LT4 Converting a LT1 into an LT4

[soggytaco]

how much do you think it would cost to convert a LT1 into an LT4. Im sure you could do it it is the same basic block.

 

[Vettelt193]

how much do you think it would cost to convert a LT1 into an LT4. Im sure you could do it it is the same basic block.

It's not realy cost effective to do the conversion. The LT4 has many different parts, and anyone that claims to have converted their LT1 to an LT4 has not done a true conversion.

What most LT1 owners do is the LT4 top-end kit... you can get that from GMpartsdirect.com

 

[Tuna]

What most LT1 owners do is the LT4 top-end kit... you can get that from GMpartsdirect.com

The gmpartsdirect.com part number is PK12550630. Priced around $2100.
Been there, done that.

 

[KOPBET]

The gmpartsdirect.com part number is PK12550630. Priced around $2100.
Been there, done that.

How much was it to have it installed for you Tuna?

 

[Tuna]

How much was it to have it installed for you Tuna?

That's actually hard to say. The installation of the LT4 upgrade kit was part of a total package of rebuilding the lower end of my LT1 with bearings and rings, new oil pump, etc.; along with installation of a new clutch and upgrading the OptiSpark and the heavy duty timing chain. I paid $4500 for the whole job - the clutch was 1500-1800 of that and they already had the engine out already.

I forgot to mention that with the OBDI cars, you'll need an updated computer chip - About $350.

If my engine had low miles on it and I didn't need or want new rings, bearings, etc,; I'd look at the labor cost for replacing a Cam and the removal of the heads. That's about all it requires.

 

[soggytaco]

Tuna,

How much HP do you think you gain? Does it also increase the redline R.P.M.

 

[Tuna]

Tuna,

How much HP do you think you gain? Does it also increase the redline R.P.M.

I never dynoed my stock LT1 but based on the dyno results of other stock LT1's (250-260 at the rear wheels), I gained 70 HP. My car dynoed at 328HP at the wheels after all the mods were done. The mods were:
LT4 heads and intake,
LT4 Hot Cam,
heavy duty timing chain
Corsa Exhaust
FastChips.com computer chip
and the basic bearing and ring work

There was more HP to be had that I didn't get because I continued to use the stock LT1 24# injectors, 48mm throttle body and stock exhaust headers. I used up my budget so I didn't replace them.

30# injectors and a 52mm throttle would provide a little more HP. Long tube headers would be helpful also - assuming that you don't have to pass visual inspections.

I had FastChips.com mail me an upgraded computer chip. Cost $350. All I needed to do was tell them my mods and they provided the properly programmed chip.
The new computer chip allowed for higher RPM. The stock chip or a mass produced chip like HyperTech will not provide the higher RPM range and will probably not let it idle correctly. With the mods done, I would shift at 6000 and had fuel shutoff set at 6500.

BTW, when the mechanical work was done, we started the car and ran it for a couple of days using a HyperTech ThermoMaster chip. It just didn't like to idle and tried to die a lot. At part throttle, it seemed okay. At full throttle, it was really flat - not enough fuel is my guess. THen the fastchip was delivered - that brought the car to life. The fastchip set the idle at 900 and provided the full throttle mapping that worked with the cam and heads.

BTW #2: I dynoed the car with the fastchip and stock exhaust at 306 then added the Corsa cat back system and dynoed again. The exhaust change added 22 HP.

Hope this helps.