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-   -   Optimal Stroke for Big Inch SBC (https://www.hotrodders.com/forum/optimal-stroke-big-inch-sbc-515282.html)

tyler2you 06-22-2018 12:17 PM

Optimal Stroke for Big Inch SBC
 
My plan is to start accumulating parts for a big inch SBC build over the course of the next year or so. Engine will be going in a 64 Chevy II with 4.11:1 gears and a TH350 (car is around 3000 lbs. with driver). Here's what I'm looking to accomplish:


- 80/20 street/strip with good street manners
- Strong torque from 2500 to 4500. Thinking something in the 500 lb ft/500 hp range. Don't want to have to spin it over 6000
- Solid reliability/longevity
- Can run on 91 octane

I've been looking at configurations and am unsure what is ideal. I am planning to use a Dart SHP block. I've read that some recommend the shorter stroke engines with a larger bore to reduce side loading on the pistons and increase longevity. Is that an issue? These seem to be the popular configurations, any other configurations I should be looking at?

3.48" stroke:
377ci (4.155" bore)

3.75" stroke:
383ci (4.03" bore)
406ci (4.155" bore)

3.875 stroke:
421ci (4.155" bore)
423ci (4.165" bore)

4" stroke:
427ci (4.125" bore)
435ci (4.155" bore)

techinspector1 06-22-2018 01:32 PM

A 355 with a blower making +40% over the naturally-aspirated power thinks it's 500 cubic inches. Mounting a blower would likely be cheaper than what you are proposing and you wouldn't have to go stupid on the cam. Forged crank, pistons and rods at 8.00:1 and 8 psi with two 600's should do it. Keep the cam short on the intake side and you could likely use an AOD. I'd sure like to see somebody do this.

tyler2you 06-22-2018 01:39 PM

Quote:

Originally Posted by techinspector1 (Post 4600322)
A 355 with a blower making +40% over the naturally-aspirated power thinks it's 500 cubic inches. Mounting a blower would likely be cheaper than what you are proposing and you wouldn't have to go stupid on the cam. Forged crank, pistons and rods at 8.00:1 and 8 psi with two 600's should do it. Keep the cam short on the intake side and you could likely use an AOD. I'd sure like to see somebody do this.

Thanks for the suggestion. I've got no experience with forced induction and am a little afraid of the learning curve involved and potential for disaster--what type of blower would you suggest?

OneMoreTime 06-22-2018 03:53 PM

The blower on a 355 will be a lot less intimidating than doing the big inch small block when you consider the damage to your wallet.

Tech is talking about a roots style blower such as a 6-71 on a small block. Of course you will need a hole in your hood to acommodate the blower..

Sam

68NovaSS 06-22-2018 03:54 PM

There are many boost options, turbo, roots, etc. What you select depends on what kind of performance and appearance you want.

Like Sam said, a roots 6-71 will give you that "in your face" look, others can be much more discreet.

What's to be afraid of? It's all in the build and tune. Like Tech said, a lot of bang for the buck.

tyler2you 06-22-2018 03:59 PM

Quote:

Originally Posted by 68NovaSS (Post 4600458)
What's to be afraid of? It's all in the build and tune. Like Tech said, a lot of bang for the buck.

That's exactly what I'm afraid of--getting the tune a bit wrong and ruining a motor. I'm probably overly concerned. It just seems like there's a lot less room for mistakes on timing, mixture, etc. with a forced induction setup.

eric32 06-22-2018 04:16 PM

I can tell you that a dart 377 shp is a very nice build as I just got done doing one but I spent over 8 grand on my build but I used a lot of arp hardware and that is including shop cost and some accessories and other things on my build below. The 377 is not a whole lot difference between it and a 383 except the 383 would make a hair more torque but a little less power on the top end but your talking about maybe 10 hp and torque between the two.

The thing with the bigger cubic 400 plus inch stroker motors is with the having to use a small base circle cam shaft and also having proper clearance in the block for a 4.00 inch stroke. The shp block will clear a 3.750 stroke but anything more then you have to have a bit of work done and to me it is not something every machine shop would be able to do if they don't do performance builds.

