The only reason is by time you recon them the cost savings isn't worth it on a 55-year-old rod with a million cycles on it. But if you are not going to recon them because of budget I'd use them myself. Good bolts always help. But you always run risks.
Combination for a peppy 340
- Thread starter FlamesAreWicked
- Start date
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ir3333
Well-Known Member
Listen to Rusty, not the quarter mile guys, or you are going to be disappointed.
Stock cam is perfect for a street driven 340...but you didn't want to hear that.
Stock cam is perfect for a street driven 340...but you didn't want to hear that.
What risks? I've been messin with cars since I was nine years old and I have yet to see a connecting rod "just let go" for no reason. There's always another factor. Broken rod bolt, spun bearing, something falling into the rotating assembly from above, it's always something else that causes the rod to break has been my experience. I'm not saying they cannot, I'm just saying from my experience, I've never seen it, so I'm sayin it's really rare. I agree about the cost, but there are some of us that can do some of the work at home. I've installed rod bolts myself in the last six engines I've built. One of those the rods even checked good on and needed nothing. They had been resized previously, but me replacing the bolts made no change. If you can install rod bolts yourself, that does negate a little bit of the cost.
Dartswinger70
Well-Known Member
I was going to say "Isn't a stock 340 rebuild pretty peppy?" true story I had a Crane SSH 320 in my 340 years ago but it was too lopey for a street car so i ditched it for a mild cam I like the latter.
FlamesAreWicked
Well-Known Member
Well then… I probably shouldn’t have used the term “peppy” to describe what I’m planning. Had the engine I bought would been been totally fine on the inside and not needing any work, it probably would be installed by now. Unfortunately it wasn’t the case. I’m taking this opportunity to go beyond that mark by a sizable amount. If I had to put a measurable goal, it would be low 12s capable on a 15 inch drag radial in decent air and my driving ability. My daily commuter is a 2020 Camaro LT1 6spd. I brought it to the track and on the stock Goodyear run flats it ran 12.56 @ 114 mph with a piss poor 2.12 60ft. I’d like this to be comparable to that. Only modifications I’ve done to the Camaro was a catback exhaust system just to make it not so whisper quiet. I call that peppy since we live in a world where you’re not even worth raising an eyebrow at unless you’re making 700hp or better. 400hp in an A-body with a stick ought to be a total riot.
An upside to this is knowing exactly what I have in it from this point on. I ordered some parts and we will see in the next month or two how “peppy” it’ll be. I’m gonna be putting some KB243 .040 over pistons in it. Assuming the deck is at factory spec, it should put my compression in the mid to upper 9s with the 65cc edelbrock head. The cam ultimately bought was a Howard’s hydraulic roller 227/235 @ .050 and .525/.530 lift on a 109. RPM range is a little lower than the previous two I mentioned.. this one is advertised as 1800-5500rpm.
Anyhow… there were some good suggestions in here without a doubt. This is just the route I decided to go. We’ll see if I chose wisely or not.. whatever performance it’ll bring will be a night and day improvement over the stock tired 318 sittin in it now..
On a side note, the Camaro was about 3-4 tenths quicker in the 1/4 than the 2012 GT500 I owned a couple of years ago.. that thing would just obliterate tires at will. I wish I would of tried it at the track on something more than a normal performance tire..
An upside to this is knowing exactly what I have in it from this point on. I ordered some parts and we will see in the next month or two how “peppy” it’ll be. I’m gonna be putting some KB243 .040 over pistons in it. Assuming the deck is at factory spec, it should put my compression in the mid to upper 9s with the 65cc edelbrock head. The cam ultimately bought was a Howard’s hydraulic roller 227/235 @ .050 and .525/.530 lift on a 109. RPM range is a little lower than the previous two I mentioned.. this one is advertised as 1800-5500rpm.
Anyhow… there were some good suggestions in here without a doubt. This is just the route I decided to go. We’ll see if I chose wisely or not.. whatever performance it’ll bring will be a night and day improvement over the stock tired 318 sittin in it now..
On a side note, the Camaro was about 3-4 tenths quicker in the 1/4 than the 2012 GT500 I owned a couple of years ago.. that thing would just obliterate tires at will. I wish I would of tried it at the track on something more than a normal performance tire..
ir3333
Well-Known Member
OK.. a 340 that will run a 12.5 quarter mile. I can't help you, i am not a racer but there are a lot of quarter mile guys on the this site that can.
Dartswinger70
Well-Known Member
Didn't they run 13.7 stock ? with tuning? the 68-71 version I mean. There are recipies out there Id look at what was done back in the day I think 12.5 is probably easily doable with a cam and tuning maybe today you'd get some aluminim heads and air gap intake etc.
FlamesAreWicked
Well-Known Member
That’s exactly what my plans are. Air gap, Edelbrock heads, and a healthy cam.
RRR,
I have to disagree with you in post #53. The rod is a highly stressed part of the engine & the OEMs made it worse by using a nut and bolt. That reqd cutting into the shoulder of the rod for bolt head clearance. That created numerous weak spots: metal removed for the bolt head, sharp edges that can induce a crack, & uneven stress[es] caused by the bolt head under load. Aftermarket bolt only rods are inherently stronger & by the time you factor in the cost of re-con factory rods [ which still contain all the defects ], new rods are the way to go.
Toilet is still flushing real good.....
