Head Games!

-

Captainkirk

Old School Mopar Warrior
Joined
Apr 24, 2006
Messages
3,371
Reaction score
1,509
Location
Northern IL
OK, need some of you portmasters to weigh in on my latest developments on my 340 build. I dropped off my '72 J-heads with my machinist over the weekend. He's going to:
1) clean and evaluate them
2) give me a quote/estimate on reconditioning
A couple of noteworthy items...these heads came off my '72 340. They have had some mild port work done to them (probably comparable to a gasket-match). They do NOT have hardened seats. His quick-assessment was that the valves should probably be replaced with new, even though this motor has less than 5000 miles on it since the last build (1976). I asked him that if new valves were required, if we could upgrade to 2.02s, he said yes...but it would require a bit of blending in the bowls. Also, these were cc'd to 67 cc's during the first build to work with the TRW 12.5 1 pistons that were installed then. My new pistons are TRW 10:1 pistons. Now, I do also have a set of X-heads off a '69 340 that already have 2.02's, but mileage and condition unknown. I would prefer to keep those heads with the rest of the engine they came off of, for later use, but I do have them as "Option 1" in the event there is an issue with the J's.
Some here have said that the earlier X-heads flow better than the J's due to the port floor shape. Would this really come into play for a street motor? (planning on this being a 400HP/12 second car)
Option 2 is, of course, Edelbrock aluminum heads. If the reconditioning figures come close to the price of a set of Eddies, ($750/head) I'd likely prefer to spend the money on them rather than reconditioning either set of iron heads. The Eddy heads are complete with 2.02's, hardened seats, and high flow ports as you probably know.
I'm not planning on doing any addition port/flow work as that would undoubtedly drive the cost above the price of the Eddy heads.
Any input will be appreciated. While this machinist has a good working knowledge of SB Mopar, it's not his specialty by any means, and I'm taking everything he says with a grain of salt. Thanks in advance!
 
From what I remember posted somewhere that the smaller valved J heads were a good canvas to make into a nice flowing head.
 
Bear in mind that the machinist has not condemned the 1.88 valves yet...only that he would suggest replacing them as there might be rust or pitting on the valve stems. I'll probably know later this week but want to be ahead of the game. And if they are going to need replacing...why not, right?
 
How far will your pistons be out of the hole? For the money, it's hard to beat a pair of the speedmaster CNC heads.
 
How far will your pistons be out of the hole? For the money, it's hard to beat a pair of the speedmaster CNC heads.
I don't know the answer to that. I don't believe the block was decked. Pistons are TRW forged 10:1 Eagle forged rods, standard length.
 
At standard deck, your TRW pistons should be "around" .018 positive deck "out of the hole". What oversize are your pistons? Here's a helpful modification for valve clearance on those pistons. Some users have had interference issues with the corner of the ledge before.
upload_2021-2-28_21-38-4.png
 
The answer to this question is a few questions for you.

What cam are you running? Provide specs!!!!!!!!
Just don’t give me a grind number or leave a link!
What is the ultimate goal of the vehicle?
 
What?????

OD DEAR LORD! Horse before the cart thread again.

Cap! You gotta have a plan!!!! You don’t even know what cam your running !!!!
WTF dude?

This should be a build question thread and not multiple threads with questions that rely on answers from other threads that are not answered.
 
The answer to this question is a few questions for you.

What cam are you running? Provide specs!!!!!!!!
Just don’t give me a grind number or leave a link!
What is the ultimate goal of the vehicle?
No cam has been selected yet, Rob.
 
What?????

OD DEAR LORD! Horse before the cart thread again.

Cap! You gotta have a plan!!!! You don’t even know what cam your running !!!!
WTF dude

This should be a build question thread and not multiple threads with questions that rely on answers from other threads that are not answered.
Heads are heads, are they not? The only mods I'm considering at this point are the possible upgrade to 2.02 intakes and whatever bowl grinding might accompany that. No major porting or milling, etc planned for now. So cam selection would come AFTER getting the heads done, correct? If I'm wrong, tell me. Oh, and ultimate goal is 12 sec/400HP street machine.
 
Heads are heads, are they not?
No
The only mods I'm considering at this point are the possible upgrade to 2.02 intakes and whatever bowl grinding might accompany that. No major porting or milling, etc planned for now.
Just a rebuilt set of heads w/possibly 2.02 valves and what ever port work may be needed.
This alone says to me your car away from any decision or plan for n the engine. Your also considering 3 different heads.
So cam selection would come AFTER getting the heads done, correct? If I'm wrong, tell me. Oh, and ultimate goal is 12 sec/400HP street machine.
Cam selection should be thought of before hand and final selection is part of the package, not the final out come of the probable work to be done.

