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View Full Version : Edelbrock heads Vs. Stock 291-c's the unequivocal truth


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jeepsr4ever
11-02-2006, 01:29 PM
Here is a set of Edelbrock Performer RPM heads for the AMC V8 vs. a set of untouched 3196291-c heads (52cc dogleg heads made in 1970). You will see the ports on the Edelbrock heads are smaller in size when compared to the 291-c heads in some areas, larger in others but offer a smoother port. The Edelbrock's combustion chamber is superior to the stock 291-c's chambers. Edelbrock claims these flow #'s
Intake:
291 090 502 Edel (true numbers)
.100 71 74 70
.200 127 156 143 125
.300 179 201 192 212
.400 209 219 213 235
.500 217 226 220 266
.600 222 232 228 243 (bad turbulence
.700 228 238 236
Exhaust:
.100 55 56 59
.200 107 112 113 98
.300 135 141 146 130
.400 142 145 150 156
.500 145 149 152 174
.600 145 150 153 184
.700 145 151 153 (Edel @ .650 lift .187)

http://i2.photobucket.com/albums/y29/bulltear/edelbrockflow1.jpg

Now we are flow testing these heads as I speak and will post up real world numbers. We will also be doing very basic port work and re-flowing the heads.


Now here we show the port size differences...they are slightly off. Its hard to measure these accurately with a caliper :idea: :?:

http://i2.photobucket.com/albums/y29/bulltear/e291intake.jpg

http://i2.photobucket.com/albums/y29/bulltear/doglegshowdown.jpg

http://i2.photobucket.com/albums/y29/bulltear/chambershowdown.jpg


http://i2.photobucket.com/albums/y29/bulltear/headsprofiles.jpg

jeepsr4ever
11-02-2006, 03:00 PM
Looks like some room for exhaust gasket porting :?:

These are later model Waggy gaskets...not for performance use. I will not be using these gaskets but look at all that extra meat!

http://i2.photobucket.com/albums/y29/bulltear/pmatch.jpg

fifesjeep
11-02-2006, 03:01 PM
I'll be willing to bet that with larger valves and a little port/polish work these will be neck and neck with Edelbrock... Probably better in the mid-range... but then again it also depends on who does the work etc. I've seen some charts from various people and each one is different... Close or around the same numbers.. Can't wait to see some numbers!

82Waggy
11-02-2006, 04:14 PM
I'm with you fifes,

Every comparison I've seen suggests that the stock heads actually flow better at valve lift below .350" , and when a proper exhaust stub is used on the flow bench and maybe a little port clean up work with a good 30 degree valve seat the stock heads can actually exceed the Edlebrocks up to .500" lift.

Can't wait to see this head to head comparison. If I may suggest, please check the AMC heads in raw stock form with stock 2.025,1.65 valves with 30deg seats and use an exhaust stub on both - other wise exhaust numbers will be invalid . Then do basic flash removal and basic clean up with a three angle 30deg valve job against the stock edelbrock.

jeepsr4ever
11-02-2006, 04:22 PM
Intake:
291 090 502
.100 71 74 70
.200 127 156 143
.300 179 201 192
.400 209 219 213
.500 217 226 220
.600 222 232 228
.700 228 238 236
Exhaust:
.100 55 56 59
.200 107 112 113
.300 135 141 146
.400 142 145 150
.500 145 149 152
.600 145 150 153
.700 145 151 153


Those are stock numbers for 3 different heads (via Ken Parkmans test). Edelbrocks walk all over the stock heads...ported you can get a set of heads to flow well but we are talking over port, brass shims and epoxy.

82Waggy
11-02-2006, 04:45 PM
Is that Ken's test with or without the exhaust stub?

I know edelbrocks out flow stock above .300 or so lift, but Ken indicated he thought a basic port and valve job on stock heads would keep up with them.

BTW: Interesting that the highly sought after 291 castings don't flow as well as some of the later castings, eh?

jeepsr4ever
11-02-2006, 04:56 PM
Yes well they were only ever sought after because of the stock combustion chamber. Ask most that build extreme racing engines and they will tell you the 291 is not a good choice for serious performance but we also arent talking about engines under 600hp. Here is a 290 based stroker with iron heads that makes approximately 800hp.

http://i2.photobucket.com/albums/y29/bulltear/cordovaadkinv8.jpg

fuzz401
11-02-2006, 05:42 PM
Hemmy's car :t:

jeep_man_401
11-03-2006, 05:12 AM
I'm going to have to dig up my flow numbers from my Indy heads. I had them flowed after I ported them for my 401. I know I beat their CNC machine up until over .500 lift. :lo1l: at least going by their book numbers.

