HPDE/Time-Attack Build - 9.0:1 2.3L or 8.5:1 2.4L

[High PSI]

Brief background: Car is a 2g GSX that currently has an old "Stage 4" 6-bolt SBR 2.3L in it. It spun a bearing last summer due to an oil-cooler failure. I split my time between Australia and the US (where the car is), and will be state-side at the end of July for a couple weeks. I want to fix the car then, so I'm looking for a ready-to-go shortblock that I can swap in while I'm home (don't have the time to have the current shortblock - which is still in the car - rebuilt). I'm currently torn between these two options, both about the same price:

Option A:
2.4L G4CS
Weisco HD 8.5:1 Pistons, Ceramic Coated
Eagle Rods
Clevite 77 Bearings
Standard Main Studs
No Oil Pump (provide my own)

Option B:
2.3L 6-bolt
Ross 9.0:1 Pistons
Eagle Rods
ACL Main/Connecting Rod Bearing
ARP Main Studs
OEM Oil Pump w/ Straight Cut Gears

Car is being build for HPDE/Time-Attack work. I have 93 Octane available, and will be pairing this with a billet bastard 20G built by JuaMX141, which he said should be good for airflow in the the 47-48 lb/min range.

Which would you go with if you were me?

 

[FIBA M - EC17PSE]

With racing in high rpm area the 2.4 really struggles due to how thin the walls get. A race team here in the UK went through 3 blocks and kept running the 2.4 even though i said its not a wise idea, for a daily or small fun sure but racing hell no, the 2.3 might be the same if the bore is the same and not needing to hone it for a clean surface,

Ideally you want to run a long rod setup, either 2.0LR or 2.2LR, you will get more torque with the 2.2 and thats about all i know of that , i myself am going to do a 2.0LR for strength and reliability even though racing is not down to being reliable it helps to make something less prone to break so soon and the LR setup will help with this,

 

[TSiAWD666]

2.4 all the way, but I'd opt for higher compression and give up on the 93 octane and run 100 octane or higher that is available at the track. Either engine's I think going to be stuck with at most an 8k rev limit for safety but that's not personal experience, just what I think I remember reading during my research years ago when I was figuring out my personal track car's engine. I run an 8k rev limit on my 2.3 not only for the engine to survive but also to reduce issues with the transmission, and my engine's been racing 7 years without issues, and the trans only just died at 6.5 years.

Don't forget to make sure to delete the balance shaft.

 

[mountain_man]

I'm currently gathering parts and researching for a 2.4 long rod build. Here's a couple of the better write-ups that may help you make a decision: Stroker Pro's and Con's & Stroker Motors Explained

 

[High PSI]

With racing in high rpm area the 2.4 really struggles due to how thin the walls get. A race team here in the UK went through 3 blocks and kept running the 2.4 even though i said its not a wise idea, for a daily or small fun sure but racing hell no, the 2.3 might be the same if the bore is the same and not needing to hone it for a clean surface,

Ideally you want to run a long rod setup, either 2.0LR or 2.2LR, you will get more torque with the 2.2 and thats about all i know of that , i myself am going to do a 2.0LR for strength and reliability even though racing is not down to being reliable it helps to make something less prone to break so soon and the LR setup will help with this,

Thanks Bobby....I think?! You certainly put the fear in me!

I understand the 2.4 has thinner cylinder walls, but the rod-ratio is the same (well...slightly better) than the 2.3 and there are no reports of people wearing out those walls. Certainly if they went through 3 x 2.4 blocks due to that you would hear about the occasional 2.3 doing the same? What sort of racing were they doing?

 

[High PSI]

2.4 all the way, but I'd opt for higher compression and give up on the 93 octane and run 100 octane or higher that is available at the track. Either engine's I think going to be stuck with at most an 8k rev limit for safety but that's not personal experience, just what I think I remember reading during my research years ago when I was figuring out my personal track car's engine. I run an 8k rev limit on my 2.3 not only for the engine to survive but also to reduce issues with the transmission, and my engine's been racing 7 years without issues, and the trans only just died at 6.5 years.

Don't forget to make sure to delete the balance shaft.

Wow, all the heavy hitters stepping in! Was hoping I would catch your attention..

So the only problem is that I’m on a time limit at the moment (2-weeks to swap in a new shortblock to at least get the car moving around) and thus stuck with the two available shortblock options above. As such it’s 8.5:1 CR 2.4L vs 9.0:1 CR 2.3L. Do you think the extra .1L of displacement is worth giving up the .5 CR?

