Casting number question for 327 heads - Team Camaro Tech
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post #1 of 34 (permalink) Old Feb 20th, 10, 04:49 PM Thread Starter
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Casting number question for 327 heads

Hello everyone,

How important is the casting number for replacing heads on a 327? I am a tad confused. I have seen a lot of different numbers.
Will double hump heads with a casting number of 3917291 work on my 327? Its an original 327/210.
Also, will they bolt right on, and do I need to change the cam at the same time? If so, what type of cam do I use with the new heads?
Thanks soooooooo much for all the help and guidance! I truly appreciate it.
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post #2 of 34 (permalink) Old Feb 20th, 10, 08:32 PM
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Re: Casting number question for 327 heads

If you use 3917291 Double Hump Heads, 3919803 4 Barrel Intake with a Comp Cams 270 Magnum Hydraulic Cam and Lifters Set, you will basically have a 327/275 Motor.

Review this thread:

https://www.camaros.net/forums/showthread.php?t=171383

It contains a lot of good information.

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Last edited by Camaros-n-Chevelles; Feb 20th, 10 at 09:55 PM.
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post #3 of 34 (permalink) Old Feb 20th, 10, 08:35 PM
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Re: Casting number question for 327 heads

The casting numbers are for identification purposes.

The 291's were, I am pretty sure, early model 327 heads that don't have accesory holes in them. I am certain they have small combustion chambers and most if not all had 1.94 intake valves.

They will work on any SBC, but you should get them checked out at a reputable machine shop-check for cracks, seats, other wear items like valve guides. And the valves should be inspected too.

You may have to find some brackets to run power steering and probably AC, but they are probably out there or can be made.

No, you don't have to change the cam...the same cam that works on a 291 headed SBC will work on one with 461's, 462's, 041's,186's, and so on. definatley get the valve springs checked too.

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post #4 of 34 (permalink) Old Feb 21st, 10, 12:23 AM
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Re: Casting number question for 327 heads

The 291 heads are known as the 68 Turbo Flow Heads and considered the Ultimate GM Iron Casting with a 64cc Chamber. Same mold continued to approx 71 with minor changes. They had either the 1.94/1.55 or 2.02/1.6 dia Valves. These where Grumpy Jenkins favorite SBC Heads. He preferred the smaller Valves because he could design his own Valve Angles using the extra material. These heads are capable of flowing equal to any modern head but will cost you a fortune in machining to equate Grumpy's Specifications which will rev a 327ci motor to 9000+rpm.

These heads with the 1.94/1.55 Valves in STK Specs will rev a 9.5:1 327 easily to 7000rpm and hit 8000rpm with 11:1 or 11.5:1 Static and 2.02/1.6 valves using a 288 to a 297 Cam.

Other words; considering cost, if you don't have the pistons to obtain at least a 9.5 Static compression with a a 64cc chamber and say a 280 cam you better off using Vortex Heads with a smaller duration for a 327 or 350 LT1.

Buy the way, 68 DZ 302 owners will rape you for a set of STK 291 2.02/1.6 291 heads if the date is compatible for their block and KILL you if the Heads are Jenkins Specked; mean while, the lowly and forsaken 327 walks away with the prize ;o)

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post #5 of 34 (permalink) Old Feb 21st, 10, 12:30 AM
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Re: Casting number question for 327 heads

You wouldn't want to use the old 327/210 heads, the double humps as mentioned above are a great improvement, even without port work, the bump in compression and better flow will be excellent gains.
Get the compression at or above 10:1, mill them down if you can, it would help even more.
double humps can support tons of power, my friend had a set on a 362" with tons of work, probably more work than they worth, motor made upwards of 500 with 11.2:1, comp 292 and aluminum internals.
I think he actually lost power by going with dart platinum heads, think he lost some compression due to the larger chamber.

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post #6 of 34 (permalink) Old Feb 21st, 10, 01:34 AM
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Re: Casting number question for 327 heads

I tell you what: If you have a set of 291 2.02/1.6 in good condition put a set of TRW Speed Pro L2166NF30 Pistons for a 11:1 Static Compression (DO NOT MILL them down - Surface Mill if required) and a Crane CCH-290 or equivalent with matching springs in her topped with a Holley 750Dp/Edelbrock RPM most BBC's will not touch you = my modest HFT 7500rpm 425Hp 327 Formula. If you want SFT go for a Sigerson F296-1 (or equivalent) and blow everyone away with 8200rpm shifts ;o) Springs must match Cam and a Girdle or Shaft Rockers are mandatory with this Cam.