The Indy heads had a ton of meat in the exhaust ports also. I ported them out but later found that the headers were smaller then the port size I ended up with. :(:

Seems to me that us AMC guys need a good quality 1 7/8" header that is affordable to run...

Head flow is key, but you have to have the headers to match. :t:

82Waggy
11-03-2006, 07:56 AM
Looks to me like both the 291C's and the Edelbrocks suffer from shrouded valves, as the flow numbers at valve lift below .300" is somewhat less than the later 58cc heads.

Went back and read Ken's report again. He seems to conclude that the Edelbrocks are slightly better than a bone stock AMC head (my own observations indicate this is only true at valve lift above .300") but not as good as a properly cleaned up pair of later AMC heads. He did basic port deburring, some minor smoothing, and a good 3-angle valve job and was able to outflow the Edelbrocks - up to .500 lift at least.

I'm right in the middle of working a pair of 090 castings myself. I'm machining the bowls to be uniform and sizing them appropriately for the valve diameters (2.025,1.65), doing a 3-angle 30degree seat valve job with stainless valves and hardened exhaust seats, smoothing the humps slightly in the ports, deburring the ports and port matching to the manifold/headers, and polishing the chambers out to 65cc's. Will then flow bench to see what I get and then choose a cam that provides the lift needed for optimum flow. Note that I am going for low rpm torque and not intending to exceed 5000 with a CR in the 9.2:1 range.

I'll report back when I see what I get.

82Waggy
11-04-2006, 06:40 AM
Got to play around on the flow bench last night at my machinest place.

We put on a freshly built monster aluminum Pontiac race head.

Intake flowed well over 400cfm at 28hg and .800 lift - holy smokes!
Exhaust flowed well over 300cfm at 25hg and .800 lift - used a 2.5"d x 4"l stub tube.

Interesting to see that at above .750 lift the flow did not change much and that an exhaust stub tube made all the difference in the world. Used modeling clay to fair the inlet of the intake port.

I'm going to put my AMC 090 castings on in both stock form and after port clean up this coming week. Will let you all know what happens.

jeepsr4ever
11-04-2006, 04:13 PM
Good to know, yes please post up all data you can.

More on the Edelbrocks
http://i2.photobucket.com/albums/y29/bulltear/edeamcinffo.jpg

Dusty
11-09-2006, 07:38 PM
out of the box and bolted on in a little gremlin with a 401 that a friend of mine races here in sonoma county he has always run amc cast iron but for the price the edelbrocks were hard to beat. his motor is .030 with speed pro pistons built 8 years ago with the PAW equivilent of the summit
8601 so pretty mild setup with a torquer. he noticed a definate increase in off the line hp and its about flat on the higher rpm performance


111!!!

Mudrat
11-12-2006, 05:35 PM
Couple things:
1) MC couldn't you have at least CLEANED the AMC heads before taking pic's :wink:
2) I'm ignorant - what the hell does this chart tell me?? :oops:


Intake:
291 090 502
.100 71 74 70
.200 127 156 143
.300 179 201 192
.400 209 219 213
.500 217 226 220
.600 222 232 228
.700 228 238 236
Exhaust:
.100 55 56 59
.200 107 112 113
.300 135 141 146
.400 142 145 150
.500 145 149 152
.600 145 150 153
.700 145 151 153


Those are stock numbers for 3 different heads (via Ken Parkmans test). Edelbrocks walk all over the stock heads...ported you can get a set of heads to flow well but we are talking over port, brass shims and epoxy.