 

[High PSI]

I'm currently gathering parts and researching for a 2.4 long rod build. Here's a couple of the better write-ups that may help you make a decision: Stroker Pro's and Con's & Stroker Motors Explained

Thanks for the links. Read the first before and just read it again to see if I missed anything. Found not so and didn’t really assist much as basically said pro’s/con’s of 2.4 are identical to that of a 2.3.

Second one was new to me though and provided some good info. Also noted that since this wouldn’t be a LR 2.4 rod ratio would be the same as the 2.3, which maybe goes to support Bobby’s point that the 2.3 is a better choice as it has thicker cylinder walls to handle the stress?

As an aside, I see the poll is 3 for the 2.3L, 0 for the 2.4L. That + ACL race bearings (standard on 2.4L), that it comes with a straight-cut year mitsu 90 oil pump (nothing on the 2.4), and not having to deal with the timing nuances means I’m now definitely leaning towards the 2.3 a bit..

 

[FIBA M - EC17PSE]

Thanks Bobby....I think?! You certainly put the fear in me!

I understand the 2.4 has thinner cylinder walls, but the rod-ratio is the same (well...slightly better) than the 2.3 and there are no reports of people wearing out those walls. Certainly if they went through 3 x 2.4 blocks due to that you would hear about the occasional 2.3 doing the same? What sort of racing were they doing?

Sorry if i did, im just giving some issues i have seen to folks who race in the series im going to race in, they do time attack and after the 3rd engine they gave up on that car and sold it as they got fed up of it keep cracking the cylinders! I dont blame them really,
I dont know much on the 2.3 as i have never really read up on it, i assume its a destroker from a 2.4 block?

One other guy that runs an evo block is going to do a 2.2 perhaps in a LR setup for an inbetween setup. He also has raced in the time attack series but dont want engine issues like the other people had.

If you limited you rpm as John does the bigger blocks may be ok and safe but how long we dont know as they all vary strength wise,
I do think upping the comp ratio is a good idea also

 

[delta448]

The deciding factor for me would be the rods and pistons being used. If they both are going to have 150mm connecting rods, I'd choose the 2.3. If there's any option to use a longer rod with the taller G4CS block, then the 2.4 is better no doubt about it.

With a 100mm stroke in both, the short rod in a 2.3 4G63 is as much or more a power limit than thinner cylinder walls are in a stock bore but longer than stock con rod G4CS 2.4. There is a bit less valve shrouding on the bigger bore 2.4L using the DOHC head, which will help your airflow.

Ask for sonic testing of the walls if you go 2.4. The 63 block should have between 4.5mm-6mm wall thickness stock, and the 2.4 block needs to have at least 3mm minimum at the 8 measurement points in each cylinder. A 3mm cylinder wall thickness has been proven to hold more than 180 horses per bore.

 

[High PSI]

**Update**. I have gone with Option B based on the suggestions above. Also the seller of the 2.4L dissappeared and didn't give me much choice. Anyway, the 2.3L 6-bolt is finally in the mail and on the way to my home as we speak, so I'm happy to have that behind me.

The only thing I'm struggling with now is what head to use - my old 7-bolt head, or the ported 6-bolt head that's on the car now. I have a set of HKS 272s (were in the 7-bolt head) and Comp 101200 Cams (are in the 6-bolt head). I will be using the Comp 101200 Cams as from what I've researched they are a bit better (bigger) for my setup.

With regards to the heads, here are my two options:

Option A:
7-Bolt
Unported
Crower Springs
Ti Retainers
Sodium Filled Exhaust Valves
Black Nitride Coated Swirl Polished Intake Valves
Would be looking to pair this with an Evo3 IM

Option B:
6-Bolt
SBR "Stage IV" Competition Valve Job and Stage IV Port Work
Stainless Steel Swirl Polished and Undercut Valves
Manley Springs
Ti Retainers
Would be looking to pair this with a Cyclone IM

I've read, and read, and read about the differences between the 7-bolt and 6-bolt head. If I had time and money on my side I would probably send my 7-bolt head to Curt Brown and call it a day, but again I'm short on both so looking to use what I've got. Again, this is an HPDE build with a Bastard 20g (at least for now).

Pictures of the 6-bolt ports below:

 

[High PSI]

Engine out. Both heads at a local machine shope at the moment. Looks like I'll be going with the 6-bolt head due to my time constraints. Have a cyclone intake manifold on the way as well.

 

[bastarddsm]

what intake will you use?

 

[High PSI]

what intake will you use?

Cyclone.