Valve seals

[RustyPile]

Something that has been overlooked in this discussion.. Your heads appear to have had extensive valve guide work performed in the past.. From the factory, there are no guides installed. the guides are drilled directly into the head and the valve "rides" against the head.. Over time these "holes" (guides??) wear and the valve becomes loose in the hole. The hole can be knurled (tightened), but that's not a good solution as the knurling soon wears away.. The holes are bored oversize and guides are pressed into the head. My guess is the heads were machined for PC seals after the guides were installed.. In every picture, the replacement guide is visible.. The seals are designed to fit on what's left of the head protrusion above the spring seat, not the replacement guide.. This area is thin and has broken away, leaving nothing for the PC seal to fit over. This probably is not due to bad machining so much as bad quality control. Somebody didn't inspect the work before installing the PC seals. I came across this breakage a lot back in the '60s and '70s when I was building race engines.. This can be repaired by replacing the guides with ones of a different design but the procedure is expensive and should only be done by someone who knows exactly what they're doing. for pretty much the same money, you can replace both heads, their service life is over.

[Accelo]

Silverados have had cast blocks and aluminum heads for years. Use a quality gasket you will not have any issues with aluminum heads.

[bry593]

I've considered the Etec heads, but have yet to purchase any. Aluminum heads will permit a higher compression ratio to run on 87 octane gas. This means more mpg as higher compression means greater efficiency.

Yes, it will cost more initially, requiring special head bolts and gaskets, and they are somewhat fragile (easy to strip threads), but.... more efficiency!

I'm really kicking around the idea of dumping my vortecs in favor of some etec. The iron vortec 64cc, combine with early intake closure cam in a long stroke 383 just detonates like crazy once the mech and vac advance hit the zone. This despite GM's claim that it "runs on 87". GM is full of **** ....

[Liz]

Recent Events Revisited...
Here we go again. Recently the old recent events post was removed, and as soon as it was it seems all of you decided it was free for all time AGAIN. Here's how it is. NO political, NO religion debates will be tolerated. We allowed them a few tries and well it just doesn't work it turns into a nightmare for us to deal with. Anyone harassing another member, not following the rules, trolling, etc. WILL BE BANNED for 24 hrs without warning. Second offense will be 2 weeks, 3rd strike and your out. This means that all of my staff and I are tired of playing preschool teacher, learn to live together or you will not be here for very long.

Josh

https://67-72chevytrucks.com/vboard/...d.php?t=712381

[68LAlonghorn]

I called Summit to look into new heads based on your suggestions (2.02 Intake/ 1.60 Exhaust with 72cc combustion chamber) and I wasn't able to give the guy the information he was asking for. I told him I had a '68 327 stock and was looking for replacement heads, to which he started asking for intake and exhaust runner volume, space between pistons and valves and other questions which I was not able to answer. I told him I was just looking for something I can replace my current heads, but he said I was more complicated than that. I was hoping for an easy swap but does not seem like it. I may have to spend some additional time learning more about head specs. I was looking at ordering the Edelbrocks 5089 or similar, to go with my Edelbrock intake and AVS2 Carb, but seems like the truck is going to be sitting for a bit longer.

[RustyPile]

Originally Posted by 68LAlonghorn

I called Summit to look into new heads based on your suggestions (2.02 Intake/ 1.60 Exhaust with 72cc combustion chamber) and I wasn't able to give the guy the information he was asking for. I told him I had a '68 327 stock and was looking for replacement heads, to which he started asking for intake and exhaust runner volume, space between pistons and valves and other questions which I was not able to answer. I told him I was just looking for something I can replace my current heads, but he said I was more complicated than that. I was hoping for an easy swap but does not seem like it. I may have to spend some additional time learning more about head specs. I was looking at ordering the Edelbrocks 5089 or similar, to go with my Edelbrock intake and AVS2 Carb, but seems like the truck is going to be sitting for a bit longer.

I've never had that problem with Summit. I'm guessing you got ahold of a new sales guy. All Chevy V8 small blocks have the same bore center-to-center measurement, head bolt pattern, water pump fitment points, etc. Runner volume is also not a consideration because your engine is basically stock not intended for racing application and max HP output. For the most part, piston top configuration determines piston-to-valve clearance, not head shape. Within a few thousandths, sbc valves are in the same location relative to the piston. The piston is configured for valve clearance, not the head or valves. This interference usually occurs with high lift, long duration, wide LSA, and "extra large" valves.. If you don't have piston-to-valve interference now, if you keep the same camshaft, you won't have interference with any of the heads in my list.. Telling him "stock engine" is all he needed to hear. Why would he even all those questions????

