Pistons, compression ratio and balancing stock stroke 440

[Mark B]

Please bear with me as I don't usually make posts this lengthy. I prefer to be short and to the point but this will not be the case this time.
I have pulled down the engine that came with my project to see what I have. I have never had it running because the car was in a basket when I purchased it. Previous owner said it was fresh rebuild but could give me no specifics. Here's what I have found. '74' HP block with forged crank and six pack rods and damper. Pistons are stock standard bore looks like they just honed the block and installed new rings. I can feel a small ridge at the top but haven't measured it yet. The pistons are down in the hole .160" ! Has fresh 906 heads and a new unknown cam with about .430 lift and an unknown duration and no markings I am familiar with. I would guess maybe an elgin or some other generic big block cam. It's barely broke in and the lifters don't look quite right so I will be tossing it. Has a factory six pack setup on it, mallory electronic distributor with no vacuum advance and a melling high volume oil pump.
I know the compression ratio is in the toilet with these pistons and yes I could just buy some stock six pack pistons bore it and call it a day. But I would like to go with a lighter piston so I could balance it to use a neutral balance flywheel.( I am changing from an automatic transmission) I was looking at the Icon IC9953-030 . They weigh 882 grams with pins. Would that be light enough to allow internal balancing without heavy metal? If my calculations are right This should get me to about 9.2:1 compression. Then all I need to do is pick out a cam and timing set, rebuild the carbs, probably find a vacuum advance distributor,etc,etc. This will be a street driven car with M/T, power brakes, A/C and /3.54 gears.
What do you guys think?
What else am I missing?

 

[jusglazin]

Well I've been down that road before. Make sure it's balanced properly before you put it together. My 1st 440 was a 74 HP with 6 pack rods as well. At the time I didn't know they were 6 pack rods. I had a machine shop balance the assembly with a new neutral damper. The guys claimed it balanced but I should have knowno with the ton of Mallory they added something was wrong. When I fired it up it shook like a washing machine. Not knowing the cause I replaced everything trying to find the cause. I ended up pulling it and replacing the rotating assembly. If I were you I'd just find some lighter rods while you have it apart. Those rods weren't that great anyway and add a lot of weight with little or no extra strength.

 

[DLevel]

I'm working on a 440 right now for my brothers wagon project . Started off with a motor home donor block that had the 6 pack rods in it.I've had a couple of these engines come into my shop and it didn't matter that they were early 70s they always had the 6 pack rods with the older steel crank and balancer. I'm using the Wiseco street pro flat tops and the steel crank internal balanced with a minimum drill out. The rod weights were all over the place so I weight matched them within a couple grams of each other . Polished the beams and then shot peened them . That process took around 20 grams off of them which helped on the balance. If you need to know a Bob weight I could get that for you.

 

[Mark B]

DLevel
Yes, was going to polish the beams, install ARP bolts and resize the big end while I'm at it. How heavy are the pistons and pins you used?

 

[DLevel]

Yes, was going to polish the beams, install ARP bolts and resize the big end while I'm at it. How heavy are the pistons and pins you used

Let me look up the balance card tomorrow and I will get back with you.

 

[moper]

The problem is mainly the rods. Theyare heavy, so heavy they require the counterweighted balancer. They are also no stronger overall than the standard 440 "LY" rods because for all that extra beef (and accmpanying mass) they use the same size rod bolts. The weak area in mopar rods is always the bolts. So if it were me, I would replace the sixpac rods with LYs, and replace the pistons with KB hypers or a similar forged flat top. In that configuration the crank's counterweights alone are more than enough to internally balance the assembly. Then you get lighter rods, lighter pistons, more static compression, with no loss of strength.

 

[mentor70]

I bought the 440 source Icons that have a smaller ring pack. i called Trend performance and upgraded the wrist pins to H13 tool steel. i thought the Icon pins looked a little cheap. that brought the pin and piston balance weight to 899 grams. I also used older 440 source I beam rods and i needed no Mallory metal at all.

As stated above, i would ditch the six pack rods and go aftermarket or YL rods with ARP bolts

 

[furryfrog]

I agree with the guys here, toss the 6 pack rods as well. It is ridiculous how heavy they are! I do not know why they have a good reputation. What cam are you planning on running?

 

[lewtot184]

rebuilt stock LY rods with KB184 quench dome pistons. a little extra work to set up the quench but the engine will run on pump gas and make as much power as a 10:1 flat top piston engine.

 

[Mark B]

The only reason I wanted to keep as much as I could is because I originally only tore this down to see what I had. I thought it was a better engine than this. So now I am trying to make some changes without breaking the bank. I am keeping the rods and balancer because it is correct for the 70 six pack engine and I already own them.
I haven't made a decision on the cam yet since I just found out I needed one yesterday. I would like a smooth idle and decent response and all done @5000-5500 This is only going to be a street car and I hope to put miles on it as long as the weather is good. I estimate 10-15k a year. I am sure it will be a flat tappet cam. Don't know if I will go solid or hydraulic though.
Thanks for your responses so far. Please keep them coming. Mark

 

[Cranky]

If the 6 pack rods are prepped right, they will work fine. Yeah, they are heavy but getting rid of the casting flash and polishing the beams will take some weight off plus make a better rod. And you HAVE to install high strength rod bolts. A buddy built a motor back in 81 doing all of that and ran the heavy L2295 slugs and turned that dog 6800 and it went two years running at the track every Wednesday night and Saturday. A clutch explosion took it out. Back in the day, Chrysler decided the LY rods were the weak link in their high warranty returns with broken rods and used the heavy rods as a fix but no one thought about the rod bolts being the same size. If you're only going to 5500 with them, you'll be fine but if it were mine, I would install the better bolts. Most say you have to resize the rod but if the new bolts are not any tighter than the old ones, then they probably won't unset the fit. I've done it several times. I'll mic the rods before pulling out the old ones and then mic after installing the new ones and if the size doesn't change, I don't worry about it.

