I was looking around and thought that 391ci would be more fun than 383ci.
I was going to take the 350 block bore .030'' over and getting the(forged, 3.75'' stroke)383 crank reground .080'' off center for more stroke. For a total of 3.830'' of stroke and 391 cubic inches of displacement.
Forged 6.000'' H-beam rods are going on that crank.
With forged flat top Al pistons with 1.100 compression hight.
I was figureing that you have a 2.100'' rod journal and you take .080'' off it's still 2.020'' thick.
I was thinking of going with a 244 dur @ .05'' or so cam with around .530'' of total lift caused by 1.6 rockers with big 110+ lobe spacing.
Toped off with a pair of those soggin-dickey vortec heads moded for lift(.550'' I think) with a 2 plane intake and a 750+ cfm 4bbl carb that has a nitrous oxide wet plate under it set for around 100-125hp.
Now I realy don't know how much power this will make, at least 470hp(@ the crank shaft)I'm thinking?
And with that 3.830'' stroke how fast should I turn all this at the max?
How strong is this set up?
I won't take it over 600hp, spary included.
I can't realy find any info in 391's.
Are they a 383 with 8 more cu.in. or a totaly different machine all together?
Any one know how much it would be to get the crank reground off center like that?
I hear it's kinda cheap.

------------------
Seth
1985 Camaro
2.8L T-5 3.42LSD
Put hole in side of oil pan.
Mods, internaly balanced 88' 2.8L.
91' RS 3.1 5spd, wide open 3.23's

 

I'll display my total ignorance of the benefits of a 3.830" stroke "391" and ask why you don't just buy a commercially available 3.875" stroke crank, and build a 396 like everyone else?

------------------
Fred
94 Formula A3: 381/TH400/N2O

Advanced Tech Posting Guidelines
Detailed Mod's List
11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year

 

I agree....alot of extra work and money for no strength/performance gain. The only thing you would be able to say is that you had a 391ci motor. Makes no sense to me.

Just do a 3.75" or 3.875" stroke crank and whatever bore.

Jason

 

My original setup was a 391ci (390.5) 4.005 bore, 3.875 stroke. But like everyone else was saying. Why not just buy a 3.875" crank and save yourself the money and hassle.

 

I like creativity, so here's what it'd take for me to build something like this:

- a 3.75" crank sitting on the shelf,
- a source for inexpensive machine work to offset grind the crank,
- and some inexpensive pistons to make the combo work.

Now, maybe I don't have a crank sitting around, but cast 3.75" cranks are cheap. I don't recall the cost for offset grind the journals, but maybe $300 would cover the cost of the crank work (maybe not). So far, you've got less than $500 in the crank - great! Now, the pistons would be tricky, as a set of custom forged pistons could easily run $750. That doesn't blow the budget, but you could get a Cola 3.875" crank and some off-the-shelf JE/SRP pistons for the same money that you've got into your custom-ground crank and pistons - now you're talking about building a full-on 396 and getting a better crank in the process.

So, there's my take on it. Personally, if I'm looking for the most power on a budget, I'm going to build a 383 using off-the-shelf parts. That'll also be a cheaper engine to fix if (when?) something lets go.

------------------
1996 Impala SS - LT4 396, T56
1996 GMC K2500
1992 Buick Roadmaster Estate Wagon

 

A 3.875'' crank shaft.
I'm haveing a little trouble finding one.
Where do you find them?
What would the compression hight for the pistons be with 6'' or 5.700'' rods?
I lost my paper with all my engine math formuls.

------------------
Seth
1985 Camaro
2.8L T-5 3.42LSD
Put hole in side of oil pan.
Mods, internaly balanced 88' 2.8L.
91' RS 3.1 5spd, wide open 3.23's

 

http://www.amsracing.net/lt.html
http://www.callies.com/
http://www.fastpts.com/hazel-doc/colahome.html
http://racenet.net/f-body/engine.php

Summit and jegs sell the cranks on there as well. Might go through them some

Steven

------------------
383 Inches of stroked turbocharged fun.
If one is good shouldnt 2 be great?????
TURBO=TORQUE
TORQUE=FUN

My Car