Thread: Help Me Pick Some Heads For Christmas Present

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If we assume a 0.025" piston deck height, 76cc chamber, 12cc piston crown and a factory shim gasket at 0.022", we get a static compression ratio of 8.34:1 and that's probably pretty close to real.

Swapping to a 67cc chamber and a 0.016" Fel-Pro steel shim gasket, we get a static compression ratio of 9.20:1 and that'll help the cam out some. Just remember that you have flat tappet valve springs in the heads and you'll have to change those if you go to a roller cam later.

Here's the best tutorial I've ever seen for rocker geometry and pushrod length.....
https://www.youtube.com/watch?v=o5is9BsH5OU&t=39s
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Originally Posted by techinspector1

Swapping to a 67cc chamber and a 0.016" Fel-Pro steel shim gasket, we get a static compression ratio of 9.20:1 and that'll help the cam out some.
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On this point I have some questions. How much piston 'play' should I account for? In other words, is shooting for a 0.040" quench cutting it too close? Should I allow some breathing room and shoot for 0.045"? At one end of the spectrum I'm flirting with pre-detonation so I want to find the correct balance but at the other end of the spectrum I want to reduce that distance as much as possible since the stock piston don't induce good quench/squish.

BTW I was considering this Felpro 0.015" gasket if I measured a 0.025" deck height.
https://www.summitracing.com/parts/fel-1094

0.035" to 0.045" is considered ideal. Famed automotive journalist and engine builder David Vizard has stated that the closer he makes the squish/quench, the more power the motor makes, as well as insuring against detonation. Of course there is a limit, where the piston crown contacts the underside of the head and the game is over. Smacking the head will begin taking out the bearings and unraveling the piston. It will also smash the ring lands and capture the rings so that they can no longer function. You know how the piston part number is stamped into the crown of the piston? I have seen that number transferred to the underside of the head due to contact. if you can get it that close without lifting the head, you have achieved the ultimate squish/quench in my opinion. This would likely be in the mid to high 20's, depending on rod and piston weight and rpm's.

There is pre-ignition and there is detonation. They are two different things.
Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

By the way, one very nice tool for your garage is a glass cc burette. Nothing inspires confidence in an engine build like absolutely knowing the volumes you're working with....If you buy a kit, buy a glass burette, not plastic.....I used to use Isopropyl alcohol from the drug store and food coloring from the grocery.....red, blue, green..take your pick.
https://www.summitracing.com/parts/pow-pow351150

P.S. You can offset the cost of a kit by cc'ing heads and pistons for other builders. Ask your local speed shop if you can hang a poster. that could turn into a very nice after-school job for your son. Post ads and pass the word at local roundy-round tracks and drag strips, NAPA, Autozone, burger drive-ins, etc. Anywhere car guys congregate.
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Originally Posted by techinspector1

0.035" to 0.045" is considered ideal. Famed automotive journalist and engine builder David Vizard has stated that the closer he makes the squish/quench, the more power the motor makes, as well as insuring against detonation. Of course there is a limit, where the piston crown contacts the underside of the head and the game is over. Lifting the head will breach the head gasket as well as begin taking out the bearings and unraveling the piston. You know how the piston part number is stamped into the crown of the piston? I have seen that number transferred to the underside of the head due to contact. if you can get it that close without lifting the head, you have achieved the ultimate squish/quench in my opinion. This would likely be in the mid to high 20's, depending on rod and piston weight and rpm's.

There is pre-ignition and there is detonation. They are two different things.
Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

By the way, one very nice tool for your garage is a glass cc burette. Nothing inspires confidence in an engine build like absolutely knowing the volumes you're working with....If you buy a kit, buy a glass burette, not plastic.....I used to use Isopropyl alcohol from the drug store and food coloring from the grocery.....red, blue, green..take your pick.
https://www.summitracing.com/parts/pow-pow351150

P.S. You can offset the cost of a kit by cc'ing heads and pistons for other builders. Ask your local speed shop if you can hang a poster. that could turn into a very nice after-school job for your son. Post ads and pass the word at local roundy-round tracks and drag strips, NAPA, Autozone, burger drive-ins, etc. Anywhere car guys congregate.
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OK that's encouraging to hear and I'll stay with the 0.040" target then. I'll follow up with actual measured values though.

I'm a chemical engineer by trade so quality lab instruments are already in my quiver and will definitely be used to obtain engine vitals. I like your suggestion regarding some after school engine room work for the young man, great idea!! I'll be sure to share that with him.

