Cylinder head discussion 340 with stock above deck pistons

[Inertia]

@Inertia The Friday night street legal shoot out we participate in to do these 1/4 mile passes at mission raceway does NOT allow open headers or un muffled cars. It's a street car shootout where it's always heads up and people are just racing their cars and having fun. You can get 9 or 10 passes in while they are open because it's not a bracket race, just heads up to get people off the street and into a track where they can go all out safely.

Thnx Mike, I suspected the mufflers but clarifying for others .
I was able to watch you guys on CCTV, but didnt see the end, after those cars got stuck in the sand, lol

Next time, I'll bring some stuff to mess around, and I got an 830 dbl pump to try.

 

[Newbomb Turk]

Uncorking the exhaust requires another carb tune unless its tuned wrong now and you get lucky.
Many uncork the exhaust and go slower.

And they are taking off collector length. That kills power.

 

[Inertia]

I tried that back in the day. I put headers on my 340 Challenger, opened them up at the track and went slower. Without rejetting of course.

Generally most folk after header install, open, reported 2 to 4 tenths better, with tune, not always, but generally amongst breeds, street machines.
Extension had different effects on diff size engines .

 

[oldkimmer]

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.

I think u better check your math. If your piston is out .054 u could never even gat the head on with a .040 gasket. Kim

 

[furrystump]

You might be forgetting that it is open chamber and the lowest point of the chamber roof is probably more than he needs adding in the gasket

 

[fishmens67]

I see very little benefit from a head change without a cam change.
A cam change is the first place I would go looking for more horsepower

 

[fishmens67]

One of the most fun builds I ever did and charged my friend 5.00 to do it (5.00 worth of jawbreakers)
340 with stock crank
J or X heads slightly polished
484 lift purple shaft hyd cam
Port o sonic intake
750 double pump Holley
Stock 10.5-1 pistons
Stock rods
1 7/8 headers
727 with J converter
3200 pound 72 duster
Super stock springs
10 M/T slicks
Low 12.2’s new driver 2nd time out
I built this engine with friends in his pool room. We laughed and hollered the whole time eating jawbreakers.

Break it, fix it, repeat. I had a Lakewood bellhousing, aftermarket clutch and pressure plate, 3 inch custom made driveshaft, Lakewood ujoints, 2 sets of gears after breaking every weak link possible. Fought pinion angle issues before we ever knew to measure it. Good old Direct Connection failed to notify us that installing super stock springs threw your pinion up 8-10 degrees. That was a fun learning experience. This guys feelings are a little soft so I’ll let you guys tell him how to fix his car. Peace out.

 

[Newbomb Turk]

I think u better check your math. If your piston is out .054 u could never even gat the head on with a .040 gasket. Kim

My math is fine. I wasn't talking about using a closed chamber head. I think the OP asked what Chrysler said about how far they should out of the deck.

I think (I can verify when I put my turd back together) with a .039 gasket and being .054 out of the hole I have .040 quench which means the chamber relief is about .055, which when I typed it seems less than what it is. Maybe I'm .060 out of the hole.

But the math is something close to that so the head will go on.

 

[318willrun]

The original intent was a discussion about heads. My car is not strictly a drag car it's a street car I like to take to the strip. I don't even think most people responding to this are reading the whole thread. Seems like you are just arguing with each other and making assumptions about driving ability. As I stated before it's been down the 1/4 at one event where I made maybe 9 passes. The track we had in town shut down but I raced there for 4 seasons and made 150 or more passes on a 330' track. Even though it's a short track you still get to practice launches. That was before I got radial drag slicks and nitrous. Now I am hoping to get a bit more power out of it. I am aware that I can get my 60' better but rather than starting to high and breaking things and working down to the right launch rpm I am starting low and working my way up. This season is coming up soon and hopefully I'll get to the track 3 or 4 times. I haven't started slipping the clutch on launch yet because I need to raise the rpm more on launch before that will realistically help. At the old 330' track with bfg radials I couldn't launch more than 1800 without spinning the tires badly. So I started there and kept increasing it a little bit at a time, haven't found that upper limit of suspension or tire grip yet. Then I'll start to slip the clutch on launch. I am getting good ideas from reading some of the comments but it seems like a lot of assumptions are being made that could be cleared up if people were reading the whole thread

In your original post (post 1), you said what you had, what it ran, and that you wanted a "bit more out of it" .. "down to the 12's". You were thinking heads, thus your question. These folks are just trying to say you have a bit more to get out of what you already got. IF you work with what you have, you will get to your goal WITHOUT buying heads. But yes, you can get a good aluminum head and it will make more power.

 

[318willrun]

Mike has Cancer, - he's on his second round of chemo .
He wanted to pull the heads off his car and mess with them to occupy his mind.
He was gonna port match and just mess with them.
He asked me about aluminum heads. I told him I wasn't his best source, and to come ask here.
He didnt realize his car was such a slug, and he is such a shitty driver.
I didn't even know he had posted here till Rusty tagged me, and by then, - I did what I could to mitigate.
Under normal circumstances, he would have been very grateful.
I don't think he'll be back .

I understand. I wish him well in health and with his car.

 

[Inertia]

I understand. I wish him well in health and with his car.

