62vette

Hi. i have a 5.3 lm7 which was built for boost with 243 heads.3.800 bore ls9 gaskets Btr ls3 blowercam 227/244 613/596 115 ls6 intake holley sniper t/b will it run ok without the boost or will it need a head skim/change of cam also currently has 80lbs siemans what injectors would you recommend will be run with holley hp ecu
paul

G Atsma

What is your current compression?

62vette

believe it ended up around 9:4:1

RB04Av

With that cam it'll be extremely weeeeeek at low RPMs (let's say, below 4000 or so). Above that it'll be only moderately weeeeeeek.

For a N/A 5.3 on gasoline, 36lb injectors or thereabouts, are probably adequate. 80 is too much.

What is this in? What is it being used for? What transmission? What gears? What weight?

Forcefed86

iTrader: (4)

It’ll run fine. IF you replaced the cam with something more NA oriented, you could prob pick up 15-25 chp at different RPM ranges depending on the cam and combo. It’s not going to be a night/day difference. Could also spray it with a 100-150 shot for the same effort/cost and it would be a night/day difference.

62vette

it will be installed in my wifes 59 vette. a cruiser th350/3.36/ around 2900lbs

RB04Av

For a use like that I'd look at a cam with maybe 216 - 200° @ .050" intake duration and maybe 5 - 6° more than that on the exhaust; 110 - 112° LSA. Something roughly kinda like this https://www.summitracing.com/parts/hrs-190295-12 or https://www.summitracing.com/parts/btc-btr31824100. That'll get it back up to at least somewhere near a stock power level in the RPM range it'll need to be operating in. Especially with a stock torque converter and those gears, the one you have now will be a total dog. The white Bosch injectors would be about right.

Out of curiosity, what was this engine originally intended for?

Forcefed86

iTrader: (4)

To say it will be extremely weak is an overstatement IMO. It’s a light car… you’ll be fine don’t over think it.

You are probably talking 4-5% HP difference between a tighter LSA cam. Then you could shift the power up or down depending on what you want. With an LS6 intake, you’ll prob peak semi early. So ideally, less duration and a tighter LSA with more overlap would be beneficial. But again… you are talking 4-5% hp. I wouldn’t pull apart a motor for that personally.

Now if you have E85 available and wanted to get a little wild on compression, there is quite a bit more power to be had. But again, you only see roughly 3-4% gains per full point of compression gained. So the making the usual baby mills on a set of 243’s won’t net you much HP for your $.

But if you bumped it up to say 13:1 ish with a good cam and switched to E85. You are talking 20%+ gains in power. Which would be pretty substantial.

I just slapped together stock bottom end Alum JY 5.3. sold the 243’s and picked up the cheap 706’s with smaller chambers no one wants. Then milled .100 off the 706’s and fly cut the stock pistons a tad with a DIY tool. Ended up with about 13.3:1 5.3 for peanuts. Should have gone to .120 and been closer to 14:1. (intake fitment after milling that much is also something you'd have to address.)

That’s an awful lot of work VS a 100 shot!

62vette

was gonna be used in my 62 vette with a P1SC procharger

RB04Av

That'll work GREAT for a weekend cruiser for one's wife. Not that "wife" necessarily wouldn't enjoy it, or whatever; only, doesn't sound too much like a reasonable match of equipment to purpose.

In the UK?

We're not in Kansas anymore.

The original plan probably would have been fine. But that's a pretty significant re-purpose. Unlike the other poster who doesn't seem to understand your purpose or situation, you're not looking for "HP"; you're looking for LOW END performance. Idle or just off-idle about 95% of the time. At the RPM where the motor will be forced to run, in a purely public-road ("cruiser") application on UK roads with their 50 - 60 km/hr speed limits, you don't need "HP". Being concerned about "4-5% HP difference" isn't the correct focus.

The RIGHT thing to do for yourself would seem to be, match the motor to its new VERY DIFFERENT application, with minimally invasive and/or expensive changes. Simply swapping to a more appropriate cam and properly sized injectors fills that requirement as well as anything else possibly could. Assuming of course that you end up doing anything AT ALL. After all, as said, it'll "run" "OK" as is; no reason you "can't" just drop it in as-is; just, it'll be FAR FROM optimum, and there's ALOT to be gained by adjusting it. Just like the weeeeek old 350s of the 70s and 80s that people on this side of the pond used to build, you'll end up with a low-torque, hard-to-tune, very inefficient disappointment, unless the fundamental mismatches are straightened out as much as practical.

