X-Head Flow Numbers - What to do

-
blewbyoutobad

blewbyoutobad

FABO Gold Member
FABO Gold Member
Joined
May 23, 2010
Messages
1,425
Reaction score
477
Location
Missouri City, TX
So during Thanksgiving I decided to try and find some free horsepower laying around the garage. I'm building my 340 for the final and last restomod of my 69 Swinger 340. With the cost of the restoration at $20K I can't afford a new set of heads so I have to make my X-heads work. I gasket matched them back in the 80's (yes I'm old) and ran them until this last tear down. I ported the intake and exhaust on one cylinder, opened the push rod pinch point for the intake on another cylinder and then ran numbers on a cylinder as they were before. I'm trying to decide if this is worth all the work. I have good numbers for the ported intake but I am a little dis-appointed in all the exhaust flows. I wanted to get at least 180cfm on the exhaust. I can post pictures next week when I get the head back. What direction do you think I should go? Will exhaust flows in the 145 to 155 range support 240 to 260 intake flows? Camshaft is my old Lunati solid (yes from the 80's). Specs are roughly .507 lift on I & E and 292/ [email protected] duration. Real lift is .487 with a .020 lash. I can post more specs on the motor if you all are interested. If the chart is not legible I'll see about posting a better pic.
Thanks to all who post. I appreciate your input.
 

Attachments

  • x-head flow numbers.jpg
    158.3 KB · Views: 1,046
I dont know what your over all goal is for your car ..the exhaust side of the X head is the week point , i dont know how much pocket work was done but thats the g spot...if you are building a street set up I thnk what you have is awesome
 
It's definitely for street fun. Do you think its worth the trouble to take the intake up to the 260 or just leave them at 230. I did a lot in the exhaust pocket and thought it would be better. I'll post pics next week when I get the head back.
Thanks
 
Did you polish the exhaust side along with porting? I did my x heads the same way as you and was able to get 238 int and 176 exh. I polished the crap out the exhaust side. Not sure if that made any difference.
 
There are a few opinions on the ratio, but basically i like to get the exh to better than 75% of intake port flow. Some will say 70, some say 80...lol. The mopst important thing is that you have good numbers and then you can cam it properly.
 
Thanks Scot
I used an 80 grit on both ports. I did not have it really slick. I'm also wondering about the short side turn in and how much that affects it. I'll post pics next week.
 
blewbyoutobad said:
It's definitely for street fun. Do you think its worth the trouble to take the intake up to the 260 or just leave them at 230. I did a lot in the exhaust pocket and thought it would be better. I'll post pics next week when I get the head back.
Thanks
Click to expand...
yes please do I am a X headed 340 owner and builder and always interested in this subject :D
 
As I mentioned the cam is an older Lunati (24 years old but in good shape), I lost the cam card so I degreed it when I installed it in the shortblock. Here's the numbers.

104 Centerline I & E
248 Duration @ .050 I & E
.507 Lift I & E
Intake
20 BTDC Open
48 ABDC Close

Exhaust
58 BBDC
11 ATDC

31 Overlap??

Running A Holley Strip Dominator
750 Carb
1 5/8 Headers
Flat Tops Poking out .012"
3:91 Gear & 4 Speed
28.5" Rear Cheater Slicks, May need 4:10 or 4:30's
Expecting power from 3000 up

Sound Right/Wrong? Open for suggestions.
Thanks all,
 
Nice grind,overlap probably in the 68 to 75 ratio,108 lobe centers.If you actually do battle,at the track or street/strip ,go get it.Just food for thought,each cfm+= 2 horsepower set up right.
 
The key to getting the exh ports to work is grinding out the valve guide flush to the roof like it was never there, along with the obvious valve job, bowl blend, and short side radius profiling. Take this advice with caution as porting that heavy can carry the risk of finding water, but thats how I do my heavily worked ports. I also find tulip shape exh valves to be around 10 cfm or so better than nail head valves. I liked the Mopar Performance exh valves they were about 25* back angle, but can't seem to find them anywhere.
 
If you lay the exh short turn back too far..you will get better numbers, but you will move them way up in the lift range, and you really want the exh port to start moving air quick/soon in the early valve opening stage.
Go straight up from the seat and just kinda round the top of the turn, cut the guide flat with the roof, try to almost straighten the roof kink and of corse get the bowl in the 90's of the seat, also straighten the curved angles on the center ports around where they go around the head bolt. Dont widen or try to gasket match the exhaust port window any larger than the rest of the port... cause the gaskets r BIG and when you make the window bigger than the rest of the port... it slows the air 'hurts velocity' down and u lose flow, it becomes blockage for the air moving behind.

i would go for the 260cfm and try to work the exhaust ports more or cam it split pattern with added lift and duration on the exhaust, also consider while the exhaust actually picks up flow with a header tube...the int loses flow with an intake....so in actuality, the ratio you see on paper is not the running ratio ;)
flow it with an intake bolted on and see what you really have.lol
 
Neat info ,Justin.Do you flow inductions,as a unit?.Part for part,adjusted accordingly?By the way,remember to double the lick nuts,on the solids 410.....
 