FuzzFace2
11-12-2006, 05:50 PM
It shows flow rate for valve lift on the 291, 090, 502 heads. Move the head cast numbers over to line up with the flow numbers is all you got to do.
When you line them up right then post, the format goes to heck!
Dave ----

Mudrat
11-12-2006, 06:02 PM
Ahhhhh OK gotcha. Is the flow rate in CC's or CF??

jeepsr4ever
11-16-2006, 01:29 PM
UPDATE

Intake:
291 090 502 Edel (true numbers)
.100 71 74 70
.200 127 156 143 125
.300 179 201 192 212
.400 209 219 213 235
.500 217 226 220 266
.600 222 232 228 243 (bad turbulence
.700 228 238 236
Exhaust:
.100 55 56 59
.200 107 112 113 98
.300 135 141 146 130
.400 142 145 150 156
.500 145 149 152 174
.600 145 150 153 184
.700 145 151 153 (Edel @ .650 lift .187)

82Waggy
11-16-2006, 04:20 PM
What are you comparing here? Looks like the stock AMC numbers that were tested without a stub or intake fairing.

Did you flow the Edelbrocks? If so, did you fair the intake port and use a stub on the exhaust?

jeepsr4ever
11-16-2006, 06:00 PM
The post shows the stock edelbrocks compared to the stock heads.

82Waggy
11-17-2006, 08:50 AM
Here are the flow numbers for a set of Stock AMC 291 castings. These numbers were obtained by Ken P., as were the above numbers you posted. Note the exhaust numbers obtained by using a stub to simulate a header. Ken noted that the above numbers were incorrect as he did not use the stub and determined that using an open port resulted in invalid data.

Lift Int,Exh,Exhw/stub
.100 69,53,53
.200 142,95,101
.300 192,130,143
.400 218,143,161
.500 221,144,167
.600 224,145,169

Note how much better the dogleg exhaust flows with a stub tube to simulate a header.

Here is a quote from Ken regarding this test:

[These heads had extremely badly pitted seats, and for the exhaust I was using a 1.68 valve. Both of those things will not make a big difference for flow. The intake shows the slightly poorer flow [of the 291 castings] compared to the later heads, but is typical. Notice how much difference the exhaust stub makes. The dog leg really comes to life with the stub, and of course that is the way it is on the engine with headers. I have now learned most of the exhaust flow numbers are done incorrectly (including my own from earlier testing). This is much more representative, and the AMC dog leg really is good.]

Ken then did some minor porting, a good valve job, and sized the throats appropriately for the valves.

Here are the results:

From Ken: [Next test with the basic work on the mill. I sized the throats correctly for the new valves, did the most minor unshrouding, but that got rid of the machined lip in the combustion chamber a 291 has. Also used the mill to square the port opening and size the pushrod pinch. Just a little bigger, trying to target velocity for about a 6500 rpm max 360. Then I did basic blending of this machine work. On the exhaust I did basic hand porting of the throat.]

Here are the results with your Edelbrock data added for comparison:

Lift 291Int,Edl Int,291Exhw/stub,Edel Exh
.200 137.8,125,107.9,98
.300 192.7,212,153.1,130
.400 236.5,235,177.9,156
.500 256.8,266,220.0,174
.600 248.0,243,227.5,184

[Now we're getting somewhere! I got most of the low lift intake flow back, and the upper lift flow is taking off. The drop above .500 lift tells me I have some more work to do yet, but the improvement are huge. The exhaust is amazing. That was not much work, and fantastic results. The dog leg really is that good, and way ahead of the ported rectangular SS heads with a 1.74 valve. Awesomely good design that dog leg! ]

---

Note that neither the AMC or Edelbrock heads appear to benefit from intake valve lift in excess of .500 as they both show a drop in flow - and that in bone stock form AMC heads show little appreciable gain in flow above .400 valve lift. With basic port work the AMC 291 heads were able to rival if not exceed the out of the box performance of the Edelbrock heads (at least within a margin of error) - Later AMC heads such as 090 or 502 castings theoretically flow a little better than the heavily shrouded 291 castings used in this test. Ken also determined that a 30 degree intake valve seat yielded even better intake flow numbers than the 45 degree intake seat used here.

My point is that a proper inlet fairing on the intake port and the use of an exhaust stub when bench flowing heads is necessary to get readings close to actual conditions as leaving the ports open ended is not the same as having an intake and exhaust manifold installed that helps straighten out the flow. The design of the dogleg exhaust port is heavily dependent upon the exhaust manifold/header for proper flow. It would be interesting therefore to know if you flowed the Edelbrock heads in this way for proper comparison.

jeepsr4ever
11-17-2006, 11:33 AM
The reason we found for the loss in lift above .500 was that it just gets too turbulant. It was found the shape of the port is not smooth and causes this turbulance. We did not use a exhaust spud or stub to simulate a header. After porting we couldl use a exhaust stub to simulate a set of headman headers and repost the numbers. Exhaust stub for the exhaust eh? Hmm I will see what our guy here has to say about that.

