Head Help

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Duster1973

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Ok I bought an absolutly mess of a 340 engine!!! I'm getting ready to take it back out of my car and I'm going to compleatly rip it down this time. The question that I have is this. The guy I bought it from claimed that it had X heads on it. What if any was the big advantage of the heads? How do you tell for sure that they are the X heads? And what kind of flow numbers should I expect from them if they are unported or basicly stock?
 
To ID the heads you will see a X cast into the head. The big advantage to the X head was that it had 2.02 intake valves vs the J head 1.88 valve. They both had 1.60 exhausts. I don't know the stock flow numbers off hand but they were the same. There is an O head which should have the same last casting #s: 915 which also had the 2.02 intake valves.
 
Not sure yet. The motor was supose to be all ready to go but the springs on the head was only showing 50 p. of pressure so those were replaced. However when it didn't run any better we did a compression test and when I was getting numbers like 88, 110, 25, 108, 5 I knew that I had to pull the motor. I'm just ....upset... to put it nicly. I was wondering about flow number becouse a couple builds that I read on paper said to port to 260 cfm. I don't want to have to redo the motor again for awhile.
 
Take your time with it. And re: what articles say about flow numbers and your build in general, you need to make sure "everything" works together. Not only for the motor but for the rest of your drivetrain and components, what you are expecting out of your vehicle and what type of driving you do. Be realistic (incl. your budget), again, take your time and start building your car on paper.
 
Stock X heads flow somewhere around the 200 - 210 cfm, stock. And that would be the better flowing castings. Poorer castings down 10 cfm's.

Beware of fully poerted heads and the set up your going to run with through out the rest of the car. Also, if the cam is not lifting to the point of where the head flows this much, then it is mostly a waste. Not allways, but often the lift needs to be at peak lift and numbers like what your looking for are very high lifts.
 
Rumblefish thanks for the numbers. You and GTXperience are right about everything needing to work together. So I guess I should ask this. I was going to reuse everything I can to keep the cost down which would include the stock rotating assembly, the mopar single plane intake, the heads, a comp cam 294/306 duration 519 524 lift cam, 1.6 roller rockers, modified 770 holley double pumper and 1 5/8 headers. Anything stand out as wrong? How much if any port work would/should be done on the heads to have them flow well enough? It'll be a street/strip motor and I will be putting it on the bottle at some point.
 
Look up BJRracing here. He ports heads for a living and races.

But with the 1.6, the build you mention requiring a full porting for the flow numbers listed sounds about right. I think your on track.

The only thing I myself would do is step up in tube size. 1-3/4. Fitment may be an issue. On my E-body, the Hooker super comps fit inside without a problem save the Lakewood bellhousing issue and denting needed. If it was a stock bell, there would be no problem.
 
That's a pretty nasty cam for stock heads. Combined with a single plane intake you won't have much bottom end torque. If your running a 4000 stall and pretty deep gears (3.91-4.56) you'll be ok but you need to get the flow numbers up on those heads or it won't work right with that big cam.

BTW: It's real easy to tell a X head. Just look at the area between the spark plugs and you'll see a large X cast onto the head. Also the casting number ends in 894X

Here's the stock flow numbers on my 68 340 heads.

lift-----int. cfm-------------Exh. cfm
.200-----120------------------95
.300-----167------------------131
.400-----200------------------148
.450-----209-----------------153
.500-----205------------------155
.550-----202------------------158

You'll notice I highlighted figures at .45 lift cause this is where the intake was at peak.

Here's the same heads after I ported and polished them and installed back cut swirl polished stainless valves.


lift----------int. cfm--------exh. cfm
.200---------129-------------104
.300---------188-------------135
.400---------236-------------155
.500---------243-------------165
.550--------250-------------170
.600---------239-------------174

I again highlighted the peak intake flow numbers.

I am an amateur (Have only done 4 sets of heads total) so I'm sure these numbers are nowhere close to what they can do but it gives you an idea.

