For once I agree with Stu. I don"t know what he is basing his opinion on but my 5.7 stroker (397) has had no issues running 17psi.@ 6500. There are several stroker motors on the forum running 14+ psi. Driving a supercharger on a serpentine belt above 10 psi is your challenge.
Haven't got that far yet. This 6.1 block just fell in my lap a few weeks ago throwing a major curve ball in my 5.7 build. Luckily I hadn't pulled the trigger on the 5.7 kit yet. The 6.1 block/heads are at the machine shop now getting checked out. Still haven't picked a vendor yet for parts either which brings up a whole different headache. Arrington, MMX, Inertia???? Just want to start out making sure I'm not crazy for wanting to do a boosted 6.1 426. Most of the kits are very similar in bore and stroke. 4.080 stroke and 4.065/4.080 bore. I dont want to lose the oil squirters on the 6.1. though. Heard sometimes they need to be machined out do to clearances?
You will be amazed at the performance gain you will get using a cog drive. IMO, it's really a big deal and you won't regret it. I basically used my original mounting plate and cut the area the sc bolted to, leaving the rest that bolted to the engine. Then made 1" pipe spacers and bought a common mustang SC mounting plate (cheap) and bolted it onto the spacers. This moved the SC forward a 1-1/2" forward. Used a 6" diameter x 3" cog pulley on a ati balancer. Used a 3" diameter cog on the SC. Mounted a top and bottom pulley to act as guides/tensioner. Once everything was aligned/shimmed I cut the bottom pulley removing what wasn't used. The belt is relativey loose and is the original test belt I installed during assembly.
with the 6.1s keep the bore as close to stock as you can, a lot of 6.1s get thin when you get to 4.08, I had one here that was .100+/- .01 on #'s 3,5,7,2,6,&8 all on the thrust side. I told the guy I won't build that thing for a boosted engine with 4+ stroke crank not @ the 16-20lbs he wanted to throw at it. ..if he would of wanted 3.72-3.79 stroke, I'd do it,less side loading longer rod cylindes stay rounder.....soooooooooo he went else where.
all the big name Hemi guys sell good well thought out kits, only real difference is the price point.
Oilers become an issue with 4.08+ crank and big rod bolts.....
If it were me and I was dead set on Boosted 420-426 Ci I'd sell the 6.1 block and get a new BGE block and start there. with the BGE block your at 4.09 bore to start, and the added .4 of deck ht(9.28 vs 9.24) gives you better piston stability. the bores are .170-.325 thick on a stock bore BGE the SRT392 blocks(2011-2016) are .170-.250 thick so right off the bat your going to get better ring seal with the higher pressure....I've seen it a few times with 420-430CI 6.1s builds they make 50-75 less Hp than similar BGE build ,same cam profile same boost levels (16-22) the higher the boost the more power drop off . the 6.1s just don't seal as good as the BGE blocks when you get into higher boost levels with the long cranks....same with the eagle 5.7 vs the 03-08 5.7 eagle block bores are paper thin.
Now ...if you or anyone else comes across a 6.1 Block that needs sleeves, the Darton M.I.D system, is a great option....if you are willing to spend the money. on average the sleeves and machine work is about $2200-2500, which is the big con on going this route.
The Pro for going the Darton sleeve route, is bore , the sleeves start out at 4.10 and have a wall thickness of.220. you can build a 4.125 Bore with a 4in crank and that yields a 427, which leaves .2075 wall thickness , which is plenty strong , you will lift the heads before the bores distort at that thickness....Most engine builders agree a min wall of .200 for boost to keep everything nice tight at 12+psi.
you can go as large as 4.14 bore and keep a .200 wall, 4.14X4 =431Ci, 4.14X4.05=436,4.14X4.08=439......for the long term I'd stop at 4 in stroke...for the F--K it , it's only money build. I'd try a 4.15X 4.10=443.6 leaves .195..is that .005 going to matter , I don't think so.
With the 4 in crank you can use a 6.125 C to C rod, and have a piston with a pin height of 1.10 , piston will be plenty stable at the Pin Height and the rod ratio is more friendlier 1.53 vs the 4.08's 1.50, now you can use a 6.2in C to C rod which would use a 1.04PH piston, not the best for High RPM boost.
the 1st BIG NA 6.1 we did for my Nephew was 466Ci ,Darton sleeves bore to 4.2 which left us .170 wall used a modified 4.25 stroke crank turned down to 4.2, 6.1 rods and 1.035Ph pistons. we managed to squeeze 870Hp @ 7100. with BGE heads.
Man... crushing my dreams here. So I know you said keep it as close to stock but I really don't want to stay around 370 cubes. With that said what's your opinion on how far I could stroke a 6.1 respectfully? 405? 410? I know there are many combinations of bore/stroke to reach a certain CI. I'm a big fan of running optimal ported heads and pretty much everything else will be modified as well IE: intake, fuel system, exhaust and so on. I'm also leaning towards 12# boost definitely ran off a cog system.
Don't mean to crush the dream, just don't like people spending good money for less then great results. keep in mind that the 2.9 whipple drag pack cars are 354 Ci and roughly 1200hp, my friend Ray's Hennessy Demon is 1000hp at the rear wheels 18lbs and @376Ci and the 422ci/4.5 whipple i finished up for his kids Duster @20lbs is doing 1250 to the wheels.
Get the block sonic checked , and see where it's at , ideally you want a minimum of .200(+/- .01) after bore on the Thrust side of the block ., as you look at the block from the front, that's Lifter side on the drivers bank and outside on the passenger bank.
Make sure they check it top,middle and bottom, and in the 12'oclock,3,6,9'oclock positions. the walls can be thinner towards the bottom and as much as ..05 less in the other directions. 70 someodd % of the side loading is in the top 2 inches of piston travel.
Remember the longer the rod you can fit in there the less side-loading, with thin walls it's more important for longevity with a boost application.
there are and have been plenty of people who run and have ran 4.05/08 cranks with a 4.08 bore and less then .170 walls , you just have to ask your self do I want 800Hp this year and 750 next year and re build it in 3 years. or is 750 fine for the next 5 years.
also the tune has to be dead on with thinner walls, detonation can lead to cracks.
You can hard block the bottom 2 inches and regain rigidity, run areal good efficient cooling system.
3.90/4.00 in crank gets you to 404-414 with a 4.06 bore....remember with a Hemi+boost you don't need as big of a bore to make power as you would with a wedge head(lSX,SBC,SBM,SBF,BBM)
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