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Discussion Starter · #1 ·
So with the outside temps rising into the low 30’s for the first time in many days if not weeks here in New Hampshire, I finally braved the cold of my garage and removed the drivers side valve cover to try and identify the cylinder heads on the 406 in my 69. They appear to be GM 14011034 - Bowtie, cast iron, 64cc chambers, 184cc port volume, angle plug, "Phase II" heads (photos below). I did some reading up on these heads and while they seem to have been a pretty good high performance head offered by The General some years ago, I’m a little bit disappointed as I feel they may be a bit small for the rest of the engine combination I have, but an engine designer I'm not so here I am asking for input.

The paperwork from the machine shop that freshened up the engine just before I purchased the car indicates the camshaft is a flat hydraulic Engine Pro MC1996 .509/.509 lift, 246/246 duration @ .050, advertised duration of .306/.306, lobe separation of 106/112 and rpm range of 3,200 to 7,000 rpm. The current intake manifold is an Edelbrock Bowtie II Victor Jr. and my plans are to replace it with an Edelbrock RPM Air Gap over winter. Looking for thoughts on what I have, I know the cam isn’t a good option for the street which is where this car will spend most of it’s time with an occasional trip to the strip. Should I be considering cylinder heads as well or run with these?

The rocker arms are 1.5 aluminum roller rockers, but no identification on them that I can find (photos below). Does anyone have any ideas what they are from the photos?

Thanks in advance, Scott







 

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The cam timing looks similar to what I’ve put in a few strokers. The last flat tappet I used was in ’04 but whether hyd flat, hyd roller or solid roller the timing events I’ve used have been about +/-10 from where you are. I think it’s kind of a sweet spot for larger SBC’s on the street. I like the largest Lunati hyd roller VooDoo. And have used it a few times.

•Advertised Duration (Int/Exh): 294/302
•Duration @ .050 (Int/Exh): 243/251
•Gross Valve Lift (Int/Exh): .560/.565
•LSA/ICL: 110/106

This cam with custom LSAs from 108 to 112 has been pretty good. I know a lot of people like the tighter LCAs but this cam on 112 in a 377 was very happy even with a pretty steep overdrive.

Compressions have been 9.7 to 11.5. On the 11.5 I only use two degrees of advance.
I’d usually run AFR 195 or a little large for the street.
 

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I would do a 215 Dart Pro1 or RHS, 2.08 to take advantage of the big bore, with some bowl work.
Keep the victor jr.
then spend some $ on a HR cam and lifters... 240/245 or so.
it will be just as streetable and make way more power everywhere.
 

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I would run it as-is since you plan on keeping it a street car....mostly ;)
Are the heads a little small...yes, but you're not looking for all out performance.

IF this is a new to you car....I would see where it stands first before making a bunch of changes.....you may be surprised.
 

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Discussion Starter · #6 ·
I would run it as-is since you plan on keeping it a street car....mostly ;)
Are the heads a little small...yes, but you're not looking for all out performance.

IF this is a new to you car....I would see where it stands first before making a bunch of changes.....you may be surprised.
Okay so a little background. I've had the car two years, put around 3k per season on it. Already got rid of the over sized Barry Grant racing double pump mechanical secondary carburetor with no choke that was polluting the oil with fuel and giving lousy mileage and just okay performance. I replaced it with a Holley #83670 - 670 cfm Street Avenger aluminum 4-bbl carburetor with vacuum secondary and electric choke. Fuel mileage went from averaging 7.5 mpg to 13.7 mpg after 13 tanks run through it and all styles of driving, performance is better and the oil no longer smells like fuel so that was some good progress. I also got rid of the MSD distributor that had no vacuum advance and the 6AL box. I purchased a rebuilt stock distributor that I went through and removed excessive shaft end play and then retrofitted with a Pertronix Ignitor III module and coil.

Like any of us motor heads out here, I like performance and would like to get the most out of what I have even if it means some changes (that's part of what this hobby is all about after all). I'd love to see 500+ HP and 500+ ft lbs of torque out of this 406 without any power adders, but I don't NEED that much however it sure would be great if I could do it. The Victor Jr. intake and cam are really designed to work above the rpm range that I drive the car. When I purchased the car, the MSD 6AL rev limiter had a 6,400 rpm chip, but I'm keeping it down to 6k maximum so I would rather match components to make the most power down at a lower rpm thus the plan to swap the intake with an Edelbrock RPM Air Gap. A cam change I'd be fine with and even heads IF it would get me enough gain in the performance department.