If you plan on re-using the cam and intake you have IMHO you need to get the flow numbers up to at least what mine are but more preferably.
 
I got a question for you 1973. Whats your intended usage for this car? That's a big cam my friend. You will need at least a 10:1 compression ratio, 3.55 plus gears and a 3000 rpm stall convertor.

No power brakes with this cam. Your idle vacuum will be far too low, probably 7".

LOL, Fishy responded while I was thinking. I'm thinking a bit slow after 4 beers though.

BTW, nice job on the flow numbers Fishy!
 
OK, I just checked that cam out. It's 250 degrees of intake duration at .050 lift. You'll be lucky to see 4 to 5" of vacuum. You better be good with carb tuning and scratch using a Edelbrock, AFB or Thermoquad.

This is a Holley HP style only cam.
 
We could go round and round (like we usually do ;-) but again, all parts/sub-assemblies/work considered need to be thought out before going forward. Duster, what rear end gears, convertor and tire size are you running? What RPMs do you plan on turning? When you say street/strip, I am going to assume that it is mainly street with a little strip use. Since you are trying to use the original rotating assembly, I am thinking you are on a budget (like many of us) so is port work (especially full port work) realistic at this time?

Also, this is a 340 but for some reason (maybe something I read in another one of your posts), I am thinking that this is a '73 340 (correct me if I wrong). If correct, consider two things. First, you are running a cast crank (which is fine for a healthy street build) and secondly and most importantly, your compression (again, with using the stock rotating assembly) is probably not going to support what you plan on doing with this. If this is not a low compression '72-'73 motor, then disregard the majority of this paragraph. Anyway, there are questions on suspension as well but let's leave it here for now. I know that your father and older brother are also on here and I know that will help vs if you were just doing this by yourself.
 
Yea the cam is big for the street but it's a steet/strip car...if I ever get everything working together right. I do have 3.91 gears and the stall is supose to be a a 3500 but it seems to flash alot closer to 3200. Thats what you get when you buy cheaper parts. Some day I'll learn. Thanks for all the help everybody I really appreciate it. I'll be yanking the motor next weekend and will know more then.
 
IMO, cam too big, intake is wrong, and carb is too big...for starters. The compression issue will be more than "reuse all parts". So I'll stay tuned to see what the examination shows.
 
What intake would you use and why? Just trying to as much information as I can to get it right.
 
Duster1973 said:
Yea the cam is big for the street but it's a steet/strip car...if I ever get everything working together right. I do have 3.91 gears and the stall is supose to be a a 3500 but it seems to flash alot closer to 3200. Thats what you get when you buy cheaper parts. Some day I'll learn. Thanks for all the help everybody I really appreciate it. I'll be yanking the motor next weekend and will know more then.
Click to expand...

I don't know what brand of converter you have but just because it doesn't stall what it's rated at doesn't mean it's a junk converter or mis-labeled. Generally you have to have a pretty torquey engine to get them to flash what their rated at. If you had it behind the 340 your referring too when it was sick it probably just didn't have the low end grunt to stall the converter any more. In fact it's a miracle it stalled that much with the compression being so low on it. Heck it might stall 4000 when the engines rebuilt. Especially if you use a smaller cam and dual plane intake.
 
Thanks Fishy. I didn't know that. I put converters right up there with quatum physics, black holes, woman, and other other things I don't really understand.
 
ramcharger said:
OK, I just checked that cam out. It's 250 degrees of intake duration at .050 lift. You'll be lucky to see 4 to 5" of vacuum. You better be good with carb tuning and scratch using a Edelbrock, AFB or Thermoquad.

This is a Holley HP style only cam.
Click to expand...

Sorry I missed this one early when I was going through before. Your right you should have seen me banging my head off the garage wall the first times with an edey carb. The guy who is going to go through my engine for me runs his car off the money he makes tuning other guys cars, in fact he sold me the carb I have for it now for $100.00 and that included the rebuild and tuning it. He said something was wrong with the motor last year I just didn't want to listen.
 
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