Capt, you have a lot of thinking ahead of you.

Is there a time slip you want to achieve?
What are your rear gears?
Tire size?
Trans?
Converter? Or 4 spd?
Chassis mods?
Actual car weight?

These are honest questions a bunch of companies will ask when ordering parts. Like a converter company will ask, tire size, cam size, engine size, compression ratio, at weight, Etc....

A 340 @ 10-1 with an Edelbrock headed top end (750 cfm/AG) regular headers and a 230/480/110 cam with a good distributor & carb tune will make 400 hp. This would use a minimum of a 2500 converter & 3.55 gears on 26 inch tires. The f you suspension is worked out to hook and the car is light enough, you can run in the 12’s.

More converter? Deeper into the 12’s.
More gear? Deeper into the 12’s.
Lighter car, deeper into the 12’s.

Check the 12 second thread in the racers section.
If the membership did the right thing, as in a detailed listing of the build and car, this will be a snap to do!
:thumbsup:
 
To make 400hp, you need intake flow of roughly 200 cfm or slightly more. Might be doable with smaller valves, but in my opinion 2.02" valves would be a worthwhile upgrade.
 
Rumble, you seem to be getting more angry as you age. Not all of us have a million terrabytes of information like you and some other senior members. Help us not so knowledgeable guys out. We're looking for mentors, not a reason to defect to the LS/Coyote camp. Respectfully, Paul.
 
Heads are heads, are they not? ...................
No, they are not. Heads hold the key to most of the power potential of the engine (along with cam selection). A stock iron head flows ~190cfm...a stock Edelbrock head flows ~ 250cfm, Fully ported Edelbrocks flow ~ 293cfm (at least mine do), Indy heads (fully ported) can go north of 320cfm, etc. Those are big differences in power potential (~375hp-650hp). In order to take advantage of that head flow you need a cam that can operate in the range to maximize flow....What Rumble was saying in his response is true, you need to look at the whole package and make a plan. Start with a goal (an ET, HP number, etc.) and build from there. Obviously there are many critical components, but good flowing heads are essential to making big power.
 
Rumble, you seem to be getting more angry as you age. Not all of us have a million terrabytes of information like you and some other senior members. Help us not so knowledgeable guys out. We're looking for mentors, not a reason to defect to the LS/Coyote camp. Respectfully, Paul.

Well, yea, un-intentionally, I was a dick. Don’t mean to be one, but full erect I was, my apologies to all including OE poster. Thank you Paul.

CAPT.! Having a cam to lift the valve up is a big help but not the end all. If there is a good cfm flow number around a bowl ported head, you can get going real good with just that.
 
So far I’m seeing 10:1 compression TRW forged pistons but am going to assume that the goal is 10:1. If so, some head milling and careful head gasket selection is in order. The goal is 12 second car with 3.91 gears and a four speed as posted in the cams away thread. I don’t recall the tire size being used, but tires and suspension is going to play a large part in a 12 second car. I’m thinking the J heads with the proper cuts in the chambers for 2.02 valves, bowl porting (I would do a good gasket match at this point to) are good for around .530 lift. So to really take advantage of the heads, adjustable rockers aren’t a bad idea. It really would help to consolidate these threads, because what you want is doable in several different ways, but it helps to get everybody on the same page.
 
First of all; thanks to all the replies! Second, apologies for the mix-n-match threads. Maybe I can get a mod to blend the two. Anyway...
So here are the basic goals:
12 second/400 HP+ smallblock, pump gas
Here are the specs I'm working with:
*standard weight '72 Duster
*A-833 4 speed
*3.91 or 3.55 8.75 rear end. Planning on starting out with the 3.91
*Headers w/duals
*Single quad, most likely Holley DP
*Dual plane. Have an Air Gap RPM to use as well as others.
*Mopar EI

So, there you have it. Am I missing anything?
 
Race only?

12 second implies just into the 12s, with unlimited suspension, you only need a P/W of .081 to get there so, at 3400 pounds race weight, that would be 275hp

But on street tires, and with street suspension, you might need a P/W of .094 so 320 hp.
But if you want a low 12 second in street trim you could be looking at a P/W of .115, so 390hp

So obviously, each of those builds is gonna be considerably different.
@Rumble said you had some decision to make, and I agree.
Cuz 400hp in a streeter is way overkill. Even with 3.91s, if the tires hook, you can't get to peak power in Second gear until just before you are speeding. And the ride takes about 5 seconds from a dead stop. But more than likely your street tires will NOT hook,and they will spin all the way....... and spinning ain't winning.
If that is what you are after, and you have the money, I find no fault in the doing, on account of that was what I wanted, and did,lol. But I didn't have any track goal in mind.

