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Old 03-10-2010, 12:49 PM
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383 race short block convert to street use

I acquired a 4-bolt 350 Vortec motor at the end of last year, which needs a +40 bore due to cylinder wall damage caused by a dropped valve seat. I dropped the bare block + crank off at the machine shop on Monday. While I was there, the guy who runs the shop (their main business is building engines for race teams) asked me if I'd considered going the stroker route with it. I told him, as money was a bit tight, that I'd be sticking with stock cubes. HOWEVER, by sheer coincidence, a 383 short block suddenly cropped-up yesterday not far from where I am... had a look at the motor today and have struck a deal on it. So, total change of plan. The 383 needs a little bit of work because it's been set-up for race use. But, here's the spec (from memory):

Decked (standard deck height), bored +40 and line bored
Cam Motion solid roller cam (duration up in the mid-260s at .050"/.650"+ lift)
1.5/1.6 Harland Sharp roller rockers
6" Eagle I-beam bushed rods (SIR6000BBLW)
Scat 9000 series 3.750" steel stroker crank
SRP forged flat-top pistons with SRP moly rings
Studded mains
Lifter valley screen kit installed
Lifter valley drain holes plugged
Oil restrictors
Rollmaster billet steel timing set with 9 crank keyways
Oil pan stud kit
Melling HV oil pump

The engine has never been completed, so is effectively a brand new build. The pistons and rods have been weight-matched and the whole rotating assembly has been balanced (ext. balance).

So, from the online research I've done, I'll need to unplug the lifter valley drain holes and replace the oil restrictors with pipe plugs. I'm assuming the lifter valley screen kit can stay (seems like a good idea)? The cam will obviously have to be swapped-out for a much milder cam suitable for street use and I won't be using a solid roller. The aforementioned machine shop/engine builder has told me he has a tried-and-tested combo using a 383 that makes 500HP+ and is totally streetable. This is based around a solid flat tappet cam (don't know the specs), Dart Pro 1 215cc heads, Victor Jr. intake and a Holley 750DP carb. Sound plausible? In any event, I'll be getting the engine dynoed and broken-in at his place, so he must be confident.

What sort of RPM limit is this short block safe to? The crank and rods are both rated to 7,500rpm from what I've read, so I was thinking of setting the limiter at 7k and aiming to shift around 6,500rpm (depending on the power curve, obviously). What do you think?

What about the oil pump? Should I leave the HV pump on and use a deep pan, or swap it out for a standard volume pump and standard pan?

My application is a 2,000lb street/strip car with manual trans and 3.54:1 gears. Car is a weekend warrior and doesn't have any luxuries such as A/C (doesn't even have windows), so I can live with a rough idle and 'compromised' streetability, but still want enough torque to smoke the 295 tyres when dropping the hammer in 2nd or 3rd gear.

Thanks!

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Old 03-10-2010, 01:12 PM
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i would leave the screen kit in, take out the restricters like you said, sell that cam, & buy a cam that will fit your build. everything else will be fine. i would use a hv oil pump & a t type pan, afr 195 heads are not that much more than the dart heads & flow to hell & back (215's are a little big, but would work), a solid flat tappet 249-259 .050 dur. .543-.561 lift lunati cam, & turn it around 6,500 rpm. that should put you in the 525 hp range & have awesome torque too.
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Old 03-10-2010, 03:22 PM
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I've been playing around with some combos in Desktop Dyno and I don't understand something... why is it that any combination of solid flat tappet I try cannot beat the Comp XR282HR (hyd. roller) for power or torque? The XR282HR wipes the floor at all points in the rev-range with every solid flat tappet I've tried. I thought solid flat tappets were a step above hyd. rollers? I'm confused!
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Old 03-10-2010, 03:43 PM
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Roller lobes can be ground with a higher rate of acceleration because there is no flat surface of the lifter to scuff into the lobe. Hydraulic roller tappets are quite heavy though and I think most manufacturers will advise that they will cease to follow the lobe profile at somewhere around 6200. Rev-Kit spring assemblies are available to position in the lifter valley to assist keeping the lifter roller in connection with the lobe at higher revs.

I try to discourage installing flat tappet cams any more due to the changes in oil formulas. As you know, extreme pressure lubricants have been removed from off-the-shelf oils, so the car owner must use an aftermarket product to protect the lifter faces.

