Jakester136

Hi guys I just recently picked up a really nice old 86 K20 4x4 truck, I need some help here to start diagnosing a problem. Previous owner didnt know to much about the engine build besides 40over, new valves, new crank, 'big cam' and it has roughly ~8,000miles on the build.

OK; so it does lope substantially, sounds extremely good at idle almost sounds like a 383 stroker and has very snappy throttle response in neutral/park. It doesnt burn or use oil that I can tell and doesnt smoke at all

it did foul a plug the day after I got it, pulled all the plugs, two were very gunked up and some looked lean. They were autolite 24 plugs, I replaced them all with autolite 25 platinums. drove for 3 day havent fouled one yet

Visually, Iron heads of some sort, Edelbrock performer intake with riser plate, edlebrock carb that looks new(not sure on size yet) fuel pump looks like an OEM pump because it still has the fuel return line and long tube headers with 'paper gaskets'

Problem Im having is it feels down on power for what it is, very very sluggish off the line, then gets going decently after im rolling. I realize some of the problem may be tall gears but even at that its awful dang slow. if you put it in reverse and try to back up a hill from a stop it can barely even get up it.

SO what are y'alls thoughts? Too much cam not enough heads? Too much fuel, not enough fuel? intake too small? fuel pump?

Looking forward to hearing your thoughts I sure would like to get this thing spiffed up

Thanks,
Jake

cambirdracing

iTrader: (4)

"big cam". Sounds like you don't have enough convertor in it for the cam. What gearing? How tall are the tires?

Jakester136

35" tires, not sure on gears, whatever would have been stock in 86 most likely. Transmission is a Turbo 400, supposably shift kit and small stall, I dont notice a stall but it does shift quick and firm.

Jakester136

I think your probably right, what would you reccomend?

Jakester136

I imagine since its 3/4 ton it probably has atleast 3.73 or 4.10s, that seems to be common for those trucks

cambirdracing

iTrader: (4)

I use these guys for our drag cars:

http://transmission-specialties.com/

They are moderatly priced for racing applications, might be too much for a "daily" vehicle.

You can dig around Jegs for something more of what you are looking for:

http://www.jegs.com/c/Torque-Convert...10555/10002/-1

Probably best to make a phone call to get a lot closer to what you want than to ask on here. Try to give them as much information as you can when you do make a call.

1994Z28Lt1

iTrader: (1)

You got a timing light? Usually with a larger than stock cam you will want a little more initial timing. I have no idea what cam is in it but I would aim for at least 12 degrees btdc with the vacuum line disconnected if its got vacuum advance.

You will probably have to mess around with timing some and figure out what the motor wants. sometimes guys will intentionally retard their timing so it lopes harder. Might sound good to some but doesn't make power.

warriorcustoms

iTrader: (10)

In a 4x4 350 You need a cam thats in the 220s or so A 230s cam wont have ***** unless you put it in low 1 & low range I had an 86 S10 Jimmy & swapped a 4.3 V6 with an Isky 280 adv dur 480 lift cam & it loped its *** off like a V8 Fooled lots of people LoL It was a turd in drive & 4 high!!!!!! A 22x @ .05 woulda been way better Unless your mud draggin then just get a stall It helps a lot if you can get specs like #s off the snout/nose of the cam Yeah its more work But It could be simple like he installed it straight up instesd of 4* advanced!!! Just my 2cents

Uwilllosetomy93lt1

I'd find out and post cam specs first. Definitely sounds like tooo much cam overlap and perhaps LSA too high (wrong car/truck application)... Bogging?

fly442

with 35 tires and stock gears it is going to be a dog. Need to check and see what gears you have.

stevo1988

Heavy Truck, Stock Converter, Big Cam and Big Long-tube headers sound like a combination for sluggish power down low. Also without having cam and head specs its hard to isolate the problem. In all reality most people over-cam their vehicles. Alot depends on on the LSA of the cam in relation to the heads and also the duration in relation to the torque converter, gears and vehicle weight. Bigger is not always better. Combine that with your large headers and high rise intake your motor might be weak processing air/fuel at lower RPMs. Cams that have tighter LSAs tend to be lopey at idle and with decent cylinder heads that might put a damper on low end power as well. For a 4x4 truck it would be best to build a motor that creates torque down low as opposed to building it like you would a muscle car. Torquey motors like high air-speed rather than volume when processing your mixture. It would be best to have more restricted intake and exhaust along with a cam that provides good valve lift but not so much duration (kinda the same way you put your finger in a garden hose to spray water further) The motor you describe sounds like it needs some revs before it makes any hauling power. Horsepower doesnt mean anything if you have to rev up fast to use it, Torque is what will get you moving