Thread: Help me out, thinking weird again

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Originally Posted by roadster32

If you are going to use it on the street i would beware of the ally rods, I had a set from Miller that were called street duty for my old 6/71 blown 427 Ford and they stretched

Aluminum rods are as strong if not stronger while under engine load.

When you wind it up, let off the gas and let the engine slow the car down is where you risk stretching a rod on the street.

Been doing some research on this engine combo.... with the 3.25 stroke I think I want the 6.200 rod length....or do I want 6.125??? My understanding is the longer rod puts the wrist pin a bit higher in the rod, (strength issue for the piston), then of course the age old debate on rods that longer is always better.... Remember, I'm a Ford guy so be gentle please!!!!

Alum rods will split down the bolt hole from fatique just setting around torqued up--even if just on the shelf---

Dave---the longer rod will have a piston with a shorter compression height---distance from center of pin to deck surface--usually a much litghter piston

however--the ring pack will be more tightly gathered at the top of the piston and will usually have to have a spacer rail to support the oil ring--

with the piston grooves more closely to the top of the piston, the valve notches come closer to the back of the ring groove which creates a weak place for the top to break away will the slightest amount of detonation

pin oil holes also are quite varied in design with these short deck pistons, from nothing but a broached groove in the Probe stuff to drilled passages in others--
pin locks range fron single snap rings to tru arcs, dual tru arcs, triple spiral locks and a round wire type lock that combines with a beveled pin end to lock it in place

And unlike the fords---the chevs have right and left pistons depending on which cylinder valve arrangement---

and don't forget that we are now using the Honda bearing size in a lot of race engines --including 1400hp 500 cid pro stock type engines that run up past 10,000 rpm

sleep tight

from 6.125 to 6.200 rod dif your looking at 075 that in the piston will let move thing ring pack down some but you can use a 043/043 /3mm ring pack or 1/16 1/16 3/16 .i would go with the 1.175 ch with the 6.200 rods. but 6.125 would be 1.250 ch and run 1/16 rings and would let you have lot of room to lower the top ring land down for NOS and you not going that way ? you want to try to stay above more the 1 inch CH if you can

Originally Posted by jerry clayton

Alum rods will split down the bolt hole from fatique just setting around torqued up--even if just on the shelf---

Dave---the longer rod will have a piston with a shorter compression height---distance from center of pin to deck surface--usually a much litghter piston

however--the ring pack will be more tightly gathered at the top of the piston and will usually have to have a spacer rail to support the oil ring--

with the piston grooves more closely to the top of the piston, the valve notches come closer to the back of the ring groove which creates a weak place for the top to break away will the slightest amount of detonation

pin oil holes also are quite varied in design with these short deck pistons, from nothing but a broached groove in the Probe stuff to drilled passages in others--
pin locks range fron single snap rings to tru arcs, dual tru arcs, triple spiral locks and a round wire type lock that combines with a beveled pin end to lock it in place

And unlike the fords---the chevs have right and left pistons depending on which cylinder valve arrangement---

and don't forget that we are now using the Honda bearing size in a lot of race engines --including 1400hp 500 cid pro stock type engines that run up past 10,000 rpm

sleep tight

Thanks Jerry.... I understand all that stuff except the "sleep tight" part....I know have 8 more notes on my research scribble sheet!!!!!!!!!!!!!!

Originally Posted by pat mccarthy

from 6.125 to 6.200 rod dif your looking at 075 that in the piston will let move thing ring pack down some but you can use a 043/043 /3mm ring pack or 1/16 1/16 3/16 .i would go with the 1.175 ch with the 6.200 rods. but 6.125 would be 1.250 ch and run 1/16 rings and would let you have lot of room to lower the top ring land down for NOS and you not going that way ? you want to try to stay above more the 1 inch CH if you can

Ok, so from you and Jerry I get the idea I should get a set of 6.2 billet rods and forget the aluminum rods, right????

Any particular things to watch for on bob weights doing a Chevy, or won't too light on rods and pistons be a problem??? Found a set of titanium 6.2 rods, and a couple sets of Oliver, Carillo, etc..... Billet 3.25 cranks are around, most seem to have the Honda sized rod journal as Jerry mentioned... Large radius, lightening holes, and knife edged ok???

Originally Posted by Dave Severson

Ok, so from you and Jerry I get the idea I should get a set of 6.2 billet rods and forget the aluminum rods, right????

