70 replies to this topic

[LXCHEV]

Would love some advice here from the Chev boys.... I'm finally building a new engine after my epic blowup last year! It will be another mild, street-friendly 383 Chev. But I still want to race it / abuse it occasionally too. Would even consider NOS down the track... maybe.... but not a priority.

Starting point (what I already have):
350 4 bolt block, virgin bore. Will bore to either 0.020 or 0.030 depending on piston options.
Hydraulic flat tappet cam, freshly re-ground - 242/242 @ 0.050, .323 lobe lift (.517 valve lift with 1.6 rockers), pretty sure from memory 107 LSA.
Pro Topline (now called RHS) Iron Lightning angled plug heads: 200cc intakes, 2.02, 1.60, freshly re-co'd. 72cc chambers.
RPM Air-Gap dual plane intake.

What I'm about to buy:
383 crank (3.75" stroke) - internally balanced
6" I beam rods
Pistons to suit
Rings/bearings/gaskets etc etc.
Aiming for around 10.5:1 static comp

Since it's a mild build, I'm going conservative, and don't think I need a forged bottom end (engine machinist agrees).

Thinking along the lines of:

SCAT cast iron crank (9000) series
SCAT "Pro Comp" I beam rods - have heard awesome things about these.
Where I'm stuck is piston choice. Need to find something good to suit this combo and my requirements. If I get forged, the choices seem endless. Hypereutectic's seem more limited.

Probe, SRP, Speed Pro, Keith Black etc etc...

For a street engine like mine, what are the:

Pro's & Con's for hypereutectic pistons?

Pro's & Con's for forged pistons?

Thoughts?

[myss427]

No con's on forged its the cost only. Hypereutectic pistons are fine, all standard late model GM motors run them, even the LS7 uses them. So cant be too bad. Revs are the killer for them though. Also 107 LSA is to tight on a street engine, better to go 110 and get good vacume for your brakes, just won't sound as choppy on the idle.

Edited by myss427, 12 May 2011 - 12:17 PM.

[Punchy]

An engine is just an air pump. You made mention that your wanting to have a mild engine with the ability to have options later on.
Great !
Dont limit your options by fitting less "stress" tolerant pistons now..for the small increase in funds put the forged pistions in. If you change your mind later on about the engines state, heads and cams and springs are far less costly than tearing down bottom ends and refitting them and rebalancing etc.

With the selection of cyldiner head quench areas avaliable to you in chevs you could put a goot forged flat top pistion in, or a relieved done for valve clearance now toallow you the flexiablity of growth and more power later.

Bottoms ends just squeeze air and go round and round and put power to something hanging off the back of it. Heads cams inlets etc is where the power is made.
Make a "Good" bottom end up and the rest is open to experiment.

Holden v8 people are a little more restricted in our choice of head options which then dictate pistion and cam selctions..

Have fun!

[dattoman]

I was told to stay away from the KB pistons and got the Speed Pro coated skirts for mine
Static 10.5:1 (not forged... I doubt I'll NOS)
But that all depends on your head chamber volume

I'd prefer alloys myself
But if you already have the Lightnings.. go for them
I only know 1 guy using them.. Tiny

[LXCHEV]

Thanks guys, some great feedback.

Firstly - if price is the single negative for running a forged piston, then awesome. That doesn't concern me to invest a little more cash up front. And as Punchy mentioned - it would help me future-proof this bottom end.

It was more things like rings gaps, clearances, heat expansion / properties, noise, weight etc.... all little things I've heard about forged pistons, but never really knew much about them. Is all this stuff irrelevant now these days with modern forged pistons?

Lastly - to dattoman's comments -

Yeah the KB pistons have lots of good, and lots of bad stories...
Due to their design, it's critical to run much larger than usual top ring gaps. But if done correctly, they seem to work great, seal like a dream, and not pull the top of the piston off like you hear a lot of people talk about. I'd still prefer to use another brand with a normal top ring gap though.
The coated Speed Pro's are certainly high up on my list. Also Probe, and SRP.

And yes - I already have the Iron Lightning heads, so I'm sticking with 'em for now. Would love (and prefer) alloys too, but that can wait for the next build-up. Besides Tiny, I've seen a few other guys running these heads, but they certainly don't seem overly common. Depending on which batch, some people have had huge problems. They're good heads though, as long as they are thoroughly checked and tweaked where required.

Keep the comments coming....

[Struggler]

Hi Brett,

I like the 9000 series crank and ProComp I beams (use the 7/16 bolt option).