To say it in another way, 400hp at 3400 pounds is a P/W of 400/3400= .1176, and with unlimited suspension, has the potential to go about 11.5@116 mph. But with street suspension and tires expect to be a second or so slower.

Now, to make 400hp with XJOUorZ heads
for use with pumpgas
is gonna cost you a wheelbarrow of money and and, flippin' AND; a crazy for street, cam.
 
Last edited:
Race only?

12 second implies just into the 12s, with unlimited suspension, you only need a P/W of .081 to get there so, at 3400 pounds race weight, that would be 275hp
Yes, AJ...as long as it breaks the 12 mark I'll be a happy camper. Street only. Stock suspension, worked over with new bits, but still stock. The only track time it might see would just be for the ET slip. But most likely not even that. Just want the "butt-dyno" to be happy.:p
 
Yes, AJ...as long as it breaks the 12 mark I'll be a happy camper. Street only. Stock suspension, worked over with new bits, but still stock. The only track time it might see would just be for the ET slip. But most likely not even that. Just want the "butt-dyno" to be happy.
Well in that case, as I posted the numbers, you don't need 400hp to have a chitload of fun.
My combo has undergone three iterations, the smallest of which went 12.9@106 right off the street with 3.55s.The Wallace makes 106 mph to be ~335 hp, easy peasy with a 360.
I'm gonna go back to mind my own business now, but I'll just add that if the whatever gears are currently installed, leave them there and take it easy on the cam, you will only need about 222 to 230 degrees intake duration to hit your target. You can probably mill those 12/1 pistons to get the shape you need with open-chamber heads to get you a tight Quench. After that adjust the compression with a dish to work with the cam you chose.
I suggest you put the power into the heads, and crank the pressure to the max, so when the big-cam bug bites, that you don't have to start all over.

But more important than anything, I wanna mention, that with a 4-speed your lowest driveable speed becomes an issue.
If you have a 2.66 low gear 4-speed and 3.55s then at 700 rpm, your lowest speed becomes 5.9 mph with an 84" roll-out or 26.7" tires. And you won't be driving that with a 292 cam, and 25* of idle-timing.
And if you have to toe the clutch,for any amount of time, that 3600# Zoom-clutch will not be your friend.
The 3.91s will get you down to 5.35 mph, not a whole lot better.
If you expect to be driving slowly on a regular basis, you are gonna need to bring the idle-speed down, and retard the thechit outta the timing. AND, your Transfer slot sync is gonna have to be spot on.
To get down to 4mph with 3.91s, your idle speed will need to get down to 523rpm. Your 292 cam will not go there no matter how far you retard the timing; it will not have enough power to pull itself. And on the way down, it will start bucking like a wild horse.
If 4mph, which is a fast walk, is important to you then yur gonna need to get around the gearing issue, or stick a small cam in her, which will have more low-rpm power so you can hit that 523 rpm target.

I'll tell you what I did.
I swapped that 2.66box out in favor of a Commando box, which has a 3.09 in it, and I installed 3.55s out back.
Now 4.0 mph is 552 rpm. And I got rid of the 292 cam, in favor of a 270/276/110. Which would idle down to 552 no problem; but I had to retard the Idle-Timing to ~8* to get it to stop bucking. This cam had lots of power down there to pull itself around on anything including grass.
But you have 3.91s so your target is 608rpm with the Commando box. That means, if you wanted to, you could install the next bigger cam, say a 276/110 cam, but you may need to retard the timing a lil further to get rid of the bucking.
I tell you these things cuz I'm working up to something;
namely, the 270 cam is pretty small, about 223*@.050. To make power with that small a cam, I used OOTB Edelbrocks, and pumped the pressure to 185 psi.
This was an excellent combo. I put enough valve spring on it to regularly rev to 7200. And that lil cam did pretty darn good up there, posting 106mph in the quarter with 3.55s in Third gear, reving 6600.

And the best news is, geared for 85=2100/65=1600, and with a set-aside carb tuned for economy, this thing killed it; posting nearly double of what I was expecting.