Last edited by techinspector1; 03-10-2010 at 03:52 PM.
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Old 03-10-2010, 03:50 PM
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Quote:
Originally Posted by techinspector1
Roller lobes can be ground with a higher rate of acceleration because there is no flat surface of the lifter to scuff into the lobe.
Understood and I would expect a hyd roller to out-perform a hyd flat tappet cam for that reason. However, I thought solids were a step above? Whatever flat tappet solid I select in DD, I cannot get it to beat an XR282HR. Just wondering how accurate that is? Also, how realistic is it to expect a hyd roller lifter to withstand 6,000rpm+. According to David Vizard, hyd. roller lifters can collapse at much over 5,000rpm without modding the lifter body etc. My local (v.experienced) engine builder didn't want to know about a hyd. roller cam, citing the heavy valvetrain. He seemed to think hyd. rollers are good for regular street cars (trucks, regular cars, etc) but not for anything 'serious'. He reckoned I should definitely install a solid flat tappet in my application. DD seems to say otherwise though! I'd sooner trust an experienced engine builder than a software app, but it had got me a tad confused.
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Old 03-10-2010, 04:19 PM
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For any kind of performance application where the owner doesn't mind adjusting the valves as part of routine maintenance (say for instance with every other oil change), the solid flat tappet (cheaper) or solid roller tappet (more expensive) camshaft is the way to go. Hydraulic flat tappets and hydraulic roller tappets are maintenance-free and self adjusting over the life of the motor. I added some verbage to my post#4

I'm not sure what you mean by "a step above". I'm just gonna line out the options for newbies who might be reading....

Solid flat tappet. Cheapest means of valve control. Periodic valve lash adjustments necessary. Max revs for cheap. Lightweight, can use with less valve spring than heavier solid roller setups. Limit valve spring pressures to avoid scuffing lifter. Lifter can also scuff cam lobe if motor is run without extreme pressure lubricants.

Solid roller tappet. More expensive. Periodic valve lash adjustments necessary. Needs more valve spring and/or rev kit. Heavier than solid flat tappet. Used in banzai, cost-is-no-object, max horsepower, max rev builds.

Hydraulic flat tappet. Reasonable cost. No lash adjustment necessary beyond initial adjustment when assembling motor. Reasonable street rev limits. Will pump up and lose control, limiting revs. Limit valve spring pressures to avoid scuffing lifters. "Put the motor together and forget it". Lifter can scuff cam lobe if motor is run without extreme pressure lubricants.

Hydraulic roller tappet. More cost. No lash adjustment necessary beyond initial adjustment when assembling motor. Reasonable street rev limits. Will pump up and lose control. Will also leave lobe profile due to heavier weight. "Put the motor together and forget it". This type of system is used by OEM car makers.

Last edited by techinspector1; 03-10-2010 at 04:28 PM.
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Old 03-10-2010, 04:35 PM
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Thanks for the info. I'm familiar with the theory, but was puzzled by the greater output that DD showed for the hyd. roller. The difference was quite significant. Still, I can see that DD doesn't give the full picture... it, presumably, assumes perfect valve control at all times.

So, on the kind of motor I outlined in my original post, would you agree with my engine builder that a solid flat tappet is the best option, regardless of what DD seems to show?

By the way, there are some production cars in the UK that use solid cams... TVR, for instance, use a bucket and shim arrangement on their AJP8 (V8) and SP6 (inline 6) engines. Pain to adjust because the only way to adjust the clearance is to swap the shims out for thicker shims.
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Old 03-10-2010, 04:37 PM
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You couldn't pay me to use a flat tappet cam of any kind for my personal use, no matter the application.
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Old 03-10-2010, 06:17 PM
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desktop dyno can't tell if it's a solid or hydraulic roller. it just asks if it's solid or hydraulic roller. no way to compare. i haven't lost a lobe on a flat tappet cam, but i don't build engines everyday. i have put three different solid flat tappet cams in my 406 (changing for power, not bad lobes), & one hydraulic in a f150 4x4 ford truck. i never added any type of additive at all to the oils in any of them. i guess i got lucky. my mopar 451 stroker will get a solid flat tappet (with additive added).
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Old 03-10-2010, 06:20 PM
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So, are the only reasons anyone would choose a solid flat tappet over a hyd. roller 1) cost and/or 2) the ability to rev past 6,000-6,500rpm?

Just trying to understand before I go spending my hard-earned.
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Old 03-10-2010, 07:32 PM
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Also you can not compare solid lifts to hydraulics because the solid has to overcome the lash setting before valve lift starts. So if a solid cam is rated .575" lift it's actually .559" after the 0.016 valve adjustment.
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Old 03-11-2010, 01:01 AM
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My view is that DD is overly optimistic about the capabilities of the average hydraulic roller and it's valvetrain. You will only get those kind if hydraulic roller results with high end race hydraulic roller lifters and valvetrain.

Sounds like you don't mind the maintenance and desire the power - solid flat for sure. Trust your builder, sounds like he knows
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Old 03-11-2010, 06:14 AM
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Why not run a solid roller? If you just want a weekend toy a solid roller is the best of everything, and doesn't cost that much more than a hydraulic roller.
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