I have used a heap of KB's and never had a problem. The Speed Pro machined top hyper is a good looking thing too. Both would be fine with a hyd cam combo. That said they are not for nitrous use and if you feel more comfortable with a forged piston so be it. SRP is good value and KB do make good forgings as well as the hypers. Any 6" rodded 383 piston should balance up with your 9000 crank fairly easily.

Most of the newer design pistons are low expansion and won't be noisy or cause any other drama. Its only the KB Hypers that have the large ring gaps.

Your cam will be fine if you aren't going to rpm like a mofo (personally I like the tight LSA !).

Are these the heads you were using before ?

[LXCHEV]

Awesome, sounds like I'm on the right track. The 7/16 rods were the ones I was keen on.

This hydraulic is actually my original old cam that I've used previously (prior to my last solid cam). It was an awesome cam, totally streetable, and still pushed my LX down the 1/4 in 11.77 seconds (with 3200 stall and 3.7's). That's why I'm keen to re-use it. I'm not chasing 1/4 times anymore, but if I can still run high 11's I'll be rapt. (Back then I had 4-into-1's with twin 3" system - now I have Tri-Y's and twin 2.5") - I guess time will tell what this new combo will do.

PS. Yes, these heads are the same, and only heads I've ever had. After my blow-up when I dropped the valve, my machinist was able to save the damaged head. One new valve seat, 3 new valves, and he honed the guides. Fingers crossed no more probs...

I'll keep you guys updated, thanks again for the advice, it's awesome!

[LXCHEV]

Which bits are you referring to?

[mr5000]

will be keeping my eye on this mate of mine wants me to rebuild his 350 for his daily never tweaked with anything but holden v8 and jap crap keep up the good work i only vaguely remember you driving lx chev its been to long

[TempesT]

ohhhh lx chev, just throwing my hat in the ring, I got myself srp forgies and eagle H beam rods for the 400 to my door for 1k. That was when the AUD was under 1 USD too.

[LXCHEV]

LX Torry Freak - there are pics of my blowup in this thread: http://www.gmh-toran...up/page__st__25

James - yeah Q built a fully forged bottom end for his - pretty sure you're right in that it was all SCAT stuff. And yeah - definitely aiming for flat tops, I have to with the big head chambers. Blown alky hey?! hahaha.

Ryan - I can't even remember driving this damn car now!!! haha. Only been 14 months, but feels like 5 years :(

mumbo - I'm gonna chat with my machinist and re-look at the other valves too. You're right, I don't wanna risk it.

TempesT - cheers mate, handy to know! H beams would be nice!! haha.

[lxsstorana]

Hi Brett,

This is what is in my 383 Chev motor that is in my grey SS hatchback. I bought the SS in mid 2008 but the motor was built it 1998 and left sitting for 10 years. The original owner used good quality parts to build a tough street motor and he bought it piece by piece (much cheaper to buy a complete running motor).

Anyway, here are some of the details including 1998 prices.

Cheers Mick.

------------------------------------------------------------------------------------------------------

350 Corvette engine block 250.00
Crower 5.7 conrods 1400.00
Romac Ext Bal Harmonic Balancer 250.00
Wade Billet camshaft 240.00
Edelbrock Performer RPM cylinder heads 2200.00
Edelbrock Performer manifold 300.00
Edelbrock alloy t/c cover 150.00
Edelbrock elite series tappet covers 160.00
Crane H/P roller rockers 450.00
Crane H/P hydraulic lifters 200.00
ARP main stud kit 100.00
ARP alloy head stud kit 260.00
Scat 383 steel stoker crank 600.00
Cylinder head dowel kit 16.00
Timing case bolt kit 20.00
Felpro full gasket set 76.00
Felpro head gaskets 130.00
Yella Terra flywheel c/b weight 80.00
Surface grind deck face 120.00
Keith Black pistons 383 chev 700.00
Double row timing chain kit 85.00
Brass welsh plugs 26.00
Cam bearings 30.00
Main bearings 56.00
Conrod bearings 56.00
Crane chrome moly pushrod set 160.00
Hi vol late model engine sump 250.00
Milodon alloy water pump 260.00
Mellings high vol oil pump 60.00
Mellings oil pump pick up 16.00
Oil pump stud kit 16.00
Chev steel flywheel 280.00
Rebore & hone cylds 168.00
H/P ext bal engine balance 250.00
H/P piston ring set 160.00

And lots of other bits and pieces for bolts, carby, dissy, starter motor etc etc.

[lxsstorana]

Here�s some technical stuff that you may be able to use (but I don�t have a clue what it means ).

