1968 327 reubuild, vortec heads or not?

[lil hoodlum]

I am torn on which direction to go and would appreciate some input.

I have a 1968 327 sbc that is in the machine shop. The short block is complete. I ordered a set of ProMax Performance cast iron Vortec heads. The heads are drilled for the earlier style intakes and Vortec style intakes. Problem is when the earlier style intake is bolted on there is a small gap on the top because the intake runners are much taller.

I orginally wanted to get the motor more or less stock and factory appearing except an HEI distributor will be used.

Stock intake, four barrel carberator, stock air cleaner, stock ramshorn exhaust manifolds, stock alternator brackets etc.



I am torn as to just buy a new Vortec style intake and move forward or find another set of heads that will accept the correct oil tube fill intake manifold?


Will post up engine work done, specs, and numbers shortly.

[lil hoodlum]

The motor was "supposedly" rebuilt sometime before I purchased it. The pistons were .30 over.

After taking it to the machine shop the said it needed to be bored .60 over because the was a ridge on top of the cylinders and some rust and pitting in the cylinders.

From what I can tell the motor was orginally out of a 1968 El Camino.

[lil hoodlum]

The motor is still on the engine stand and the Vortec heads are installed on the motor with the self-aligning rocker arms and correct legnth pushrods.

As stated the heads are made by ProMaxx Performance. ProMaxx Performance bought our Patriot Performance and so there was a name change. The part numbers are the same.

ProMaxx Performance SBC Vortec heads. Part Number 723-2151. 185cc
http://www.jegs.com/i/Proform/723/2151/10002/-1

[lil hoodlum]

Work done on the block as follows:

Dissassemble and inspected.
Degrease block and R&R Cam bearings.
Power hone, cut pistons with honing plate.
Line-hone main bearings and set bearing clearance.
Clean and Polish crance shaft, and shot blast.
Resize Connecting rods and set bearing clearance.
Seperate and assemble rods & pistons.
Balance rotating and recprcating (spelling?) assembly.


The replaced one connecting rod as there was some damage on the bottom end from possible contact with the block. New timing chain, oil pump and screen, replaced freeze plugs, new cam bearings, ARP rods and nuts used on connecting rods, MC1991 Cam and HA817 lifters, and new oil pan and oil pan bolts.

[lil hoodlum]

Cam Specs:

MC1991

Hydraulic flat tappet, Stage 3.
Duration @ .050": Intake: 224 Exhaust: 224
Advertised duration: Intake: 298 Exhaust: 298
Valve lift: Intake: .465 Exhaust: .465
Lobe separation: Intake: 107 Exhaust: 117
Power Range: 2000 - 5500 RPM
Idle: Fair

Comment: Good low to mid torgue.
Fuel Economy: Fair

Interchange numbers:

CS1138R
229-1991




I admit that I am fairly clueless as to what all of these specs mean but I am sure some more knowledgable people will ask.


I will take some photos of the motor on the engine stand and will talk to the builder tomorrow.

Hopefully some good folks on here will give me some good input.

[lil hoodlum]

Heads I am considering buying and using instead of the Vortecs.


3890462 1966-1967 Camel hump 302, 327, 350, 161/65CC port. Heads are fully rebuilt and assembled to stock factory specs and have screw in rocker arm studs.

3927186 1969-1970 Camel hump 302-350, 63CC. Heads are fully rebuilt and assembled to factory spec and have pressed in rocker arm studs.

3947041 1969-1970 302, 350 same as 186 & 187 heads. 64CC. These heads will need to be rubuilt.

[Tiger Joe]

http://www.jegs.com/i/Edelbrock/350/27033/10002/-1

This intake says vortec intake with oil fill tube. might help give you the look you are after

[garyd1961]

Originally Posted by Tiger Joe

http://www.jegs.com/i/Edelbrock/350/27033/10002/-1

This intake says vortec intake with oil fill tube. might help give you the look you are after

That is not a vortec intake. A vortec intake only has 8 bolts, 2 on each corner.

I can understand wanting to keep the factory look but you could have bought a vortec crate engine for what you have already spent on the short block. I would use the vortec heads and an aluminum vortec intake. You can paint the intake to make it match a little better.
The vortec heads just flow so much better than the old camel humps.

I should have read the whole thread before I posted. I thought you were looking for hp by your description of the build. I have 9.4:1 compression and run premium gas but it's not a daily driver.
In my opinion 300 to 350 hp is perfect for these trucks but you need torque in the low rpm range. Low compression and a big cam usually makes power in the higher rpm range. You may end up spending more on gas with the 72cc heads than you would have with the vortecs and premium gas.