82Waggy
11-17-2006, 05:48 PM
Part of the turbulence problem could very well be attributed to the lack of a stub tube on the exhaust or an inlet fairing on the intake port.

The exhaust port is not designed to simply dump out of the head and will not flow properly without a manifold.

The intake is designed to work with a manifold as well - simply trying to pull air in through the hard square edge of the head will not do. For the heads I did the other day we faired the inlet with modeling clay - making a shape around the port similar to the shape of a jet engine nacelle.

These things make a HUGE difference in the results.

jeep_man_401
11-20-2006, 05:02 AM
These are the flow numbers I got on my Indy heads after I reworked them...hoping I didn't lower the flow. I think I did alright just by going by feel and eye.... 111!!! (bottom row is the flow :wink: )

My cam's max lift is .560 anyway. And the cam was made going by the catalogs flow numbers...maybe next time I will use a roller with these numbers. :mrgreen:

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00885.jpg

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00886.jpg

Out of the catalog...
http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00887.jpg

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00888.jpg

jeepsr4ever
11-21-2006, 04:10 PM
Interesting numbers.

On Kens test with the stub I wonder about the stub size for the dogleg. As you can see the AMC blueprint and actualy dogleg vary quite a bit


The AMC dogleg print (in black), the actual dogleg after machining (stock (in red)) and a port from Hedman headers (dotted in green). Now our test was done with a 1 7/8 hole on the exhaust which might account for the lower flow and we used a port matched stub on the intake. I will use a hedman header stub on the exhaust next time but I believe it will hurt flow. I am hoping to get a set of 1 7/8 thorleys to use one port as a stub.
http://i2.photobucket.com/albums/y29/bulltear/DGS.jpg
We are working on header flanges for the AMC dogleg heads and header/intake gaskets as well for proper port matching and custom header building.

AMX69PHATTY
11-21-2006, 04:38 PM
No wonder I had to do so much grinding, chamfering, and flaring
to match the ports on my cheapy headers to match the gaskets.
Especially in the DogLeg area.
Header folks probaly hate the DogLeg profile.
Have to use some kind of a swaging tool on the tubes I guess.
But whent they welded'em to the flange plate
they almost eliminated the dogleg shape with the weld bead.

jeep_man_401
11-22-2006, 12:48 AM
{We are working on header flanges for the AMC dogleg heads and header/intake gaskets as well for proper port matching and custom header building.}

That would help, as the supply of good headers is limited. I really need a set of 1 7/8 on my 401...the Headman headers are crap. :(:

82Waggy
11-26-2006, 08:05 AM
Slightly oversized on the header flange wont hurt anything.

Verses no stub at all, you will be amazed at what a difference even a slightly undersized stub will make. Even a round tube of a diameter that encompasses the port will improve flow over no stub at all.

Holeshot
12-01-2006, 11:50 AM
Thanks for the great thread, guys!!!

Holeshot
12-03-2006, 05:52 PM
Hooker "Super Comp" headers come in 1-7/8" but are quite costly. Hedman supposedly has big-tube stepped race headers for AMC but I've never been able to verify that they are in fact available...

Hedman:
* HED-95100-6-E2 Husler 2" prim, 3.5" coll., Coated, Stepped CALL
* HED-98310 68~80 AMC 1-5/8" primary 3" collector $ 105.95
* HED-98310-6 same as above, with ceramic coating $ 325.39
* HED-99190 Jeep CJ fenderwell exit, 1-3/4" 3" $ 105.95
* HED-99196 same as above, with ceramic coating $ 325.39
* HED-99200 Jeep CJ 72~86 1-3/4" 3" collector $ 105.95
* HED-99200-6 Same as above, with ceramic coating $ 289.95
* HED-99240 Cherokee J10 Waggoneer 74~79 1-3/4" 3" col $ 105.95
* HED-99250 Cherokee J10 Waggoneer 80~83 1-3/4" 3" col $ 105.95
* HED-21107 3 in. dia. 3-bolt to 3 in. outlet, with O2 reducers $ 15.69
----------------------------------------
Hooker:
* HOK-10979 weld-on oxygen sensor fitting $ 11.69
* HOK-11037 3-1/2" coll to 3 1/2" pipe 3-bolt O2 reducer $ 23.95
* HOK-7103 SuperComp 68~74 1-7/8" prim 3-1/2" coll $ 385.95
* HOK-7103-1 Same as above, ceramic coated $ 565.95
* HOK-7105 SuperComp 1-3/4" prim 3" coll $ 299.95
* HOK-7901 Comp 1-5/8" prim 3" coll auto on floor only $ 141.95