Z28Roxy

iTrader: (4)

I ran a milder cam than that N/A, similar compression, sure it wasn't stellar compared to a wild N/A build but it was a lot faster than just bolt ons. Very fun to drive too even just N/A. Good power from low end all the way to 7k, though I have about an extra liter than you on displacement. I also did upgrade the lines and whatnot to run E85.

As far as injectors, meh go big or go home. You've got a Holley that can control high or low imp injectors which gives you more options. I ran 72 lb/hr N/A and with the stock PCM but with the Holley and turbos going on I went up to 160 lb/hr. Bigger injectors won't hurt anything other than your wallet, think about it, a high horsepower street car might have huge injectors but be using very little fuel at idle.

RB04Av

Problem with injectors that are too large is, getting a narrow enough pulse width to idle properly, without them being EXTREMELY sensitive to their dead time. Makes idle and other low-speed & low-power tuning more difficult. Best to match them reasonably well to the engine's requirements.

Stock 4.8 / 5.3 / 6.0 injectors (non-flex-fuel) are something like 28 or 29 lb/hr or thereabouts. A stock 6.0 comes real close to maxing them out. A somewhat hotter than stock 5.3 benefits from a bit more than those. No need to put ones in that are like 2˝ times stock though.

The white Bosch ones should be a piece o cake to tune while being PLENTY more than the bare minimum.

Y2K_Frenzy

I’d see if I could get the 80’s dialed in or not prior to buying another set.
@RPM WS6 See it’s not just me. People are calling a 243 head and mild cam combo “slow” these days.

Forcefed86

iTrader: (4)

Why is 1 power adder more or less “wife friendly” than another exactly? If it’s the type of wife that would be disappointed with the lack of a blower… then I’m sure she’d rather have a “go fast” button than nothing at all! Would be a hell of a jump compared to a cam swap anyway.

If it were me… it would be more of a situation where I may want to occasionally drive/track my “wife’s car” and want it to be quicker. Then a healthy n20 shot would be even more appropriate.

Never claimed to know the Ethanol situation in his area, simply asked. Its all over the world, not just KS.

I’ve built/owned many sub 3000lb LS cars. The last thing any of them needed on the street, was more low-end torque. Esp without full time drag radials of some sort. I see them as sports cars and not tow trucks.

I’ve tuned several cars (including my own) on Delphi 80’s on pump gas with zero issue. Getting the PW low enough to idle well isn’t really an issue on most hi-z injectors and aftermarket ECU’s these days. I can idle pump gas on 220lb Bosch CNG injectors! Should have zero problems idling any decent 80lb HI-z injector. I even run 80’s on my wave runner! No reason to go smaller IMO.

G Atsma

It's all part of modern dick measuring.....

RB04Av

Let's see... seems to me that some form of "adder" that requires filling a bottle, pushing a switch, and so forth, at which point one gets some fixed (100 HP or whatever) blast of juice, is NOT "wife's cruiser" friendly material. ESPECIALLY not on the roads in the UK, which if you go there, you'll see what I mean. There aren't many wide-open stretches where one can just blast to the max in the manner that nitrous lends itself to.

We're not in Kansas anymore.

OTOH a system that operates automatically and responds somewhat more or less linearly to the throttle such as a blower or even a turbo, and doesn't require occasionally filling a bottle, could much more readily be put to use in such circumstances.

According to the OP, he's looking for a "cruiser". Any advice that fails to take his stated purpose into account, and instead runs off at the mouth about their own tuning ability and "more power" fetish without being affected by what the OP is actually doing, is just bishop-buffing and self-aggrandizement. NOT "advice".

So have I. THE LAST THING any of them needed was a low-compression motor with too much cam and injectors that render it untunable under the conditions it's going to be used under. I can't tell you how many people I knew with Novas, 2nd gen Camaros, etc., who built motors like that (it was big carbs back in those days, not injectors, butt the end result was the same), and put them in cars with highway gears and stock converters; and then proceeded to get humiliated by stock 2-bbl cars.

The combo in question will be slower than a STOCK 243 head and STOCK cam combo. ​​​​​​​

Y2K_Frenzy

Always make sure to measure from underneath.

Y2K_Frenzy

I need to upgrade to be that slow… 241 heads and stock as a bas+ard..

RB04Av

I fell ya, mang. Same here. I have less than what you've got. (not referring to the male organ dimension jokes, although, who knows)

98LS1auto

iTrader: (3)

My engine is built for boost. 9.5:1 compression. Never have put any boost to it. Times are in sig. No its not very fast. Still 10 second car. So not bad.