I would be happy running right under, or at, 400rwhp and comparable rwtq. I also don't plan on going with a blower or even running N2O, so I was thinking of going with a lighter setup; possibly hypereutectic pistons. I will also have stock ported LT1 heads and will be running a decent sized cam in order to take advantage of the ci increase.

Any suggestions would be welcome...

 

Random thoughts:

Bottom end....

cast crank is good
KB hypers are good & pretty light
Speed pro rings are good and alot less $ than gapless
Scat I-beams are fine (with or without upgrades... up to you)
Clevite or King bearings
Melling HV oil pump ok

don't need to break the bank on this stuff.

Read the threads here on cylinder heads... send them to a pro.

Check the DCR (lots of threads on this)

A very mild cam will get you there (400rwhp) ~220 @.050.

Good luck.

-Mindgame

 

Yeah I was planning on going with Keith Black pistons and wasn't sure whether or not I was able to simply prep and polish my stock crank. As far as the connecting rods go, I've read where a 5.85" was a nice median between the stock length and the 6" rods. With my setup, would the length make a whole lot of difference?

As far as heads, I'll be having Lloyd work them over and decide at that time whether or not I'll go with Joe's cam or not. Now I have a couple more questions...

How will increasing the ci drop my gas mileage? I figure I'll be all right as long as I'm still above 20mpg with my manual. I know there will be a significant loss after the cam, but what about the bore?

Thanks!

 

Oh sure, your max piston velocity just dropped a whopping 13 fpm!

All sarcasm aside, go with the 6" rod and the lighter piston. There will be NO discernable differences in power output at this level.

Your gonna take a hit in mpg but hey... there's no free lunch right?

If you bump the compression (check out the DCR threads) and use mild cam timing, you should be able to maintain mpg on the other side of 20 easily.

-Mindgame

 

Now when you mention a mild cam in such a setup, what sort of numbers are you advising? (duration, lift...)

 

I also found this in a previous thread...is it true that in order to achieve 377ci that a bore is needed along with stroking?

"The amount of displacement gained by increasing stroke is more significant, although it also eventually becomes relatively static as the increase in stroke becomes a smaller percentage of the original."

"377 CID = 4.00" bore, 3.750" stroke (+27 cu. in.)"

"Formula: bore^2 x stroke x # cylinders x 0.7854 = CID"

 

The formula is correct: 4.000 bore and 3.75 stroke gives about 377 cubic inches. If you have a used block, however, you'll need to bore it to clean up. .030 oversize is a normal overbore with lots of pistons available. That gives you about 383 cubic inches.

Because the bore diameter is squared to figure displacement, increasing bore a given amount is much more significant than increasing stroke the same amount. It's easy to stroke .270 (3.48 to 3.75) or much more, but it's difficult to increase the bore of a SBC very much in a stock casting. Some aftermarket or Bowtie blocks let you go about 3/16 over the stock 4.000 bore. So, effectively you can get more cubes in a SBC by stroking.

FWIW, using a .030 over bore in a 400 block (4.155 final size) with a stock 350 stroke (3.48 in.) gives about 377 cubes. That got you the 27 cubic inches with +.155 total bore, but it took +.270 stroke to get there.

Go figure.

 

So could someone explain what exactly needs to happen in order for me to achieve 377 cubic inches out of my stock LT1 350? Would I have to follow the 377 CID = 4.00" bore, 3.750" stroke in order to achieve this?

 

To keep it to 377 with a 3.75 stroke, you really can't replace pistons, which you really should do for the stroker. If you replace pistons, your need to enlarge the bores or at least resurface them. This means your finished bore size would be larger than 4.000, and your engine would be larger than 377.

OK, you COULD reuse the stock pistons, put in the 3.75 stroke crank and use 5.565 long rods. That's kinda how Chevy made the 400: they used the same compression height piston as the 350, and shortened the rods by 1/2 the stroke. (Oh yeah, they recored the block and bored it .125 and picked up another 23 cubes). To confuse things even more, GM's 383 crate engine has a 4.000 bore and a 3.80 stroke crank. So it's really a 382, right?

