Another Head Thread...

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Wilson

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Searched without a solid answer....what kind of power increases, if any, could be expected if you started with the following, all in good working order:
Stock '69 340 "10.5-1" short block
Stock cast intake and exhaust manifolds
Stock 340 or mild cam (450ish lift, 215-220ish @050 duration)
650-750 AVS or Eddy carb.
....and replaced the X heads with a mild aftermarket OOTB head (and i'll define that as Eddys
that have been checked and corrected if needed but no porting, LAXs from IMM, maybe a Magnum-style, etc.) The gasket thickness and chamber volume could be optimized for compression.
Obviously headers, better intake, and more cam would lead to bigger increases. Not really looking for an exact HP#, just wondering what the return would be on a stockish engine.
Thanks...Matt
 
First, verify where your pistons sit at TDC. Spec is around .019 above deck. If you get closed chambered heads you could have an issue here and need to address it by either running a thicker head gasket to get proper quench or remove the pistons and have them cut down. I did the latter of the two.

Why not port? Yes too much flow can hurt but increasing low lift flow can help your small cam.

Why small lift on the cam? You can run way more and have a very good streetable engine, if that's what your after.

What are you after? Intended purpose, trans, grears, etc?
 
It's a 69 Barracuda, 4 spd, 3.23's, currently 27" rear tires but will be going to 26", pretty much a stock appearing resto type deal. Engine is 030 over with stock replacement pistons 2332P (Speed Pro maybe, or TRW?), X heads, 750 Eddy, Electronic dist, orange box, Timing 18 initial, 34 total in by 2500-3000 (stock tach not real accurate!) MIGHT consider 3.55's but no lower; exhaust mans. are staying, at least for the forseeable future. Figured with these gears and exhaust that i'd rather error on the small side of cam.
 
Leave it as it is or change it all. No magic bullet. Headers would help as would intake. Bigger heads won't gain you much without a better carb/intake and headers/exhaust. Bigger cam will gain you some but not without other improvements. You want it to accelerate quicker? Put in some 3:73's or some 3:91's. That 340 will sing then.
 
There's a guy on here says he built a 340 with stock cam and edlebrock heads that dyno 400hp. Probably has air gap and headers.
 
All I can do is give you my actual track crank hp figures as a guide if it helps from my weight/mph and the set up was at first>

All Stock '71 340 Cuda, DC. .484/284 hyd., ally dual plane, can't remember exactly which 1 (was in 1980), small tube hdrs, 750DP, car ran 13.3's@101 = 301hp...3.55's, B&M s/holeshot verter, 8x26" slicks.

Added, Fel-pro .039 h/gskts, so CR was prob 9.5>9.8?, a DC. 590/312 solid ft cam, MSD6A, Holley Strip Dominator int., 850DP, 2" open spacer, hedman 1.3/4" race hdrs, 4.30's, 10x28's, and a T/A 4200 verter, Pinion Snubber, long shocks, ran [email protected] = 367hp.
 
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I'm running 12.10 113 mph through the same exhaust manifold and slightly modified stock intake. This is a 410 so they don't compare as far as that goes, but don't discount the exhaust manifolds. IIRC stock eddy heads are worth about 15/20 cfm over a stock x head. However the eddy heads present some issues. It's hit or miss that the drivers side exhaust manifold will hit the head where it turns back towards the block. If you buy a header flange and get longer studs and extra gaskets. It will space it out enough to clear. Also alternator fitment can be a pain. You may have to modify the adjusting arm to bring the alt up so it doesn't hit the head. Then a longer belt. My cam is about .557 lift. You also need different head bolt/stud kit with the eddy head. 3.73 gear would be good. What you have for a center section can dicteate what choices you have for gear. The intake is your restriction. 750cfm would be the minimum carb. Back when these cars were new, one of the easiest performance gain was to put the bigger AVS on it.
 
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Bang for the buck a good aluminum intake is worth more. Be careful of any that are taller, it can be tough to get the stock air cleaner to work with say an rpm airgap.
 
Wilson said:
Searched without a solid answer....what kind of power increases, if any, could be expected if you started with the following, all in good working order:
Stock '69 340 "10.5-1" short block
Stock cast intake and exhaust manifolds
Stock 340 or mild cam (450ish lift, 215-220ish @050 duration)
650-750 AVS or Eddy carb.
....and replaced the X heads with a mild aftermarket OOTB head (and i'll define that as Eddys
that have been checked and corrected if needed but no porting, LAXs from IMM, maybe a Magnum-style, etc.) The gasket thickness and chamber volume could be optimized for compression.
Obviously headers, better intake, and more cam would lead to bigger increases. Not really looking for an exact HP#, just wondering what the return would be on a stockish engine.
Thanks...Matt
Click to expand...
You wanna know the answer?
The flow difference between the x heads and the eddys all the way throughout the lift range will be the diff in hp.
So if you keep all else but change heads, and the eddy heads on average do 15 cfm better than the x heads ...then you made about a 25-30 hp increase over stock, with stock cam.

