Cylinder head discussion 340 with stock above deck pistons

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nfhDODGEnfh

nfhDODGEnfh

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I have a 340 block with approximately 10.25:1 compression bored .040 over, j heads with 72 cc chambers, comp cam xe268h, air gap intake, holley 780, Doug's headers, and a 100 shot of nitrous. 3.55 and a close ratio 4speed. It ran 13.1 last season with the spray. I'm wanting to get a bit more out of it on the track and am thinking about upgrading to aluminum heads. I've seen discussion about how aluminum heads can lower compression by 1 point due to heat dissipation. Is this true? And would the 65 cc head make up for this difference and get me back to where I was? I've been looking at the eddys for the 340 pop top pistons because that already how my motor is set. The shocker 185 wirh 65 cc look good aswell. I know I've seen a few other threads with similar convos but some of them are fairly old and don't address my exact concern. Wouldn't the aluminum head also help me fight detonation against the nos with the better disapation of heat? What heads would you consider to be best to get me down into the 12's?
 
nfhDODGEnfh said:
I have a 340 block with approximately 10.25:1 compression bored .040 over, j heads with 72 cc chambers, comp cam xe268h, air gap intake, holley 780, Doug's headers, and a 100 shot of nitrous. 3.55 and a close ratio 4speed. It ran 13.1 last season with the spray. I'm wanting to get a bit more out of it on the track and am thinking about upgrading to aluminum heads. I've seen discussion about how aluminum heads can lower compression by 1 point due to heat dissipation. Is this true? And would the 65 cc head make up for this difference and get me back to where I was? I've been looking at the eddys for the 340 pop top pistons because that already how my motor is set. The shocker 185 wirh 65 cc look good aswell. I know I've seen a few other threads with similar convos but some of them are fairly old and don't address my exact concern. Wouldn't the aluminum head also help me fight detonation against the nos with the better disapation of heat? What heads would you consider to be best to get me down into the 12's?
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The short answer is no. The myth of running more compression with aluminum heads or them being more detonation resistant is all Tom foolery. Unless you abuse your engine.
 
Newbomb Turk said:
The short answer is no. The myth of running more compression with aluminum heads or them being more detonation resistant is all Tom foolery. Unless you abuse your engine.
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So these heads in theory would bump my compression up considerably then? I mostly street it around but go to the track several times a year. On the street I give it the beans on a regualr basis too.
 
Newbomb Turk said:
Yeah, as long as the pistons don't hit the heads. How far out of the hole are your pistons?
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I would have to ask Inertia as he was the one who helped me assemble that years ago. I beleive it was the stock amount for the motor. Does .010 sound correct.

@Inertia
 
nfhDODGEnfh said:
I would have to ask Inertia as he was the one who helped me assemble that years ago. I beleive it was the stock amount for the motor. Does .010 sound correct.
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I think the books says for OE stuff .017-.018. But that was using an .028 gasket or something close to that.

On my engine the piston is out of the deck .054 IIRC. But I'm running 12:1 and that gives me .040 quench with an .041 gasket. Or .039. I forget what they are.

The Chrysler book outlined how far the piston should be out of the hole for compression and quench. IMO you can go out as far as you need to for quench as long as the top ring is not popping out of the bore.
 
Here’s why I ask, say you start with 275 hp out of a stock 340. Then just adding the 100 shot you’re at 375 hp running 13.1. Not even considering the headers. I’m at about 400ish HP mid 11’s. I’m an auto your stick, but there seems to be low hanging fruit without changing heads. I’m 410 Ci you’re 340, but still seems there is power not being used.
 
furrystump said:
Here’s why I ask, say you start with 275 hp out of a stock 340. Then just adding the 100 shot you’re at 375 hp running 13.1. Not even considering the headers. I’m at about 400ish HP mid 11’s. I’m an auto your stick, but there seems to be low hanging fruit without changing heads. I’m 410 Ci you’re 340, but still seems there is power not being used.
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2.0 60' 13.1 at 108mph im running micky street slicks 235/60r15 if I can increase horsepower and get a better 60' that would be even better. I've always wanted to get better heads and increase some power. And lower the weight on front end too
 
nfhDODGEnfh said:
I have a 340 block with approximately 10.25:1 compression bored .040 over, j heads with 72 cc chambers, comp cam xe268h, air gap intake, holley 780, Doug's headers, and a 100 shot of nitrous. 3.55 and a close ratio 4speed. It ran 13.1 last season with the spray. I'm wanting to get a bit more out of it on the track and am thinking about upgrading to aluminum heads. I've seen discussion about how aluminum heads can lower compression by 1 point due to heat dissipation. Is this true? And would the 65 cc head make up for this difference and get me back to where I was? I've been looking at the eddys for the 340 pop top pistons because that already how my motor is set. The shocker 185 wirh 65 cc look good aswell. I know I've seen a few other threads with similar convos but some of them are fairly old and don't address my exact concern. Wouldn't the aluminum head also help me fight detonation against the nos with the better disapation of heat? What heads would you consider to be best to get me down into the 12's?
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Just give it a little more spray.
 