IMO, this (stock pistons, short rods) would be a dumb thing to do, but it would give you a 377. If you went to aftermarket pistons .005 oversize you'd get a 378, but you could use 5.7 or 6.0 rods, but the pistons would be costly. So why not do the standard thing: bore .030, get a shelf piston and rod and crank and go with a 383? If you just want to tell people it's a 377, LIE!

One more way to get a 377: .030 over bore and a 3.695 stroke (special) crank. Now this would be the expensive way to go. Shades of Nextel Cup engines which have an absolute maximum displacement of 358.0 cubes. Now they use big bores, around 4.180 or so and short strokes, but to reuse a block let's say they hone it out .005 every rebuild. To get 358.0 cubes, here's a few bore/stroke combos: 4.180 x 3.26; 4.185 x 3.253; 4.190 x 3.245; 4.195 x 3.237. You get the idea. None of that makes sense to me for a street engine, but in a Cup engine everything is purpose built so ANY crank stroke is available.

Keep on walking...


My $.02

 

I am going to pressent a slightly different pint of view on this, which I have come to recently. A 30 over bore may not be the best way to go. Production blocks have pretty thin cylinder walls. At 30 over, and certianly by 40 over, most blocks are getting to the point where the cylinders may be thin enough to cause problems with ring sealing, due to bore distortion. This is especially likely with very high-po buildups. So, once you have gone 30 over, you are only leaving enough material left for perhaps one more overbore.

OTOH, as was pointed out, the best selection of off the shelf pistons are in the 30 over size. OTOH, there is a fair number of OTS 10 over pistons. And a 10 over "custom" is not all that much more expensive than a 30 over piston. At 10 over, you are leaving plenty of material for future overbores and the thicker cylinders will improve ring seal (or even outright splitting of the wall). Of course, you lose ~6ci with a 10 over v. a 30 over build.

I think a nice combo would be the 3.800" GMPP forged crank and "custom" 10 over piston with the correct CH for the rods chosen. That would be a "384".

Rich

 

Interesting. Tell me a bit more on this idea of yours... (ie. what length rods, specific piston, rings, etc) What sort of goals would one have if they happened to go such a route?

Thanks for the insightful replies guys. Keep them coming!

 

Well, it's just a thought. That GM crank seems like a nice piece for the $$$. The 3.8" stroke give a little bit more displacement than the typical 3.75" in a 383 and avoids the potnetial clearance issues of the 3.875" 396, sort of splitting the difference. I don't know enough about your plans to recommend a specific piston. But once a "custom" piston is selected having them drilled to the desired compression height is part of the price for a custom. Which, as I said, is not much more than the price of a top shelf catalog size. Now, if you planning a real bargain motor, you probably don't want premium pistons anyway.

With a 9.000" deck height and a zero deck you would need a 1.100" CH piston with a 6.000" rod, a very reasonable combo provided you were willing to go with a custom piston. No huge advantage to the whole thing I guess, just a little different and quite workable.

Rich

 

As I mentioned previously, I'd like to keep the entire rot. assembly relatively light. I've heard nothing but good things about the KB hypereutectic pistons so wouldn't mind looking in that direction. As for a crank, I'm open for suggestions. I plan on staying N/A and ideally would like to see ~400 to the rear wheels.

Thanks!

 

Sometimes these threads can take a strange twist. One minute we're talking about a 400rwhp budget build and the next we're on to custom pistons.

If you only go .010 or .020 over, no big deal... use the the minimum overbore necessary, get it all sorted out and on with the stuff that'll make the real difference in output. KB's ~$25.... a custom to work with the 3.8" crank ~$70.

Good luck.

-Mindgame

 

I never said this would be a budget build, just something that's going to be very streetable and will put down considerable power. As I stated, I don't want my gas mileage to drop below 20 mpg and I know a lot of this can be compensated in the tune itself. I'd also like to keep the cam below something like a 230/236. Lobe separation makes no difference to me and I'm aware that the closer the LSA is the less streetable the cam will be? I wouldn't mind a .110 LSA as long as the surge can be controlled via tuning.

FACT 1 - I definitely want a lightweight rebuild (hypereutectic pistons, lighter rods, etc)

FACT 2 - I don't want my gas mileage to drop below 20 mpg highway considering I have a manual.

FACT 3 - I'd like somewhere in the vacinity of 400 to the rear wheels with comparable torque...extra torque from the higher displacement isn't particularly necessary...