Wade Camshafts from North Melbourne
Grind 1069 Lift at lobe .297
Running Clearance Ex Hyd - In Hyd
Timing EX opens 79 closes 32
IN opens 38 closes 72
Lift at tdc No. 1 inlet follower - .058

Engine 383 Chev
Bore dia 4.030� (102.36mm)
Stroke 3.750� (95.25.mm)
Cyld head vol � 71cc (before machining)
Cyld head vol after machine � 64cc
Head gasket vol � 9cc
Vol above piston before machining 11cc
Deck height 012�
Remove 010� from deck face (0.254mm)

Crowerod Tag
Part No. SP93205B
Engine Chev
Rotat Wt: 425 Total Wt: 600
Recip Wt: 175
C to C: 5.700
Eig End Dia: 2.225
B.E thickness: 0.940
Pin End Dia: 0.927
W.O: CA19679 ID ©
Lube; motor oil
Bolt Part No. 90828
Stretch .004 � 006
Torque 50 ft lbs

[LXCHEV]

Cheers for the detailed reply Mick, it's great info.

Just to follow up - I've now finally settled on the bits!

* SCAT 9000 'Pro-Comp' series internally balanced 383 crank
* SCAT 'Pro-Comp' 7/16 6" I beam rods
* SRP 0.020" forged flat tops
* Speed Pro rings
* Clevite bearings

Not a bad bottom end for just over $1400!

Will also be going with ARP 4 bolt main studs and a Pro-Race 'race' series balancer.

Let the building begin!

Being only 0.020" over-size, it's actually going to be a 381 now. Doesn't sound right does it!

[Struggler]

Good stuff and more than capable of getting the job done !

Good luck with it

[MRLXSS]

Good to hear mate!!!

Looking forward to finally seeing the beast back on the road!

[LXCHEV]

Ok the plot thickens....

I would seriously love some opinions on the differences between a hydraulic flat tappet cam and a hydraulic roller cam. I have to admit - I'm tempted! (And yes, I'm sticking with a hydraulic, no solids here).

Obviously the cost is the first big negative for a hydraulic roller... so let's put the cost aside for a minute.... and just discuss the characteristics, street manners, HP and torque gains.... how much is really in it? Opinions and personal experiences greatly appreciated...

I was flicking through some yankee mag today at the newsagent... they were doing a back-to-back test on a mild 350 Chev, a little bit tamer than my 383. First up, hydraulic flat tappet... something like 230 duration @ 0.050 and can't remember the lift. Made around 350HP and 400 foot pounds. Then they swapped it out for a hydraulic roller.. heaps smaller, like 215 or 220 duration. Made something like 375HP and 415 foot pounds, with heaps more vacuum and much nicer manners.

So with a slightly more aggressive combo like my 383 what kinda gains 'could' there be? (Keep in mind, approx 10.5:1 comp, big heads, dual plane intake).

What are some fairly common hyd roller cam profiles used in 383's and what power do they make?

I'm wondering what would be the roller equivalent to my flat tappet (242 @ 0.050, .517 valve lift, on 107 LSA)?

What if I went for the same type of specs with a roller? How much angrier would it be?

Thoughts?

[LXCHEV]

The key thing I'm trying to do with this engine, is to build it as a genuine streeter that cruises big km's, long trips, holidays etc... yet still goes hard at the strip when required. It's gonna be a 90% cruiser, 10% racer....

[rexy]

Used to run a big solid in the 383 holden.
254in/262ex at 50 thou with 602in/620ex valve lift. 106 LC 10.7:1 comp
Swapped it for a hyd roller of 230/234 duration and 563/574 valve lift. 110 LC 11.3:1 comp
Both made about the same outright power (small advantage to the solid) with the roller making noticeably more midrange torque.
To be honest both are easy to live with on the street. Slightly better brake vacuum with the roller.
I do hate adjusting tappets and for that alone it was worth it.
It has a manual box behind it and I suspect that with an auto the solid may have been a bit harder to live with but who knows?

Edited by rexy, 07 July 2011 - 11:50 PM.

[LXCHEV]

Thanks Rexy, awesome info! That's a great comparison.

[Struggler]

I have never been a hydraulic (or solid !) roller fan but a friend has been using one for a while and loves it. He has a 400 with AFR 195's and an RPM Air Gap. Comp Cams hydraulic roller � 242 / 248 @ 50 on a 108 lobe. It runs 11.3 @ 118 in 3500lb Firebird. Drives it around town regularly. Once you man up for the $$$ they don't work too bad ! Having said that I have recently spent up on a solid roller and am amazed at the power it made, and no stress running it in ! FWIW the hydraulic rollers are very popular in the US.

JMHO