toolmanmike said:
Just give it a little more spray.
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I'm already spraying approximately 30% of peak power. When I hit it around 3250rpm I'm probably close to 50% don't really want to hit it much harder than that. I have jets to go to 125hp and higher. But I want to upgrade heads to for more power regardless. I think it would be a fun upgrade to do and would like advice and knowledge on the subject of upgrading j heads to aluminum woth my combo. The faster the better in the end and if the aluminum heads get me more power across the board and also prevent detonation then I can safely up the nitrous too.
 
I’d pull the spray and work on tuning or driving, that combo should run mid to low 13s without the bottle and mid 12s with the 100shot.
 
If running the car is something you can see yourself doing for a long period of time, I would get the most aluminum head you can. That way you can grow the rest of the car into the head. Future stroker, more compression, it becomes more strip than street. Etc. The pursuit of “quicker” can be addictive.
 
nfhDODGEnfh said:
2.0 60' 13.1 at 108mph im running micky street slicks 235/60r15 if I can increase horsepower and get a better 60' that would be even better. I've always wanted to get better heads and increase some power. And lower the weight on front end too
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You should be 1.7 1.8 60 ft with traction is the carb tuned?
whats the best time without the juice?
Best mph no spray?
shift rpm?
launch rpm?
should be close to 13.1 no spray
 
Please don’t take my questions as a knock on your car. Not meant that way. I just think there is more in what you have.
 
vntned said:
I’d pull the spray and work on tuning or driving, that combo should run mid to low 13s without the bottle and mid 12s with the 100shot.
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The car has 12.6 afr at WOT same afr while under spray. 37* timing before spray and down ro 34* while spraying. I tuned that off the spark plugs as maximum before you get black specks on the porcelain. I can drive...... My friend has the same setup as me with no spray and runs 13.8
 
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a-bodyguy said:
You should be 1.7 1.8 60 ft with traction is the carb tuned?
whats the best time without the juice?
Best mph no spray?
shift rpm?
launch rpm?
should be close to 13.1 no spray
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Haven't done a no spray yet because I've only done the 1/4 at one event. There is no track close to me. My friend with similar setup and no nos runs 13.8. I launch at about 2500-3000 I'm gonna run a 2 step next time I go out and tune that. I shift about 6250 because my cam is good from 1600-5800 so I come right back into the power. I spray at about 3000rpm. It hooks and books when I launch no spin. Once I have the 2 step setup I can play more with launch rpm.
 
nfhDODGEnfh said:
2.0 60' 13.1 at 108mph im running micky street slicks 235/60r15 if I can increase horsepower and get a better 60' that would be even better. I've always wanted to get better heads and increase some power. And lower the weight on front end too
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I don't want to sound like a prick but the last thing you needs is heads. You're running at least 108 MPH and that should be a low, low 12. I'm betting with some engine tuning and more money spent on your clutch tune up and chassis you could easily see another 2-3 MPH. That puts you into the 11's.
 
So my ‘64 Dart had a ‘71 360 with stock small valve ‘587 heads, H116CP pistons (9.2:1cr actual), a CompCams 268AH10 cam, Eddy LD340 intake, StreetDemon 750, exhaust manifolds, close ratio 4spd and a 3.55fd rear gear, and it ran a 13.50et.

Your setup should run better than 13.8s off the bottle. Is the car overly heavy? What is the actual car? And what’s your 60ft, 1/8th mile et and mph, compared to the 1/4 et and mph of the same run?
 
vntned said:
So my ‘64 Dart had a ‘71 360 with stock small valve ‘587 heads, H116CP pistons (9.2:1cr actual), a CompCams 268AH10 cam, Eddy LD340 intake, StreetDemon 750, exhaust manifolds, close ratio 4spd and a 3.55fd rear gear, and it ran a 13.50et.

