hello all, im fresh into the ls motor scene and am looking to put a ls based vortech 5300 into my older buick regal and boost it with a moderetly sized 76 mm turbo. needless to say ive got alot of research to do but id like to ask a couple quick questions.

now this will be a budget build for the most part, so id like to keep the stock bottom end and if possible swap most of the accessorys adn intake from a ls1... is this possible on a 5.3?

i know the stroke is same as a stock ls1, but the bore is much smaller... my question is can a set of stock ls1 heads be fit and ran safely on a smaller bore 5.3 without valve shrouding issues?

ideally id like to keep the smaller bore for now to facilitate holding boost and keep cylinder wall flex under power to a minimum.....but whats the safest bore possible in a vortech 5.3 iron block?

since im walking out of the "turbo buick" world of 7 years and into the "turbo ls" world, ill prolly have alot of dumb rookie questions.....

 

the only dumb question is the one you dont ask. we are all here to learn and help others. ls1 heads will fit but look into ls6/ls2 heads. same 64 cc chambers (drops compression bout 0.3 over 5.3 heads) but slightly larger 210 intake port over ls1/5.3l 200. will allow little more air and boost in. as for the bore, several people have taken the block out to the 5.7l bore but must be careful, especially with forced induction. will have to have the block sonic checked to make sure it will handle the bore without overheating problems. hope all this helps

 

yea im looking for a compression drop out of the ls1 heads and in genneral a better flowing head. i was (more or less) wondering if the combustion chamber in a stock ls1 head will hang over the bore of a 5.3? thanks for the response.

 

Nope you will be fine with the 243, 799,or 241 heads on a 5.3 and boost.

 

How much compression are you interested in dropping? How much boost are you shooting for? I know Parish8 did a dyno experiment with a 4.8L engine a few years ago (he tried to blow it up to find the limits) and it pulled awesome numbers -- like in the 700 rwhp range if memory serves (try a search for 4.8 with Parish8 as the thread author).

I'd stick with 243s if you want 64cc chambers and 317s if you want larger (317 and 243s are the same, except 317s have solid valves instead of hollow/sodium filled, and 317s are 72cc chambers). Awesome castings untouched, and with a good p&p program (like at WCCH) the heads become crazy good for the money invested.

 

id like compression in the high 8 to 1. but mid 8 to 1 is acceptable. id like to try throwing 93 octane at it with about 14-15 lbs in the end... does anyone know what kind of valve job is delivered on a stock ls1 casting? 3 angle? would a 5 angle help or just be throwing money away?

 

I'd look into 317s. My 408 is 8.65:1 to GM MLS gaskets (compressed .051) and has 28.9cc dished pistons. At minimum, I'd run 243s. They're cheap these days (check out corvetteforum.com for the occasional deal in $300 range). 317s can also be had on the cheap.

However, you won't need that low of compression for 14-15psi. You can get away with 9 or 9.5:1 on these genIII engines up to 15psi IMO. Especially if you run a nice meth kit from Julio (same guy as the GN Julio -- alky controls )

 

Hellbent (TJ) has a track record of running several 10:1 motors (L33, LQ9) up to 19 psi with good fuel without problems for long periods of time. It seems like the entire key is no detonation, not the amount of boost.

 

I would shoot for 9:1 at minimum, but that's just me. You can push 14-15 lbs to it w/ 93... It will be a dog when you aren't in boost if your compression is too low. I run 10lbs on a stock 5.3 (9.5:1) and I would push to 12 if I had the injector capacity for it.

 

Well, yeah, but the chance of detonation is one side of the equation and pressure, heat, octane and timing are on the other side. What we are playing with is the lowest chance of detonation -- we need to know the fuel type and the boost target.

TJ ups the boost by running more octane (good fuel), great intercooling and lower timing -- and might be able to tolerate more risk in the setup. You can play with any of those factors to reduce the chance of detonation, but if you want 15 psi and 93 octane, CR, intercooling and timing are the remaining options. We assume everyone wants the most timing they can run (e.g. most power) and will run adequate intercooling. Now, if you want to give on the 93, the CR can obviously be higher (same deal with timing) and paying for very expensive intercooler options -- A2W with a chiller and methanol, for instance (although both add other constraints to equation).