ToniH

GM has a kit to upgrade LT-1 to LT-4! I saw it while browsing something at http://www.gmpartsdirect.com. It sounds a good option for you LT-1 guys who are considering a top end rebuild.

Here it is: http://www.gmpartsdirect.com/results...ber=pk12550630

Regards,

Toni

Nathan Plemons

The only problem is though that for the same money you can buy a Hot Cam kit and have your LT1 heads ported to easily outperform the stock LT4 stuff that you get in this kit.

93Blackrose

:iagree: True.

biggrizzly

Just to pull this thread a litte bit more...

Does anyone know of a tech-tip article or other naration about how to perform a top-end modification? Not neccesarily using the GM LT-4 upgrade. Information like, what additional parts are recomended (ie. waterpump, opti-spark,etc).

This sounds like a promising upgrade to do without changing the entire motor.

SouthernSon

Nathan, do the folks with the ported LT1 heads upgrade to the lighter, sodium filled LT4 valves for the higher RPM's? Is this easy to do?

Black96Corvette

Don't waste the money on it, just buy the LT4 Hotcam Kit, Long Tube Headers, Gears ;) The stock LT4 heads don't flow that much better than the LT1's ( i dont think ). On Gm's webpage they say taht just bolting on the LT4 heads to the LT1 yields 30hp, that cannot be true.

STL94LT1

:iagree:

cprgmr

I'm going to be doing the top end sometime this spring and I'll be doing a complete write-up (with digi-pics) on everything. Look for it around April or May. :)

RichS

I hate how they advertise these "top end kits". The way they word them just by putting on a set of LT4 heads and intake make it a LT4. So many cars on the board even list there motors as LT4s just because the heads. It's more than just the heads. I would also just put the money into the LT1 heads and pick a cam.

95wht6spd

I agree, but you are also getting a new extra set of heads that have more potential for porting and you can sell your old heads or put back on if you sell the car. I am looking into getting my heads done by TEA, I sent them an e-mail but no response. Check this out: http://forums.corvetteforum.com/zerothread?id=496730

LT1 port and polish is $1500 min. + $475 Hotcam kit. If we could get the LT4 kit as a group purchase fro less than $1975 I might do that, plus I could sell my LT1 heads for $300+ probably or keep for the future.

SPEED750

you guys are missing the boat.this kit has the LT4 HOT CAM!this is a tried and true combo.this kit, long tube headers,new chip (ED WRIGHT) and your cranking out 435 plus HP.I've seen this in more than one magazine. :chevy

Z06_BluByU

Flow numbers for all.. LT4 vs. LT1 vs. Ported LT1.. huge chart of info.. check it out

http://www.malcams.com/legacy/misc/headflow.htm

Darkness

Good stuff :thumbs:

gtsyellow

how much more could GM have done to the bottom end? i'm sure you LT4 guys know the details. GM doesn't use forged pistons in small blocks, the 1&4 have the same crank & rods. so i'm guessing the rings are different? someone else also asked about valves and what's being used. the ported LT1 heads can use the 2.00/1.55 combo or the 1.94/1.50 combo. most of the guys choose a manley or ferra stainless valve for strength and quality. the higher end valves are worth CFM over the GM stuff. to make up for a slightly heavier valve more spring is needed. an example would be the hotcam spring floating at 6000-6200rpm on a LT1 but going to 6400rpm on a LT4. the weight is showing. comp cams make a single and also dual spring that fits the LT1 head. i highly recommend the 986 spring for mid 500 lifts or more than 6300rpms. they don't cost all that much and the strength to quality ratio is outstanding. they have 135# on the seat & have a maximum safe point of .600 lift and low 7000s in the rpms. well within the relm of more aggressive roller cams. a dual spring also will not drop a valve in your engine if it breaks like a single spring can. a guy at the track last year had no problem limping a dual sprung engine home after one of his main intake springs broke from extreme rpm. the LT1 head also has a 170cc runner compared to the LT4's 195cc. smaller runners promote faster air velocity and greater efficiency. a hyd roller 350ci engine will perform better with a 170-180cc head than a 195cc head provided they flow similar numbers. lower rpm use is stronger with a smaller runner.


[Modified by gtsyellow, 5:09 AM 2/20/2003]

FELNGR8

It depends on the year of your car. For the 94, if you also do the recommended heavy duty timing chain, then you go into the opti conversion that includes a different timing cover, later opti and different opti drive. There's a tech tip on the opti conversion. The 95 I'm not sure what the difference in the timing chain would affect on the other accessory drives.

From everything I can find to read, it seems that porting the LT1 head right yields more power than just substituting the LT4 stock heads. Like it yields more to unshroud the valves than to open up any portion of the intake from the plenum to the valve area. That's the porting work I'm getting, basically concentrated around the valve and combustion chamber. Back from there to the plenum is already open enough for any street engine, LT1 or LT4.

I'm not getting the lightweight valves or the RPM kit for the lifters. Which means I can't plan to spin the motor to 7 grand. Would the bottom end hold up if I did?? Most say no.

I'm getting top end work on my 80K miles LT1. The valves only needed a little cleaning on the back side before doing the valve grind. With Mobil 1 from the factory floor these things just don't suffer any wear. I don't know what kind of usage would REQUIRE all these parts to be done. But if you want to go to LT4 heads, it's nice to have a port matched intake and gaskets in the kit. Send the heads away for a porting job before bolting them on and you could get a monster power boost from this kit.

I'll have to check with the experts, but I don't believe that anything I'm doing disqualifies my car as a numbers match original for eventual judging. Installing this kit would of course do that. Just something to consider.


[Modified by 94lt1torchred, 1:48 PM 2/20/2003]

Goody

The crank is the same in size but the rod journal areas have been rolled and filleted to allow for greater strength and durability at higher RPM's. The differences between the LT1/4 has been gone over so many times. One of the LT4 guys can list the webpage that describes specifically the difference between the two engines.

I've gone the ported/polished LT1 heads with the Hot Cam route for my useage. Will be doing the swap in the future. Trying to convince the wife to let me rebuild the engine at the same time.

John Row

Here's the differences between an LT1 & LT4

home.tir.com/~steveher/lt4.html