4.34runner88

Ok i have looked through this forum and found very little help but maybe one thread. i have a 4.3l chevy carbed in my 4runner. brakes worked fine before hand. put this new engine swap in the brakes became like a rock running or not (to stop i gotta literally stand on my brake pedal) so i replaced my brake master cylinder with the TG 1" bore upgraded one same issue. so i then looked through this forum found out it might be my brake booster. i got a new one same issue again. my brakes have been bleed so much the fluid is new in it. I got a stock master cylinder to see if it will help but it has yet to be installed to find out. wanna see if it could be something else before i do that.

in the pic i posted you can see the hose coming from the old brake booster to the front of the carb for the vacuum with the valve thing and the old brake master cylinder. (things have been updated under the hood and re organized this is a older pic) but the same issue occurred with the upgraded cylinder.

any help appreciated.

Terrys87

iTrader: (1)

I have gotten bad boosters in the past, so would not rule that out. The white piece in your hose is a one way Check Valve, I wonder if it is functioning correctly. I looked at my truck and it is installed the same way mine is, The flat part facing toward the booster.

MMA_Alex

usually boosters fail by having the diaphragm tear which creates a vacuum leak. typically the symptom is a rough idle when pressing the pedal, which doesn't sound like the case here.

if the brake pedal feels the same, with a hard pedal engine on or off you're probably not getting vacuum to the booster. check the line. might be worth throwing a gauge on the end of the hose and seeing what you're getting for vacuum

4.34runner88

I did remove the valve and used a single hose (I still have the valve). Didn't change anything. I also let it run and still drove it around. Had a idea to see what would happen if I pulled the hose off the booster after I turned it off. It just released all pressure that was in it. I also pulled the hose off the carb while running. Made it idle bad so I put it back on. It has just blown me away as to why it's doing this.

AKHeathen

put a vacuum gauge on a manifold vacuum port (i think it's the right one, but check your edelbrock papers) it may not be pulling enough. this could be from an aggressive cam or poor idle tuning (mixture, AND timing) if it's not tuned well, then the throttle plates will be too far open to offer much vacuum. if it's a big, bad, cam, then look into getting a vacuum pump, sold mainly just for this situation.

btw: what model carb is that? cfm? engine mods?

4.34runner88

the model card is edelbrock, cfm i believe is no bigger than 600cfm. engine mods all stock internals besides .20 bore stock pistons. MSD box, MSD distributor, MSD coil. the engine runs smooth and idles around 500-600 rpm at idle, no fluctuations in idle.

AKHeathen

there is a model number, usually stamped on the top vein or body, near the top. it would be like 140x-xx or something, and by the way, a bit large for that motor. you are looking for the 340-4xx range, but it's okay if you have vacuum secondaries. you can have it seemingly running good, but be pretty far off on the mixture, and possibly only find out with fouled plugs or piston/valve damage, and the idle stops are most certainly too high at that point. i suspect you are not all that familiar with carb tuning, which is a learned art. did you at least warm it up and set the idle mixture screws as per the instructions? side note: it appears to be from the soft-cam era, so if there's any considerable amount of mileage on the motor i would look into upgrading the cam soon. 87-96 fullsize truck 4.3? what did you set the base timing at? msd settings/chip/model? doesn't look like a 6al, mc4 or something? i would still take the manifold vacuum readings. idle, ramp-down and decell readings, because that's when vacuum is made.

4.34runner88

ill have my buddy take some pics for me. i am not state side at this time not till 6 more months. and yes this carb thing is new to me. i know my stuff just got into something new. what do you mean idle stops?? and yes i let it warm up before tinkering with it. but when i wasn't home i had it sent to a shop to get tuned so idk if they did it right. doubt they did lol. the engine has maybe 300 miles on it. the engine is a 96 with vortec heads. explain base timing?? i am certain the msd is the 6al (is adjustable through the rpm range with 2 adjustments one through the 1k rpms and the other in the 100 rpm range). im trying my best to remember what it all has. last time i saw it was when i was on leave. so bare with me on this.

4.34runner88

best i got. there old ones i had saved. don't mind the crazy wiring. a lot of things have been redone from my buddy so its much neater than this.

AKHeathen

idel stops are the throttle plate stop screws where you usually adjust just the rpm. when tuning a new carb, they are typically turned up so it idles fairly high, then once warmed up and choke off you turn them down and adjust the mixture and re-adjust them as necessary. it's usually something like: 800rpm warmed up, and then adjusting the mixture gets to like 1300 and you turn it back to 800 and keep going till max idle with the mixture is 800, then you lean it either 1/4 or 1/2 turn, can't recall..... the new carb comes with these instructions, and they are fairly simple and strait foreward, so rarely need to have a shop do it. where you get a shop is when you start to build it up and it needs to be jetted and further tuned, but the issue now is vacuum, so it's a throttle closed thing only. that is why i focus on just the idle circuit adjustment, vacuum is hardly made in anything off-closed throttle. another key point: i notice that your distributor vacuum advance port is not connected to anything. you say you have an msd pro billet distributor and 6al, so i'm assuming the distributor is taking care of timing via vacuum advance, and that should be plumbed into the left front port, not manifold vacuum. it will run like poo on manifold vacuum, but still run. the difference is that it is throttle respondant (load demand dependant) on the proper port, and actually change the timing opposite of what you want on manifold vacuum. the 6al should take care of enhanced igniting, but still takes it's timing from the distributor. also, it appears you have the brake booster hooked to the pcv/crankcase vent nipple. the brake booster port should be at the back of the carb. i'm a tad rusty, but i can't belive i missed that in the beginning.

