GM CT350: Another Question

[skinny z]

Just poking around the web on a Saturday morning looking at engine options and again I've come across GM's CT350.
Now, I'm looking over the spec sheet and I see a maximum engine speed of 5800 RPM.
What would be the limiting factor for such a modest RPM ceiling?
Camshaft specs notwithstanding, is it the reciprocating assembly that keeps the revs down?

CT350.jpg

Thinking of possibilities, that short block with my heads and one of CamKing's hydraulic rollers for about a 6300 RPM HP peak would fit the bill nicely.
Unless the short block would grenade with some hard drag strip use. Not to mention cross country cruising.
And I'd have new pair of Vortec heads on the shelf too.
I have a retrofit roller ready to go.

What do you all know about this?
It's certainly a popular circle track platform and I'm sure those guys don't keep it below 6 grand. Or do they?

Related threads all get into cam selection and whatnot but I haven't seen the RPM question addressed.

[lefty o]

id say it will live just fine if kept under 7000. the cam in the engine listing is the factor making it a 5800rpm max package.

[mag2555]

How about it being due to the cast pistons there folks!

[tjs44]

small cam and cast pistons.Tom

[skinny z]

I figured it was the cam spec that defined their RPM ceiling. It still begged the question about the short block though.

I had drag raced a more less stock bottom end 350 of late 70's vintage for several years in a row with no issues and a top rev less than 6500. Cast crank and whatever crappy rods came in a 1979 truck engine. Only thing I did was swap to a flat top hypereutectic pistons and ARP rod bolts.

I'm guessing this crate engine is pretty much the same except no bolt upgrade.

The other thing I can't get a handle on is how they get to the 9.1:1 CR.
One "internet spec" says it uses the ZZ6 head gasket at .051" and a flat top piston .025" down.
The GM spec sheet lists the head gasket at .026". The piston must be dished with about a 12-16 cc volume.

[skinny z]

How about it being due to the cast pistons there folks!

small cam and cast pistons.Tom

Yeah. And there's that.
Although, I've seen the 12514101 GM piston listed as hypereutectic. And I've had no issues with any that I've used. Even to 6500+.

[F-BIRD'88]

You don't need to rev up this crate engine any higher.
My 350/ vortec head motor was near the same but flat tops 10:1. 214-224 hyd cam.. Ran best shifted at 5000 rpm.
Any higher it slowed the ET. Althou you could buzz it over 6000 rpm. It just does not need a ton of rpm.

Same short block different racey cam and heads, intake used to buzz it 7500 rpm.

The pistons in this crate engine are dished.
Approx 13-15cc

[rebelyell]

CT350 aka x602 is a Factory-Sealed motor intended for restricted classes of Circle Track competition; its rpm also limited by relatively weak valve springs.

CT350 aka x602 is essentially an rpo L31 (x672 or x673) without its OE roller but with a smallish HFT; plus a decent but Left turn only pan & special seal bolts ... JME Instead of x602, suggest begin w/ a brand new L31 replacement; then pick your cam-springs and pan YMMV.

[skinny z]

CT350 aka x602 is a Factory-Sealed motor intended for restricted classes of Circle Track competition; its rpm also limited by relatively weak valve springs.

CT350 aka x602 is essentially an rpo L31 (x672 or x673) without its OE roller but with a smallish HFT; plus a decent but Left turn only pan & special seal bolts ... JME Instead of x602, suggest begin w/ a brand new L31 replacement; then pick your cam-springs and pan YMMV.

The L31 is something I hadn't thought of. And I'm very familiar with the Vortec platform too.
I'll check that one out.
Would that be the same same crank and rods at the CT350 do you think? Because that to me would define any HP limit. Maybe 425 with the crank being the limiting factor?
Different websites list the crank as being either nodular iron or a 1053 forging.

[rebelyell]

some 602 have cast crank some forged; dunno 'bout their rods. It's my understanding their current motors have Cast piston and not hyper (hyper more brittle and more prone to crack).

New GM current production L31 (from Springfield MO USA) have forged steel crank, powder steel rods, billet steel roller cam (although it has no fuel pump eccentric) and block has 4-bolt mains (on 2-3-4) and a completed fuel pump pad (ready for mechanical FP). Gandrud GM of Wisconsin has them from USD $3700 - $3850 delivered.

https://www.gmperformancemotor.com/category/GENG.html

[skinny z]

some 602 have cast crank some forged; dunno 'bout their rods. It's my understanding their current motors have Cast piston and not hyper (hyper more brittle and more prone to crack).

New GM current production L31 (from Springfield MO USA) have forged steel crank, powder steel rods, billet steel roller cam (although it has no fuel pump eccentric) and block has 4-bolt mains (on 2-3-4) and a completed fuel pump pad (ready for mechanical FP). Gandrud GM of Wisconsin has them from USD $3700 - $3850 delivered.

https://www.gmperformancemotor.com/category/GENG.html

I'm seeing the variety of crankshafts as well.
It was surprised to see the L31 has a forged 1053 crank. And the powdered metal rods aren't bad either. Still has factory bolts though.
Can't find one here in Canada. At least not from a quick search. Plenty of US distributors.

[BOOT]

I've shifted my 77 350 stock shortblock 6k idk how many times both gears. Far as I know it's never been out of the car.

Also had a 70's four bolt that was shifted at 6k and sometimes 6500 that I rebuilt with a northern kit, diff cam of course but used the hyper pistons(factory rods/bolts/crank).

[rebelyell]

some 602 have cast crank some forged; dunno 'bout their rods. It's my understanding their current motors have Cast piston and not hyper (hyper more brittle and more prone to crack).

New GM current production L31 (from Springfield MO USA) have forged steel crank, powder steel rods, billet steel roller cam (although it has no fuel pump eccentric) and block has 4-bolt mains (on 2-3-4) and a completed fuel pump pad (ready for mechanical FP). Gandrud GM of Wisconsin has them from USD $3700 - $3850 delivered.

https://www.gmperformancemotor.com/category/GENG.html

I'm seeing the variety of crankshafts as well.
It was surprised to see the L31 has a forged 1053 crank. And the powdered metal rods aren't bad either. Still has factory bolts though.
Can't find one here in Canada. At least not from a quick search. Plenty of US distributors.

if serious, visit your nearby GM dealership's parts dept manager ... part numbers 12691672 and 12691673

[skinny z]

I've shifted my 77 350 stock shortblock 6k idk how many times both gears. Far as I know it's never been out of the car.

Also had a 70's four bolt that was shifted at 6k and sometimes 6500 that I rebuilt with a northern kit, diff cam of course but used the hyper pistons(factory rods/bolts/crank).

if serious, visit your nearby GM dealership's parts dept manager ... part numbers 12691672 and 12691673

Yep. Been there and done that too.
The current 350 shortblock is considerably stronger though. GM forged 1053 crank. Elgin rods w/ 7/16ths ARP hardware. It does have Sealed Power hypereutectic pistons.
And it's getting up in run time.
Any rebuild and I'd be doing myself a favour by getting the crank and rods MPI'd. Plus a overbore. It all adds up.
So that's kept the wheels turning on maybe buying new.
Still looking around.

And visiting a GM dealer near me.

[BOOT]

Wish I went GM back when I bought this atk crate https://youtu.be/JyEFm7ee3Hk Or at least pulled all the covers/plugs and fogged it down right when I got it. Funny thing is the 355 I mentioned earlier has been sitting for over a decade in the same garage w/o problem and I didn't fog that engine, so you know they used junk oil.

Oh well it'll be fine when I'm done with it, when ever that will be LOL