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Discussion Starter · #1 ·
Hi guys
Engine machinist has put me onto Scat website but it seems pretty scimpy on details.

Looking at a 383 Scat Rotating Assy.

1-91255 BIE
ProComp9000 Cast crank
ICR6000 6" 4340 I beam Rods
Forged 4.030 Dished Pistons

CR is listed as 10.4 w 58cc Heads.
What would it be with 54cc stock heads or 55cc AFR 195 (AFR-1031) I plan on changing to later?
What maximum CR should I be looking for with UK Fuel 95 RON Premium / 97 RON Ultimate ?

What's the difference with the premium pistons over forged ?

TIA

Mitch
 

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First off, what are your goals for this engine?

Scat generally makes good stuff, ive used them in both my ford and chevy products without any issues which is a statement for me. Im really hard on parts :thumbsup:
 

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Discussion Starter · #3 ·
First off, what are your goals for this engine?

Scat generally makes good stuff, ive used them in both my ford and chevy products without any issues which is a statement for me. Im really hard on parts :thumbsup:
Only as a weekend driver. Since I spun the rod bearing i might as well go up a bit in size. I don't need a forged crank yet. I've alreay got a CC XFI 268 cam in which ran quite sweet. Do I go up a size whilst it's apart though ?

Thanks
Mitch
 

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I wouldn't unless you got a good set of heads or well ported stockers. although if your looking for a good budget 383 Rotating kit coast high performance has a 383 kit starting at 1018.95 with forged pistons, 4340 forged rods and a cast crank that could probably more than survive what your wanting to do. they can balance in house too for about 180 more.
 

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I am building a SCAT infested engine right now. For a few extra bucks you might as well spring for the forged steel crank, H-beams and good forged pistons. That way you know it will last and take whatever you throw at it.

For your SA, this is what I am building. I am currently building an LT1 with all forged SCAT w/ H-beams lite, 12.3:1 CR, AFR 195 Comp Ported heads, ported intake, 58mm TB (small hole drilled for idle), 42# injectors, PCM for less tune (for now), big enough cam ( I haven't decided specifically yet but something near 243/251 597/601 or [606/610] @110 LSA. Make sure you get really good springs, top of the line). If you want specifics just ask.

I feel a person should make the decision to put quality parts in now and not have to worry about it later. For a few hundred extra you could have a really nice forged bottom end. Good luck!
 

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Discussion Starter · #6 ·
I've got some prices for machine work which doesn't seem so bad.

What sort of RPM's would be safe with the cast crank Vs Forged and I beam rods Vs H beam etc
 

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I've got some prices for machine work which doesn't seem so bad.

What sort of RPM's would be safe with the cast crank Vs Forged and I beam rods Vs H beam etc
A stock cast crank can spin 6k but not consistently before it heads south looking for an exit strategy. I- beams are the weaker of the two. Personally for few hundred extra dollars its cheap insurance to buy H- beams and a forged steel crank. Thinking about and considering how much time, money and energy is going into your project H-beams and a forged steel crank seem logical. But hey that is MHO. My set up can be spun to 7k if I need it to and I will have no worries doing it....but I won't take it that far. If you're just wanting a mild street mannered car with no interest interest in racing etc but just wanna have fun driving it then yes a stock cast crank and stock rods and ported stock heads will fit the bill. But what are your honest and true intentions? Help us help you and we can get you on the right track.
 

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"What maximum CR should I be looking for with UK Fuel 95 RON Premium / 97 RON Ultimate"

What is the U.S. equivalent to this? Is it 93 AKI and higher? I believe you will be fine since your fuel meets a descent octane rating...93 U.S. I believe. Therefore you should be able to run up to 12:1 and be okay since LT1's are reverse cooled. Double check the octane ratings and make a call. You would also be safe at 11.5:1.
 

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Guys run 12.5:1 on LT1s with 93. Have a good tune.

Also the factory crank is stronger than after market cast cranks. A guy on tech (Vtec) is running a stock bottom end block (besides cam) at 9.4 in the 1/4.

So if you are replacing the crank just go a forged crank.

