SHP dart block build, a discussion

[73Nova]

Im strongly considering building up a new short block for my Nova in the name of torque and drivability. Ive kind of come to the point in my "hot rod life" where a giant cammed, small inch, 7,500+ rpm motor isnt what i enjoy for a drive around town, to work, to anywhere really. { Eric68 if you read this there will be no need for an "i told you so"} Yeah the thump and boom this motor makes is sweet and it pulls like a bitch through 7500 rpm but its really a pain when i get down to it. Basically im looking at an increase in cubic inches and a decrease in rear gear. This car will only be raced a few times a year and really just for fun, it will see more street time than anything. So heres where the questions start.

My current car/combo looks like this
-350ci sbc, 11:1 compression
-200cc racerites
-team G, 750 mighty demon
-296/302, 258/[email protected], .562/.562 on a 108
-1 7/8" x 3 1/2" super comps out a 3" x-pipe and dynomax ultraflo's
-Richmond 5 speed
-9" rear with 3.89's, when coupled with the 1.24 4th gear makes a "4.82 rear gear"
-Nova weighs 3500 with me in it

I guess my first thought was to get a SHP block from dart, stick a 4" scat crank/rods and srp pistons in it and make 427". Then reuse the stuff i have on the top right now, maybe go to a nice hydraulic roller or possibly keep the cam I have in there now. I dont how know well it would work though. I know the 200 cc heads would be a limiting factor but how limiting would they be? Would this thing take a crap at 5000 rpm with the small cross section on those heads and 427 inches? What would YOU do for a build here? Now remember im not rich,i dont really have a budget per sey but im not going to be buying a set of 2500 dollar heads, although later on down the road that may be a possibility.

So i guess heres my questions.
-1. If I went 427" and reused my 200 cc heads how limited would this thing be? Would it be a stump pulling turd?
-1a. If 427 inches is not going to work well with 200 cc heads, would 400 inches be a much better idea? Would i be giving up much power going with 400 inches?

-2. If I reused my current cam would the cubic inches calm it down a bit or would it still be a "testy punk"

-3. If I reused everything, what kind of power and RPM numbers would i be looking at with 400 inches/427 inches?

-4. Would i be much better off power and drivability wise to drop back on my cam profile. Lets say for sake of arguement i set my compression at 10.5-11:1.

Whats say you??? Let the opinions roll in and feel free to give your ideas that i may not have come up with. Im open to them all.

[SS4REAL]

Re: SHP dart block build, a discussion

I am fairly confident that the new Dart shp block cannot accomodate a 4" stroke.. And I "think" it is good to
a 4.155 bore.. So, if 3.75 or 3.875 stroke is used you will be in the 406-415 ci area provided
you don't bore to the max
IF you want 4 stroke, go with the dart little M block or the World Products block..
I really like my Little M with 400 mains, 3.875 stroke. When NA I had it in my Monte Carlo SS
with a 238/242 crane hyd roller retrofit set up, 10.5 comp. Dart 215 heads..
Was really nice with 3.70 gears, 2400 stall, 700r4. Would idle at 800 rpms all day.
I think if you stay small, like 415 ci, your 200 heads would be fine. Just dont go really
big on the cam.
Your Nova is 400 lbs lighter than my Monte, so even 3.50 gears would be fine if you have 1:1 5th
gear youll have a nice driver.

[SS4REAL]

Re: SHP dart block build, a discussion

addition: I think your cam is still too big for a street engine... but yes, you'll gain a couple
of inces of vacuum with more CI
Your 750 would be fine.. just give it 1-2 sizes larger jet on secondary.. maybe same
on primaries with smaller cam.
I ran an 825 mighty demon, but could have used a 750.
My engine ran great on 91 octane, even when I'd add a 150 shot..!!

[73Nova]

Re: SHP dart block build, a discussion

Ok so lets say i decide to go with
-4.125 bore
-3.875 stroke {415ci}
-aprox 10.5:1 compression
-200cc racerites
-super victor
-750 mighty demon

Lets pick out a general guide line for a cam

I kind of want to run a hydraulic roller. Since i can get most of the parts out of the junk yard it really cuts the cost there. What would you run for a h/r cam? Remember this is a 5 speed car that weighs less than 3500 lbs with me in it and no power prakes. I was thinking somthing around 290/296 advertised, 242/[email protected] around .600 lift on a 108 Wouldnt that be pretty darn driveable with 415 inches? Or would that be too much cam with my heads being on the small end?

[GibTG]

Re: SHP dart block build, a discussion

An eighth inch longer stroke won't fit? I thought GM blocks could handle a 4" stroke with enough work...

Assuming the port centerline length of your heads is approximately 5.3 inches theoretically the average cross-sectional area should be good to around 6000 RPM for a 414/415 cubic inch engine. The manifold face should be about 6.5% larger than this area and the valve throat area should about 15% larger, but even though the theoretical area at the valve throat would suffice for a 6000 rpm engine a valve this size is still small for a 4.125" bore and 23° angle - so 6000 rpm may be slightly optimistic.

I would cam somewhere around 285-290° at the seat for a hydraulic roller on narrow lobe centers. You may want to employ some higher-than-stock rocker ratios as it would probably be the only method of getting a decent amount of lift. This may require address valve control issues though as you will have a fast valvetrain for a hydraulic roller.