I appreciate all the thoughts and ideas from those that have and will reply, it gives me plenty to consider and I'll learn from everyone's input as well.
 

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500hp aint happening with that carb.
Quickfuel 950 is very streetable, talk with them about it.
I wouldnt worry about "powerbands" an intake or cam may have a powerband of X with 350 cubes, but its not the same with more cubes.
induction and exhaust play a big role of where power is made.
fuel system needs to be up to the job too to support a 500hp engine.

If you want gas mileage, short duration cam with low overlap is where its at, but to make power with those you'll need good induction and exhaust (breathing)
My 383 has a tiny 224 cam, get 20mpg freeway (hp 950 carb) with OD.
 

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Discussion Starter · #8 ·
The cam timing looks similar to what I’ve put in a few strokers. The last flat tappet I used was in ’04 but whether hyd flat, hyd roller or solid roller the timing events I’ve used have been about +/-10 from where you are. I think it’s kind of a sweet spot for larger SBC’s on the street. I like the largest Lunati hyd roller VooDoo. And have used it a few times.

•Advertised Duration (Int/Exh): 294/302
•Duration @ .050 (Int/Exh): 243/251
•Gross Valve Lift (Int/Exh): .560/.565
•LSA/ICL: 110/106

This cam with custom LSAs from 108 to 112 has been pretty good. I know a lot of people like the tighter LCAs but this cam on 112 in a 377 was very happy even with a pretty steep overdrive.

Compressions have been 9.7 to 11.5. On the 11.5 I only use two degrees of advance.
I’d usually run AFR 195 or a little large for the street.
FriendlyViper, are you saying I could keep that cam but throw some 195 or larger heads on it and end up much better off?

I looked at the AFR's you mentioned, price is on the higher side compared to Darts or RHS heads that 67RS502 suggested. How do you think changing to either of those heads would do with everything else I've got?
 

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Discussion Starter · #9 ·
500hp aint happening with that carb.
Quickfuel 950 is very streetable, talk with them about it.
I wouldnt worry about "powerbands" an intake or cam may have a powerband of X with 350 cubes, but its not the same with more cubes.
induction and exhaust play a big role of where power is made.
fuel system needs to be up to the job too to support a 500hp engine.

If you want gas mileage, short duration cam with low overlap is where its at, but to make power with those you'll need good induction and exhaust (breathing)
My 383 has a tiny 224 cam, get 20mpg freeway (hp 950 carb) with OD.
67RS502, I took a look at the Quickfuel site but couldn't find an HP 950 offering, anything I found at 950 cfm didn't have a choke which living in New Hampshire is useful. I wish I could figure out what size the Barry Grant carb was that I took off, perhaps I could rebuild and re-jet it and maybe get away with it during the months of June, July & August when a choke isn't quite as necessary up here.

Good mileage in the sense that I'm not dumping fuel into the crankcase and wasting it (and contaminating my oil) was my concern. When I went with the Holley 670, it was the size that kept coming from all the carburetor selectors at various web sites based on 406 cubic inches and maximum rpm of 6,000.

I did look at the Dart and RHS heads you suggested, a set of those would help on the induction side. Car has headers into a 2.5" system back through the mufflers and then 2.25 tailpipes. If a set of those heads and the cam I have now would do a bit better than the restrictive heads that are on there now, that might be a reasonable way to go for now and then down the road do a retrofit roller cam?
 

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Discussion Starter · #10 ·

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ZZ430DropTop67RS, the color is darker on mine than what Summit shows but otherwise they do look very similar if not identical. From what I've read Harland Sharp roller rockers are of fairly decent quality aren't they?

Thanks for your input.
They are very decent. Several years ago I used the 1.6 version on a late model race car with a high RPM 377 and they held up great.
 

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FriendlyViper, are you saying I could keep that cam but throw some 195 or larger heads on it and end up much better off?