 

[mentor70]

The only reason I wanted to keep as much as I could is because I originally only tore this down to see what I had. I thought it was a better engine than this. So now I am trying to make some changes without breaking the bank. I am keeping the rods and balancer because it is correct for the 70 six pack engine and I already own them.
I haven't made a decision on the cam yet since I just found out I needed one yesterday. I would like a smooth idle and decent response and all done @5000-5500 This is only going to be a street car and I hope to put miles on it as long as the weather is good. I estimate 10-15k a year. I am sure it will be a flat tappet cam. Don't know if I will go solid or hydraulic though.
Thanks for your responses so far. Please keep them coming. Mark

i put a Comp cams extreme energy 268H hydraulic cam in my 70 440 six pack engine in 1997, best thing i every did on that engine.

today id prolly look at a Lunati Voodoo of similar specs if i did it again.

 

[Canyon707]

I have a set of ly rods that I could part with.

 

[dieseldazzle]

The only reason I wanted to keep as much as I could is because I originally only tore this down to see what I had. I thought it was a better engine than this. So now I am trying to make some changes without breaking the bank. I am keeping the rods and balancer because it is correct for the 70 six pack engine and I already own them.
I haven't made a decision on the cam yet since I just found out I needed one yesterday. I would like a smooth idle and decent response and all done @5000-5500 This is only going to be a street car and I hope to put miles on it as long as the weather is good. I estimate 10-15k a year. I am sure it will be a flat tappet cam. Don't know if I will go solid or hydraulic though.
Thanks for your responses so far. Please keep them coming. Mark

I used eagle rods with 1.094 pin and an off the shelf diamond piston then had it balanced to my six barrel dampener so it will look original and used a b and m flexplate.

 

[66Satellite47]

I ran LY rods in several of my motors. I didn't ever run the 6 Pak rods. The LY rods held up well. I had SPS bolts in all. Shot peened in most. My 440 motors were run to 7000 RPM all the time. My first low deck motor with a cut down 440 crank & low deck rods went 7400 RPM all the time. My second low deck used 440 LY rods, held up well at 7000+ RPM.

 

[lewtot184]

The only reason I wanted to keep as much as I could is because I originally only tore this down to see what I had. I thought it was a better engine than this. So now I am trying to make some changes without breaking the bank. I am keeping the rods and balancer because it is correct for the 70 six pack engine and I already own them.
I haven't made a decision on the cam yet since I just found out I needed one yesterday. I would like a smooth idle and decent response and all done @5000-5500 This is only going to be a street car and I hope to put miles on it as long as the weather is good. I estimate 10-15k a year. I am sure it will be a flat tappet cam. Don't know if I will go solid or hydraulic though.
Thanks for your responses so far. Please keep them coming. Mark

the cheapo summit 6401 cam will do what you want, especially if your using cast iron exhaust manifolds.

 

[Cranky]

I ran LY rods in several of my motors. I didn't ever run the 6 Pak rods. The LY rods held up well. I had SPS bolts in all. Shot peened in most. My 440 motors were run to 7000 RPM all the time. My first low deck motor with a cut down 440 crank & low deck rods went 7400 RPM all the time. My second low deck used 440 LY rods, held up well at 7000+ RPM.

A lighter rotating assembly is always better and a prepped LY rod with a light piston will be faster revving than an engine with heavy rods and pistons....plus it will be easier on the crank too.

 

[DLevel]

Yes, was going to polish the beams, install ARP bolts and resize the big end while I'm at it. How heavy are the pistons and pins you used?

Here's the balance card for the combination in question. As you can see on the bottom right of the card, using the lighter piston and the older standard steel crank balancer, makes the balancing an easy drill out or lathe job. It appears that even if you didn't take some weight off of the 6 pack rods, it still wouldn't require the external balancer. These heavy rods would not be my first choice on a new build but, that's what rods were in the engine when we took it apart.For an engine that might see low 6,000 rpm's once in a while I feel the ARP bolts will make this combo strong enough. I'm sure everyone has an opinion on what rod you should use but, I thought you would like info on what you have. Remember I didn't use an external weighted balancer on this. Good Luck

 

[66Satellite47]

A lighter rotating assembly is always better and a prepped LY rod with a light piston will be faster revving than an engine with heavy rods and pistons....plus it will be easier on the crank too.

We did take some weight off the LY rods in addition to shot peening them. My first low deck used the short low deck rods & fairly lite Arais pistons. Seemed like a fast revving combo, went 7400 RPM all the time. The second low deck motor used LY rods shot peened, SPS bolts, Venolia pistons cut for B1 heads that I never got around to buying. The second low deck went pretty fast with both 906 & 915 heads.

 

[Mark B]

Wow,
Thanks for the responses. This is not a race motor so I don't mind using the heavy rods. I have a bone stock 70 440 magnum with the heavy rods in a Ramcharger and it has never let me down. In fact it used to get 13-14MPG until the headers rotted off. Went back to truck manifolds and lost 2-3 mpg. Anyone have a source for big block headers for a 78 Ramcharger?
My question was more on the balancing so I could just use a neutral balance flywheel. I am going to try using the icon pistons, polish the beams on the rods, install some ARP bolts, check the big end bores and cross my fingers that it wil balance without mallory metal.
I have gotten a couple suggestions for a cam and I will be looking into that in the next few days. I'll let you know what happens.