Add a 750 and you may see an average 10+ more, add headers and you may have another +12-15 hp.

So...you spend on ready to go eddy heads
- 1700 or so
A 750 carb -500
Headers -200
Stock cam still...
And you made around 50 +/- more hp.
So a 275hp/305hp 340 , depending on who rates it, goes to about 355 hp with a stock cam by adding the heads, carb, header.

Now if you just changed the cam from stock to something in the .500 lift range...you can expect more, You would be in the 400hp range.... but realizing the potential of all the other parts will eventually fall on the camshaft.

Going about it this way is expensive, you could change the cam, add the headers and carb and make the same increase without buying the heads.

Spend 700 or spend 1700 for 30 or so hp, it's all how you go about it.
 
MOPAROFFICIAL said:
You wanna know the answer?
The flow difference between the x heads and the eddys all the way throughout the lift range will be the diff in hp.
So if you keep all else but change heads, and the eddy heads on average do 15 cfm better than the x heads ...then you made about a 25-30 hp increase over stock, with stock cam.

Add a 750 and you may see an average 10+ more, add headers and you may have another +12-15 hp.

So...you spend on ready to go eddy heads
- 1700 or so
A 750 carb -500
Headers -200
Stock cam still...
And you made around 50 +/- more hp.
So a 275hp/305hp 340 , depending on who rates it, goes to about 355 hp with a stock cam by adding the heads, carb, header.

Now if you just changed the cam from stock to something in the .500 lift range...you can expect more, You would be in the 400hp range.... but realizing the potential of all the other parts will eventually fall on the camshaft.

Going about it this way is expensive, you could change the cam, add the headers and carb and make the same increase without buying the heads.

Spend 700 or spend 1700 for 30 or so hp, it's all how you go about it.
Click to expand...


Wish I remember the members name but there is a guy on here claiming 399 hp @ I think 4800 rpm with a dyno slip. 340 with eddy heads and stock cam and guessing airgap and headers.

Even if wrong an makes less. But it's more expensive to build power with heads over cam but you'll end up with a more streetable package.
Look at the new hemis and LS engines that's there basic formula. Even 340 and magnums to an lesser extent.
 
OP, be aware that your current static CR is really more like 9.6-9.7. If you put on 60779 closed chamber Edlebrocks, your SCR will jump up to 10.1 IF you put in .055" thick head gaksets. That will give you a good quench gap in the .035-.040" range between the stock pistons-above-deck-height and the quench areas on the heads. (Make sure you check each pistons' above-deck height at top and bottom.)

You just made you engine more flexible for later changes by going to heads with better flow, and keeping the CR up. I think the below statement puts it nicely:
273 said:
.... it's more expensive to build power with heads over cam but you'll end up with a more streetable package.
Look at the new hemis and LS engines that's there basic formula. Even 340 and magnums to an lesser extent.
Click to expand...
 
Wilson said:
Searched without a solid answer....what kind of power increases, if any, could be expected if you started with the following, all in good working order:
Stock '69 340 "10.5-1" short block
Stock cast intake and exhaust manifolds
Stock 340 or mild cam (450ish lift, 215-220ish @050 duration)
650-750 AVS or Eddy carb.
....and replaced the X heads with a mild aftermarket OOTB head (and i'll define that as Eddys
that have been checked and corrected if needed but no porting, LAXs from IMM, maybe a Magnum-style, etc.) The gasket thickness and chamber volume could be optimized for compression.
Obviously headers, better intake, and more cam would lead to bigger increases. Not really looking for an exact HP#, just wondering what the return would be on a stockish engine.
Thanks...Matt
Click to expand...
If you move to our EQ head, with 1.6 rockers you should pick up about 20-25HP...not a ton but a nice power addition, and a solid head. Are you looking for more power only or is something wrong with your current heads? A cam with 220@ .050 or more, our heads will start to make more than 25HP over stock heads even with ex. manifolds.
 
Thank you to all who replied! Post probably should have been titled "How much HP is gained with __ increase in head flow" or something similar. No problems w/ engine, just looking for more and trying to decide if this car will remain a resto-cruiser or morph into a semi-stock looking hot rod.
 
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