Edelbrock heads Vs. Stock 291-c's the unequivocal truth

[jeepsr4ever]

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)



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

[jeepsr4ever]

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!

[fifesjeep]

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]

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]

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]

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]

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.

[fuzz401]

Hemmy's car

[jeep_man_401]

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. 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.

[82Waggy]

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.