Just putting Mr Gasket on a stock LT1 (quench is .026 instead of .052 if I recall) gives a compression bump to 11.4:1

You can send your stock heads to AI or LE and get a cam to match and lay down over 400rwhp.
 

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You should read up on dynamic compression ratio. It is much more important than static compression ratio when determining how high you can go without detonation. If you stick with the XFI 268, you need a static compression ratio of less than 11:1 to keep your dynamic CR less than 8.5:1. The only way you can run high static CR is if you use a big enough cam that delays the IVC event enough to keep the dynamic CR in check.

I-beam rods are perfectly fine in high performance applications. In fact, the high-end Callies and Howard cams ($1000 range) rods are I-beams. If search for I-beam to H-beam comparisons, you'll find that for a given HP range, the I-beams are typically lighter with the same strength.


Sent from AutoGuide.com App
 

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Discussion Starter · #11 ·
Ok I'm looking to build a healthy 383 Weekend Driver around the 400 HP mark
Going with Scat Forged crank kit for solid Bottom end.

Scat 1-41829 BIE
4340 Forged Crank
Pro Comp I Beam Rods w7/16 cap screws
Forged Pistons Dished 10.4 CR with 58cc heads (Head Volume +16cc ?? )

The block is going to be CNC bored 4.030 and honed in CK21 hone.
Decked and squared ( i guess to 9.000 )
Machinist said CR would be around 10.8 with 54CC heads and higher once the Block is decked.

Cam going up to Comp Cam XFI 280 as i wanted originally

Still wanting to use my good stock heads for now. Plan on upgrading to AFR 195's next year after getting bottom end built and running.

Currently car has
MAC Midlength Headers - Pneumatic Exhaust Cutout Pre Cat - 3" stainless Exhaust
Comp Cams XFI 268 Cam - 918 Beehive Springs - Comp 1.6 Ultra Pro Roller Rocker Arms
GM Performance LT1/LT4 Timing Set - NGK Platinum Plugs - JEGS 8.0mm Red Hot Plug Leads
30# Modified Bosch 3 Injectors - LT4 Knock Module - SLP Air Foil - Moroso CAI
!AIR - !EGR - Throttle Body Bypass

Other Additions to build (Reccomendations please)
HV + pressure Oil pump
Good Windage Trag & Road/track Sump
Dampener (ATI) ?
ARP Main Studs to fit windage tray
Total seal rings (Not sure what set)
ARP Head bolts ( are these torque to yield or reusable)
Head Gaskets ??

Where would that lot put me ?


Thanks
Mitch
 

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Mr Gasket 5716 compressed is .026" on a stock engine this gives you 11.4:1 compression.

10.8:1 is only .4 above a stock LT1.

Guys run 93 and run 12.5:1.

High volume oil pumps are bad, they will suck the pan dry before the oil makes it back down to the pan.
 

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Mitch,
I think you're on the right track for a solid mild rebuild. Everything you have will work. Here are a few things though from my experience. Jegs wires are TRASH ( I had them trying to save a buck and they caused all sorts of frustration), ATI damper not needed if internals are properly balanced and ur not over 500hp, I would use LT headers, I would not upgrade ur injectors for what you want, instead of air foil just upgrade ur TB to a 58mm ( airfoil is a waste of money), tune out your emission or keep them it;s up to u (pcm for less automatically tunes them out unless specified), ensure you get only the Melling oil pump, lt1's come with a windage tray, no need to upgrade your pan and use ARP everything. Your rings, pistons and gaskets should be a recommendation from your builder. I think I answer what you were asking but if you have any more questions please feel free. Good luck!
 

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AFR 195s are also a waste if you ask me.

Unless you are going for a balls to the wall all out horsepower monster just get LE3 or AI 200cc heads.

383s with AI heads make over 500rwhp.
 

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AFR 195s are also a waste if you ask me.

Unless you are going for a balls to the wall all out horsepower monster just get LE3 or AI 200cc heads.