This was and will ever be my favorite combo. The next bigger cam I installed; a 276/286/110 cam, took me months to sort out, and cannot touch the previous cam as to fuel-economy nor bottom-end torque, and seems only a lil stronger on the top, despite the track results that say otherwise.
BTW
To retard the timing on the fly, I installed a dash-mounted, dial-back, timing retard box. You might as well get one, cuz it will cut your tuning time drastically. And there is no other way I can think of, to retard your timing from say14* at 750 to 5* at 550, which is what it's gonna take to soften the power pulses to keep you out of the Prancing-Pony rigamarole.
 
Last edited:
I should probably also mention I'm planning on sticking with the stock 1.5 rockers and shafts as well. Gotta slow down the Money Train somewhere.
 
Well in that case, as I posted the numbers, you don't need 400hp to have a chitload of fun.
My combo has undergone three iterations, the smallest of which went 12.9@106 right off the street with 3.55s.The Wallace makes 106 mph to be ~335 hp, easy peasy with a 360.
I'm gonna go back to mind my own business now, but I'll just add that if the whatever gears are currently installed, leave them there and take it easy on the cam, you will only need about 222 to 230 degrees intake duration to hit your target. You can probably mill those 12/1 pistons to get the shape you need with open-chamber heads to get you a tight Quench. After that adjust the compression with a dish to work with the cam you chose.
I suggest you put the power into the heads, and crank the pressure to the max, so when the big-cam bug bites, that you don't have to start all over.

But more important than anything, I wanna mention, that with a 4-speed your lowest driveable speed becomes an issue.
If you have a 2.66 low gear 4-speed and 3.55s then at 700 rpm, your lowest speed becomes 5.9 mph with an 84" roll-out or 26.7" tires. And you won't be driving that with a 292 cam, and 25* of idle-timing.
And if you have to toe the clutch,for any amount of time, that 3600# Zoom-clutch will not be your friend.
The 3.91s will get you down to 5.35 mph, not a whole lot better.
If you expect to be driving slowly on a regular basis, you are gonna need to bring the idle-speed down, and retard the thechit outta the timing. AND, your Transfer slot sync is gonna have to be spot on.
To get down to 4mph with 3.91s, your idle speed will need to get down to 523rpm. Your 292 cam will not go there no matter how far you retard the timing; it will not have enough power to pull itself. And on the way down, it will start bucking like a wild horse.
If 4mph, which is a fast walk, is important to you then yur gonna need to get around the gearing issue, or stick a small cam in her, which will have more low-rpm power so you can hit that 523 rpm target.

I'll tell you what I did.
I swapped that 2.66box out in favor of a Commando box, which has a 3.09 in it, and I installed 3.55s out back.
Now 4.0 mph is 552 rpm. And I got rid of the 292 cam, in favor of a 270/276/110. Which would idle down to 552 no problem; but I had to retard the Idle-Timing to ~8* to get it to stop bucking. This cam had lots of power down there to pull itself around on anything including grass.
But you have 3.91s so your target is 608rpm with the Commando box. That means, if you wanted to, you could install the next bigger cam, say a 276/110 cam, but you may need to retard the timing a lil further to get rid of the bucking.
I tell you these things cuz I'm working up to something;
namely, the 270 cam is pretty small, about 223*@.050. To make power with that small a cam, I used OOTB Edelbrocks, and pumped the pressure to 185 psi.
This was an excellent combo. I put enough valve spring on it to regularly rev to 7200. And that lil cam did pretty darn good up there, posting 106mph in the quarter with 3.55s in Third gear, reving 6600.

And the best news is, geared for 85=2100/65=1600, and with a set-aside carb tuned for economy, this thing killed it; posting nearly double of what I was expecting.

This was and will ever be my favorite combo. The next bigger cam I installed; a 276/286/110 cam, took me months to sort out, and cannot touch the previous cam as to fuel-economy nor bottom-end torque, and seems only a lil stronger on the top, despite the track results that say otherwise.
BTW
To retard the timing on the fly, I installed a dash-mounted, dial-back, timing retard box. You might as well get one, cuz it will cut your tuning time drastically. And there is no other way I can think of, to retard your timing from say14* at 750 to 5* at 550, which is what it's gonna take to soften the power pulses to keep you out of the Prancing-Pony rigamarole.
Here's the interesting part...this is Round Two for this motor combo. The way it was built, with the 3.91 and a single plane with Holley 650DP and the .450/.475-298/308 cam that was in it, I drove it all the way from Chicago to Tulsa. No bucking/prancing Pony nonsense or any other shenanigans other than rotten gas mileage. So not sure why that should happen now?
 
-
Back
Top