can we put LG4heads intake and carb on a 400 block??? my friend has a 87 camaro with a lg4 305 and we came across a 400 block for free, what would have to be done for this to work under the stock lg4 induction???

 

ud have to have them drilled for steem holes...but dont do it they wont flow worth a crap and it will just totally suck ***** dont waste ur time and money your better off with a lg4 then that idea...

 

ok well how about the stock 400 heads and intake with the LG4 carb on top???

 

Your compression ratio would also go through the roof with those heads. I had similar heads on a 350 and it had over 11:1 compression. 1/8" more bore and the longer stroke will put it much higher than that yet.

The LG4 intake, if its the aluminum one, is better than the iron intake the 400 came with. As for the carb... depends. Is the LG4 carb computer controlled?

 

Baloney. LG4 heads flow better than stock 400 heads.

1.94"/1.60" valves, basic port clean-up, dished pistons to control compression, a real cam, headers, LG4 control system, it'll run circles around a stock 400.

 

but come on wouldnt it be wiser to put the money that u would spend working those heads and lowering the compression twords a good set of afordable aftermarket heads that flow even better allowing for more power potential...

 

I've reworked an oldsmobile CCC Q-Jet to feed a 403 that I swapped in place of the 307 vin 9 in a cadillac.

 

hey five7... bologna

just saying

 

Perhaps. But that isn't what you said.
You get the idea. . .

 

you guys are awesome lol wish you guys lived around here so id have someone to talk to lol but yeah it will definately be comp controlled, would like to reuse his stock setup keep everything "looking" stock and getting halfway decent mpg... any recomendations on a cam... pistons???

so just get the ports cleaned up and have the larger valves installed on the LG4 heads and theyll bolt on and go??? what about "drilling for steam holes??

any guess as to how much power it would make???

 

You need to drill the steam holes.

Note I didn't say it would be the best possible. Bolt this kit on http://www.sdparts.com/product/SD806...merIntake.aspx - after drilling the steam holes, of course - and it would pretty much look stock but would run even better.

Keep the cam reasonable, like a Comp XE268. You'll need dished pistons, probably in the 15cc range.

That's an easy 400 HP with decent economy when you aren't getting on it.

You may have to go with larger primary jets in the CC q-jet. Secondary tuning should be assumed regardless.

Have that free 400 block checked over carefully. Don't spend a dime on machine work or parts until the machine shop blesses it as rebuildable. As always, if it sounds too good to be true, it probably is.

 

so have the block magnafluxed???

i was thinking of building the same thing for my car except i already have the vortec heads and intake on mine... so i could make approx 400hp and around the same amount of torque with vortec heads, performer intake stock Qjet with bigger jets and a basically stock rebuild 400ci short block?? ???

approx how much hp with the LG4 intake and heads???

 

Having the block mag'd is always a good idea if everythings apart, especially with the 400, as they are somewhat more crack-prone than the other small blocks.

I only suggested avoiding the 305 heads as I thought you were just going to drop them onto a stock, untouched, original 400 shortblock, which would present alot of compression and detonation issues. If you will be buying new pistons anyway, then go for it, they are fairly good heads. I liked them alot on my 350.

Small chambers with a dished piston is one of the best setups there is for keeping detonation under control with high compression, it works better than a mid-size chamber and flat tops, and is MUCH better than big chambers and domes.

If you have the aluminum LG4 manifold, then it won't be significantly different power-wise than the Performer. They are very very similar, so if you already have an aluminum LG4 manifold, use that instead of buying a Performer.

You will need a different manifold if you used Vortec heads though, as the port layout and bolt pattern is different. I would suggest just jumping right to the Performer RPM if you do buy an aftermarket manifold for either Vortecs or the 305 heads.

400hp and 420+ft-lbs would not be hard with a properly built 400ci with a decent cam and good compression... Myself, I would suggest using Comp Cams XE274 in that 400... I'm using one in my 350 and, despite how it might look on paper, is very streetable and makes good low end torque, and would be even moreso in a 400.