Got some info from the shop that flowed the head. I'll be working this week and next to finish these and get new flow numbers. I'll post when I get them and some pics as well. Thanks for all the comments.
 
Hey everybody,
Finally finished the port job on the X heads. Got some pretty good numbers. I am going to run these on a rebuilt stock 340 short block with the solid cam mentioned above. Calculated CR is 9.52. I was hoping for more CR but hey I had these heads and it cost nearly nothing to get them to these numbers. Intake is a Holley Strip Dominator with 750 DP. 4 speed and 3:91's. All my money is in the restoration so I used what I had and decided to save for 2 years then build a stroker. This motor is for the restoration post "Third Times Charm".
Thanks for your input.

Just learned my scan of the numbers screwed up. I'll post them tonight when I get home.
 
Waiting with bated breath!

I think, IMO, that a new cam is in order after you have the head flowed for the final time.
The Holley Stip Dominator is a very good intake manifold.

The older heads have flow ratio problems when compared to new heads. While a lot can be ported to correct this, it can also depend on how far you want to go in porting them. The wider/larger the flow balance in the intake and exhaust flow rates, the larger the duration split for the cam is needed.

In the old days of racing, Crane cams (and MoPar) would suggest a extra amount of duration of up to 12*'s to help rebalance everything. This is still a available from Crane. Most other cam companies have a smaller split in the durations. It vari's a lot.

It is a big plus that your having your heads flow tested!

From the last test on the latest head work, you can start to figure out what and where you need to be on the cam specs. You allready know that duration equals RPM range it will operate in. Now, get a cam that takes advantage of the head flow abilities with as much lift as the head can handle.

Considering your on the street and not the track, do not choose a cam with more lift than the head flows at peak. It really doesn't make sense at this point to go beyond the heads max flow in lifting the valve beyond that point.
Your going to pick up a good amount of power that you'll notice and feel with the head mods and a new cam.
 
Hey Rob,
Thanks for the input. I could not get my scanner online at home so here's the numbers. Nothing done here is extensive and all I wanted was something decent that would do justice for the car it's in. Let me know what you think.

.100 .200 .300 .400 .500 .600
IN 74 139 202 249 252 255
EXH 44 96 134 156 165 172
 
What do I think????

I think nice freakin job there! WOW! Home ported with respectable flow numbers to enable your car quit well my friend!

And what was the cost to you? A few bits and time? Besides flow testing that is. But I'd like to know that cost. I have not paid for that myself.............yet............

This is where I often say that a home porting job can be a cost effective measure vs. the purchase of Edelbrock heads and there extra cost to look at much less any added work if need be.

Percent wise........ with a minor give and take.....
.100 / 60%
.200 / 69%
.300 / 66%
.400 / 63%
.500 / 65.5%
.600 / 67.5%

While the close but still ruff percentages show your work to be good though lacking in a minor way on the exhaust, just offset the exhaust duration a little more in duration and lift if possible. With these numbers, you now can consult a grinder with all the other knows and wish's for your engine.

Do note though that each cam grinder will have there opinion as wide and varied as us here.

Perhaps Moper, Skews or 1 wild and crazy can give you a pointer on more finishing work if you desire.

1 wild and crazy (1W&CG) has a thread up on iron heads here. Maybe 2? And Skrews just did a 360/308 head thread. And in which, I have to say, thanks fellas and nice work.
 
those are very nice numbers ...I am working my X heads right now and would be very happy with those numbers!!
 
I found two secrets in doing this work. If you can do a good gasket match and blend on the short turns it will make a huge difference. I did not ground the guides down like most recommend. Its a street car and needs the guide length for longevity. I just smoothed them up. I agree on the exhaust that if I could have seen 185 or 190 I would be jumping up and down, but I dont have a flow bench in my garage. The other secret was the shop that did the 4 angle valve job. The fourth angle was blended into the port. I also did not open the port more than 85%of the valve size. More work could be done, but I don't want to spend my life working on heads. I want to finish my car. This just goes to show what you can do if you have the time. Also don't worry to much about the pinch point on the intakes. The gasket match and blend will work very well. :blob:

Thanks for all that post

PS Rumblefish
My shop charged about $50.00 to do Int and Ex for 2 cylinders. I am very confident they all are as close as the two that were done.
 
Those are nearly identical #'s of what I got from my X heads I did several yrs. ago. IMO, Justin has a real good point about how a pipe picks up the exh flow and the intake can slow down the intake flow so the percentages are not nearly as bad as they look. Wish I had a bench (and a place to put it, LOL) to play more.
 
If the lobe lift is correct I have probobly run that cam in a 360.With 10.5to1 comp and Jheads went 11.0's at 122 and replaced the MP 292 hyd. It's an old loose lash grind with 8 or 10 degrees more exhaust to intake duration. Sweet little street cam. Put some 4.3o's and 4000+_ converter and get over the flow numbers. The intake ports are FAR more important than the exhaust.
 
You must log in or register to reply here.
-

Back
Top