Give me a minute and I'll give you a list of heads that will be "Bolt-on" for you..

If you want cast iron, these will work.
https://www.summitracing.com/parts/sum-152123

If you want Vortec, however, these aren't in stock:
https://www.summitracing.com/parts/sum-151124#overview

Good aluminum head for street use:
https://www.summitracing.com/parts/edl-60899#overview

AFR is a very good brand. Here's one of their aluminum offerings:
https://www.summitracing.com/parts/afr-1001#overview


There are many others, these are just for starters..

[68LAlonghorn]

Thanks so much RustyPile, that really helps. I like the Edelbrocks, but a bit above what I wanted to spend. Would the Edelbrock EDL-5089 work?

[RustyPile]

Originally Posted by 68LAlonghorn

Thanks so much RustyPile, that really helps. I like the Edelbrocks, but a bit above what I wanted to spend. Would the Edelbrock EDL-5089 work?

If you mean "will they fit?". Yes they will. The large runner size makes them suitable for a large displacement or high revving small displacement engine. Not at all what you're looking for.. For a stock engine, why would you choose a $1200 cylinder head over a $400 head?? Higher cost doesn't always mean better buy..

Your engine will probably NEVER be revved above 3500 - 4000 RPM.. Don't buy what you "like", buy what you NEED.. You don't NEED $1200 high revving heads.. If you're looking to me for a recommendation, Go with either of the cast iron heads (preferably the Vortec), or the Summit aluminum head. If you have $1200 to spend, buy the $400 heads and put the other $800 somewhere else on the truck.. OH!, spend part of it on your wife..

[68LAlonghorn]

Originally Posted by RustyPile

If you mean "will they fit?". Yes they will. The large runner size makes them suitable for a large displacement or high revving small displacement engine. Not at all what you're looking for.. For a stock engine, why would you choose a $1200 cylinder head over a $400 head?? Higher cost doesn't always mean better buy..

Your engine will probably NEVER be revved above 3500 - 4000 RPM.. Don't buy what you "like", buy what you NEED.. You don't NEED $1200 high revving heads.. If you're looking to me for a recommendation, Go with either of the cast iron heads (preferably the Vortec), or the Summit aluminum head. If you have $1200 to spend, buy the $400 heads and put the other $800 somewhere else on the truck.. OH!, spend part of it on your wife..

Understood. Which aluminum heads are you referring to? the link you sent for "Good aluminum heads for street use" are Edelbrock 60899 at $865 a pop. Maybe you meant to send a different head?

I'll keep on reading and I'm sure I'll figure it out. Thanks again.

[RustyPile]

Sorry if I confused you. Those Aluminum Edlebrock heads aren't really intended for a bone stock engine. The $400 heads I referred to are these cast iron heads, the Vortec being my first choice:
https://www.summitracing.com/parts/sum-151124

or these:
https://www.summitracing.com/parts/sum-152123

If you're "dead set" on aluminum heads, Edelbrock wouldn't be my first choice. Those AFRs are a bit cheaper and will probably work better than Edelbrock. AFR (Air Flow Research) has been in the head business a very long time. Much longer than copycat Edelbrock. For you, flow rates are more of a concern than metallurgy of the heads.

Let me see if I can do a better job explaining the mechanics of cylinder head selection.. Intake runner cc description is a way of measuring the size of the intake runner. The larger the number, the larger the runner. The larger the runner, the larger the flow rate. Large displacement engines turning a high RPM require a very large runner. Lesser displacement engines, such as your 327, have to turn higher RPM to benefit from the high flowing large runners. The air/fuel mixture at low RPMs in those large runners moves too slow. Large runners, coupled to small displacement and low (street level) RPMs lead to the fuel droplets separating from the air. This causes all sorts of run problems. For a stock engine on the street, runners in excess of 165 - 170 ccs don't add much benefit, because of the low RPM average.

I'm definitely not talking against the use of aluminum heads. They definitely have their place. Aluminum heads have their advantages. They dissipate heat much better. This means they handle detonation better at higher compression ratios. Timing settings can be more advanced or more aggressive without that dreaded "ping".

