cdrod

Hey guys, What's the most torque I can get out of a stroked small block? I've heard the phrase "there no replacement for displacement" but I just don't want a big block. I'm looking for lots of torque and don't want to rev past 5500-6000 rpm for a daily driver.

oldsmobiledave

You need to be more specific about the engine build to get an accurate answer. What heads, compression, valve train, piston etc are you willing to pay for?

captjim

That is a tough question to answer. You can stroke a 403 (which is a small block) and get big block inches. But, a well thought out 10 to 1 375/380 should put out torque in the low 400 neighborhood. Mark has dyno'd some of these, perhaps he will chime in.

oldcutlass

The term big and small block in the Olds sense is a misnomer. The dimensions are pretty close with the 455 deck height being a bit taller. HP/tq has a direct correllation to $$$$ spent. 400-425hp/440-450 tq is a reasonable expectation from what I've read in the past.

cdrod

I never thought about stroking the 403, I guess you'd end up with about 417-418 cid with a 3.5" crank throw. How much can you overbore with the siamese cylinders? Is a 403 strong enough to stroke with the windowed mains and all?
Here's more details about my build:
1. I want to build a motor with a 1500-5500 power band, street driven car, want lots of torque, don't want to rev the s**t out of it.
2. I have a set of Mondello-built ProComp heads, but my engine builder is concerned about the increase in intake runner size. My stock #7s have 160cc intake runner, the ProComps have 188cc.
3. Performer RPM intake with 750cfm Q-jet.
4. TH200-4R trans with 3.42 posi rear-end, 1800-2000 stall convertor.

captjim

Not sure I understand this line of thought. The BBO is taller, wider, heavier, uses a different crank and heads, different mains, etc. It is "bigger" is almost every sense. perhaps the difference is not as pronounced as a Chevy or Ford, but it IS "bigger".

oldsmobiledave

The 85-87 442s used a 2400 stall converter fro the factory and you should too. A 403 mildly bored with a 330 crank and good heads and valve train and 9.5:1 compression will meet your needs and be fairly cheap to build. Look at some of Dr Dan's builds.

oldcutlass

Thats basically what I meant.

z11375ss

Why don't you just put in a 502 Chevy and be done with it?

captjim

Just my opinion, but the strength and simplicity of a 350 stroker (375/380 cubes) makes it a better choice than a 403 stroker. The cylinder walls are sooooo thin. Honing is tricky. Stick with the 350, use 400 SBC off-the-shelf parts, easy-breezy.

captjim

Because he isn't an idiot!!

70cutty

Why don't you want a big block?? It's the best option for power. Even a j-headed 455 will be much more fun than a SBO for a lot less $$$$.

oldsmobiledave

If you took my 470 cid SBO for a ride you would change your mind in a hurry.

captjim

Please explain this statement. How is a J-headed 455 a LOT less than a SBO?

cdrod

Talk like that is just ****-stirrin'

cdrod

OK, I'll bite. How do get 470 cid out of a sbo?

oldsmobiledave

With a diesel block and a stroked 425 crank.

cutlassefi

You can make 425lb-ft of torque pretty reliably with a 380 small block.
If that's enough for you then go with it.
However if you're looking for upwards of 500lb-ft then more cubes will be in order. You could do a stroked 403 at that point but I'd take the next step and just do a DX.
I do mostly big blocks but that's the way I'm headed, a DX. Not sure what your budget is but it's another option.
And tell your builder to look at low lift numbers. A Procomp head flows about 20-30% more than a mildly ported 5, 6, or 7 head starting at as little as .100 lift. That tells me port velocity is not an issue.

coppercutlass

I don't have tq. Numbers but my 10 to 1 355 with iron heads ( not ported ) , th350 3000 stall and 3.73 gears will roast them from a 20 mph roll. If I flat foot it or even just jab the pedal it will just light the tires up. My car is once again all steel . Some might not consider my set up "street friendly" but it pulls enough vacuum for power brakes , idles great , the slippage of the 3k rpm stall converter is very minimal around town to be honest. The only thing that would bug some is the rpms at highway speed . But I have had 3.42's and 3.73's and to be honest I'm happier with the 3.73's despite the slightly higher rpms at highway speeds. That's just my experience with my small block.

rootney

What size rubber you runnin?

cdrod

Mark,
We cc'd the intake runners and the ProComp intake runner is 28cc bigger than stock; I just don't see how this works for my low-rpm street motor. My builder feels like the ProComps will "want" a higher rpm power band (2500-6500) and the HP/TQ peaks will be higher as well. I guess I don't understand how the low flow (.100) numbers prove adequate port velocity. A bbo iron head and a sbo iron head in stock form both flow about 50@.100, yet it's not recommended to run bbo heads on a sbo. So what's different about the ProComp head?