Your setup should run better than 13.8s off the bottle. Is the car overly heavy? What is the actual car? And what’s your 60ft, 1/8th mile et and mph, compared to the 1/4 et and mph of the same run?
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You have a 360, my best 60' I posted above. It was 2.0, 1/8 8.5@86, 1/4 13.1 @ 108. I can probably shave a bit off my 60' but as I said above I've only done the 1/4 for one event. There is no track close to me anymore. So fine tuning launch rpm isn't easily available. This thread is originally about what heads are good for this setup. Will edelbrock performer rpm heads with the 65cc chamber net me hp gains. Not necessarily to get into the weeds about my pass times. This race season I'm going to try and dial it in better. But more hp is always good. Might just end up having my j heads ported, as aluminum is expensive. Does anyone have experience with putting Eddy heads on a setup like mine?
 
I have to agree with Newbomb, you should be running in the 12s easy with no nitrous, maybe a better cam, or something else is the problem.
 
nfhDODGEnfh said:
Haven't done a no spray yet because I've only done the 1/4 at one event. There is no track close to me. My friend with similar setup and no nos runs 13.8. I launch at about 2500-3000 I'm gonna run a 2 step next time I go out and tune that. I shift about 6250 because my cam is good from 1600-5800 so I come right back into the power. I spray at about 3000rpm. It hooks and books when I launch no spin. Once I have the 2 step setup I can play more with launch rpm.
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2.0 hooking is really bad for that setup
your mph is mid 12s
your going slow 1st half of quarter
tune the carb
700 or 750 dp be a better carb then the 3310 holley imo
what color spring is in the secondary ?
try the yellow spring
 
a-bodyguy said:
2.0 hooking is really bad for that setup
your mph is mid 12s
your going slow 1st half of quarter
tune the carb
700 or 750 dp be a better carb then the 3310 holley imo
what color spring is in the secondary ?
try the yellow spring
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I find it interesting how far we have gotten from the original intent of this post. It's a question about heads. And it had turned into a bunch of guys saying that I'm slow..... like I said before a couple times. It's been down the 1/4 in one event. Of course it needs to be dialed in and I can hopefully find more speed in other areas too. Are you guys getting those numbers et/mph from internet calculators or having a similar setup with Timeslips showing these mid 12s or 11s as newbomb said without spray? That seems awfully fast for a car that might make 350 at the crank maybe less. If I can get my 60' down a couple 10ths I'll be in the 12s for sure. And it's something I'm gonna work on regardless. But I'm asking about aluminum heads. I plan on messing with the carb this season aswell but my WOT afr seems pretty good at around 12.6 and is similar while spraying. I run the light spring in my secondary. Could change the cam to a bit higher rpm but it's a street car mostly. By tune the carb you mean lean it out some more? Seems like it's in a decent range. I have an afr gauge in the dash. It idles a bit rich but WOT doesn't seem to bad
 
nfhDODGEnfh said:
I find it interesting how far we have gotten from the original intent of this post. It's a question about heads. And it had turned into a bunch of guys saying that I'm slow..... like I said before a couple times. It's been down the 1/4 in one event. Of course it needs to be dialed in and I can hopefully find more speed in other areas too. Are you guys getting those numbers et/mph from internet calculators or having a similar setup with Timeslips showing these mid 12s or 11s as vented said? That seems awfully fast for a car that might make 350 at the crank maybe less. If I can get my 60' down a couple 10ths I'll be in the 12s for sure. And it's something I'm gonna work on regardless. But I'm asking about aluminum heads. I plan on messing with the carb this season aswell but my WOT afr seems pretty good at around 12.6 and is similar while spraying. I run the light spring in my secondary. Could change the cam to a bit higher rpm but it's a street car mostly. By tune the carb you mean lean it out some more? Seems like it's in a decent range. I have an afr gauge in the dash. It idles a bit rich but WOT doesn't seem to bad
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my 70 duster was 1.90 60 ft L-60-14s street tires auto stock stall 3.23s trapped 108 in 2nd gear
my stock 340 vert nothing but weiand stealth 650 dp 3.23s 235/60/14s 2.05 60 ft
With traction and a 4sp your 60 ft is slow
my combo was not matched 243@50 508 lift 108 lsa
single plane 650 carb
needed 4.30 gears slicks and 4000 stall to be matched
108 is mid 12 that means you are slow for that mph and your 60 ft is slow
You should be happy theres a free 6/10s hiding in your car
then add your heads for 3/10s more
people are trying to help you
 
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