[68LAlonghorn]

Originally Posted by RustyPile

Sorry if I confused you. Those Aluminum Edlebrock heads aren't really intended for a bone stock engine. The $400 heads I referred to are these cast iron heads, the Vortec being my first choice:
https://www.summitracing.com/parts/sum-151124

or these:
https://www.summitracing.com/parts/sum-152123

If you're "dead set" on aluminum heads, Edelbrock wouldn't be my first choice. Those AFRs are a bit cheaper and will probably work better than Edelbrock. AFR (Air Flow Research) has been in the head business a very long time. Much longer than copycat Edelbrock. For you, flow rates are more of a concern than metallurgy of the heads.

Let me see if I can do a better job explaining the mechanics of cylinder head selection.. Intake runner cc description is a way of measuring the size of the intake runner. The larger the number, the larger the runner. The larger the runner, the larger the flow rate. Large displacement engines turning a high RPM require a very large runner. Lesser displacement engines, such as your 327, have to turn higher RPM to benefit from the high flowing large runners. The air/fuel mixture at low RPMs in those large runners moves too slow. Large runners, coupled to small displacement and low (street level) RPMs lead to the fuel droplets separating from the air. This causes all sorts of run problems. For a stock engine on the street, runners in excess of 165 - 170 ccs don't add much benefit, because of the low RPM average.

I'm definitely not talking against the use of aluminum heads. They definitely have their place. Aluminum heads have their advantages. They dissipate heat much better. This means they handle detonation better at higher compression ratios. Timing settings can be more advanced or more aggressive without that dreaded "ping".

Thanks for the explanation, that makes sense. So based on that information, maybe that specific AFR head wouldn't be the best choice then, as it has an intake runner of 195cc? I'll look at other AFR's, as they do seem pretty good and at $549 a head vs the iron ones at $393, the price is not that much more.

Thanks again, this really helps.

[Accelo]

I only see AFR heads that cost about $1000 per side?
https://www.airflowresearch.com/180c...cylinder-head/
For your motor I would get the 64CC chambers with the 180cc intake.
Are you looking at a bare head for pricing?

If these are too expensive the Cast Iron Vortex heads are inexpensive (especially compared to ARF) and will give you more flow than any 202 head from the 60's ever though possible.

More information here on the Vortex heads.
https://www.motortrend.com/how-to/97458/
Real valve seals, like the heads you removed. Also takes the center bolt valve covers, eliminates 90% of the leaking problems from the earlier head perimeter bolt covers.

[68LAlonghorn]

Originally Posted by Accelo

I only see AFR heads that cost about $1000 per side?
https://www.airflowresearch.com/180c...cylinder-head/
For your motor I would get the 64CC chambers with the 180cc intake.
Are you looking at a bare head for pricing?

If these are too expensive the Cast Iron Vortex heads are inexpensive (especially compared to ARF) and will give you more flow than any 202 head from the 60 ever though possible.

More information here on the Vortex heads.
https://www.motortrend.com/how-to/97458/
Real valve seals, like the heads you removed. Also takes the center bolt valve covers, eliminates 90% of the leaking problems from the earlier head perimeter bolt covers.

these ones are $549 each, which is not much more than the iron ones, which are close to $400 a head. https://www.summitracing.com/parts/a...olet/year/1968 . That being said, they are 195cc, which sounds like it's too much for my stock engine.

[RustyPile]

Originally Posted by 68LAlonghorn

these ones are $549 each, which is not much more than the iron ones, which are close to $400 a head. https://www.summitracing.com/parts/a...olet/year/1968 . That being said, they are 195cc, which sounds like it's too much for my stock engine.

Your last sentence is ABSOLUTELY correct.. Most aluminum aftermarket heads are geared toward a high level of performance. They're just a part of the overall package. Now that you're beginning to see how these things work and play together, I think you understand why I initially suggested the iron heads.. Which ever you choose, good or bad, you're gonna be stuck with 'em.. Most of those aluminum heads will just all but demand you change camshaft and manifold to match the flow rate. Then you'll be looking at changing the torque converter and possibly a lower (higher numerically) differential ratio.. Money, money, money, money.......

Go with either of the iron heads, preferably the Vortecs, and get that aluminum word out of your head.. Remember "NEED" over "WANT" every time.

[RustyPile]

Originally Posted by Accelo

I only see AFR heads that cost about $1000 per side?
https://www.airflowresearch.com/180c...cylinder-head/
For your motor I would get the 64CC chambers with the 180cc intake.
Are you looking at a bare head for pricing?

If that question is directed to me, I gathered all my information, including prices from the Summit site.

