340 for Cruising and Fun 1/4 mile Passes

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Siksty7 Dart 270

Siksty7 Dart 270

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I picked up an over bored 340 (4.070) block which the machine shop says needs to go to 4.080 to avoid piston slap. Here's a recipe I'm considering:
Stock stroke cast crankshaft,
steel I beam connecting rods,
4.080 D.S.S. forged flat top 4032 alloy pistons with valve reliefs zero-decked,
.051 compressed head gasket
Stock Magnum heads, measured at 64 cc chambers, with Hughes 1110 valve springs,
Custom grind Hydraulic roller cam 270/278 Adv. 212/220 @ .050, .485/.506 gross lift on 110 LSA, 106 ICL,
Hydraulic roller retrofit lifters,
Nice pushrods,
Edelbrock Performer RPM airgap intake,
650-750 CFM Edelbrock carb,
Stock electronic ignition appropriately curved
Long tube 1-5/8" headers into cutouts/2.5" exhaust,
A904 with mild shift kit & +1 thin frictions and steels,
2500 stall A and A torque converter
3.23 sure grip in an 8 3/4 rearend
26" tall tire
Otherwise stock 67 4 door Dart

On paper this engine yields: 10.1:1 Static CR, 8.23:1 Dynamic CR, 167.57 PSI Dynamic Cranking Pressure, 138 Volume/Pressure Index

I want to: run pump gas, smoke tires from a dead stab, cruise at reasonable RPM for 60 MPH, have respectable 1/4 mile passes (would love to get in the 100mph club, but not required), not overheat in traffic running a mechanical fan and shroud on a 22" radiator, re-use many current in-use parts

Is the quench I will achieve adequate?
Is that kind of cranking pressure manageable?
What potential street/cruising reliability issues am I overlooking.
 
Last edited:
Well… IMO

You can use hyper slugs instead. Cheaper lighter while being very durable. Piston slap is a loose fitting piston. Hypers run tighter the forged pistons. .050 is considered max for any quench.

The stock OEM heads are OK at best IMO. With the listed cams lift, a bowl porting, while not needed, would be a nice help and addition to do if your heads are not cracked and I’d bet they are.

On the Hughes cam, I have never seen and advertised and a at .050 number. 212@050 is small but fine for a stock converter.

Find out the weight of the lifter vs others. This is the Magnums second biggest draw back, lifter weight, IMO.

That would be the correct intake to use IMO over the cheaper chink intake and the 650 will provide enough cfm for the job. A 750 is fine as well, I have found the 600 Edelbrock to have a slight better throttle response over the edelbrock 750, which I currently run on my 5.9 with a rpm intake.

Stock distributor for the year of the car I assume and not a Magnum distributor. Use a MP distributor & get the advance springs for it. A FBO limiter plate is a good thing as well. Chrome box or multi spark box for ignition.

Skip the cut outs on the exhaust.
PM me for exhaust

A 904 is nice, I’d use a 904 variant OD trans.
The 3.23’s leave a little on the table, I’d use 3.55’s with the OD trans for cruising. Ether way, you’re not going to max out the rpm’s at the track to take full advantage of the gears in the trans, rear and tires listed. You’ll probably change into third just before the stripe at the end of the 1/4 mile. But should brake 100, not guarantee.

The issues I see….

Turn more rpm than intended for the street, even worse for the Hwy. While I suggest 3.55’s that will turn more rpm, you’ll burn rubber and get to speed a little easier.

I’d run a .038 head gasket instead and use 91/93 octane, it’ll work with your static and cranking compression numbers.
Been there, done that, still doing it, can’t stop doing it.

I suggest a hyd roller cam if 226@050. It’ll work with the 2500 stall.

My wife’s 360 runs trick flow heads, rpm intake, TTI exhaust stem to stern, it’s 11.3-1 and works on 93 octane. Likes a 50/50 race fuel mix a lot.

I’d get a larger radiator that goes from frame rail to frame rail. I run a champion which is fine until it gets to summer time. Florida is HOT.
The car has a 2500 stall, 904, 3.55’s on Mickey T’s flame tread 26X10 tires.

It’s not fast off the line but will leave 60’ plus rubber stretch marks on the pavement and has great top end power that just keeps on going.

Cam used below. Valve lift should be recalculated @ 1.6.
Lift /1.5X1.6= new lift.
IMG_0668.jpeg


IMG_5342.jpeg
 
rumblefish360 said:
Well… IMO

You can use hyper slugs instead. Cheaper lighter while being very durable. Piston slap is a loose fitting piston. Hypers run tighter the forged pistons. .050 is considered max for any quench.