You'll also want to get a set of headers on there eventually as well... 1-5/8 would be about the minimum tube size you'd want, with 1-3/4 being a much better way to go (though more expensive). Hooker and Hedman both make some nice sets... the Hookers cost a bit more, but usually perform a little better as well as they have the larger 1-3/4 tubes (unless you go with shorty headers, then both Hooker and Hedman, as well as the others, are about equal)
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I only asked, because being an '87 car, it will have a knock sensor, which will be a problem with the 4.125" bore of the 400... no 400s ever had a knock sensor that he could change to, like he could if it was a 350.

 

The Performer RPM Vortec doesn't come in a spreadbore style, meaning an adapter in order to keep the CC q-jet. Since MPG was included in the mix, I was thinking it made more sense to keep the cam mild and stay with the Performer. A 400 will have plenty of power, anyway.

 

Aftermarket heads + aftermarket intake + 400 short block + LG4 carb & distributor = big power with the right tuning & exhaust.

 

whats this about a knock sensor??? cant i just drill the block for it??

 

The problem is not the location, it just goes in the coolant drain hole, which the 400 has. The problem, is that they are displacement specific - mainly bore size. Thats why different size engines will use a different knock sensor... the 305 has one, the 350/383 has another, etc. But the 400 has an odd sized bore, so you can't use one from the 350 like you can for a 383. Since the 400 never had any computer control systems, it never had a knock sensor designed for it.

I've HEARD something about being able to use one from a 350 in a 400, since the bore is close to the same (4" vs 4-1/8") but I don't know if theres any truth to that.

 

whats the worse that could happen using the 350 sensor???.. is there a way to just dummy the sensor???

 

Put some teflon tape on the threads before installing it - desensitizes the sensor...

 

My old car had this exact setup. 400 with original 882 heads, performer intake, LG4 computer carb, LG4 computer distributor. Also had the 88+ serpentine setup and single e-fan. It was alright, mostly a low-rpm torque monster. I swapped in secondary metering rods from a mid-70's caddy with the 500, but never really got the carb tuned perfect. I had fuel starvation issues at WOT, the fuel bowl wouldn't stay full, resulting in the car bucking violently on a full throttle launch. It also pretty much fell flat on it's face around 3500RPM. I wouldn't recommend it, I'd rather do TPI or TBI on a 400.

 

ok who else agrees that it will be extremely hard to tune a 400 with a CC LG4?

 

Its not hard. Its no different than tuning a 305 or 350 with the same carb, assuming the 350 knock sensor works, as Ward seems to suggest.

 

If the carb runs out of fuel, get more fuel to it. You can get a .149" needle/seat for q-jets that will keep it full. Assuming the fuel pump is up to the task, of course.

 

so im gonna go with "its not hard" as per 5.7... thanks man lol

 

Most of the fella's here at the track disable the knock sensor entirely, especially when tuning, because of the false knock readings they're forged internals always seem to provide. IIRC, some of the V6 third gen's didn't even come with a knock sensor, for that matter. I think you'll be just fine w/the 350 sensor for your 400 though....

 

I'm 90% certain this was caused by your fuel pump - using a good electric in or close to the fuel tank would get rid of this.

You can actually run a big block with an LG4 carb (tuned of course) and distributor since the carb can support 500hp at the stock CFM and maybe 550hp with it maxed out by a tuner - 400 would not be a problem.

 

Tuning a CCC Q-Jet to run well on a 400 is easier than it is to make a normal Q-Jet run well on one. The ECM will control the timing under all conditions and the fuel mixture at idle and part throttle. The knock sensor is a non-issue. I've gotten to where I don't even swap them out when I do 305-350 swaps now. I have yet to have a TBI truck fail the forced knock test when swapping a 305 to a 350 in a TBI truck. In fact the later model 305 Vortec runs the same knock sensor as some 350 corvettes. I also know the stock 307 oldsmobile knock sensor worked just fine in the 403 that I put in its place.

 

430 hp and 525 ft/lbs with vortec heads and a lunati cam.

 

Uh, the OP specifically stated they want to use the LG4 induction system. . .

 

I know. But I was just pointing out that the vortec heads offer good performance potential. A possible sale of the LG4 manifold and then using that money to buy a vortec specific manifold could be a good choice. *shrug*

 

Okay, just making sure.

One limitation would be the manifold, because at the current time there isn't a spreadbore Vortec RPM available (meaning squarebore to spreadbore adapter on top of a Vortec RPM, or a "regular" Vortec Performer).