Thread: 72elk

Tweet

Please read through this tutorial on the L31 Chevy heads.
http://www.crankshaftcoalition.com/w..._cylinder_head
Write down questions that you have and ask them at the end. These are what I would advise for someone looking for a bolt-on hp increase where you don't want to do a lot of work. Make the seller agree in writing that you can excnange the heads or get your money back if you magnaflux them and find them cracked. Get the stock self-guiding rocker arms with the heads. You will not need the pushrods, they are shorter than conventional Gen I pushrods because the L31 used a roller cam. You can use either self-guiding rockers with no guide plates or you can use conventional rockers with guide plates. You cannot use self-guiding rockers with guide plates. I would use a cam with up to 0.500" lift or just a little more (these heads will stop increasing flow at about 0.500" valve lift) by taking the retainers to a machine shop or a friend who has a surface grinder or Blanchard grinder and having them machine 0.080" off the bottoms of them. This is called a "ghetto grind" and will allow clearance between the bottom of the retainer and the top of the valve guide oil seal at full lift when using a cam with more lift. I would also drill and pin the studs. The article says that it is a stop-gap measure. Baloney. It's a permanent fix for preventing studs from pulling out of the heads. Mr. Gasket makes a kit to do it.
https://www.summitracing.com/parts/mrg-806g

I would not use an Avenger carburetor. Use an Edelbrock 650 AVS or AVS2 on an Edelbrock 7116 manifold. Install 1 5/8" full length headers with an H or X pipe installed immediately after the collectors. Build the motor 9.5:1 static compression ratio with a zero deck and 0.039" to 0.041" head gasket. Use a cam not to exceed 216 degrees duration @0.050" tappet lift with max lift around 0.500". This will make a very streetable 370-390 horsepower, depending on your tuning abilities.

Read through this thread to understand zero decking.....
http://www.hotrodders.com/forum/zero...ck-184870.html
.
.

Great article. Thanks for the info, I think I finally have a plan to follow. It's always tricky getting money out of my wife but that's good because otherwise I'd be broke. I currently have a 1948 Plymouth that I'm going to sell but it needs a new carburator. So, my wife agreed that I need to buy a new one and put it on my ElmCamino swapping its carburator to the Plymouth. I've also convinced her that if I'm going to all that work that I might as well get a new performer rpm manifold at the same time (per your earlier recommendation).
With the current info you offered I like the idea of going with the vortec heads. In doing an internet search I found a new pair for $680 from Machine Shop Pros who say they have been in business for 40 years and offer a 7 year warranty. The heads come with new guides, new stem seals and 3 way valve job. I know that they would still need some work to meet all of your recommendations but I was wondering if you think this is a fair price and would get me going in the right direction. Have you ever heard of them? Their web site, machineshoppros.com, doesn't address the vortec heads but there is a pretty good description in the eBay ad. Again, I do appreciate all the info you gave me and would value your opinion on this. At this time I will go ahead and buy the carb but wait in the manifold until I get heads.

If I get vortec heads, are their exhaust ports different than those with stock heads? If so how do I get headers to fit my 1972 el Camino with vortec heads?

Same exhaust ports; should bolt right up.

Thanks! By the way, I've got a 48 plymouth as well. It's for sale if you know anyone that's interested...it has a 350/350.

Nice, you could stick it over on the P15D24 site; that website is all 46-48 Mopar guys. Got some pictures?

Picked up a set of refurbished vortec heads today. They have been pressure tested, new guides and valve job. Now to study up on what needs to be done to them

The heads did not come with rocker arms. I will use self guided rocker arms but the question is should I go with roller rockers or standard? Also should I stick with the stock 1.5 ratio?

For a 300hp street engine, I'd just go with the stock stamped ones. Stock Vortec engines are 265hp, I think. Just a set of headers and a Performer RPM intake & mild street cam will probably put you over 300. Does your engine have a factory roller cam?

You'll need to post everything you know or can find out about the heads you bought. Have they been fitted with different springs and retainers to allow more valve lift over stock? Stock L31 heads were designed for a valve lift of no more than about 0.430". Every yahoo and cowboy will tell you that they will take a 0.480" valve lift....and they will, IF YOU USE UP THE 0.050" SAFETY MARGIN THAT CHEVROLET ENGINEERED INTO THE PRODUCT. The correct way to get more lift out of the L31 heads is with a different spring and a different retainer......or you can conduct the ghetto grind on the stock L31 retainers, where you turn them upside down on a surface grinder table or Blanchard grinder table and grind 0.080" off the bottoms of them. That will allow a valve lift of 0.500" and still keep a safety margin. Use a socket (I think 1/2") to gently tap the valve guide seals down onto the valve guides solidly before assembly.

You can use cast iron rail rockers like the original L31's used, or you can opt for aftermarket full roller rockers such as these offered toward the bottom of this post, by Pace Performance. Here is the stamped steel rocker arm like Chevrolet used on the L31 motor.......
Chevrolet Performance stamped steel 1.5:1 ratio, narrow body rocker arms with balls and nuts....
https://www.summitracing.com/parts/nal-12495490

Chevrolet Performance does not manufacture a 1.6:1 stamped steel rocker. You will have to go to an aftermarket manufacturer if that is what you want, and they won't be stamped, they'll be aluminum full rollers. Please stay away from the Comp Magnum rollers, they are a joke, having a roller tip and a conventional fulcrum. That's exactly backward from the way they should have been designed. They should have had a conventional tip and a roller fulcrum. The roller tip is useless. Their only saving grace, in my opinion, is the fact that they are a true 1.52:1 ratio rather than a hit or miss stock Chevy 1.5:1 (or more, or less) due to manufacturing tolerances.

https://paceperformance.com/i-895190...-aligning.html
I know nothing about these particular rockers and will not recommend them nor say anything negative about them. I am offering them up just so you can see that they are available in an affordable product. You should expect to pay close to $300 for a quality, known brand of rocker or you can take a chance on these.

If you use any 1.6:1 rockers, I would recommend that you use a Louis Tool to correct the holes in the heads where the pushrods come up through from the lifter cups. Actually, I would do this operation to ALL L31 heads, regardless of rocker ratio.
https://www.summitracing.com/parts/pow-pow351305
.

Don't know anything about the existing cam except that it is not stock.

The heads are being supplied with stock springs and retainers. Valves have a 3 way grind

I've found a guy that has a set of Comp Cam b hive springs 26915 new in the box for $50. Looks like they will work, any comments?

To bring you up to date, I may be going over board with the heads but more is good right? I picked up a set of vortec heads on eBay from a head shop, they are the 906 castings. Took them to a local head shop and they checked out good and are in prime original shape. I ran accros a guy on a local web site that had recently bought a house with a lot of stuff left in the garage. He advertised comp Cam b hive springs no 26915-16, retainers no 795-16 and seats no 705-16 all for $50 so of course I picked them up. I still need to get locks but don't know what I need. I've also got the Mr Gasket pin kit. I have the Eldebrock AVS thumper 650 carb and the eldebrok RPM manifold is on order. Not sure what push rods I need and with the new springs what Cam specs I should be looking at. I think I'm going to be WAY over 300 hp, but that's ok. Might as well go for 400. Any help you can give would be appreciated.

Have you called Comp and asked them yet?