I know you've built several of these sbo strokers and your advice is based on personal experience, so where will the torque peak be with a 375 cid sbo using the ProComp heads? What do I need to do to get the ProComps to pull strong from 1500-5500? With the OD trans, a lock-up convertor and my gearing & tire size, I should be right at 2000 rpm @70mph. Shouldn't my cruising rpm be in the power band?

Rootney:
I'm planning to run a 265/40R17 or maybe even a 285/40R17 tire in the rear with stock (boxed) suspension arms and stock rubber bushings.

cutlassefi

The Procomps are pretty tight at the pushrod. That'll add to the velocity.
Torque peak will depend on compression, intake, carb, exhaust, cam, cam timing, overlap etc.
If you're concerned about torque and contemplating doing a stroker, then I'd go all the way to the 3.600 stroke with a Honda Journal. Use the shortest rod possible with the available piston. That will help the torque come in a bit sooner.
The bowl area on the Procomp is the single biggest difference vs bb stocker. That's very important for consistent/quality flow on any head. For a 380 or so engine I wouldn't think twice about using the Procomps.

cdrod

Can I make 400 lb-ft at 3800 rpm with the following build?
CID=375
CR=10.5:1
Hyd. Roller Cam
Cam: dur=221/229@.050", lift=.549/.565, LSA/ICL=112/106
ProComp heads w/roller rockers
RPM intake
750 Q-jet
1-5/8" headers

cutlassefi

Yes, but I'd squeeze the lobe sep to a 110 or take some exhaust lobe out of it.

cdrod

What exactly will this do? Are these changes because the PC head has a better exhaust port?

cutlassefi

It will lower the rpm at which you make peak torque.
And no, it would be done strictly to better achieve your goals. Has nothing to do with head flow.

cdrod

Would it help my build to advance the cam 2-degrees instead of installing it straight up? Wouldn't that lower the TQ peak a little?

cutlassefi

No not really. If you advance the cam you're also advancing the exhaust opening. I'd rather reduce the exhaust and put the intake opening where I want it.

70cutty

You can find a running 455 for $1000 or less, to build a SBO to have similar TQ will cost you a lot more than $1000.

70cutty

How much did it cost you build that 470??

oldsmobiledave

From carb to pan it would cost you about $12k to duplicate. That assumes you have to buy everything. If you get a deal on a diesel block and a 425 crank and buy a used set of heads and intake then the costs are down. If I was to re-do a stroker SBO I would use a billet crank which of course adds to the cost.

Wise Performance

Made 714 TQ with a 465ci SBO N/A to answer your question.

oldsmobiledave

My chassis dyno session shows 552 TQ and 555 hp as peak numbers. Not bad for 11.2:1 compression engine with a flat tapper cam on 94 octane.

captjim

That is disingenuous. Yes, he will have a "running engine". At best it will be 40 years old with who knows how many miles. It will not be a fresh engine. Let's keep it apples to apples.

olds 307 and 403

Remember he is also wanting decent mileage. If he keeps it low-mid 9's compression, smaller can and added stroke, it will be plenty fun. The 350 seems to get much better mileage than 455's, even mild ones. A 403 with a .040" overbore and a 3.5" stroke equals 425 cubic inches. I have the rotating assembly in my basement, block needs machining. I am going to play with my current 350, maybe build it in 2016.

oldsmobiledave

Miles per gallon are over rated. It is all about SMILES per gallon.

jensenracing77

I had a snappy 350 with a 4 speed, 3.42 gears and was getting 16 MPG. I know it was not 400 tq but still a very quick fun street car. I would sure think you could get at least 16 MPG with a hotter engine and a 200 4R transmission.

bccan

My basics listed below, docile @ low throttle settings, 91 octane, can probably pull close to 20mpg on highway if I could drive it less than 80. Hope to run high 11 if I can keep Qjet fuel bowl full past the 1000' mark @ strip (I'm workin on it). BUT it has a lot of thought, time & money spent to get there. You won't get all this cake & get to eat it too with a run of the mill 350-380 build, simply can't have it all. You could do it w/ BBO for a bit less money.

That opinion stated, you can still build a really fun 350ish engine pushing 350hp, maybe 400 tq that will be quite bearable to drive with a little bit of gear & especially w/ manual trans.

cdrod

Can anybody else share thier experience running ProComps on a mild small block build? I really want to use the aluminum ProComps but don't want my engine to be lazy in the low rpms.

olds 307 and 403

The port velocity is supposed to be very good on out of box Procompo heads. Procomp's low lift flow numbers are better than factory #7 heads with big valves added. You can push 390 cubic inches with a 4.155" bore, Honda rod journal and 3.6" stroke. 4.125" and 3.6" stroke equals 385 cubic inches.