Big Block Vortec Heads

[Nonstop]

Hi everybody!

So yesterday, I scored a set of L29 heads from Pick N Pull for a total of $45. They are going to replace a set of peanut port heads on a 454. It is mainly a tow rig. The heads look good (although greasy and oily) and have a rebuilder tag.

So, I have been reading up on the swap. I have already ordered the rocker studs to adapt to adjustable rockers. The cam in my truck is a mild Comp Magnum (I think - it has been almost 20 years since I built it). So I have two questions now:

1 Is there anything else I need? I have been reading about rotator eliminators, are they needed?

2 What gains can I expect? I hope it is worth the effort.

Thank you for any light that can be shed on this! I am finding all sorts info that is all over the board!

 

[bucket]

Make sure you have enough valve guide/retainer clearance for your current cam. You will want to install springs that work with the cam too.

Rotator eliminators do just that- take place of the rotators for more valvetrain stability.

 

[Nonstop]

Thank you! Is it necessary to replace the rotators with the eliminators, or can I still use them?

Thanks again!

 

[Dale A]

Check into the height of those studs. I read where the use of the stud makes the valve train taller to the point that the stock valve covers may not accommodate them.

 

[TubeTruck]

@bucket and @Dale A are correct. The stock springs are only good enough for the stock cam. Any more lift than stock and you need new springs, which may involve cutting new seats. Run the eliminators or get some retainers when you get new springs, the rotators take up valuable spring height and are an emissions thing really. They rotate the valve to prevent carbon buildup and keep valve temps more even. When running a cam above stock you need to do the adjustable valve train (which you already got). That requires tapping the head for new studs. You can reuse the original rockers but you will need taller valve covers due to the increased height. You will also need pushrod guide plates since the rockers can now move. I'm sure you know but you will also need a new intake since the peanut ports are a lot smaller than the standard oval port. You will also get a bump in compression. I believe the peanut port heads are around 120cc and the L29 heads are 100cc, which I think bumps it 1-2 points of compression

I don't know how much you will gain but you will notice a huge difference. I've heard the L29 heads referred to as "GM's best kept secret". They have the best flow numbers on the exhaust out off any oval port head and the intake is ok. I've read where people have ported the intake runners and installed larger valves only to have reduced flow numbers. The swirl the intake runners produce is apparently really good.

If I had to guess, with the bump in compression, the cam, and the increased flow numbers I would say at least a 50hp gain.

 

[Catbox]

Are you installing these heads on a Mark IV block?
I have read that they are not backwards compatible.
This is due to the coolant passages that are in the Mark VI heads.
I never really dug any deeper as I have the whole thing to work with.

I have been reading a lot on the L-29 engine do's and don'ts as I just scored the entire engine from the junkyard a few weeks ago.

I have also read that it is very easy to break into the water passages while porting them.
So I would not recommend anything other than a cleanup.

Google has been helpful.
Search for "L-29 builds" and you should find lots of good stuff on them.

 

[Catbox]

Here is a good read from somebody that did some porting and had them flowed...

https://www.chevelles.com/forums/13...eads-actual-flow-numbers-stock-vs-ported.html

 

[Catbox]

I love the google machine...

You must be registered for see images attach

 

[Nonstop]

Thanks, I have seen those posts. This is going to be l29 heads on a gen IV block, so it should be good! Studs and guide plates are en route, and I guess I will order 2 sets of eliminators. I already have a performer intake, so I am thinking I should almost be set. I am going to clean them, put on the hardware, and run them. I am not doing any porting, just replacing stock peanut ports with these. The truck currently is built for torque and just looking to increase that. I have read some good things about these heads, but then I also read to forget these and get 049s. Cannot find those for $45.

 

[bucket]

The gen6 heads work on a markIV block as well as as a gen 5 block.

Now, I have not personally messed with gen 6 heads yet, just gen 5. But it's my understanding they are nearly identical, the exception being that the gen 6 head doesn't have the stupid shaped coolant passages or the tiny ports. With that said...
The conversion studs fit under the stock valve covers, as long as you keep with the included adjuster nuts and stock rockers. The heads do not need tapped for the studs, that's the purpose in the conversion stud kit.

The stock heads also employ guide plates, but they are for 5/16 pushrods. When upgrading the cam, you will probably want to go with 3/8 pushrods which will require matching guide plates.

Some engines only have rotators on the exhaust valves. Some have them on the intake valves as well as the exhaust. I think you will find that the eliminators don't fit over the intake valve guides without some minor machining. For some reason, GM made them slightly larger.

 

[Nonstop]

I am sorry for all the questions, but one more (for now...). So just to clarify, I can use the retainers that are currently on my peanut port heads (with no rotators) on the new heads and I will not need the eliminators? That would be fantastic IF I can! If not, no biggie, just looking to see what I can reuse.

Thank you all again!

 

[bucket]

No, the rotator eliminators just make up the difference in height so you can run springs that use the stock type installed height. Around 1.9" iirc.

 

[TubeTruck]

The gen6 heads work on a markIV block as well as as a gen 5 block.

Now, I have not personally messed with gen 6 heads yet, just gen 5. But it's my understanding they are nearly identical, the exception being that the gen 6 head doesn't have the stupid shaped coolant passages or the tiny ports. With that said...
The conversion studs fit under the stock valve covers, as long as you keep with the included adjuster nuts and stock rockers. The heads do not need tapped for the studs, that's the purpose in the conversion stud kit.

The stock heads also employ guide plates, but they are for 5/16 pushrods. When upgrading the cam, you will probably want to go with 3/8 pushrods which will require matching guide plates.

Some engines only have rotators on the exhaust valves. Some have them on the intake valves as well as the exhaust. I think you will find that the eliminators don't fit over the intake valve guides without some minor machining. For some reason, GM made them slightly larger.

Stupid internet. All the research I've done on this engine and most of it was wrong. After reading your post I went out and took a head apart. Yup, rocker studs screw in and it has guide plates. I read over and over again they were pressed in and had to be pulled and tapped. Haven't read anything about being able to keep the stock valve covers but I'll take your word for it and hope it's true because I have 454SS covers I want to run. My rotators are on all valves but they are on the bottom, contrary to all the pics I've seen but it does make sense now about having to grind the valve guides to fit the eliminators.

 

[bucket]

Stupid internet. All the research I've done on this engine and most of it was wrong. After reading your post I went out and took a head apart. Yup, rocker studs screw in and it has guide plates. I read over and over again they were pressed in and had to be pulled and tapped. Haven't read anything about being able to keep the stock valve covers but I'll take your word for it and hope it's true because I have 454SS covers I want to run. My rotators are on all valves but they are on the bottom, contrary to all the pics I've seen but it does make sense now about having to grind the valve guides to fit the eliminators.

When I was originally putting together my gen 5, I found out the internet was completely wrong about them too, lol.

One thing that may make a difference, I ended up sticking my gen 5 long block in my '90 (mark IV) 454 SS pickup. I used the conversion stud kit, but used the stamped steel covers that were original to the truck. So I suppose there could have been a clearance issue with the aluminum covers.

 

[bucket]

I suppose if the aluminum covers don't actually fit, it has to be really close to fitting. You could probably use a steel-core rubber gasket in addition to the o-ring that fits the cover. That would provide some clearance.