Anything over 6500rpm you require a Forged Crank, Rods and Pistons Plus a Stud Girdle. Others may tell you different but do do you really want to win and have no break downs.

Who is that Dude with the Funny Grin blocking the view of my Jenkin 291's?





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Last edited by Z15CAM; Feb 21st, 10 at 02:24 AM.
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post #7 of 34 (permalink) Old Feb 21st, 10, 01:34 PM Thread Starter
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Re: Casting number question for 327 heads

WOW!! Thanks soooooooo much guys!! This forum is the absolute best!!
You guys are so willing to help people like me out, and its really appreciated!!
Thanks again to everyone! You guys ROCK!!
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post #8 of 34 (permalink) Old Feb 21st, 10, 01:58 PM Thread Starter
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Re: Casting number question for 327 heads

Quote:
Originally Posted by Z15CAM View Post
I tell you what: If you have a set of 291 2.02/1.6 in good condition put a set of TRW Speed Pro L2166NF30 Pistons for a 11:1 Static Compression (DO NOT MILL them down - Surface Mill if required) and a Crane CCH-290 or equivalent with matching springs in her topped with a Holley 750Dp/Edelbrock RPM most BBC's will not touch you = my modest HFT 7500rpm 425Hp 327 Formula. If you want SFT go for a Sigerson F296-1 (or equivalent) and blow everyone away with 8200rpm shifts ;o) Springs must match Cam and a Girdle or Shaft Rockers are mandatory with this Cam.

Anything over 6500rpm you require a Forged Crank, Rods and Pistons Plus a Stud Girdle. Others may tell you different but do do you really want to win and have no break downs.

Who is that Dude with the Funny Grin blocking the view of my Jenkin 291's?





Thanks so much for the help!
I did some seaching and am having a hard time trying to find the Crane CCH-290 Cam and springs.
Is there an equally good cam, lifters and springs set out there that you (or anyone) can recommend?
Thanks a lot!
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post #9 of 34 (permalink) Old Feb 21st, 10, 02:54 PM Thread Starter
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Re: Casting number question for 327 heads

"I tell you what: If you have a set of 291 2.02/1.6 in good condition put a set of TRW Speed Pro L2166NF30 Pistons for a 11:1 Static Compression (DO NOT MILL them down - Surface Mill if required) and a Crane CCH-290 or equivalent with matching springs in her topped with a Holley 750Dp/Edelbrock RPM most BBC's will not touch you = my modest HFT 7500rpm 425Hp 327 Formula"

So what you are saying here is that if i replace my heads with a set of 219 with the 2.02/1.6, add the pistons, add the cam and springs, and put a 750 carb and an Edelbrock RPM intake on my engine, it will get to 7500rpm's AND 425 Horses!!! Is this correct, or did i misunderstand? That seems like a huge jump to me! Please let me know...I would be soooooo happy with that result!!
Is there anything I need to do (or should do) to the bottom end if I replace all of these parts?
Thanks again!

Last edited by brewcity; Feb 21st, 10 at 06:47 PM.
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post #10 of 34 (permalink) Old Feb 21st, 10, 03:36 PM
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Wink Re: Casting number question for 327 heads

Quote:
Originally Posted by Z15CAM View Post
The 291 heads are known as the 68 Turbo Flow Heads and considered the Ultimate GM Iron Casting with a 64cc Chamber. Same mold continued to approx 71 with minor changes. They had either the 1.94/1.55 or 2.02/1.6 dia Valves. These where Grumpy Jenkins favorite SBC Heads. ...