Holeshot
12-04-2006, 11:03 AM
http://home.comcast.net/~dhoelcher/amc/post/headspecs.jpeg

jeepsr4ever
12-19-2006, 10:38 AM
Did I read these numbers right? sothe Eddies outflow the indy street heads?

These are the flow numbers I got on my Indy heads after I reworked them...hoping I didn't lower the flow. I think I did alright just by going by feel and eye.... 111!!! (bottom row is the flow :wink: )

My cam's max lift is .560 anyway. And the cam was made going by the catalogs flow numbers...maybe next time I will use a roller with these numbers. :mrgreen:

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00885.jpg

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00886.jpg

Out of the catalog...
http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00887.jpg

http://i4.photobucket.com/albums/y116/jeep_man_401/DSC00888.jpg

Holeshot
12-19-2006, 10:48 AM
note that the home porting wizard's test pressure on the previous post's pic is only 8", while Indy used 28"!!!!!

Makes a HUGE difference!!!

:occasion9:

jeepsr4ever
12-19-2006, 02:58 PM
Ah yes

401 Pacer
08-16-2007, 06:50 PM
Please permit me to further confuse and astound y'all....

Flow numbers don't mean sh1t

What I mean is that they don't tell the whole story. Some critical, but almost always overlooked, considerations include the BALANCE of flow BETWEEN the intake AND exhaust port. Too much on one or the other and you hit a wall.

This can be compensated somewhat with exhaust tweaks (more or less restriction) but only so far.

Anudder thing is turbulence....when and where. I know some porters (not the kind who clean the crapper at the bus station) who listen to the air flow while they work their magic. Think: snazzy stethoscope.

I reiterate, numbers don't mean sh1t UNLESS you know how to apply them effectively. Remember "Advertised Duration"? Case closed! :?:

Holeshot
08-16-2007, 07:29 PM
Flow numbers DO mean a LOT!!!!

That's one set of data we have to compare one head to another.

Flow numbers give us at least some data to compare.

As far as intake -vs- exhaust, that is yet another variable that is open to interperetation, and can vary with type of induction & exhaust used.

Perhaps nearly as important as overall flow numbers, is having each port flow the same as the rest do. The home port job without a flow bench may yield ports that vary 10~30% between like ports, meaning you may have one port flowing 300CFM and another flowing 270CFM. Try to get correct mixture distribution with that!!! Not gonna happen, never will run to full potential.

So having a set of flowed heads (& intake) is EXTREMELY important to extracting max performance by allowing equal mixture distribution and tuning to the edge without getting a lean & detonating cylinder.

Speaking of balancing the flow, a stockcar wrench I knew would use pingpong balls to shove into the primary header pipes to check for equal length - each pipe should hold the same number of balls.

Also, rust inside of the primaries can reduce diameter and flow enough to be measured on the dyno.

401 Pacer
08-16-2007, 07:58 PM
Ya ain't gettin mah meanin!

Flow numbers, like most data, can and IS manipulated to the point that it's almost useless more often than not....and when the tests are done under different parameters (such as level of suction etc) then it's worse than apples and oranges.

What I be tryin to say is: THINK! Don't blindly go by numbers. Ask people who you respect (or have solid reputations) what their REAL WORLD RESULTS are.

Guess I've been watching too many commercials "New and improved!" :roll:

Not bustin your chops, I just want people to be critical thinkers.

jeepsr4ever
08-16-2007, 09:13 PM
Most times you flow the heads and then get a cam grind to get that 82% efficiency variable between intake and exhaust....just to put it to bed :wink:

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