Mine is pretty snappy and makes power just over 6000 rpm and has a ton of torque even though I am running a single plane intake with a 1 inch tapered spacer and runs nice and does decent for street manors and I have over 14.5 inches of vacuum in park. Mine sits in a 96 chevy s10 with a 2800 to 3200 stall converter with 3.42 rear gears with a 350 turbo transmission and a posi unit. Truck runs strong and really picks up at 2500 plus and is not soggy on the bottom end at all.

I can cruise at 65 mph at about 3000 rpm right in my cam power band and at about 2500 rpm at 55 mph

Dart shp block 4.155 bore x 3.480 stroke. Block decked and using arp main studs.

276/280 228/[email protected] 547/547 lift 107/110 lsa custom Mike Jones
Hydraulic roller cam

Howards .750 wheel sized hydraulic roller lifters. Run over $800 bucks

Dart pro 1 platinum 200cc heads ported and gasket matched and bowl blended

Edelbrock victor jr intake that is gasket matched and cleaned out and ported for most flow possible.

Scat forged crankshaft and scat H Beam rods with Icon forged pistons flat top
Pistons.

tyler2you 06-22-2018 04:39 PM

Thanks Eric, that's great info.

I've got a pretty hot little 360ci SBC in it now. It's probably a solid 400 HP motor, so I want to do something that's going to be a significant upgrade. Current motor is fairly high compression (11:1) and the block has a repaired starter mount that may not last so it's probably not a good candidate for power adders or other upgrades. Putting together a 355 for a blower may be the way to go.

What kind of power numbers do you think you're getting with your 377 motor?

eric32 06-22-2018 06:53 PM

With unported head flow numbers Desk top dyno says a hair over 500 horse and torque but I think that is a little bit over stated a hair before ported heads and stuff. I based my 377 off of a crate motor that had a similar Howards hydraulic roller cam like mine but a little smaller and with lesser flowing entry level skip white NKB aluminum un ported heads then my dart pro 1 platinum 200cc heads and with similar compression it was rated at 480 horse power and about 475 ftlbs of torque. Dart had a 372 (4.125 bore x 3.480 stroke) that had a flat tappet cam with low 220's @ 50 duration and forget the lift and it was rated at 470 hp and torque as well.

I had my dart heads really worked over well as well as my intake so I should be knocking around the 500 mark give or take a little bit. I can barely touch my throttle and once I am past 2500 rpm it gets up speed like nothing and it replaced a 350 that had about 375 to 400 hp at the most and about 425 ftlbs of torque. It has made quite a night and day difference in power and the 377 with the short stroke and big pistons really flow the air well and the nice short stroke and less thrust on the pistons compared to other combos and it sure does snap the throttle really fast and reves pretty good.

64nailhead 06-22-2018 07:57 PM

Your goal of a sub 6000 rpm build with good street manners AND 500HP/500ft lbs is EASILY accommodated with boost. So easy in fact that you grab a 2 bolt stock block and bolt on a set of chinesium heads, with stock rods and crank and the lowest budget forged slugs out there for a mild boost build.

But I've read your responses to a boosted build, so back to the NA build. If you have the budget, which you'll have to have, then use the SHP with a 3.875 stroke if you don't want to clearance the block and a 4" stroke if you can handle clearancing the block and leave it at the original bore only because it makes sense to save a couple of overbores for later. But if you must bore a brand new block, then go .060 as the SHP should take .080-.100 later. Either way you'll be into the 414-440 range, and you're going to need all the cubes you can get. From there buy the best heads available - AFR in the 210-215cc range and grind a custom hydro roller with gobs of lift in mid 230's. Top it off with a 780-850 cfm carb. I'd estimate a minimum of 7k in parts and most likely 10K. The secret is going to be in the cam to make it streetable - it will be s tricky grind IMHO. Vinnie has a 434 that makes north of your HP goals by a fair amount and IIRC is north of 10K in his build from more than 5 years ago. He has a humongous cam that I don't believe anyone would consider daily driver friendly. Hopefully he throws in his two cents before too long.

