hey guys i am going to be puting in a mild 400 in my car soon.... i am going to use my 305 heads and be using a mild cam and also be running headers of some sort...

i have an 86 lb9 that i will be using the tpi off of...

ill use 22 pound injecters... 350 chip.. and a 350 nock sensor

will it run ok like this?

i know the 305 heads ont he 400 if that is even going to be posible is going to hurt flow but i am using them just for a while till i can get desent heads..... will these lb9 86 heads be ok on a 400?

 

Those heads will choke the hell out of a 400. The runners are too small and the valves are too small, and really the chambers are too small which means you'll need to run 93 most likely to avoid detonation. Also you may have problems with the 350 knock sensor picking up false knock and retarding your timing....I know this can be a problem with some other combo's but I'm not sure about the 400. The 350 chip will probably get it cranked and running, but it will be FAR from optimal. That thing is going to need some serious tuning to be driveable.

 

would i be able to use stock 400 heads and keep my ac and all of that... thats what im trying to do i have a v belt set up as we speak i just dont want to looz the ac and crap like that....
also then should i get a 400 nock sensor? i didnt know it would work with tpi

 

I have a question kind of similar about a stock 350 chip. I have a L31 vortec 350 with .480 Int. and .480 Exh. cam Hyd. roller, 1.6 roller rockers, SLP runners, BBK adj. fpr, 24lbs accel injectors. Could the stock prom chip handle this for a little while until i get a modified prom? I know it wont run as well as if i got the modified chip but i just want to get it running for now ya know. Thanks,

 

i also dont care if its not making as much power as it could.. i justw ant to get by till i can afford to tune it the right way.... if it will make more power then my 305 then i dont care about tuning issues later on i will managa....

do they make a 400 nock sensor that will work with my tpi.... if so i will get that instead of the 350 nock sensor...

 

If the 400 heads have the threaded holes for the accessory brackets you can use them and it'll work just fine. The 305 heads will run and drive in a pinch but you need to have the steam holes drilled in them to prevent hot spots between the cylinders.

I really don't know what to do about a knock sensor. You could use a knock sensor and memcal from a '94+ 6.5L truck but you'd have to burn your own chips. The '94+ programming won't run with your older '165 ECM.

 

The L31 should run on the stock 350 chip for now. The 350 knock sensor and memcal will work fine since the L31 bottom end isn't really any different from an older 350. If it's a MAF setup it will probably do alright, a speed-density computer is a bit more picky.

 

some one has had to have run a simulare set up on a 86 tpi set up... any other idea guys .. i realy want to use a 400 guys...

i have alwase loved the idea of having a 400 under the hood... i know soem way this is posible i just need it to work and run decently to get me around till i can get more money to put into it to tune it right....

also my 86 lb9 is MAF if that helps at all

 

if i have to ill co to CARB but i realy realy want to keep the TPI set up for the better gas milage ill be able to get from it.....

 

Thanks, "J" it is a MAF system. Ill try and get the modified prom as soon as i can.

 

You'll be fine as long as you use an adjustable fuel pressure regulator to "trim" your fuel curve. The 400 will need more fuel faster and run out of RPM quicker when compared to a 350 and will need a higher fuel pressure than stock when running the stock chip. You’ll want to make about 4 wraps with Teflon tape around the knock sensor and then tighten it no more than you have to so it doesn’t leak. This should prevent most if not all the false knock you might get from running the 350 sensor in the 400.

I've run the HO 58cc with 1.84/1.50 valve 305 heads on a dished 408 before and made a little better power than the basically stock 76cc heads with 1.94/1.60 valves. The flow from the 76cc heads were a fraction better,, so most of what little increase I saw came from the compression increase with the 305 heads. Throttle response was better with the 305 heads, but WOT there was very little difference (less than .05 seconds estimated – when factoring the difference of the temperatures when ETed). As others have stated, make sure you get the steam holes drilled for the 400.

I’ve got an old magazine article where a guy took his 305 TPI and swapped a low buck 400 in it’s place (only difference was the short block – even ran the same cam) and went from mid 15 second runs to low 14 second runs. Not mind boggling, as one would expect,,, due to the stock heads and totally stock TPI limitations. However if you go with a cam around 215 – 220 on the intake, 225 – 230 on the exhaust, keep the lobe spread at 110 or 111 degrees, gut the plenum, and at least remove the lip at the intake base entry,,, you should run high 13s without any problems. Throw on a good set of headers and decent exhaust (on a sticky track) it should run mid 13s for sure. That’s not blazing fast for a 400, but with a head swap and a better induction system later on down the road,,, you will be MUCH faster.