Comp's "thumpr" cams, as much as I hate the marketing, may be worth a look since you could get a 107° lobe separation angle that your small-valve 415 would prefer, their only downside is the huge dual-pattern spread making them seem quite large overlap wise.

[73Nova]

Re: SHP dart block build, a discussion

The valves are a 2.055/1.6 btw

[Freiburger]

Re: SHP dart block build, a discussion

I am fairly confident that the new Dart shp block cannot accomodate a 4" stroke.. And I "think" it is good to
a 4.155 bore..

A STOCK block can be massaged to 4.00, why not the SHP? And the SHP is advertised to 4.165 and I'd be ok at 4.185 in some cases.

[GibTG]

Re: SHP dart block build, a discussion

The valves are a 2.055/1.6 btw

I was going off of Brodix numbers. Did you install the larger valves?

[yellomalibu]

Re: SHP dart block build, a discussion

IMO, a 406 or a 427 street motor would absolutely love the 200cc runners of your heads. The added bore and stroke would increase the velocity, giving you excellent throttle response and lower rpm torque and driveability.

The 258/[email protected] camshaft will still be pretty radical for a true street cam, although the extra cubes will calm it down some. If you could find a hydraulic roller with about ten degrees less duration, that would be a better choice for a street car (again, IMO).

The signal the carb will "feel" from the added bore and stroke, will pull more fuel through it, so don't go-a-changing jets (or carbs for that matter) until you try what you already have on the new combo first. I'm sure there are calculators around to let you know how many cfm are required per cubic inch, but they will want to know the max rpm. If you realistically won't turn the new motor over 6000, a much smaller carb than you think will suffice. (Holley's website offers a carb selection page that tells you what you "need") Granted, a larger carb (or even bigger jets) will probably go faster at the track, and make more horsepower on the dyno... but your fuel mileage will absolutely suck out loud... ask me how I know .

I'm sure there are several people around here who are more knowlegable than me, and they can correct me if I am wrong... but a lot of this stuff is really personal preference. It's what YOU want for your "street" car. I didn't mind driving on the street with a converter that stalled at 5200rpm... others think that's insane. I don't mind standing on the ("power") brake pedal to stop due to lack of vacuum ... but I realize the safety I'm sacrificing, and drive accordingly.

[SS4REAL]

Re: SHP dart block build, a discussion

I am fairly confident that the new Dart shp block cannot accomodate a 4" stroke.. And I "think" it is good to
a 4.155 bore..

A STOCK block can be massaged to 4.00, why not the SHP? And the SHP is advertised to 4.165 and I'd be ok at 4.185 in some cases.

I was just going off Darts website specs of Max recommended stroke: 3.75, max rec. bore 4.165.

I had thought about this block for a build too. But decided against it since I am using forced induction
and they say it"s "good" till about 500 + HP.

I'm sure it can be massaged to take the 4.00 or 3.875 stroke, but why not just do a Little M block and save
yourself the machine shop time to clearance...?


I would be more inclined to use a Hyd Roller with 230 - 240 ish durations and about 550 - 575 lift.
You won't be spinning this thing much over 6000 rpm anyway, especially with hydr. roller valvetrain,..
would be a little pricey maybe to get it to spin over 6500 with special parts to control valvetrain weight.

The compression at 10.5 is perfect. The 3.875 stroke is nice.. Good stroke/rod ratios, etc

[GibTG]

Re: SHP dart block build, a discussion

Good rod to stroke ratios?

Has some forgot that they don't matter?

And even if you disagree with me, the difference in RS% is less than .1 - that's pretty insignificant.

[73Nova]

Re: SHP dart block build, a discussion

The valves are a 2.055/1.6 btw

I was going off of Brodix numbers. Did you install the larger valves?

I ordered the heads from Brodix with cnc machined chambers and 2.055/1.6 valves.

[nosnerd]

Re: SHP dart block build, a discussion

i would agree with yellow malibu...415 or even a 427...shoot for 238int/246ex @.050 for a PUMP GAS street motor...

COMP CAMS extreme energy profiles would be perfect for ya....

or call bill metzger at LAZER cams...he used to cut all our custom stuff...
used to run a 285/[email protected] with .775/.748 on 116 lsa (555bbc 2x4 on 400 shot....8 yrs ago)...he knows his stuff..


al

[73Nova]

Re: SHP dart block build, a discussion

Ok then so lets say i end up going with this...

-415-427 inches wichever fits best in the block
-Reuse my 200cc racerites 2.055/1.6 valve and CNC'd chambers, heres a link to the flow mumbers http://brodix.com/heads/raceritesb.html

-10.5:1 compression
-a hydraulic roller lets say for sake of arguement its 288/294 adv. 240/[email protected] .575/.575 lift on a 108 in straight up { i just made that cam up off the top of my head}
-super victor
-750 mighty demon

I know this is a fairly general question, but what kind of rough power numbers would a run of the mill motor like that make? At what RPM? Im trying to decide if this is worth it or not. I would think it would be north of 500 hp @ 6000 RPM and a big old flat tq curve with around 500 ft lbs for a peak in the 4,000 RPM range. Is that out of line to expect that?

[Robert1320]

Re: SHP dart block build, a discussion

73' Nova, 11:1 350 RR200's and a fatty solid FT cam, 5 speed, 9" rear, has gone 11.88 on 89 octane and drives anywhere

Just change pistons, add a turbo and up the octane to 92.
It will be more fun than the big small block.