[special-K]

This sounds familiar. My '67 GMC is to be an era correct hot truck. I had a 350, then found a '68 327 I built for it to be all the more with the theme. I even traded the '68 heads to my machinist for '67-earlier (64cc) heads without the accessory bosses. He didn't like my Eldelbrock intake with straight runners (made sense) with oil fill, and provided an air gap dual plane...which will perform much better. I'm using Z/28 valve covers and dual snorkle air cleaner. It's as much about appearance as performance. But now it doesn't have the oil fill and that intake is a square bore. The look is compromised. engine has been on the stand waiting, and I wonder about doing aluminum (painted) or cast iron Vortex heads for even better performance. Also built it with using an automatic I had with the 350 but changed to using an M22. So considering kicking the cam up a notch or two. Pondder ponder ponder. I'm right where you are at. I'll probably leave mine as is just because it's all done buttoned up tight ready to drop in. Can't say for sure, but if I was where you are at Imight be going with the modern heads. If the misfit of the Vortecs with old style intake bugged me I might just say screw it and go with Vortec intake. Did I miss pictures of that match-up or could you show us how that looks? In the end, details are very impotant to me and it sounds like to you. I build for me, not others, and if it doesn't matter to others that means nothing to me. But, fact is, it's just a little detail only seen when sitting with the hood up. Mine is compromised using old style heads, by the intake. I guess I could find a proper old style intake, but the air gap will perform better and is on there. I'd get a Z/28 intake if I changed it.

[Marshy]

The Vortec heads use a raised ceiling port that the old manifolds won't line up to, even with some grinding on the ceiling of the lower manifold opening can't account for the difference without welding/machining IIRC. Your best best is to call summit and ask them if they have an intake that will fit your heads and have the front oil fill tube. There might be something out there that's easily over looked.

Regarding issuing a 72cc combustion chamber, that's a really good way to go to get your CR down. However, I wouldn't recommend it blindly. Ask your builder to give you the deck clearance and piston relief volume so you can estimate your CR now and with the 72cc heads. You should (ie your builder) needs to know the deck clearance to choose a head gasket anyways so you aren't asking an oddball question anyways.

Did you chose a cam already? I'll review if you did... you might want the smaller heads if you are using a large duration cam. That's where you get into dynamic compression which dictates what octane you need, not necessarily static compression.

[toolboxchev]

Originally Posted by Marshy

The Vortec heads use a raised ceiling port that the old manifolds won't line up to, even with some grinding on the ceiling of the lower manifold opening can't account for the difference without welding/machining IIRC. Your best best is to call summit and ask them if they have an intake that will fit your heads and have the front oil fill tube. There might be something out there that's easily over looked.

Regarding issuing a 72cc combustion chamber, that's a really good way to go to get your CR down. However, I wouldn't recommend it blindly. Ask your builder to give you the deck clearance and piston relief volume so you can estimate your CR now and with the 72cc heads. You should (ie your builder) needs to know the deck clearance to choose a head gasket anyways so you aren't asking an oddball question anyways.

Did you chose a cam already? I'll review if you did... you might want the smaller heads if you are using a large duration cam. That's where you get into dynamic compression which dictates what octane you need, not necessarily static compression.

X2 on that!

[lil hoodlum]

Originally Posted by Marshy

Regarding issuing a 72cc combustion chamber, that's a really good way to go to get your CR down. However, I wouldn't recommend it blindly. Ask your builder to give you the deck clearance and piston relief volume so you can estimate your CR now and with the 72cc heads. You should (ie your builder) needs to know the deck clearance to choose a head gasket anyways so you aren't asking an oddball question anyways.

Did you chose a cam already? I'll review if you did... you might want the smaller heads if you are using a large duration cam. That's where you get into dynamic compression which dictates what octane you need, not necessarily static compression.

Hi Marshy,

I have posted the cam specs in post #5. I'm not really familiar with what all of the specs mean. I know it has to do with the opening and closing of the valves and what not but that is about it.

[lil hoodlum]

So today I was able to stop by the machine shop and speak to the builder about the motor.

I told him my cocerns about having to use the premium gas and that I was wanting to avoid that. I told him about the 72cc combustion chamber heads that I am thinking about using. He plugged the numbers into the computer and said it would bring my compression ratio down to 8.7:1 or he may have said 9.0:1. Anyway he said it would bring the compression ratio down and I should be able to use regular gas and that he still thought it would be a good motor. He said he felt the 72cc heads would be a better choice.

So, my next steps will be to figure out what to do with the Vortec heads. Hopefully Jegs will take them back or will give me credit in exchange for the heads. If they will I will purchase the 72cc ProMaxx heads from them.

Or another option the builder said they would rebuild a set of double hump heads. He said they have plenty in their storage unit to choose from.


I feel better about the new direction the build is going as I really have my heart set on using the oil fill intake. I would be even happier if the double hump heads are pre '69 as they won't have the accessory holes in the head. Yes, I allready have the correct exhuast manifolds and alternator bracketry along with the correct pulleys and short water pump.


I will say though that I thought the motor looked badazz with the Vortec heads bolted on.

[TheGhost]

The "double hump" heads as rule of thumb are 64 CC heads. So, you would be in the same place as the Vortec heads.

Just some thoughts...