I'm very sorry. I didn't intend to target that response at you, I meant a general response and edited it.

 

[RustyRatRod]

I see very little benefit from a head change without a cam change.
A cam change is the first place I would go looking for more horsepower

It's certainly among the more easy swaps regarding engine parts.

 

[RustyRatRod]

The original intent was a discussion about heads. My car is not strictly a drag car it's a street car I like to take to the strip. I don't even think most people responding to this are reading the whole thread. Seems like you are just arguing with each other and making assumptions about driving ability. As I stated before it's been down the 1/4 at one event where I made maybe 9 passes. The track we had in town shut down but I raced there for 4 seasons and made 150 or more passes on a 330' track. Even though it's a short track you still get to practice launches. That was before I got radial drag slicks and nitrous. Now I am hoping to get a bit more power out of it. I am aware that I can get my 60' better but rather than starting to high and breaking things and working down to the right launch rpm I am starting low and working my way up. This season is coming up soon and hopefully I'll get to the track 3 or 4 times. I haven't started slipping the clutch on launch yet because I need to raise the rpm more on launch before that will realistically help. At the old 330' track with bfg radials I couldn't launch more than 1800 without spinning the tires badly. So I started there and kept increasing it a little bit at a time, haven't found that upper limit of suspension or tire grip yet. Then I'll start to slip the clutch on launch. I am getting good ideas from reading some of the comments but it seems like a lot of assumptions are being made that could be cleared up if people were reading the whole thread.

I'm sorry Mike. I tried to stay within the boundaries of your original question with my answer. I hope nothing I said got you upset. I do hope you'll keep responding.

 

[Mattax]

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

I have an afr gauge in the dash. It idles a bit rich but WOT doesn't seem to bad

Right now my 3310 has the lightest spring and has a decent WOT afr. I could bring jets to the track and try leaning it out to see if I get more mph,

Maybe too late, but as far as the AFR goes, those numbers are ballpark. To find out the best AFR for your combo, yes you'll have to make some tests at the track or the dyno. I realize that's a PIA.
Go with a plan that involves one change at time. Be prepared to alter the follow up depending on results.
Idle should be a little rich. Certainly richer than stoich. As long as it comes off idle strong, no flat spots, its ballpark correct. If you want to start a different thread about the carb, we can dive deeper.

Hopefully, in spite of the side tracks, you got some helpful info about heads.

 

[furrystump]

I wish him well.

 

[Swinger 340]

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?

I fully loaded stock Dart with the 340, should be low 14's to high 13's, depending on its rear gearing. Sounds like a lot of money spent to gain .02. Sounds like traction or driver issues. The 60 foot time should help in figuring that out. Correct what needs correcting.

 

[Dale Davies]

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?

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?

Aluminium heads do not lower the compression. They do absorb a bit f heat which generally allows .5 point more compression.
Add water injection. Distilled water with about 2% water soluable oil (machine shops use it). Have the water come on when you hit the bottle. Advance the timing 2° and lean the fuel a bit. Run the head that gives the compression and port energy for strong power with fuel economy. With water injection you could run 13:1 to 14:1. The water slows the burn so that is the reason to add 2° to the timing. You can lean the mixture a bit for fuel economy cruising and the water turning to steam in the combustion process expands 1600× compensating for the lean burn. Approach the tune with caution so you do not hurt parts. With water injection, pistons run cool.

 

[Dale Davies]

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.

Your math does not add up.

 

[PROSTOCKTOM]

Back the OP question.

I've ran flat top pistons .025" out of the block on steel connecting rods with a .042" compressed head gasket.

It can be done, but you must have everything measured out correctly and you also need to make sure you have proper piston to valve clearance.

Tom

 

[Newbomb Turk]

Your math does not add up.

Read better. I'm going off my memory. I'll measure it when it goes back together. The numbers may not be perfect but they are close. Plenty close enough for you.

 

[Newbomb Turk]

Your math does not add up.

Just ran it again. I'm within a couple of thou.

Try to do better next time.

 

[7e5hangten360]

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?

hi. i am going to try to give you the answers to the questions YOU asked. first things first , your actual compression ratio right now is closer to 9.5:1 ( i get 9.4). you could safely use a 65cc head and get around 10.2:1. that is assuming everyone is wrong and that you have stock replacement pistons (l2316 speedpro or similar) with the top of the piston being 0.018 in. off the deck. that means there should be no problem to use the aluminum heads, compression ratio wont be too high. contrary to others, i would use the edelbrock 340 heads not the 360 heads from them. the 340 heads are relieved in the chambers so the pistons dont come in contact with them. or use the tfs heads, they come cnc ported from tfs, but, not sure about the pistons being too close to the heads on a 340. also, as a rule of thumb, a nicely ported set of j or x heads would flow about the same as a set of un-ported edelbrock heads. have the aluminum head ported, and you got even more power potential. to answer your original question, i gained 2-3 tenths going from home ported cast-iron heads to professionaly ported edelbrocks on a 360 with stock stroke. yes, they make more power. now, if you want my advice, lower your shift points 200-300 rpm each pass till you get to 5500 and give it a real try. and to do like others, here is my recommendation : put some 4.10 or 4.56 gears in the rear before you do the heads ! you will like it, even on the street !