LT4 Kit for LT1

[Injuneer]

109mph trap speed on a 3,650# car works out to about 375flywheelHP, or about 307rwHP on an A4 and 321rwHP on an M6. You'd have to be trapping 113.5 if making 420flywheel. Rob's numbers, and his dad's look just about right.

[N20LT4Bird]

what is the equation you are using? According to your equation, my g-tech #'s are too high?

[N20LT4Bird]

That seems low to me. M3eater is running 106mph and has actually dynoed the car @323 rwhp. So if my car is running 109 mph, it would have more than 321 rwhp.

[Injuneer]

Originally posted by N20LT4Bird
what is the equation you are using? According to your equation, my g-tech #'s are too high?

Did you actually run the 109 on a drag strip, or is that a g-tech result?

What is the actual race weight (including driver) of your car?

If I enter my MPH in the equation - one I developed by using one of the popular "HP from MPH and ET" formulas, then adjusting it for 4th Gens that I had actual engine dyno number on - I get exactly what the engine developed on the engine dyno. 127.6MPH = 635flywheelHP, at a 3,760# race weight.

You also have to be careful throwing around the % drivetrain losses. I've got actual figures that indicate the T56 drivetrain only loses about 13%. And I don't think the 4L60E is as high as the 18-20% that some people like to use. A "loose", non-locking TH400 however, is well over 20% loss.

[Joe 1320]

Originally posted by N20LT4Bird
what is the equation you are using? According to your equation, my g-tech #'s are too high?

G-techs are darn close on the ET, but read 3-4 mph too high. I ran my g-tech at the track along with the strip timers. My ET was 13.14 and the g-tech showed 13.17.... close enough. The mph using the strip timers was 105.4, the g-tech read 109. Way off. They are good for comparisons on mods and driving technique, good for a pretty close ET, the MPH still needs work.

[wolfdogs]

Originally posted by coloradoformula
I too was considering the LT4 conversion kit. Only question I have is if I will still be able to pass Colorado emissions. Until I know for sure I think I'll wait.

proper programing will get you thru emissions, with cats in tac of course.

with my lt4hotCAm and mods..my 97 CompTA beat our bolts-on's 97 firehawk in every emissions category but 1 !

[N20LT4Bird]

The only thing I have used the G-tech for was rwhp. I have run the car at the track many times and run around 109 without nitrous and 119 with nitrous.

I would just assume that the G-tech is off, but M3eater said that he DYNOED at 323 rwhp and ran the quarter at 106. Assuming our cars are close in drivetrain and weight (maybe their not) it would seem logical that my car was making more than 323 rwhp??

I didn't mean to "throw" around a 20 percent figure, it was just one of those age old things.

[N20LT4Bird]

Oh sorry, missed that question - race weight is around 3800. This figure is approx. Unladen is about 3550 + 200lbs (me) + FULL tank of fuel.

[Rob]

You can't just go by another car making a known HP. My WS6 dynoed at 324rwhp or something like that and I pulled 111mph. HP is only one aspect. RPM range, torque, area under the curve, gearing, driver, etc all play into it.

The only time I dynoed my TA, I got 318rwhp. I also went 111mph. That's decieving though because torque was 455rwtq.

Its hard comparing just numbers.

[Al 96 Ram Air T/A]

I need to get involved...

Can't seem to figure how everyone states that building up LT1 stockers (heads) is cheaper...it really frustrates me.

Let's start at the $2300 mark for the LT4 package from Summit.

If I where to try to duplicate the same with LT1 components, here's the list an estimated price:

port and polish LT1 heads $1500 (cheapest I've seen, most are about $2000)
1.6 roller rockers $300
gaskets $150
LT4 Hot cam $175
LT4 timing chain $75

total price approx. $2200 (this is very conservative, it's much closer to $2600 when you factor in shipping, quality of porting, etc.)


Now, while this seems to me to be essentialy the same price as the LT4 kit, let's not forget with the LT4 kit, I get to keep my stock parts!

So, if I were to sell the LT1 heads (about $275) and LT1 intake (about $125), I could recoup about $400 bucks more, bringing the LT4 package down to a very reasonable $1900. You can't buy a set of ported LT1 heads for that much when you factor in shipping and core charges.

I've been researching this for three years..three v-e-r-y long years. To say that porting LT1 heads is "much" cheaper is dead wrong. In fact, it's far from the truth. LT1 head porting shops are raping us. $2000 for a set of heads that still only flow about 270 cfm is really a joke when you think about it. Now, I will admit that you can get more power out of ported LT1 heads than stock LT4, but we're not talking much. But, port the LT4 heads and the ported LT1's can't keep up.


There is only one set up I've come across over the years that has me thinking. Edelbrock has released there own LT1 castings, said to be similar in design to LT4 castings in flow. These only cost $1050 for the pair, with no core charge. The good news is that you don't need a new intake manifold for these to work. When I spoke to an Edelbrock engineer on the heads, he said using the LT4 Hot parts with Edelbrock heads will net you the same gains as using stock LT4 heads. And because there is no core charge, you can still turn around and sell your LT1 castings.

Assuming the same costs as above, the Edelbrock/LT4 Hot set up will cost $1750...after selling your LT1 heads...a cool $1475!!

The only question is, do the Edelbrock heads flow as well as the LT4 heads they were designed to compete with? That remains to be proven...I'm hoping at a minimum it will force the head shops to cut their prices. Why Ford heads cost half as much really bothers me!

Am I making any sense???

[Injuneer]

Al.... you are making complete sense.

The only place that you might find some savings in your numbers is in the head porting. I think there are some people getting very good results for $1,000 on the LT1 head porting. One of the guys that seems to be producing some exceptional results for less than $2,000 is a guy named Lloyd Elliott. I don't know him, and have never seen his heads, but people on CamaroZ28.com seem to like them, and are getting proven results, both on independent flow benches, on the dyno and at the track.

Like I said, I do not know Lloyd, I'm not "endorsing" him, and I know there are others doing similar work for simliar prices..... I'm just giving one example.

I think the LT4 "kit" makes sense for a lot of people.... proven parts, of known, CONSISTENT quality. But there are always some people who want to port their own heads, do all there own work and save some $$$$ below what the LT4 kit costs. There are always some people who want a meatier cam than the HOT cam... and the cost of the cam isn't going to vary that much with a more radical profile.