piston questions

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question: does it have to fit the factory spring locations? because i have plenty that'll fit but... ya know...
Well....if he wants a C body 8 3/4 that will bolt on TOP of the springs, you might as well cut him some wheel tubs out of an old bed so he can do the mini tub with only one seam!

:lol:
 
Well....if he wants a C body 8 3/4 that will bolt on TOP of the springs, you might as well cut him some wheel tubs out of an old bed so he can do the mini tub with only one seam!

:lol:
i like the way you think and would like to subscribe to your newsletter.
 
question: does it have to fit the factory spring locations? because i have plenty that'll fit but... ya know...
Stock spring location but with an axle flip so perches can be cut off. Text me a day or so before you come down this way.
 
Being that you brought up manifolds for a carbureted magnum
What would you suggest in a 3/4 ton truck w/a stick and 3.55s that tows besides being a daily?
I'm thinking for cam something comparable to a comp 260- comp 268ish only in a roller equivalent.
A tunnel ram and two 1150 Dominators.
 
Long as someone's passing out truck 8-3/4s drop one off here with the super rare 5 on 5-1/2 lug pattern haha
 
A tunnel ram and two 1150 Dominators.
C'mon now I know better than THAT....
And I have an M-1 dual plane coming....
And that way I can avoid the round round discussion about a head drilling fixture at least...
As of 15 min ago I also now have an original 360 magnum bell housing and flywheel coming for this project.... Helping to narrow down parts for the motor and also helping to answer the balance questions, being this is an original flywheel for one of these engines, should be balanced for (at least a stock) 360 magnum....
 
Like I'd said probably 3 pages ago now my asking about what pistons to buy, will/won't I have to have it balanced, etc is slowly starting to come together....
 
You CAN use the H405CP pistons you already have in a 5.9 Magnum block IF you get the rotating assembly balanced. There are also factory style replacement pistons available as part number H655CP and these have the factory style dish in them. If you compare the specs you will find you gain a little but of compression with the H405CP over the H655CP with everything else remaining the same. Is the goofy four valve relief piston crown on the H405CP the most efficient design? Nope. The dish in the H655CP is a copy of the factory Magnum piston and it's intention is to increase mixture motion on the compression stroke. You would probably use less fuel to make the same power with the H655CP (or a factory Magnum piston if you were not already over bored) than you will with the H405CP.

Use the compression calculators available on sites like Summit or Diamond racing to play with the numbers. But ultimately, you will have to decide if you want to run the pistons you have or buy new ones. Then, if you are ok spending the money on new ones, do you need more compression like KB107 or H116 or will the H655Cp work for you.

If it was me in this situation, I would sell the H405CP pistons and buy the H655CP for this truck engine. Then make sure you know what heads are going on it and what head gaskets you will be using and get the Magnum cam reground using the suggestion they give at Oregon Cams.

Sorry for the long post. Trying to be clear.
I was out there in the garage yesterday. The pistons in the motor now are the h655cp.
But between my original screw up with the lining up of the dots on the timing chain with the triangle instead of the round dot and I cranked it over on the stand, with a bar and ended up bending a few valves, and then the new EQ heads that I bought and just bolted on out of the box and crashed #4 exhaust valve because the stem to guide clearance was too tight as assembled by EQ, Im just leery about reusing those pistons.
Then the fact that freshly reconditioned stock injectors stuck wide open on me and washed it out/ thinned out the oil, I'm hoping I can get by with just a dingle ball hone and another set of rings and bearings.... Again trying to use what I got..... But being leery of pistons that have already taken the beating they have, and figuring I'd better get new ones again while I'm back in there, because of it.... Or would these really be alright to reuse? Like rusty said, I DON'T want a repeat. And want to build the best engine I can while I'm at it ... As I've said this wasn't my first rebuild, and I've done others since. But my first one that didn't turn out right. But I can't get that part of it out of my head, I'm wanting to start over from scratch like an engine that's never been into before.
 
I don't know if you can buy singles in the H665CP's? If you can, that may save you a few bucks if you only need one or two. Make sure you get the ring gaps right for Hypereutectic pistons.
 
First, before I even get into rings ring gap etc is to decide what pistons to buy if it don't/can't reuse these. The whole point of the thread in the first place is to figure out which ones would be best for what I'm doing. ..
 
If there’s no holes in em use the same pistons. If there are marks from crashing valves, polish the sharp edges off and send it!!! Especially if the bottom end has already been balanced for those pistons. You’re overthinking it.
 
I agree with reusing them after a quick inspection. The valves contacted the pistons on an angle, even with those valve notches, so the force on the piston itself was minimal. But if you are set on new ones to ease your mind you can get the exact same ones, make sure they weigh the same as these old ones, and then run them without another rebalance. If was balanced before and the piston weight does not change, whichever piston you use, it will still be in balance.
 
Got these as a stock replacement, just the fact that they're 30 over should be a negligible effect on balance.... The whole point of this thread is that as long as it has to come back apart if there would be a better choice for what I'm wanting out of it....if not then great .
Now's the time if so ... I've always wondered why, and always considered the 360s dished pistons as it's downfall. Especially in the LA days but they're still dished in the magnum days...
 
Got these as a stock replacement, just the fact that they're 30 over should be a negligible effect on balance.... The whole point of this thread is that as long as it has to come back apart if there would be a better choice for what I'm wanting out of it....if not then great .
Now's the time if so ... I've always wondered why, and always considered the 360s dished pistons as it's downfall. Especially in the LA days but they're still dished in the magnum days...
They had to dish the piston in the magnum to get the compression ratio down with the closed chambered mag heads. They need it to run on junk 87 octane gas. They’re 9.0:1-9.1:1 depending on how you top off the chamber and which chamber you measure. For what you’re doing the stock piston, or stock replacement piston will be fine.
 
Are they really 9:1 or are they as the older ones which were listed as 8.2-8.4:1 that were really in the 7's?
 
So they did get more accurate in their claimed spec by then..... My last engine job was a /6 and those are also a claimed 8.4...i got exactly there with 0.100" of a shave between the block and head..,...
 
Yes the machining and tolerances got much better. They measure pretty close to factory spec.
 
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