So I got the heads delivered this weekend and they look pretty good overall. Do you guys have any advice on anything I should be looking for with regards to QC'ing the heads? Also any prep, cleaning, conditioning of the heads prior to install? Of course I'd love to port/polish but that's beyond my skill set and an entirely different question.

My initial inspection has been looking for any casing defects, cleanliness, etc. I did find shavings at the bottom of the rocker arm stud bores left behind from the tap process. Also I noticed one of the intake walls had some tooling marks (see photo), should I be concerned with this or leave as is?

20171211_071946_resized.jpg

20171211_072428_resized.jpg

20171211_071750_resized.jpg

I'd recommend a good cleaning and blowing compressed air everywhere (be sure to wear eye protection!) I also like Glyptal to paint the inside portions - under the valve covers and inside the galley but not on any gasket surfaces. A quart of this stuff goes a long way and I use Harbor Freight cheep China bristle brushes.

Glyptal 1201 Paint - The Eastwood Company

Paint the outside with a good quality engine paint.

Glenn

Duplicate, please remove.

I would check the rocker stud holes to see if any of them go through the roof of any intake runners. That could be a source of sucking oil into the motor. If they poke through, unscrew them and slather the threads with Aviation Permatex. I would completely disassemble the heads and give them a good washing. Nobody cares about your equipment like you do.

You want to make sure that the rails of the rockers will not contact the tops of the retainers throughout the full range of lift. If the retainers are unloaded by the rockers, the locks could drop out and the game is over.
http://image.superchevy.com/f/955873...mage_large.jpg
Roll the motor through 720 degrees to insure that you have clearance on all 16 rockers.

This photo shows the L31 head with aftermarket conical valve springs and reduced diameter retainers. See how far above the locks the valve stem tip is? I'm not sure, but the L31 valves may be a little longer from the stem tip to the lock groove than conventional SBC valves that use the conventional rocker tip placement on the valve stem (pushrod hole in the head or guideplates).
http://www.powerperformancenews.com/.../VORTEC-07.jpg

Here's another photo, showing a negative lock for decreased installed height (higher spring pressure) and pushing the valve stem tip further out of the lock, a standard position lock and a positive lock for increased installed height (lower spring pressure) and sucking the valve stem tip further down into the lock.
https://www.chevydiy.com/wp-content/...17/01/23-8.jpg

If there is insufficient clearance between the rocker and the retainer with the valves that Summit used, you could possibly change locks to add clearance. Using a negative offset lock will make the valve stem stick out more above the top of the lock and at the same time, will decrease the spring installed height, adding additional force between the head and the underside of the retainer. Before I did this, I would find out exactly whose springs are in the head and the exact part numbers, then contact the manufacturer of the springs and give them the new spring pressure. You do not want to exceed the specified on-seat and open pressure due to possibly fragging the cam. Find out exactly what cam part number is in the motor and call the manufacturer to find out the particulars, using the springs that are in the heads, but installed at a shorter height. In any case, I personally would not exceed 260 lbs open pressure, with about 80-85 lbs on the seat. If this were my motor, I would check the pressure at installed and open anyway, before I ran the motor. TRUST NOBODY.

The other thing you could do, if the rockers contact the retainers, is to change to valves with longer stem length above the lock. That would prevent changing the locks and the installed height of the valve springs. I would resist any tendency that I might have to grind on the rocker rails.

See page 340 here to see how negative (-) locks could raise the valve stem tip and also decrease installed height (increasing spring tension)
http://www.cranecams.com/uploads/cat...%20Catalog.pdf

Just a thought, if you had purchased Chevrolet 12558060 heads, none of this would be an issue.
https://www.summitracing.com/parts/nal-12558060

I wouldn't worry about any blemishes on the runner walls, the lion's share of flow goes right down the middle.

If I'm not mistaken, Glyptal is the same stuff we used to paint the insides of cylinder blocks with. I think it is a GE product that was developed for coating the wiring on armatures in electric motors.
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Originally Posted by glennsexton

I'd recommend a good cleaning and blowing compressed air everywhere (be sure to wear eye protection!) I also like Glyptal to paint the inside portions - under the valve covers and inside the galley but not on any gasket surfaces. A quart of this stuff goes a long way and I use Harbor Freight cheep China bristle brushes.

Glyptal 1201 Paint - The Eastwood Company

Paint the outside with a good quality engine paint.

Glenn

Interesting, never heard of doing this. I'll look into it for sure!

