thanks for the advice guys looks like 3 options

1 install it(with smaller injectors) and see what it drives like
2 mill the heads + change the cam
3 put the procharger on it and leave the th400/ptc convertor behind it and change the pulleys untill the 59 has a stronger rear end

 

4th option:

4. Leave the heads alone; change the cam; put in smaller injectors

Kinda all depends on what you're willing to spend, and your expectations for excellence in the finished product are, and how important you feel about keeping the heads unmolested and pristine (after all, once they're milled, there's no going back)

Yes if it still has the original rear axle, that's a potential failure point.

 

You are arguing totally pointless semantics. You clearly have little to no experience and then try to dish out advise as if you do. I feel sorry for those that would listen to your advise is all. 50% of what you say here is total nonsense… and that’s me being nice.

Linear throttle my ****. I’ve built and owned centri blower cars. If setup correctly, they are violent! Nitrous can easily have a less violent curve than a blower car. It can be staged/progressive/rpm activated/speed activated… etc. You can easily have a MUCH more controllable power curve than a blower car. Stop arguing moronic points! Either setup would be perfectly fine. Anyone can press a switch… insinuating this would be difficult for a woman is comical.


Please inform me how a N20 system effects the cruisebility in any shape or form. I’ll wait…


What I’m suggesting is getting the most HP per $ invested. Swapping injectors is a waste of $ and just plain moronic. A cam swap will cost quite a bit and do very little power wise. Basically not worth the time/effort without a lot of other modifications. The OP wanted a blower originally… So why you think a mild cam swap is gonna be some eye-opening experience is beyond me. He already has an aftermarket cam that will allow the car to rev out properly.

He doesn’t have a factory converter or low compression! In what planet is 9.4: low compression? LM7 5.3’s were 9.5! The newer 5.3 are 9.6 to 9.9. He is roughly .5 less than a flat top 5.3! That’s roughly a 2% loss in power! Yet you act like it’s some astronomical difference. Much like your cam theory, that is total nonsense.

His motor would NOT make less power than a factory 5.3. You are insane to think so. The cam and setup he described would absolutely smoke a bone stock 5.3 in a like chassis in a drag race. To say otherwise just proves you shouldn’t be giving advice. The injector size makes ZERO difference in power production. Its asinine that you keep mentioning that. There is NOTHING un-tunable about 80lb injectors in a pump gas LS! The Deka 80 is the most commonly used aftermarket injector out there! You’d know that if you actually had any real experience.

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In a weekend cruiser, for a spouse, in the UK? ...

Don't keyboard-warrior things into my mouth that I never said. I DID NOT say that a woman couldn't do that, or ANYTHING OF THE KIND. The OP is building A CRUISER FOR HIS WIFE, in the UK, not some kind of max-effort race car in places where there's miles and miles of open roads. What I DID say was, that in A CRUISER FOR HIS WIFE, in the UK on UK roads, nitrous doesn't match the application. A blower or turbo might match it better, since those are always there and are linearly related to throttle input and don't require an extra bottle and whatever plumbing and switches and all that, butt he already indicated he's not interested in pursuing that approach.

LISTEN TO the OP. Tell him about things that point in the direction he's asking about going, NOT just spank the monkey about how great you are and call me names for giving COMMON SENSE advice that MATCHES his stated goals.

With the lower compression and MUCH larger cam, YES IT WILL, where he's going to need it. Sure, maybe you can put it on a dyno, and the peak HP may well be considerably greater; but at the RPMs he's going to be concerned with in A CRUISER FOR HIS WIFE, on roads in the UK with 3.36 gears and (probably? maybe? iunno, just guessing, he hasn't said) a stock Turbo 350 torque converter, he'll be just like the kids who wouldn't listen to me so I screwed up and took their money to jam too much cam into a gutless L48 for back in the 80s because "all the fast cars" had that or they wanted the "sound", who would then come back and complain that their car used to be able to spin the tires butt now it falls on its face and loses every stoplight-to-stoplight race they try to run, because it's so GUTLESS at low RPMs. THAT'S what the combo he has now, without the blower, will be like.

Yes we all know that. He DOESN'T HAVE a LM7. He has a 5.3, with whatever short block (pistons) that he hasn't specified, and heads w larger chamber than the LM7's. He has about the same compression that the LOWEST 5.3 (the LM7) had, or slightly less. A LM7 is completely happy hauling concrete around a construction site on 87 regular; any motor that will do that, in most anyone's book, is low compression. Try taking a LM7 and stick a cam in it that has 30° more duration than the one that came in it, and come back and tell us how snappy and responsive and fun to drive (CRUISE) in a car with no gears, it REALLY is.

Again, DO NOT keyboard-warrior things into my mouth that I never said. I DID NOT say that, or ANYTHING ELSE about power production in relation to injector size. What I DID say was that injectors sized appropriately - such that they're at maybe 80 - 90% DC at max power, NOT 35%, which those 80s are going to be - are going to be MUCH easier TO TUNE, especially around idle and very low RPMs, such as CRUISING AROUND on roads in the UK, where the pulse width is going to have to be down into the microseconds to get anything like decent driveability while CRUISING. Driveability. CRUISING. Earth to forcefed86, come in forcefed86.

Spend less time attacking my COMMON SENSE and polishing the pole about how much you "know", and instead try to help the OP accomplish HIS goals. NOT YOURS. He's clearly trying to DE-MAX-EFFORT this whole thing and turn it into a "cruiser", NOT go for broke with staged nitrous and all that. Let me reiterate HIS goals, so that you can calm down and re-focus, and get your hand out of your pants.

 

I have a centri blower car that is slow by todays standards, but I would still call the torque hit at 3k rpm “violent,” and the torque curve looks like someone rolled over it with a steam roller. 3k rpm might sound kind of “high” but with 3.73 rear gears 3k came pretty much just off of idle. Enough so that if you dumped the clutch at 2k or so rpm and floored it it’d would sit and spin until you let off even through 3rd gear.
That being said, I think the power level of the OP’s ride is sort of moot since it’s a classic cruiser, and a woman’s at that. It seems to me like “drive-ability” per dollar would be more of a priority than power per $. If it can be tuned to not buck and chug at parking lot speeds then I’d probably run it as is. If the 80 pound injectors make tuning it so it’ll be a good cruiser a hassle I’d swap injectors. I don’t know his wife, maybe she’d rather run a 10 second 1/4 mile even if it meant having crappy parking lot manners. But not mine though.
Maybe people are calling 9.5:1 or whatever “low” because the LS1 has a 10.2:1 or something like that.

 

i may have been wrong on the comp ratio
5.3
ljms wiseco boost pistons 3.800 bore -3.2 dome volume .005 deck clearance
243 heads 65cc chambers
molnar 6.125 rods
ls9 gaskets .055
BTR LS3 supercharger cam 227/244 613/596 115
the TH350 has a manual/auto valve body
b+m tork master convertor 1900-2100 stall
some of the calculators i have used puts it at around 10.2 although the engine builder quoted 9.8
car will mostly be a cruiser with an occasional run up the strip

 

get rid of that converter, and do a higher quality and way higher (3200 to 3600 or better) stall speed. tune it and enjoy it.....