A camshaft will affect cylinder pressure not compression ratio.

Static compression ratio is based on fixed mechanical features of the engine:
Cylinder Bore diameter, compression height of piston, combustion chamber size, head gasket thickness, etc..

A short duration high lift cam will build more cylinder pressure than a high lift long duration cam.

A camshaft can effect dynamic compression ratio(cylinder pressure).

So, when you put a bigger cam in an engine, you aren't really giving up compression. You may have lower cranking pressure, and less low speed performance, but sooner or later the extra duration will help get more air into the engine than you would have ever gotten with a smaller cam. Eventually both cylinder pressure and power will go up even if the actual static compression ratio stayed the same.

There is one side efect to this though...detonation, which is based in part on cylinder pressure and engine speed (or the amount of time the fuel has to detonate). The faster an engine is spinning, the more likely there will be a leaner mixture, and the less time it has to detonate. Because of this, an engine with lets say 9:1 compression and a very early intake valve closing may be able to trap most of it's intake charge in the cylinder at a fairly low speed. Since the engine is spinning at a low speed, it won't be able to make as much pressure before the fuel detonates. The result would be an engine that detonates at low speeds and lacks high speed performance because the cam is too short. An engine with the same compression and a later intake closing event will trap less air in the cylinder at low speeds, and wont be as prone to detonation at low speeds. At higher speeds, the engine will intake more air and make more pressure, but since the engine is spinning faster, the fuel has less time to detonate, and detonation is avoided despite there being more pressure.

All this to say...make sure you really take some time to consider your camshaft choice as it relates to static compression and not place to much focus on any one component. Everything has to work together. Otherwise you end up with and engine that sounds great at idle, but doesn't really live up to it's potential. A rough idle can be accomplished by pulling off a vacuum line... :-)

[Marshy]

BTW, I did a search on your pistons and it looks like they are made by Sealed Power (310AP60) but I could not find any info on the size of the valve reliefs.

[garyd1961]

OK, went back and read this again, 8.7:1 or 9:1 should work, somehow I thought I read 8:1 compression.
There is a reason they have so many camel humps in their storage unit. They are outdated technology, vortecs are way better.

[lil hoodlum]

I hear what everyone is saying about the double hump heads and that the Vortecs flow so much better. That is one of the reasons why I was on board with using them hence why I purchased the ProMaxx units as I thought the earlier style intakes would bolt on. They are advertised as being drilled for both the vortec style intakes and the non-vortec intakes.

With that being said I am considering purchasing these aluminum heads 185cc intake runner, 72cc combustion chamber, 2.02"/1.60" valves. The heads are still ProMaxx Performance, just not vortec style.

http://www.jegs.com/i/ProMaxx-Perfor.../2171/10002/-1

[Marshy]

You might want to ask him what the quench distance is and if you can run a thinner head gasket to gain a little more compression with those larger style heads. I recently ditched my 0.040" thick head gaskets (FelPro 7733PT2) for a thinner 0.015" gasket (FelPro 1094). The change in thickness and diameter of the fire ring reduced the combustion chamber by 5cc and gained a half a point of static compression. I figured it went from 9.1:1 to 9.6:1, and runs fine on regular octane still. It could be more or less for you depending on your cylinder volume, don't assume you'll gain half a point in compression too, you need to run the numbers.

[lil hoodlum]

Just to update everyone, I ended up going with the ProMaxx Performance aluminum non-vortec heads, the 72cc ones.

The engine was broken in on the dynometer at the machine shop who rebuilt the engine. Peak torque was 336.8 Lb-Ft @4200 rpms. Peak horsepower was 308.3 @5600 rpms.

I took the delivered the motor to another shop to do the motor swap. Finally a little over a month it is due to be installed Wednesday morning.

I am nervious and excitied to finally be at this point. I'm hoping everything goes well.

[lil hoodlum]

First picture of my truck delivering its new heartbeat.

2nd & 3rd photos are of the motor after painting Chevy orange.

[lil hoodlum]

I'm really hoping that I can get some photos of the final assembly before install. I am told they are doing the final assembly of the motor tomorrow.

I am going with a rubuilt 4 barrell Quadrajet.

[rcazwillis]

That will be a good engine for your truck. Those power ratings will work well for a daily driver. Enjoy.

[Spullar]

Those look like some nice numbers. I love the filler neck on the intake. Good luck on the install.

[lil hoodlum]

Just wanted to update this, the 350 has been pulled and the rebuilt 327 is installed. i have had the truck for just over a week.

[garyd1961]

I hate be a negative kill-joy but those numbers aren't so great. All your power is at the 4200 to 58OO rpm range way above your normal driving range. Also it will probably cost you more to drive than if you went with the vortecs and premium gas.
A GM vortec crate engine will beat those numbers by a long shot for just a little over $2000.
I hope you don't take this personally. I don't mean it as an insult to you in any way and I hope you get many years of good use out of your motor but I think your builder could have given you better advice.