I think you're confusing 291's with 292's ... ;o)
291's (and the early 462's) are of the original Camel Hump design and incorporate a simular - but different - chamber ledge design than the later design 292's.
The chamber of the 291 is smaller than the 292 - 62cc vs. 66cc.(nominal)

"Grumpy" did NOT nomally use 291's - and they were far from his 'favorite' head ... he did know of some engine builders that prefered them, but ONLY for small displacement engines (under 300ci)
... and he never called this group of heads (or the 492/292 units) "Turbo Flow Heads"
We've discussed this before Ron ... ;o)
These heads were developed years before the failed Alcohol fueled Turbo small block experiments in the early 70's

Let's not continue to confuse new guys by throwing out weird names for standard production heads

Since you have a 1968 "brewcity" the 291's are the correct casting number for the HP engine series for that year.
They are a great head as others stated and will easily support nice street performance mod HP levels.
Make sure your exhaust is opimized to make the most of these heads.

Just trying to 'keep it real' when discussing heads so we ALL know what head we're talking about ...

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post #11 of 34 (permalink) Old Feb 21st, 10, 04:46 PM
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Re: Casting number question for 327 heads

I know Turbo Fow is an expression but never the less it remains. Grumpy did uses both the 291 64cc and 292 66cc (which only came with 2.02/1.6) castings as both have identical ports and flow the same. He states the 292's chamber ledge around the intake Valve was set back further and promoted the best flow around the larger valve. He continues to say the 291 with the 1.94 valve can achieve the same charge flow by fly cutting and then grinding and additional radius in the chamber ledge to un-shroud the larger 2.02 Intake Valve and hence a 65cc chamber results. The un-shroudding is not necessary if you stick with the 1.94 Valve. The un-shrouding of the 291 Casting to fit 2.02 valve is not effective until the engine was over 7000rpm.

If you look at the Combustion Chamber of my 291's, which were originally had 1.94 valves, you will see the machining around the Intake Valves to Grumpy Specs for the 291 Castings. In his articles he states that he often preferred starting with a set of 291 with the 1.94 valves because there was more material to work with so he could achieve the desired shape for Chamber Un-Shrouding, Seat Angles and Port Entrances directly under the Valves directing flow to, or from, the Bowl and Ports. One cut he dwells extensively on is made in the Exhaust Port which is I believe a Bore Cut at 14 degree angle off the axis of the exhaust Guide and not easily done to promote exhaust flow for these heads. His Valve Seat Angles are Specific using multiple cuts combined with honing the Exhaust Bowl directly under the Valve to achieve a Venture ... etc. It took me 6 months to build my Grumpy Specked 291's which included full porting and I destroyed one set of heads just to get there. Also note, NOT all 291/292 castings have core shifts favourable of surviving Grumpy's Surgical Technics.

Yes Brewcity, by all means just use the 291's as you can not get any better OEM Iron Casting for a SBC with either the 1.94 or 2.02's. If they require new Valves by all means put in 2.02/1.6's. If the Valve Guides are sloppy it is critical to replace them. I further rcommend milling the Stud Bosses for Screw in studs and guide plates and opening the Spring Pockets to fit 1.439" Dia Springs.

Use the Pistons and Cam with similar specifications as discussed bolt on that Intake with Carb (perhaps a 650Dp). Run low gears like 3.73 or 4.10 and you will have no problems hitting 7000rpm. Anything over 6800 rpm I suggest Roller Rockers. After 7200rpm invest in a Stud Girdle. The RPM range is relative to Engine Build and 291 castings are capable of flowing a 327 to 8000rpm if they are Grumpy Specked which is a very expensive procedure to day.

There is no since getting too technical regarding Chamber Ledge un-shrouding or even using larger valves unless you want 8000rpm and 425+Hp. A Stock 11:1 327 is very capable of putting out 350/400+Hp below 6800/7200rpm.

The biggest problem starting with 291 or 292 2.02/1.6 or any large Valve SBC head is that the seats are probably pounded requiring inserts or cracked between the intake and exhaust ports after years of use.

From Mortec:

3917291....67-68...302/327/350..Camel hump,no accessory holes,64cc chamber (more like 62cc's with 2.02/1.6 Valves)
(These are the correct 68 DZ 302 (some 67 Z28's) and 67/68 L79 Cylinder Heads with 2.02/1.6 Valves and came with 1.94/1.55 Valves for lower Hp 327's 2BBL's and 4BBL's and some 350 4 BBL's)

3917292....68......327/350......Camel hump,64cc chamber (more like 66cc's because Chamber Ledge opened and came with 2.02/1.6 Valves)

As John points out they are a STD Production "Fuelie Head" with the Semi Open 64cc combustion Chamber with Great Port flow and erroneously referred to as "Turbo Flows" to day but never the less that is the way most Gear Heads differentiate them from the early 462 Closed Chamber Fuelie Castings.