I have to disagree with you in post #53. The rod is a highly stressed part of the engine & the OEMs made it worse by using a nut and bolt. That reqd cutting into the shoulder of the rod for bolt head clearance. That created numerous weak spots: metal removed for the bolt head, sharp edges that can induce a crack, & uneven stress[es] caused by the bolt head under load. Aftermarket bolt only rods are inherently stronger & by the time you factor in the cost of re-con factory rods [ which still contain all the defects ], new rods are the way to go.
Toilet is still flushing real good.....
No. More like low 15s and high 14s. Maybe with headers, tuning, slicks and a good gear, high 13s.
A SBM mopar 340 con rod is a great weapon. How on earth did they survive for years with nothing but a set of good bolts. LOL
Seen a couple engines that everything BUT the connecting rod was fubar'd. Lose a piston and that con rod kills everything in the path.
Want to take into consideration the cost to refurb/bolts vs a new scat I beam piece, sure run the scat piece if price is close. The newer lighter rod is a better overall piece. The weak point suggestion of an OEM 340 is folly.
Seen a couple engines that everything BUT the connecting rod was fubar'd. Lose a piston and that con rod kills everything in the path.
Want to take into consideration the cost to refurb/bolts vs a new scat I beam piece, sure run the scat piece if price is close. The newer lighter rod is a better overall piece. The weak point suggestion of an OEM 340 is folly.
The test cars that were heaters (low 14's) from the factory ran a best of about 100 MPH, most were in the 95-98 range. That is good enough MPH for a low 13. 60's was the killer of ET for all these cars off the showroom floor, dealer hands the keys and straight to the track, no tweaking.
You seem to know exactly what you want, so rather than ask our opinions, just build it.
FlamesAreWicked
Well-Known Member
Just a little update.. the 340 is nearly ready for me to drop in the Dart. We went ahead and opened it another .010 for a total of .040 over. KB243 pistons, Edelbrock 6017 heads, howards hydraulic roller cam with .525/.530 lift.. edel air gap intake. Harland Sharp rockers… the snowball effect definitely happened with this engine. I’m gonna use Doug’s D453 ceramic headers. I’m happy to report that the lifter bores were okay with the morel lifters and didn’t even need to grind the ribs in the valley for them to fit. Online calculators put the compression at 9.75ish static an around 8.47:1 dynamic with that camshaft.
Should make for a spicy ride with the 4spd and 3.55 gear… my clutch is just a McLoed street clutch but I’m runnin just a regular cooper rear tire so it’s gonna blow the tires fairly easy. It probably would be smart to step that up to the 500hp rated one for some insurance.
Here’s a few shots. I went by today and brought a 68-69 timing cover and balancer since my 68 Dart uses the iron water pump a the original cover was the later driver side timing mark version. Just have to finish assembly, measure for pushrods, freshen the orange paint job, and other small details..
Should make for a spicy ride with the 4spd and 3.55 gear… my clutch is just a McLoed street clutch but I’m runnin just a regular cooper rear tire so it’s gonna blow the tires fairly easy. It probably would be smart to step that up to the 500hp rated one for some insurance.
Here’s a few shots. I went by today and brought a 68-69 timing cover and balancer since my 68 Dart uses the iron water pump a the original cover was the later driver side timing mark version. Just have to finish assembly, measure for pushrods, freshen the orange paint job, and other small details..
FlamesAreWicked
Well-Known Member
Oh and the cam that was in it originally was an old Crane fireball 290 cam.. I’m gonna sell the 587 heads, 273 rockers that I was gonna use before deciding on HS rockers, and that Crane cam as a package locally hopefully
mopowers
Well-Known Member
Looks like a great combo. What intake valve closing angle did you use to calculate the DCR at 8.47?
FlamesAreWicked
Well-Known Member
T
Per the cam card, it’s 36.3° @ .050 . I plugged in the numbers on a site JustMoparJoe recommended on his YouTube channel. 8.47:1 is what it came up with so.. I’ll take that with a grain of salt.
mopowers
Well-Known Member
I'm guessing the calculator you used likely just added 15* to that @.050" number. Use this one and plug in the actual intake valve closing angle: https://www.wallaceracing.com/dynamic-cr.php. It'll be a lot more accurate. Your actual intake closing angle is somewhere around 60-65* ABDC.
FlamesAreWicked
Well-Known Member
The advertised angle is 62.3° on the card. The site asked for the @ .050 angle
Gofastmath is the site
mopowers
Well-Known Member
Use 62.3*. That's when the valve actually hits the seat and will give you a more accurate number - probably around 7.8-7.9 or so. The calculators that ask for the @.050 number usually just arbitrarily add 15* to it for the calculation, which in your case would be over 10* off of actual.
JDMopar
Well-Known Member
Looks nice! Will your lifters come out with the heads on? I have the same lifters in a 273 and they will come out with the heads on. Some have reported that the Morels won't come out with aftermarket heads. No biggie either way, but try it if you don't have the intake on yet and you'll know if you ever decide to swap cams.
FlamesAreWicked
Well-Known Member
Just Mopar Joe is building a very similar setup but in a 360 configuration and the whole reason why I even decided to try to see what figure it was gonna be was to compare to his 360.. I’ll have to plug in the numbers to another ones to see what I get. He mentioned how dynamic can really tell you the story on using pump gas or needing more than that. I was confident that I was pump friendly because I’m not using a crazy combination of piston and cylinder head in addition to the heads being aluminum.
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