I looked at the AFR's you mentioned, price is on the higher side compared to Darts or RHS heads that 67RS502 suggested. How do you think changing to either of those heads would do with everything else I've got?
I typically like split patterns with about eight more degrees on the exhaust in something like this. BUT, I think you’re not that far off the mark. If you’re staying with flat tappet a swap is relatively cheap. A roller upgrade is $$$. I’d be tempted to do heads and maybe some higher ratio rockers on your current cam and go from there.


A few years ago one of the magazines did a nice head comparison. The dyno mule was a sbc around 500 HP. The AFRs looked like a big winner. When Dart added their Platinum line I thought those were about equivalent. I’ve been really happy with AFR quality so I often spend a bit more but that’s not saying they are the best head for every build.
 

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Discussion Starter · #14 · (Edited)
FriendlyViper, If I can stick with the existing flat tappet cam for a bit longer and put some better heads on it that will reap me some benefits both now and for future upgrades (like a roller cam setup), I think that would be a good way to proceed. I was wondering about changing the rocker arm ratio as well to pickup a bit more lift with the existing cam (I realize it will change the durations a bit as well). So that brings up two questions related to proceeding in this direction;

1. I just did some checking and found some Harland Sharp 1.6 and 1.65 roller rockers. If I’ve done the math correctly, my existing cam lobe height is .339, so if I went to 1.6 rockers I’d end up with .542 valve lift. If I went to 1.65 rockers I’d end up with .560 lift.

2. Would any of the three heads mentioned thus far (AFR, Dart or RHS) accept greater ratio rockers as they come or will I need to elongate the pushrod openings to allow clearance?
 

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1.6 is what I’m thinking. If you have an older cam the ramps are probably not too aggressive for the higher ratio but I can’t guarantee that. It is possible that your current springs may work with the 1.5s but not like the 1.6s. I’d also use light “checking springs” to make sure the P to V clearance is adequate with the extra lift. The 1.65 could be fine but I'd probably go with the middle. I'd hate to buy the 1.65s and have P to V issues.

I have not had to open up the push rod openings on any current aftermarket heads (Vortec heads do need to be enlarged) for the ball park we’re talking about hear but I do check before torqueing a head down.
 

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Discussion Starter · #16 ·
1.6 is what I’m thinking. If you have an older cam the ramps are probably not too aggressive for the higher ratio but I can’t guarantee that. It is possible that your current springs may work with the 1.5s but not like the 1.6s. I’d also use light “checking springs” to make sure the P to V clearance is adequate with the extra lift. The 1.65 could be fine but I'd probably go with the middle. I'd hate to buy the 1.65s and have P to V issues.

I have not had to open up the push rod openings on any current aftermarket heads (Vortec heads do need to be enlarged) for the ball park we’re talking about hear but I do check before torqueing a head down.
Any way for me to determine if my ramps are too aggressive for either greater ratio rockers?

What amount of piston to valve clearance am I looking for to be safe if I go this route?

If I were to stay with existing heads and just change rockers to 1.6 or 1.65, I'd definitely check piston to valve clearance and if I did have the clearance, the 1.6's would be an option but I'd have to make sure the springs would handle the extra lift as well. I know on my existing heads I'd need to elongate the push-rod holes which I'd be comfortable doing with a Push-rod Slot Elongating Louis Tool. But how would I figure out what my existing springs would be tolerant of as far as lift goes?

But if I go with better heads, I'd buy them assembled and know what lift the springs they come with would handle. I'd still have to check piston to valve clearance before deciding on and ordering the greater ratio rockers. If I could go with 1.65 ratio it would only benefit the end result even more, or am I missing something?
 

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Upping the ratio on your existing heads I’ check:

Piston to valve (the convention is .080” for the intake and .100” for the exhaust) I’ve run less on engines that use a 6000 rpm limit but as they say your results may vary. If you can borrow a set of 1.65s you could find out where you’re at before committing to that ratio.

Coil bind and clearance at intended maximum lift.

Retainer to seal clearance.