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post #12 of 34 (permalink) Old Feb 21st, 10, 06:46 PM Thread Starter
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Re: Casting number question for 327 heads

Quote:
Originally Posted by Vintage 68 View Post
I think you're confusing 291's with 292's ... ;o)
291's (and the early 462's) are of the original Camel Hump design and incorporate a simular - but different - chamber ledge design than the later design 292's.
The chamber of the 291 is smaller than the 292 - 62cc vs. 66cc.(nominal)

"Grumpy" did NOT nomally use 291's - and they were far from his 'favorite' head ... he did know of some engine builders that prefered them, but ONLY for small displacement engines (under 300ci)
... and he never called this group of heads (or the 492/292 units) "Turbo Flow Heads"
We've discussed this before Ron ... ;o)
These heads were developed years before the failed Alcohol fueled Turbo small block experiments in the early 70's

Let's not continue to confuse new guys by throwing out weird names for standard production heads

Since you have a 1968 "brewcity" the 291's are the correct casting number for the HP engine series for that year.
They are a great head as others stated and will easily support nice street performance mod HP levels.
Make sure your exhaust is opimized to make the most of these heads.

Just trying to 'keep it real' when discussing heads so we ALL know what head we're talking about ...
Thanks for helping me out! It does get confussing for new guys like me to keep this all straight!
I appreciate all the help...from everyone!
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post #13 of 34 (permalink) Old Feb 21st, 10, 07:05 PM
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Re: Casting number question for 327 heads

Well sometimes we Gear Heads can get carried away with Technical Data that can confuse newbies. It's not that we are argumentative and hate one another, it's just that we like to discuss historical data. I respect John' s knowledge about these heads and learn something every time he inputs. In the long run, if you have the patience to weed through our discussions you will not find better mentors in our sport then here at TC - Welcome Aboard, don't feel intimidated or intimidate other members, try and be polite and excuse what you read at times as members put effort into helping other members. We are not perfect and relating data is not always easy - LOL

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Last edited by Z15CAM; Feb 21st, 10 at 07:36 PM.
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post #14 of 34 (permalink) Old Feb 21st, 10, 07:14 PM Thread Starter
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Re: Casting number question for 327 heads

Quote:
Originally Posted by Z15CAM View Post
Well sometimes we Gear Heads can get carried away with Technical Data that can confuse newbies. It's not that we are argumentative and hate one another, it's just that we like to discuss inconsistent historical data. In the long run, if you have the patience to weed through it you will not find better mentors then here at TC - LOL
I am definitley finding that out! You guys are the best, and i thank you.
I do have another question (of course) for all of you...
What about this Edelbrock #2099 kit from Summit: http://www.summitracing.com/parts/EDL-2099/
Is this a decent price for what I am looking to do, or should I go the route of the 291's?
Thanks!
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post #15 of 34 (permalink) Old Feb 21st, 10, 07:59 PM
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Re: Casting number question for 327 heads

I see I was still editing when you Quoted me but that happens ;o)

That's a lot of money - What size of valves and shape are the 291's in - How much machining expense to bring them up to Specs? What condition are the Cylinders and Pistons in? Are the Pistons Doomed can they be reused? What is the Static Compression with a 64cc Combustion Chamber?

You don't need an Air Gap. A used SBC Edelbrock RPM can be had for approx $50. A descent 650 or 750 depending Cam and final compression ratio can be had for $400 or less. A new Timing Gear and Cam Kit for approx $200. Bearings, Rings, Gasket Kit for another $200. Perhaps a $900 investment Plus Head Machining and Bore Hone say $400 = $1,300.00 Providing you don't need New Pistons and Bore job.

A lot depends on the condition of the parts you already have.

By the way what year is your 327 Block - It sounds like it may be a Medium Journal Block? If so, does it have the Forged Crank. Do you have Doomed Pistons?

Down load and play with Patrick Kelley's DCR Calculator here:
http://www.empirenet.com/pkelley2/DynamicCR.html

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