The stock OEM heads are OK at best IMO. With the listed cams lift, a bowl porting, while not needed, would be a nice help and addition to do if your heads are not cracked and I’d bet they are.

On the Hughes cam, I have never seen and advertised and a at .050 number. 212@050 is small but fine for a stock converter.

Find out the weight of the lifter vs others. This is the Magnums second biggest draw back, lifter weight, IMO.

That would be the correct intake to use IMO over the cheaper chink intake and the 650 will provide enough cfm for the job. A 750 is fine as well, I have found the 600 Edelbrock to have a slight better throttle response over the edelbrock 750, which I currently run on my 5.9 with a rpm intake.

Stock distributor for the year of the car I assume and not a Magnum distributor. Use a MP distributor & get the advance springs for it. A FBO limiter plate is a good thing as well. Chrome box or multi spark box for ignition.

Skip the cut outs on the exhaust.
PM me for exhaust

A 904 is nice, I’d use a 904 variant OD trans.
The 3.23’s leave a little on the table, I’d use 3.55’s with the OD trans for cruising. Ether way, you’re not going to max out the rpm’s at the track to take full advantage of the gears in the trans, rear and tires listed. You’ll probably change into third just before the stripe at the end of the 1/4 mile. But should brake 100, not guarantee.

The issues I see….

Turn more rpm than intended for the street, even worse for the Hwy. While I suggest 3.55’s that will turn more rpm, you’ll burn rubber and get to speed a little easier.

I’d run a .038 head gasket instead and use 91/93 octane, it’ll work with your static and cranking compression numbers.
Been there, done that, still doing it, can’t stop doing it.

I suggest a hyd roller cam if 226@050. It’ll work with the 2500 stall.

My wife’s 360 runs trick flow heads, rpm intake, TTI exhaust stem to stern, it’s 11.3-1 and works on 93 octane. Likes a 50/50 race fuel mix a lot.

I’d get a larger radiator that goes from frame rail to frame rail. I run a champion which is fine until it gets to summer time. Florida is HOT.
The car has a 2500 stall, 904, 3.55’s on Mickey T’s flame tread 26X10 tires.

It’s not fast off the line but will leave 60’ plus rubber stretch marks on the pavement and has great top end power that just keeps on going.

Cam used below. Valve lift should be recalculated @ 1.6.
Lift /1.5X1.6= new lift.View attachment 1716480091

View attachment 1716480092
Click to expand...
Thanks for the suggestions.
Do you know of a hypereutectic 4.080 piston that's not an out of the hole compression height? I'd prefer to go hyper, but I haven't found any that aren't a long way out of the hole and that's tough on a closed chamber head.
FYI: the cam mentioned isn't Hughes, it's an Oregon custom grind.
 
Siksty7 Dart 270 said:
I picked up a .030 over 340 block which the machine shop says needs to go to 4.080 to avoid piston slap. Here's a recipe I'm considering:
Stock stroke cast crankshaft,
steel I beam connecting rods,
4.080 D.S.S. forged flat top 4032 alloy pistons with valve reliefs zero-decked,
.051 compressed head gasket
Stock Magnum heads, measured at 64 cc chambers, with Hughes 1110 valve springs,
Hydraulic roller cam 270/278 Adv. 212/220 @ .050, .485/.506 gross lift on 110 LSA, 106 ICL,
Hydraulic roller retrofit lifters,
Nice pushrods,
Edelbrock Performer RPM airgap intake,
650-750 CFM Edelbrock carb,
Stock electronic ignition appropriately curved
Long tube 1-5/8" headers into cutouts/2.5" exhaust,
A904 with mild shift kit & +1 thin frictions and steels,
2500 stall A and A torque converter
3.23 sure grip in an 8 3/4 rearend
26" tall tire
Otherwise stock 67 4 door Dart

On paper this engine yields: 10.1:1 Static CR, 8.23:1 Dynamic CR, 167.57 PSI Dynamic Cranking Pressure, 138 Volume/Pressure Index

I want to: run pump gas, smoke tires from a dead stab, cruise at reasonable RPM for 60 MPH, have respectable 1/4 mile passes (would love to get in the 100mph club, but not required), not overheat in traffic running a mechanical fan and shroud on a 22" radiator, re-use many current in-use parts

Is the quench I will achieve adequate?
Is that kind of cranking pressure manageable?
What potential street/cruising reliability issues am I overlooking.
Click to expand...
Why not a SFT cam? I have a 9.5:1 340 running a 242/242 @.05 with 106 lsa and it pulls very hard to 6g with 1.88 heads. Turning a 31.5/ 12.5/15 slick with 4.57 ratio.