Now, onto my turbo story and recommendation - I have a 327 with a TPI (limits rpm range to low 5000's) with a chinesium 76mm T4 that makes 500 whp at 14 psi, got 19 mpg in a 3600lb car and purrs like a kitten with little 205 degree custom ground hydro roller cam. The entire build with electronics, fuel system and a decent set of small Profiler heads was less than what you're going to spend to do this NA. The entire setup was a joy to drive, fit under the hood and would smoke just about anything on the road other than something well built and thought out.
If I was to do another turbo build with a mild 500whp (600 crank) goal, then I would exactly what I described in my 1st paragraph and top it off a budget intake and a Holley Sniper TBI setup - BAM, done for less than 5K with the kind of reliability your looking for. And if you want to be even more budget friendly, then any 5.3 with the same chinesium turbo setup - $3500.

With all of this said, there is nothing wrong with your NA build, but it will be a ton of money and remember that that is a lot more bang for your buck out there. You could take the money left over and upgrade the rest of the driveline or brakes and suspension.

My two cents and best of luck to you - Jim :):)


p.s. - boost is nothing to be scared of, just need to know some basic items inorder to handle it.

vinniekq2 06-22-2018 11:16 PM

Consider my next plan if I can find a Chevy II
3.62 stroke with shp 4.155 bore and Spier 210 cc heads ( Ill let Jim pick the cam)
should make way north of 500 hp

As Jim mentioned above I did spend over 10k but I bought things like Jessel split lift shaft mounted rockers and other decent gizards. I also used a "solid" roller that most people do not use
put an 850 and big headers on it and drive it to work when gas is on sale,,,

tyler2you 06-23-2018 05:49 AM

Jim--thanks for the advice. The turbo approach does look appealing, but it appears it would take quite a bit of custom fab work to get it done on my car. Heck, it was hard enough finding a set of long tube headers for it that actually fit without bashing for the pan kickout, starter, steering, etc.

I like the idea of the Weiand Pro Street 177 blower as it looks like it could fit under my cowl hood and I see several builds on the net where folks are adding 6-9 psi of boost for 80-250 HP. It appears most of them are running 93 octane when the boost gets above 6 psi with a base 8 or 9 to 1 compression ratio. At 9 psi and above, it looks like race gas is required.

Looks like I need to put together a spreadsheet and lay out the costs for a few setups.

techinspector1 06-23-2018 02:52 PM

Quote:

Originally Posted by tyler2you (Post 4600737)
Jim--thanks for the advice. The turbo approach does look appealing, but it appears it would take quite a bit of custom fab work to get it done on my car.

I was just thinking that if you lived anywhere near a diesel muffler or exhaust shop, they would have all the equipment and expertise to fabricate and weld up the whole mess for you.

tyler2you 06-23-2018 03:26 PM

Quote:

Originally Posted by techinspector1 (Post 4600853)
I was just thinking that if you lived anywhere near a diesel muffler or exhaust shop, they would have all the equipment and expertise to fabricate and weld up the whole mess for you.

Funny you mention that. We had a great muffler/exhaust shop in town up until about a year and a half ago. The guy retired and left us with a few Midas shops and one mom and pop place that thinks 2 and a quarter inch pipes are huge and can kink and bend turns with the best of them.

tyler2you 06-25-2018 05:32 PM

I've been reading up on supercharging/turbocharging and the more research I do, the more I think something like this might be a better option for me:

https://blueprintengines.com/collect...cts/gm-454-ps2

563 HP / 545 FT LBS with a 30 month/50,000 mile warranty. I'd be interested in seeing the dyno plot to see where this thing makes power. Only drawback is I'd have to save my pennies for a while and couldn't piece it together a little bit at a time.

I see so many cases where someone makes a mistake with timing, fuel ratio, or gets some bad gas and does permanent damage with a boosted platform. The NA approach just seems to be a lower risk approach, albeit at a higher cost per HP.


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