4.34runner88

AKHeathen ill def work on the idle thing when ever i get home or get my buddy to do it for me lol. oh and my distributor is all electronic no vacuum assist or anything like that on it. and i believe you just solved my problem. by mentioning the vacuum port on the front i just looked it up. that is the PCV port. i don't have it connected to the right one on the back. i feel stupid lol but i guess it takes new eyes and someone else's know how to help a newbie at carbs like me. ill keep you informed if switching it will work.

AKHeathen

sweet, but make sure you have something giving a good timing map. you don't want it to stick at 12 degrees for the whole range, and there are benefits for it to be throttle dependant, which you don't have for sure. edelbrock builds and sells their carbs for the average hobbyist in mind, and all you have to do is follow the instructions provided to get a close enough tune to run well, and not need to go to a shop. i used to have piles of the owners manuals at my shop, even frenkensitiened a bunch of carter/edelbrock carbs for specific use, but bottom line, you could buy a vacuum secondary 500-800cfm for a v8 and tune it yourself easily with the directions. mechanical secondaries are more for racing where you account for humidity, temp, and barometric pressure, but it's not possible to tune for every situation you will encounter...... think about a better cam, and take into concideration if you need to upgrade the valve springs when you do. it's about as involved as changing out crank/rod bearings to do the springs.

4.34runner88

i sure the MSD distributor has something in it to compensate for the degrees for the whole range. the few times i did drive it. it drives great smooth operations except my 700r4 witch shifts way to fast. did it when i got it rebuilt. i adjusted the cable multiple times and still same issue. so i am waiting for it to burn up and get a monstertransmission one witch a custom VB for constant pressure and the cable is only used for shift points. other than that truck runs great and very peppy with 36s on it. and why would i need to change cams and valve springs? for better performance with the carb?

AKHeathen

the cams of that period are soft and go flat. i'm just saying to plan to do it in the future..... better yet, with a more aggressive rv cam you can better use the carb, but if/when you do, make sure the valve springs are up to the task. the cam could pull 1200-7500, but stock springs start to give valve float around 5k-5500. you might have a bad governor to make it shift like that. another option is to just get a 4l60e/ 4l65e tranny and standalone aftermarket tcm for it. they can often be had real cheap used and stand up to more power and abuse that that 4.3 will ever dish out. they are rated for like 776 ft-lbs and tow 18k behind a 6k vehicle. a little 4runner isn't gonna kill it.... and it's pretty much a super beefed up/upgraded 700r4.

AKHeathen

btw, pop open the distributor. it should just be a reluctor ring and pickup.... maybe an ignitor, depending on the model, but the timing advance/retard is still done externally.

4.34runner88

the distributor is a MSD Pro-Billet magnetic trigger mechanical advance. i have a MSD timing control for it as well but the shop who put the new carb on cut the wires to it so i gotta rewire it back (i really hate shops that have no idea what stuff is). the cams still soft even after getting a complete rebuild kit for it? and if i ever have to redo the cam i would go the whole 9 yards with it no short cuts . and i have considered the 4l60e but will it need more than just the TCM. and the TCM i have found is a pretty penny especially from monster. i have no problem getting a new 700r4 the one i want to have built is gonna hold up to 500hp way more than i need. and there is for sure something up with my 700r4 the guy who built it did all kinda things to it especially allowing it to lock up without an external torque converter lockup kit. but when i use it in the "manual" mode just shifting it myself. that thing bites hard itl throw you in the seat if your not careful with it. and i have assumed it was my valve body causing it. but no matter how i adjust it, it's still the same. but i am pretty sure your right with the governor probably being bad. I am not trying to go all out with this build to be a crazy rock crawler mud bog machine lol just a good DD for me and offroad when i feel the itch. sorry for being a little confusing, i haven't been around my project for a hot min other than the 30 days away from OKI when i was on leave and drove it some just to knock the dust off it and get it moving around.

AKHeathen

oh, if the cam has already been updated, then no worries.

4.34runner88

with my 700r4 do you know what governor i would need? as mentioned before you said it could be that witch i am thinking that as well. now that i gave it though because the guy put one in but idk if it could have been bad or just not the right weight for my set up.

AKHeathen

honestly, i would search the s10 and full-size chevy forums to get the best source and part number, as well as weights and springs selection for your application. if you do happen to need to post the question, it might be prudent to mention the lack of decell function and vacuum advance on the engine, and what the torque converter is set to, of you have that info, or if you know it's stock. that being said, you may want to diagnose it first. it could be a slipped spring or debris in the valve or port. worst case it might be a warped valve body orgasket/seal problem.

4.34runner88

since you all have helped me out so far can anyone here tell me for my fuel system if i would need the fuel to return to the tank?? all i have right now is just a external fuel pump pulling through my stock toyota fuel pump in the tank (disconnected) but the external fuel pump for the carb is run to the factory fuel pump wiring with a simple twist pressure regulator on it and fuel filter. but i dont know if i am pushing to much fuel to the carburetor or not and if i need fuel to return back to the tank. i have not had any issues with it with my current set up as it over flowing and stuff. any info will be great or if you all have better solutions for a pump, fuel pressure regulator ect.