Any particular things to watch for on bob weights doing a Chevy, or won't too light on rods and pistons be a problem??? Found a set of titanium 6.2 rods, and a couple sets of Oliver, Carillo, etc..... Billet 3.25 cranks are around, most seem to have the Honda sized rod journal as Jerry mentioned... Large radius, lightening holes, and knife edged ok???

nope in a shelf JE light GP piston there shelfs in 1.125 CH and 1.250 so a 6.250 rod or 6.125 rod . watch them cranks if you using a 400 gm block as the mains are bigger and you would have to go small journal small block from large 400 mains that one thick spacer less you go dart bock and or custom crank for the right mains but for hi RPM i would stay small sbc mains . the lighter the better on the new mass. it is hard putting steel back on the crank if it was never made to take the new bob weight if way to much. jerry been there as i have as well on some new cranks... some crank maker did a dumb thing

Originally Posted by Dave Severson

Been doing some research on this engine combo.... with the 3.25 stroke I think I want the 6.200 rod length....or do I want 6.125??? My understanding is the longer rod puts the wrist pin a bit higher in the rod, (strength issue for the piston), then of course the age old debate on rods that longer is always better.... Remember, I'm a Ford guy so be gentle please!!!!

Got me thinking.How stable even after using torque plates are the 400 Siamese bores??.I thought they moved around quite a bit and sealing might be a issue.Then add in longer rods which I would think would add thrust to the walls.Really looking for comments.Thanks.

Loger rods lower the thrust angle at max cyl pressure---siameesed walls are most stable engines out there(any brand)

Dave---it was from my parents telling us kids----good night , sleep tight---don't know where they got it

Originally Posted by 1gary

Got me thinking.How stable even after using torque plates are the 400 Siamese bores??.I thought they moved around quite a bit and sealing might be a issue.Then add in longer rods which I would think would add thrust to the walls.Really looking for comments.Thanks.

well you block rock the block. i would go better then 1/2 fill but still has to big of mains and rear seal to deal with . getting a nascar crank in it that takes a small main bearing would make this block abit of a wet dream . short rods with added stroke add to side load . the 6.250 rods help rod angle out and could go way past what the block could hold with stroke and still have less side load with the longer rod......... good night.......sleep tight..........and do not let the bed bugs bite. that my dad told us sure he added to it ...i think it was mowhawk carpet add ? many moons ago. i all so like.... watch ...out were the husky go and dont you ..eat the yellow snow ... frank zappa

If you use the later 302 crank (one with 2.1 rod) you can use a set of thicker bearings for that purpose with the 400 block--if u use the smaller crank (2.0) rod you will need spacers AND thick bearings---we install 4 bolt splayed bolt caps on 2 bolt blocks and have never had a problem needing to fill one of these blocks

Dud.Didn't consider block filler.

seen them spit thru head bolt holes on a 040 over better start with a good block first . still alot of spacing thick spacer and thick bearing? upper spacers and small steel caps is the best way if you must use a 400 block with small SBC mains .still need a seal that can be made up . still would do a fill on the block but i not the builder i could make it work but when all said and done. i think your better off with a SHP dart block

SHP SHP SHP yeah----
Pat==they make a seal for this --don't know the number off head because haven't done one for a while--yes upper spacer, smaller steel( or even alum) cap (400 bolt spacing wider) but usually used whatever customer might have---

What ever happened to the days when every body wanted the big mains for more overlap from rod journal to main journal??? damn Honda and Nascar

The head bolt cracks was common point and can be prevented somewhat by putting the tapered plugs in the water holes to support the deck and then drilling to size necessary

Originally Posted by pat mccarthy

seen them spit thru head bolt holes on a 040 over better start with a good block first . still alot of spacing thick spacer and thick bearing? upper spacers and small steel caps is the best way if you must use a 400 block with small SBC mains .still need a seal that can be made up . still would do a fill on the block but i not the builder i could make it work but when all said and done. i think your better off with a SHP dart block

You're right Pat, the Dart block is the only way to go,.,,,,had my share of grief with OEM 400 blocks waaaaaay back in the sprint car days.,... On the Dart site they show the SHP Pro block, lots stronger, raised cam, etc. Think that's probably the way to go????

PS--What do you mean you're not the guy building the engine??????