kwik_ta

I'm pondering putting one in my vette with fully ported lt4 heads, 1.6 rockers (with correct springs), em long tubes with cats, full exhaust, and most other bells and whistles. I'll be using the stock gears for the time being though. The car is primarily a weekend toy that is mostly street driven. I'm curious about the torque curve and loss on the low end.

Also I plan on porting the stock heads on the ss while adding 1.6 rockers to trasplant the hot cam from the vette into it. I never had a dyno done on the vette so i am curious who's done this and what kind of power did they make?

Kurt Crosbie

My 95 TA M6 put down 381rwhp with stock heads 1.6RR and 11.2:1.

It had a mail-order tune. Didn't notice any loss of power on the low end.

96capricemgr

With the LT4s you will see a loss of lowend, they are a bad choice for a NA 350 held inside the pcm's limits anyway. Even the guys that race with them will tell you you will need more displacement and RPM to pretend to take advantage of them but if you look for actual results that doesn't even pan out.

far as the gears, I made the mistake of doing a much milder cam before gears and even with the milder cam I will tell you I did it backwards, do the gears first.

PA94Z

That makes a whole lot of sense. He should rip the LT4 heads off his LT4 motor for LT1 heads because they are a bad choice for a 350. I don't know what GM was thinking..

96capricemgr

LS1TECH - View Single Post - LT4 VS stock P&P heads
Read the last paragraph. The first paragraph is something I said he had a problem with and I can support it.

I don't agree with Ed on everything but there is no denying his experience and wisdom.
My opinion on the LT4s though is only his ego is stopping him from admitting he made a mistake with the LT4s.

GM Performance Cars - 1996 Pontiac Trans Am - Natural Born Killers Car later went 9.88 and Ed was the tuner.
GM Performance Cars - 1996 Pontiac Trans Am LT1 - Natural Born Killers
Look at things like weight, compression, cam, and rpm necessary to get their quite similar performance. Pay particular attention to the rpm difference as it specifically applies to the OP's question. The LT4 has 7 degrees less intake duration(more lift though) and turns more rpm for the same performance from a lighter car with more compression. Seems to me ported LT4s need rpm and even given rpm in this case still aren't really working.

Far as what GM does, yes they do a lot of things right but some things they do for marketing and to give the type of people who buy new Vettes paid a little more for to feel extra special. I believe the LT5 was no longer offered for 96 so IMO the LT4 option was a stopgap to offer those who wanted to pay more for something "extra" something to spend it on. Heck they put an intake on that was internally an LT1 intake, proof they were more looking to get paid than to do something really right.

kwik_ta

I can't say I totally agree but you do provide interesting findings. I do remember a bunch of guys on the Corvette forum once ported some lt4 heads along with lt1 heads to compare them to the Afr195 heads. They bench flowed the heads and they were all quite comparable. For the record I'm using the lt4 heads cuz I'm being cheap. I realize I won't be able to afford the 396 I want the way I want to build it... Which means I also don't have the funds to build the ss to my dreams. But I can budget build both and still have fun.

I want to get into the 11s with the vette but i don't race as much as i used to. I just want to have a lot of fun taking it out on the weekends. I just don't want a car that's going to rip the tread of the tires at 7 grand but coughs at 2500. I love the way the hot cam drives but i want more... A lot more lol. But incidently that's also why I'm keeping the hotcam for the ss.

96capricemgr

There is a 3800lbs Impala that is running 10.9 NA on a stock shortblock, with ported LT1 heads and intake.............................
My street car a few hundred pounds heavier with the same basic setup engine wise runs 11.5 at somewhere between 41-4200lbs.
Awhile back the fastest NA Impala was a solid roller 396 LT4 with FAST computer and TH400 I don't know how much lighter his car was than mine but I know he used to sell aluminum bumper supports, if he went that far lightening I know it was definitely lighter, that ran 11.5 at a few more mph than I do.

There are a few fast cars with LT4s but when you start comparing them to the fast cars with LT1 heads the benchracing about how much better the LT4s are just doesn't pan out.

Far as the cam why are you looking at the 847? There are a LOT of cams that fall between the HOT and 847.

kwik_ta

Originally I wanted a solid roller 396 built to be indestructible while generating as close to 600hp as i could. It was mostly for fun and bragging rights and knowing I can compete in power with a new z06. Well thru divorce and child support and general life I can't do that anymore.

I chose the 847 mostly because of cost. It's proven to make great power and put down excellent times and blah blah blah. I'm scared to pull the trigger because I can't afford to do this more than once lol. There was a guy on the vette forum who had a custom grind billet cam made that made insane top end power. He bragged about his peak numbers on the dunk number like he was hot ****. Many of us pointed out that the torque curve didn't build power until 4 grand but he didn't care. Well later he was unhappy with the street-ability referring to it being a pissed off honduh and being able to feel the v-tec kick in because he lost the low end. I'm trying to avoid being that guy.

I want to stay naturally aspirated and plan to do some 1320 runs and some road racing on both cars. But both cars will remain primarily street use.

RamAir95TA

If you're considering road racing and street use the 847 is not the cam for you.

kwik_ta

??? What would you recommend? Is like to make enoughpower to hang with a new z06

96capricemgr

Hanging with a new ZO6 in an NA stock shortblock LT1 car is kind of asking for a lot. Yes a good heads/cam LT1 can make 425 or so rwhp. The ZO6 makes more than this with torque a stroker LT is lucky to make.

The overcamming you saw the Vette guy do is VERY common and is exactly why you should step back a little. Custom comp cams can be had pretty cheap about the same price as their shelf cams, don't let them spec one though as their tech line is BAD.
The very nice lite valves in the LT4s would help you keep the XFI lobes under control. I would be looking at something mid 220s or so on the intake side, I don't think they have any shelf XFI cams that size but I am pretty sure they have some lobes. The ever popular 503 cam from Comp should work nice too, ported LT1 setups with it tend to shift up 6400 or so but you would get a little more rpm from it due to the big port you have.

Is tailpipe emissions inspection a factor?

RamAir95TA

If you're trying to hang with a new Z06 you're going to need a hell of a lot more than you think. I barely hang with my buddies with my combo. Granted I destroy him in the 1/4 mile but from a roll he's got me.

kwik_ta

Emissions is not a factor but i will be using cats just in case