI engine was pretty chewed up, there was a bunch of grit all over everything inside that felt like sand. The wiring harness in the engine bay had been chewed up pretty bad by mice and I was not looking forward to rewiring it. My wife's uncle had the engine, that is currently in the truck, sitting around so I used that. He warned me he did not know much about the engine other than it ran well when he bought it and he had it sitting in storage for awhile. It may have not been what everyone else would have done but I am happy so I will go with it.

 

[shiftpro]

On finding Vortec heads....
Good luck finding a set that is not twisted up or cracked. Stay away from cheap china castings, or at least have a competent machinist go over them. I have been on a perpetual search for GM vortec heads for years and come up with nothing usable.
The newer (than late 70's) heads on just about everything don't lend well to rebuilding. After our beloved square bodies, nothing was built to be in service for decades. Trying to 'save weight' for 'fuel economy' is a crock imo, because it created junk smogger heads that were thin and flimsy. Even slightly overheating compromised them. Such a scam, such a shame...

 

[MikeB]

The original block was swapped out for an older 4 bolt main block circa 1978.

OK, that's cool. It limits your affordable cam choices to flat tappet, which is also fine. If you go with Vortecs and 64cc chambers I'd suggest a cam with at least a 112 LSA to close the intake valve a little later. Yes, more intake duration will also help fight detonation below peak torque RPM, but your truck with its current tires and gears won't like that much duration with its accompanying overlap.

Here are a few that may work, especially the Howards cam with 114 LSA.

https://www.summitracing.com/parts/hrs-112001-14/overview/make/chevrolet
https://www.summitracing.com/parts/lun-10120200/overview/make/chevrolet
https://www.summitracing.com/parts/isk-201256/overview/make/chevrolet

 

[4WDKC]

If you're on a tight budget find a set of 350 TPI heads, vortec heads are a gamble I bought a set from a running truck and had them checked just to be sure and a good thing i did, one was fractured but hadn't cracked yet. The shop tested it and said it wasn't leaking but wasn't comfortable telling me it was ok to use. So after cleaning, mangafluxing, decking to be flat, valve job, new seals and springs for .510 list i have about $600 total in the heads, then you need and intake. For a little more you can get new heads shipped to you with screw in studs and machined for different springs.

 

[Jrgunn5150]

I just saw a set of alloy TPI heads go for 300 on Ebay.

 

[MikeB]

...vortec heads are a gamble. I bought a set from a running truck and had them checked just to be sure and a good thing i did, one was fractured but hadn't cracked yet. The shop tested it and said it wasn't leaking but wasn't comfortable telling me it was OK to use.

Same thing happened to me. One tiny hairline crack between valve seats, visible only after magnafluxing. The machinist said the head would probably be OK, but he'd hate to see me put $300 in the pair and have the crack get worse.

Fortunately I paid only $150 for the 1997 short block and heads, and was able to use the block, crank, and oil pan to build an engine for my 82 C10. Also ended up selling the heads for $125 to a guy who was fixing up a truck to sell that had overheated enough to crack both heads badly. Apparently that's a common problem --- overheat your Vortecs and they are toast. Don't you just love lightweight castings designed to save a few pounds per vehicle?