The Eq 1.92 intake (magnum) headed 360 with 10:1 liked a 248/256 on 110 with .558/.550 lift in the same car. Aren't Magnum heads peaking at .550" lift? You already have adjustable rockers.

As far as street-able 100mph grinds this generic Howards went 101.3 with a 9:1 360 and Speedmasters out of the box. 3.55:1 spinning street tires into second gear: Mechanical Flat Tappet Camshaft; 1964 - 2003 Chrysler 273, 340, 360 2400 to 6200 Howards Cams 710862-08 | Howards Cams

The money you save with a SFT could go to a modern torque converter.

Schneider Cams, they speak Mopar...
 
Last edited:


RustyRatRod said:
You need to get a second opinion on that .080 over BS. That sounds stupid fishy.
Click to expand...
Machine shop said the current 4.070 bore is too sloppy and it needs to go to 4.080 for a cleanup. They said if I ran it, with the current bore and 4.070 pistons there would be piston slap. I believe them.
 
RustyRatRod said:
You need to get a second opinion on that .080 over BS. That sounds stupid fishy.
Click to expand...
Perhaps he means 4.080" bore
Siksty7 Dart 270 said:
Machine shop said the current 4.070 bore is too sloppy and it needs to go to 4.080 for a cleanup. They said if I ran it, with the current bore and 4.070 pistons there would be piston slap. I believe them.
Click to expand...
.040 overbore for a 340.
 
Check summit racing and jets for piston selections.
You can always call a piston manufacturer. A .040 340 piston should not be hard to find. Often they are listed in increments of .030. Which the next listing is at .060. In the past it was a normal sight to find a piston for any engine listed in .010 up to .060. Unless it was a known thing that engine could go further.
 
Siksty7 Dart 270 said:
Machine shop said the current 4.070 bore is too sloppy and it needs to go to 4.080 for a cleanup. They said if I ran it, with the current bore and 4.070 pistons there would be piston slap. I believe them.
Click to expand...
That makes more sense. I'd still get some NUMBERS for wear. A good, fresh, straight, clean bore is essential for any build, but they shouldn't be afraid to give you actual numbers. It's your money after all.
 
This is what I got from Charlie Servedio’s bench. Once the valve goes up to a certain height, it kind of stays flowing at the same rate.

And cam lifting the valve over .400 and hangs it there for any decent time will make good power. There is t much sense in my head to go do sky high lifts since there really isn’t a big improvement that would have me do a high lifts since cam. A low lift cam that hangs the valve open for a while will do the trick.
 
rumblefish360 said:
This is what I got from Charlie Servedio’s bench. Once the valve goes up to a certain height, it kind of stays flowing at the same rate.
Click to expand...
Understood. That’s where the increased “dwell” of a roller or Racer Brown “STX” SFT lobe will get the most from those .4”~.6” numbers.
 
Now that I think about it, cams like that, Crane used to grind a lot of. I think Isky also did that kind of cam.

It was like a cheater cam, but not. Same idea. Enough lift to take advantage of just a valve job or a valve job and bowl porting.

A lot of the older Crane cams came in various durations but stop around the .500 lift area. Give or take .010 or .020 in lift. But they had a lot of grinds like that. Hold on and I’ll find an old cam card.
 
There! 1 example. 236@050, .497 lift, 108 LSA, easy on the springs, good rpm ability, last forever with those springs not crushing anything.

I was going to use this with a 1.6 rocker to help intensify it. .530 lift with a 1.6 rocker. Great with the Magnum head.

IMG_1183.jpeg
 
rumblefish360 said:
There! 1 example. 236@050, .497 lift, 108 LSA, easy on the springs, good rpm ability, last forever with those springs not crushing anything.

I was going to use this with a 1.6 rocker to help intensify it. .530 lift with a 1.6 rocker. Great with the Magnum head.

View attachment 1716480112
Click to expand...
Harvey was good at it! Sad Crane got passed around like they did before folding up.

I often look at his patterns for ideas.
 
rumblefish360 said:
There! 1 example. 236@050, .497 lift, 108 LSA, easy on the springs, good rpm ability, last forever with those springs not crushing anything.

I was going to use this with a 1.6 rocker to help intensify it. .530 lift with a 1.6 rocker. Great with the Magnum head.

View attachment 1716480112
Click to expand...
The stage 2 cam back in the day, Isky and Erson had similar grinds.
 
Illahe said:
I had a Crane Fireball in my 66 390 Fairlane with 3.89:1 when I was in High School. That S.O.B. would stripe the neighborhood at will... and it earned me a restricted driving license to boot...
Click to expand...
I have a Fireball 302 in the 400 in my F250 Ford truck. It has massive balls for a big old truck.
 
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