Spring rate. If you don’t have part numbers you can pull a spring (or all of them) and measure the force at the installed height and over the nose (maximum intended valve lift). A local engine machine shop should be able to get the numbers for you once you take them off. Compare the spring characteristics with either published info about your cam with the higher rockers or a call to the cam maker. A nit picking point here, people call it “spring pressure” but it’s really “pounds force” that a spring generates when compress

The safe way is going to be pull the springs to check everything. There may be published data about maximum lift for the heads but I’d like to see it for myself. Whoops here could be costly.

If your cam maker has technical support I’d give then a call about their thoughts on rocker and spring rates. If they’re not available it could be compared to a similar cam of a different maker. We have at least one cam guy here who should have valuable thoughts on matching rockers ratios and spring rates to your cam specs.

Once you’ve got all the pieces you may need different push rods. Don’t forget to check the sweep pattern before your finish it up.
 

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500hp aint happening with that carb.
Quickfuel 950 is very streetable, talk with them about it.
I wouldnt worry about "powerbands" an intake or cam may have a powerband of X with 350 cubes, but its not the same with more cubes.
induction and exhaust play a big role of where power is made.
fuel system needs to be up to the job too to support a 500hp engine.

If you want gas mileage, short duration cam with low overlap is where its at, but to make power with those you'll need good induction and exhaust (breathing)
My 383 has a tiny 224 cam, get 20mpg freeway (hp 950 carb) with OD.
This./\/\

That motor seems like it's needing an identity. The cam and heads are mismatched in my opinion, unless they have extensive port work done I would wager they are all done making power at about 5500 rpm.
The first go around with my old 406 I had a [email protected], .590" lift little solid roller and a pair of heavily ported world SR heads. It ran good but layed over around 5800, those little heads just don't work that well with a large cube motor.
As soon as I could I bought a set of Pro Topline (old version of the RHS heads), 220's, and the car drove as good as with the old heads arod town, but under thottle it was a completely different animal. That same cam I started with and a 950 double pumper went 11.40 in my camaro, and I drove it everywhere and it was a blast.

I wouldn't mess with any of it untill you decide what you want, if you keep the heads look into a new cam, or if you want more performance get heads and a cam to match. It sounds like the motor was not terribly well thought out before you got it.

406's are great motors, with some simple matched parts they work awesome, and are naturally torquey.
 

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With the effort and expense of changing the cam and heads being considered, one option would be to first get it on a chassis dyno (or use trap speed) to get an idea of what potential gains are on the table (assuming we agree on what an optimized, modern cam/head combo would do). If it’s putting 325 to the wheels I think the $/HP ratio for upgrading would be pretty high. If it’s making 275 the money might be well worth it. I’d like to have a larger carb as part of the mix if it got on to a dyno.
 

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Discussion Starter · #20 ·
This./\/\

That motor seems like it's needing an identity. The cam and heads are mismatched in my opinion, unless they have extensive port work done I would wager they are all done making power at about 5500 rpm.
The first go around with my old 406 I had a [email protected], .590" lift little solid roller and a pair of heavily ported world SR heads. It ran good but layed over around 5800, those little heads just don't work that well with a large cube motor.
As soon as I could I bought a set of Pro Topline (old version of the RHS heads), 220's, and the car drove as good as with the old heads arod town, but under thottle it was a completely different animal. That same cam I started with and a 950 double pumper went 11.40 in my camaro, and I drove it everywhere and it was a blast.

I wouldn't mess with any of it untill you decide what you want, if you keep the heads look into a new cam, or if you want more performance get heads and a cam to match. It sounds like the motor was not terribly well thought out before you got it.

406's are great motors, with some simple matched parts they work awesome, and are naturally torquey.
I think the identity is there, it's just not as recognizable and familiar as it was back in the day - the old school way from back then I'm thinking...

I agree the cam and heads are mismatched, I'm thinking for now perhaps just stick a better matched flat tappet cam in and swap the intake manifold and drive it a bit more this way. Then down the road a bit do some decent heads and a retro fit roller setup. Any suggestions for a flat tappet that will give me the best power and torque possible at no higher than than 6,000 rpm (or even 5,500 based on your thoughts on those heads)?

No idea if the heads have had any port work done, if/when I pull the intake that might reveal if they are as cast or have had any work done to them...

Thanks for your thoughts and input, I appreciate it.

Scott
 
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