04CHASE Posted January 20, 2011 Report Share Posted January 20, 2011 2.00 and 2.100 are the rod journals not the legnth. the 6.125 is more commonly used and i beleive is stock legnth. i know its what i used in my build to help with oil issues but keeping the stroke down will also help. you will find alot of useful info on ls1tech. for stroker builds. Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 20, 2011 Report Share Posted January 20, 2011 (edited) Chase, i guess it depends on if your talking about the stock rod length for the stroker kit or the stock lq9 rod length. The lq9 is like 6.098, but the other way, yeah from the little i know about them most come with the 6.125 in a stroker kit. If you go with the 421 your using the longer stroke and pushing the wrist pin up into the rings. If you use the 6.2 rod your pushing the pin even further into the rings and asking for more oil problems. Good motor for HP, but maybe not for DD. From what it sounds like you want, a trouble free stroker, i would go with the 408 and the 6.125 rod. If you want to gamble a little more use the 6.200 rod instead of the increase to a 4.125 stroke of the 421. Have you given any thought to just going with a larger bore? On .060 over bore you get a 414 CI motor and still have the 4 inch stroke. .060 is not that great for holding up large amounts of boost, but for a NA motor i would guess its fine. Ask around to see what guys say. Chase what do you think about .060 over bore? Edited January 20, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
04CHASE Posted January 20, 2011 Report Share Posted January 20, 2011 i wouldnt do .060 over on a lq block. id stick with a 402/408 and if you wanted to boost/juice it you can. Quote Link to comment Share on other sites More sharing options...
Krambo Posted January 20, 2011 Report Share Posted January 20, 2011 i wouldnt do .060 over on a lq block. id stick with a 402/408 and if you wanted to boost/juice it you can. Agreed. LSX block for anything over that IMO. Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 20, 2011 Author Report Share Posted January 20, 2011 Well im really wanting to do a 421 ... not planning on shooting it any bc ill have enought. On just motor im just trying to figure on what i need to put in the bottom end.... everyone has a 408 and i like to be different (maybe not a good thing) yall are helping me out a lott i just need to know what i need to do bf i order it friday....... what do i need to get to do a 421 that might not use much oil im not doing no crazy compression or anything im gonaa use a set of. 799 heads that have been decked 15 thousandths.... i appricaye all yalls hlp Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 21, 2011 Report Share Posted January 21, 2011 (edited) The 6.125 rod will help with the potential of oil use. Also, call Mahle direct and talk to them, they might be able to design a piston for you or sell you another piston that is made for such things, or they may change the ring pack or something. Edited January 21, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 21, 2011 Author Report Share Posted January 21, 2011 Lol hopefully im not getting on anyones nerves but could i build something bigger than a 408 bit not a 421 that would have an oil ussage problem that would still be good and if so what do i need to use.... like what stroke crank what length rod and what size piston.... Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 21, 2011 Report Share Posted January 21, 2011 have you figure out your compression with the piston you were going to buy? You said the heads are decked .015 so that around a 62cc head. on a 421 ci motor with stock gm gaskets and flat top pistons with no relief thats around 12.86:1. Do you have a cam picked out/bought? If you do you need to figure out your dynamic compression first so you can order a piston with the right amount of dish/valve relief. Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 21, 2011 Report Share Posted January 21, 2011 (edited) yes but it requires a thinner cylinder wall and a 4.0 stroke. Both Chase and Kevin said its a bad idea, also Zippy says its not the best idea. My 2 friends are running lq9 blocks with a .060 over bore, NA motors, and have not had an issue yet, but who knows. How much do you want to spend??? http://www.erlperformance.com/gm-ls-stock-sleeve-short-blocks http://www.erlperformance.com/gm-ls-dry-sleeve-short-blocks as always sky is the limit with a high budget Edited January 21, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 21, 2011 Author Report Share Posted January 21, 2011 Im running a flat top that has valve reliefs i think there -3 or something like that and i was planning on using a stock head gasket bc the someone tld me that fifteen thousands wouldnt make that much of a diiference on the chamber size he said it would prob be the same comp of a stock gto Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 21, 2011 Author Report Share Posted January 21, 2011 I got 5 grand do my motor trans tun and trans wich i would have enough... and that ight u snt me it says,$3500 dollars and $1800 core ..does that mean if i snd my motor they take 1800 off the 3500 . Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 21, 2011 Report Share Posted January 21, 2011 i think it might means with out a core....add that amount. But i think youd also have trade in a ls2/3 block. if i figure it right with a 4.030 bore, 4.125 stroke of the 421 you want, with a 0 deck height and the stock gm .051 gaskets and your heads at 62cc...your going to run about 12.39:1 with 3cc reliefs. so much for not running high compression. Unless the deck height is being altered. if that compression is true you need to be carefull with your cam, so you can run a reasonable DCR. on a ls head the rule of thumb is .005 of deck=1 cc. .015 decked=3cc. 65cc head=62cc head after decking. it makes a big difference, about .43 on your CR ratio. http://www.rbracing-rsr.com/compstaticcalc.html that is the link i am using Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 21, 2011 Author Report Share Posted January 21, 2011 Well i could use a 15 thousandths thicker head gasjet then stock to bring it back dwn cant i? And appricate that site ima call tomorrow and get some more info but i guess what yall are saying is just stay away from a 421... and ur buddies that has them do they drive theres everyday Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted January 21, 2011 Report Share Posted January 21, 2011 (edited) one is an every day f-body and is a 427 CI NA one is weekend truck(SSS) and is a 427 CI NA you could also order a piston with a deeper cut in it or a dish. Yes you could get a thicker gasket but heads with quench pads, like yours, also like a particular distance from the piston to the quench pad, or bottom of head. I was told my trick flow heads want a .038-.041 distance. Not sure on yours and not sure how important it is but for optimum hp i chose to build that way. I'm also not sure if a thicker gasket hurts or helps seal ability. Maybe one of the other guys know that. I think, before you go any further you need to decide on a CI. Decide on what you want, best DD, most hp, or a slight risk shooting for both. After you decide that, the rest of the build can be picked out, like piston dish. Then you can find out the specs of the stroker kit installed in a stock deck block, like the deck height of the piston. After that you figure out compression, then add your cam into it and figure out dynamic compression. If a change is needed anywhere you can do it before you buy the parts. Edited January 21, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
built04SS Posted January 21, 2011 Author Report Share Posted January 21, 2011 I think ill be fine with it Quote Link to comment Share on other sites More sharing options...
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