Tknz

Hi, can anyone help with iron vs alloy tt. Iv read about people boring 5.3

I'm building a small ls tt, my max bore is 3.889 looking at 850fwhp, but under constant load, I understand the ls1 block cannot handle this but the 5.3 bored can,

How much stronger is the iron block bored to 3.889 over the factory ls1 alloy block.

Cheers

oscs

iTrader: (19)

The whole lure of the 5.3 block is the thick cylinder walls. If your plan is to bore it than just buy a 6.0l

Tknz

Sorry should have said, I'm limited to cubic inchs (class rules)

Tknz

260 is my max cubic, callies do a 2.6 crank but at 4 inch bore that puts me over by 1.4 cubic inch

oscs

iTrader: (19)

Personally in a boost application id pick the bored out iron block. I'm not sure the wall thickness of an LS1 vs a bored 5.3 though

dirty_old_chevy

If your going for the callies ultra billet, you should be able to get whatever stroke you want. How about stock bore 5.3 and a 2.85" crank? That will give you almost 256 cu/in.

Tknz

I have looked into stock bore and the 2.9 crank, but very limited to heads, I like the mast ls3 small bore heads, but they require 3.89 bore,
If the iron block bored is much stronger than the ls1 I'd be happy, but how much stronger

99tramsamc/fia

iTrader: (2)

Use a 4.0 bore minimum. Better heads.
The tall deck on the ls is going to kill that 265 incher.
Rods way to long, piston is HEAVY.... That thing needs to be in a short deck block.
How high are you planning on spinning it..
I've always loved the small cu in small blocks. NOTHING like watching the tach go by 10.
Keep a eye on the Bob weight. Where do you think it will be.

Tknz

Definitely be in the short deck 9.24,
6.56 rods 1.3ch pistons, cant get a crank smaller than 2.6 so 4 inch bore is too big

Tknz

Won't spin much past 6500 but it will be constant load for 30-40mins, I'm not sure about bodyweight yet, once I get an idea on everything, I'll hand it over to the engine builder, stuck on block choice atm,
Appreciate all the input

Tknz

*bobweight

gnx7

iTrader: (28)

What type of racing?

stock48

iTrader: (17)

I'm thinking same thing too....

Also OP I wouldn't put a huge head on a small CI like that unless it will be reving 10K RPM. Id look into the smaller TFS head or small cc AFR. That will still be huge on 260 CI. JMO

Tknz

Jet boat racing (marathon), aiming for 780hp ish, hoping to keep boost down, with big flowing heads/intake, competing with Lexus tt and nissan v8 tt,

Tknz

I'm not an engine builder but I have been told to go with the best flowing heads, let the turbos do the work and try keep lift and springs down for reliablty?? reliable is key for me more important than power

turboventura

I understand constant load but is the rpm constant too? Not familiar with that type of racing. Will you run an oil cooler as well?

dirty_old_chevy

I would imagine the turbo changes a few things, but would a 260 cu/in motor even be in the juicy part of its torque curve yet @6500rpm with big rectangle port heads?

gnx7

iTrader: (28)

There is a dry sleeved ls9 block at that bore size with head studs in the classifieds.

Forcefed86

iTrader: (4)

Trying to keep the boost low makes zero sense to me. If your building a boosted engine, let the turbo do the work. Boost isn’t hard on an engine if it’s done right. Look at the 24hour turbo Le’Mans engines.

Head flow won’t be the limiting factor for your goals, even on a factory head.

For example:
Factory short block 4.8. Worked 862 OEM truck castings, 228/230 .57x lift cam, and a Fast intake made 450/380 at the flywheel around 7k RPM. 15lbs from an efficient turbo setup would double that. Done deal!

Not suggesting you use factory parts for your application. But power shouldn’t be a problem if you don’t limit yourself on boost levels.

dirty_old_chevy

Ya that's another thing. If your rpm you rev at is around 6500, I can't imagine you'd want your horsepower to peak at much over 7000. But I'm probably missing something, and I'm all for learning. More info on how these races are ran would be interesting.