Originally Posted by techinspector1

I would check the rocker stud holes to see if any of them go through the roof of any intake runners. That could be a source of sucking oil into the motor. If they poke through, unscrew them and slather the threads with Aviation Permatex. I would completely disassemble the heads and give them a good washing. Nobody cares about your equipment like you do.

You want to make sure that the rails of the rockers will not contact the tops of the retainers throughout the full range of lift. If the retainers are unloaded by the rockers, the locks could drop out and the game is over.
http://image.superchevy.com/f/955873...mage_large.jpg
Roll the motor through 720 degrees to insure that you have clearance.

This photo shows the L31 head with aftermarket conical valve springs and reduced diameter retainers. See how far above the locks the valve stem tip is? I'm not sure, but the L31 valves may be a little longer from the stem tip to the lock groove than conventional SBC valves that use the conventional rocker tip placement on the valve stem (pushrod hole in the head or guideplates).
http://www.powerperformancenews.com/.../VORTEC-07.jpg

Here's another photo, showing a negative lock for decreased installed height (higher spring pressure) and pushing the valve stem tip further out of the lock, a standard position lock and a positive lock for increased installed height (lower spring pressure) and sucking the valve stem tip further down into the lock.
https://www.chevydiy.com/wp-content/...17/01/23-8.jpg

If there is insufficient clearance between the rocker and the retainer with the valves that Summit used, you could possibly change locks to add clearance. Using a negative offset lock will make the valve stem stick out more above the top of the lock and at the same time, will decrease the spring installed height, adding additional force between the head and the underside of the retainer. Before I did this, I would find out exactly whose springs are in the head and the exact part numbers, then contact the manufacturer of the springs and give them the new spring pressure. You do not want to exceed the specified on-seat and open pressure due to possibly fragging the cam. Find out exactly what cam part number is in the motor and call the manufacturer to find out the particulars, using the springs that are in the heads, but installed at a shorter height. In any case, I personally would not exceed 260 lbs open pressure, with about 80-85 lbs on the seat. If this were my motor, I would check the pressure at installed and open anyway, before I ran the motor. TRUST NOBODY.

The other thing you could do, if the rockers contact the retainers, is to change to valves with longer stem length above the lock. That would prevent changing the locks and the installed height of the valve springs. I would resist any tendency that I might have to grind on the rocker rails.

See page 340 here to see how negative (-) locks could raise the valve stem tip and also decrease installed height (increasing spring tension)
http://www.cranecams.com/uploads/cat...%20Catalog.pdf

Just a thought, if you had purchased Chevrolet 12558060 heads, none of this would be an issue.
https://www.summitracing.com/parts/nal-12558060

I wouldn't worry about any blemishes on the runner walls, the lion's share of flow goes right down the middle.

If I'm not mistaken, Glyptal is the same stuff we used to paint the insides of cylinder blocks with. I think it is a GE product that was developed for coating the wiring on armatures in electric motors.
.

Now you have me worried, is there something specific you see (or know about) with regards to these Summit heads that make you bring up rockers hitting retainers? I guess I'm the one asking for suggestions on empirical exercises here but just had to ask in case you saw something that wasn't right. I agree with your idea to not simply trust the manufacturing assembler but to verify myself at every stage.
I did talk directly with Summit's techs and asked about compatibility of these heads with my exact set up and they confirmed I'm good to go, but I will add this to my QC list.

I'll reiterate. TRUST NOBODY.
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Remember what the Gipper said trust but varafiy

Also, check closely that the pushrod clears the head where it comes up through the head. You should know that there is a tool, called a Louis Tool, that is used as a guide to run a 5/16" drill bit down through the pushrod passage when a fellow is going to use 1.6 rockers on a SBC......
Comp Cams Louis Tool | JEGS

You want the pushrod touching at only two places, the pushrod cup in the lifter and the socket on the rocker arm, from valve-on-seat to full valve lift.
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I'll second that. I think Summit is a great company to deal with. But when assembling an engine, you should try to check EVERYTHING for yourself, no matter who made, assembled, or sold you the parts.

Just wanted to post a quick update to say that we're still moving the project ball down field and will have more to update after the Christmas morning tornado. My son and I spent Sunday tearing down the truck in prep for pulling the motor/trans this Saturday. Should have the motor on stand and heads off by lunch after which I'll start to take measurements to confirm earlier discussion points. I'll try to follow up early next week to pick the discussion back up. Merry Christmas folks!!