Originally Posted by Accelo

If these are too expensive the Cast Iron Vortex heads are inexpensive (especially compared to ARF) and will give you more flow than any 202 head from the 60 ever though possible.

I agree with you 100%, I know from experience. Back in the days when I was building engines, the labor I had to invest on those "fuelie" heads took a week of my time.. For example, in those days, a 3 angle valve job was considered a performance improvement. Now the 3 angle cut is the benchmark of any valve job.. Except for their limited lift capabilities, there is not many equal heads out there. I recommend them for about 99% of the street applications.

[68LAlonghorn]

Well, after a lot of reading and learning from you guys I'm leaning towards the Summit racing iron heads https://www.summitracing.com/parts/sum-152123#overview. Although I understand that the Vortec heads would be better, they are not in stock and on top of that I had already purchased a new Edelbrock intake manifold and valve covers for the stock heads, so those won't fit. I think the numbers look good for my stock engine, 165cc intake runner, 72 chamber 2.02/1.60 valves. Only question I have is with the 72cc chamber, what will my compression be? Should I try to look for something closer to 64cc?

Couple additional questions:
Should I replace the rockers, pushrods and lifters while am I there?
Any head gasket suggestions? looking at this one https://www.summitracing.com/parts/f...ckup/year/1968

Thanks again for all the help with this.

[Accelo]

Stock 327 heads were 64cc.
Here are some calculations from the Summit compression calculator;
I had to make some assumptions but you get the idea.
Short story is it will make about one point difference in compression.
Ratios are likely a little high as I have 0 in the dome volume. It should be negative something for the valve reliefs.
And the deck clearance is likely higher. But is is close.
Here is the link. https://www.summitracing.com/newsand...ion-calculator
I like it as it is simpler than most.

[RustyPile]

Originally Posted by 68LAlonghorn

Well, after a lot of reading and learning from you guys I'm leaning towards the Summit racing iron heads https://www.summitracing.com/parts/sum-152123#overview. Although I understand that the Vortec heads would be better, they are not in stock and on top of that I had already purchased a new Edelbrock intake manifold and valve covers for the stock heads, so those won't fit. I think the numbers look good for my stock engine, 165cc intake runner, 72 chamber 2.02/1.60 valves. Only question I have is with the 72cc chamber, what will my compression be? Should I try to look for something closer to 64cc?

Couple additional questions:
Should I replace the rockers, pushrods and lifters while am I there?
Any head gasket suggestions? looking at this one https://www.summitracing.com/parts/f...ckup/year/1968


Thanks again for all the help with this.

It's doubtful your truck engine came from the factory with large valve 64 cc heads. Those heads were mostly found on higher performance 327s.. The truck engines "traditionally" had lower compression and milder cams than passenger cars.. 9+:1 compression ratio will work just fine on your stock engine.. It's probably higher than "stock" anyway.. 10:1 on iron heads might need higher octane gasoline or less than optimal ignition timing numbers to prevent detonation under load.

I'd leave the lifters alone, but you might pull a few of them and inspect for wear and pitting on the face.. Just be sure to put them back in the same location they came from.. Installing new lifters might cause break-in issues and take out the cam.. I'd replace the rocker arms, pivot balls, pushrods and rocker adjusting nuts..

[68LAlonghorn]

Heads are off! was not difficult, just time consuming. The pistons are stamped 020, so it seems that they were bored when they installed these heads? does this make any major difference in the compression?
Also found this regarding the stock cams, which I really think is what it's still in there: 327 Cams- up to 300hp .390 .410 195 202 duration@.050

I'm going to clean the pistons the best I can and the rest of the block and see how it comes out.

[68LAlonghorn]

Originally Posted by Accelo

Stock 327 heads were 64cc.
Here are some calculations from the Summit compression calculator;
I had to make some assumptions but you get the idea.
Short story is it will make about one point difference in compression.
Ratios are likely a little high as I have 0 in the dome volume. It should be negative something for the valve reliefs.
And the deck clearance is likely higher. But is is close.
Here is the link. https://www.summitracing.com/newsand...ion-calculator
I like it as it is simpler than most.

Thanks so much Accelo. Would the compression with the 72cc heads be ok with 87 fuel? or am I going to have to used high octane? Sorry for the dumb questions, very new to all this.