383s with AI heads make over 500rwhp.
Mitch I think for what you wanna do 195's will work just fine. I would also say that yes a really well ported stock heads combo would be beneficial too. And I agree partially with Fox, that Ai is a damn good resource. I personally would use Ai if it were me and I had to do it all over again. They also produce a nice set of Trickflows. Ai however, in my book, the top of the food chain when it comes to heads and cam combo's. They are the subject matter experts.They are pricey though!!
 

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AI, you can email them and they could spec out a cam custom grind for what you want and you will not be disappointed.

AFR 195s cost 1900 min and are tested on a 4.060 bore which is the absolute limit for a LT1. The basic heads flow 280cfm at .550 lift.

AI 200cc cost 1800 tested on a 4.030 bore (which is a 383 bore) flow 282cfm at .550 lift.

The AI heads are better than the AFR heads.

If you want to go AFR heads you might as well go at least the 210cc. Which is still a joke. They flow 311 at .700 on a 4.125 bore.

The AIs will again flow 290 at .700.

I would just go the AI and get a cam from them for an extra 395 custom ground.

If you really want heads, I can get more into some heads that will perform both of them, also for cheaper.
 

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Not to hi-jack but now you have me wondering. What heads are you talking about that can out flow Ai, AFR and Trickflow? I have the 195 comp's and run a 248/[email protected] .600/.600. Built for hi rpm this should run damn good with the AFR's. ??????
 

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The thing is with these heads you will have to either have them redrilled for a LT1 intake if you are going that way or do what I am going to do, convert to carb and distributor.

The heads are 23* Pro-Filer SBC heads.
They flow 300cfm as cast.
CFM isn't everything either when it comes to heads, its the design.
They cost 475 a head.
So thats 950 a set.
It costs 300 - 400 to convert them to reverse flow.
1350 to have a cast head that outflows AFR, TFS, AI 200cc which are fully machined heads.
The Pro-Filer heads can be machined to flow over 400cfm.

Speier Racing does a hell of a job CNC the Pro-Filer. Their econo port on a 383 with a 11.1:1 CP on a SBC (which is low for a LT1) made 588hp.

http://www.speierracingheads.com/PROFILER.htm

Once again this is for hardcore balls to the wall.
 

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Discussion Starter · #19 ·
Mitch,
I think you're on the right track for a solid mild rebuild. Everything you have will work. Here are a few things though from my experience. Jegs wires are TRASH ( I had them trying to save a buck and they caused all sorts of frustration), ATI damper not needed if internals are properly balanced and ur not over 500hp, I would use LT headers, I would not upgrade ur injectors for what you want, instead of air foil just upgrade ur TB to a 58mm ( airfoil is a waste of money), tune out your emission or keep them it;s up to u (pcm for less automatically tunes them out unless specified), ensure you get only the Melling oil pump, lt1's come with a windage tray, no need to upgrade your pan and use ARP everything. Your rings, pistons and gaskets should be a recommendation from your builder. I think I answer what you were asking but if you have any more questions please feel free. Good luck!
Thanks for the feedback guys (Fox also)
I'm in UK so getting my heads ported in USA is not beneficial.
I've no idea who is capable of porting over here although there should be plenty.
Block is going to be taken to be bored on Saturday. I'll start ordering parts after talking with machinist.

Thanks
Mitch
 

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Discussion Starter · #20 ·
AI, you can email them and they could spec out a cam custom grind for what you want and you will not be disappointed.

AFR 195s cost 1900 min and are tested on a 4.060 bore which is the absolute limit for a LT1. The basic heads flow 280cfm at .550 lift.

AI 200cc cost 1800 tested on a 4.030 bore (which is a 383 bore) flow 282cfm at .550 lift.

The AI heads are better than the AFR heads.

If you want to go AFR heads you might as well go at least the 210cc. Which is still a joke. They flow 311 at .700 on a 4.125 bore.

The AIs will again flow 290 at .700.

I would just go the AI and get a cam from them for an extra 395 custom ground.

If you really want heads, I can get more into some heads that will perform both of them, also for cheaper.
The 195's will still fit the LT1 Manifold won't they.
... are the 210's for LT4 manifold which is more expense again.

What sort of improvement would the 210's be over 195's on my 383 ?

Thanks
Mitch
 
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