[68LAlonghorn]

Originally Posted by RustyPile

It's doubtful your truck engine came from the factory with large valve 64 cc heads. Those heads were mostly found on higher performance 327s.. The truck engines "traditionally" had lower compression and milder cams than passenger cars.. 9+:1 compression ratio will work just fine on your stock engine.. It's probably higher than "stock" anyway.. 10:1 on iron heads might need higher octane gasoline or less than optimal ignition timing numbers to prevent detonation under load.

I'd leave the lifters alone, but you might pull a few of them and inspect for wear and pitting on the face.. Just be sure to put them back in the same location they came from.. Installing new lifters might cause break-in issues and take out the cam.. I'd replace the rocker arms, pivot balls, pushrods and rocker adjusting nuts..

Ok great, so it sounds like I'll be ok with the 72cc heads then. I'll follow your advise and replace the parts you mentioned.

[Accelo]

Stock 327 heads were 64cc.
This is true on the car engines. Yes, the trucks were likely lower. I shouldn't make blanket statements like that.

Typically, an overbore would raise the compression because the ratio changed. In your case it increases from 9.17 to 9.25:1 if everything was equal. However, in my experience the top of the piston to the top of the deck height changes with the aftermarket pistons. Typical aftermarket pistons are lower in the bore. Manufactures do this to cover their butts in case the block has been decked. The typical pistons are lower in the bore an average of .020. Utilizing the same .020 over bore example compression will move from 9.17 to 8.85:1 when you add the .020 additional negative deck clearance into the calculations.

The specifications keep stacking up and in the process most all of them lower the compression. (Thicker head gasket, pistons lower in the bore and valve reliefs in the piston tops.

I haven't even mentioned the quench with is so important. Keeping the distance between the head and the piston tops increases quench which is a good thing. Let’s ignore this for now.

Consider using a composition head gasket if you choose the 64cc heads and a thinner metal one if installing the large chamber heads. Remember it takes very little change in the head chamber volume to make a large change in the compression ratio.
The large chamber heads, 72cc, are the safe choice. If your head choice was aluminum or you were running a camshaft with more duration I would choose higher compression 64 cc heads.
Cheers

[68LAlonghorn]

Originally Posted by Accelo

Stock 327 heads were 64cc.
This is true on the car engines. Yes, the trucks were likely lower. I shouldn't make blanket statements like that.

Typically, an overbore would raise the compression because the ratio changed. In your case it increases from 9.17 to 9.25:1 if everything was equal. However, in my experience the top of the piston to the top of the deck height changes with the aftermarket pistons. Typical aftermarket pistons are lower in the bore. Manufactures do this to cover their butts in case the block has been decked. The typical pistons are lower in the bore an average of .020. Utilizing the same .020 over bore example compression will move from 9.17 to 8.85:1 when you add the .020 additional negative deck clearance into the calculations.

The specifications keep stacking up and in the process most all of them lower the compression. (Thicker head gasket, pistons lower in the bore and valve reliefs in the piston tops.

I haven't even mentioned the quench with is so important. Keeping the distance between the head and the piston tops increases quench which is a good thing. Let’s ignore this for now.

Consider using a composition head gasket if you choose the 64cc heads and a thinner metal one if installing the large chamber heads. Remember it takes very little change in the head chamber volume to make a large change in the compression ratio.
The large chamber heads, 72cc, are the safe choice. If your head choice was aluminum or you were running a camshaft with more duration I would choose higher compression 64 cc heads.
Cheers

Thanks Accelo. Yes, I'm looking at getting the Summit Iron 72cc heads, so it sounds like those will be ok.

[toolboxchev]

Want the classic look with modern power, check these out:

https://www.trickflow.com/parts/tfs-30210007

[68LAlonghorn]

Originally Posted by Accelo

Stock 327 heads were 64cc.
Here are some calculations from the Summit compression calculator;
I had to make some assumptions but you get the idea.
Short story is it will make about one point difference in compression.
Ratios are likely a little high as I have 0 in the dome volume. It should be negative something for the valve reliefs.
And the deck clearance is likely higher. But is is close.
Here is the link. https://www.summitracing.com/newsand...ion-calculator
I like it as it is simpler than most.

Thanks for this info Accelo. I have just ordered the Summit Iron heads, so those should be on their way soon. Now what I'm trying to figure out is what thickness head gasket I should order. I measured the deck height (hopefully correctly) and it's between 0,40 and 0.05, which makes me think I should get a thin gasket to try to get as close to a quench height of 0.040? am I understanding this correctly?

I tried to figure it out with the compression link you sent, but not sure what to enter under Effective dome volume, as my pistons are flat with valve reliefs.

Thanks