I am curious what performance mods you have done and how you like them? I am working on completly redoing a CPI 4.3 (I have a CPI fetish) I am curious about what mods work best for the most reliable HP? I will be sticking with the 4.3 so a small block swap is out due to weigh and room limits. Thanks Jim

I've been doing a lot of research on just about everysite google or yahoo brings up when you do a search. most everytime the question gets posted about 4.3 CPI performance no one has done much because you can't just bolt stuff on.

http://www.s10planet.com/forum/showthread.php?t=7349

this thread has a good idea about getting rid of the poppet valves and the single injector, but he hasn't finished it. the problem I see is you need to use very short fuel injectors to clear the upper plenum. I thought that maybe using a the replacement injector assembly for the 96 and later SCPI 4.3s could be used but they only have 19# injectors.

I've got an extra CPI intake that I'm going to modify and put 24# injectors in and run the http://www.dynamicefi.com/ EBL flash and batch fire the injectors. this setup will work good for me because I'm going to run an NV4500 behind the 4.3 . they don't make any PCM's that you can install this EBL flash on yet so if you want to keep the 4l60e trans you'll need to use a 96 to 97 PCM.

another mod to the intake is to install a switch that goes to purple wire on the tuneing valve in the center of the intake. the computer uses a relay to apply 12v to the purple wire to open the valve at 3500rpm and switch it off to close it at 4500rpm. the valve is closed at lower rpm this makes the intake act like a dual plane intake and when the valve opens it acts like a single plane intake.

and theres the just put in a v8 mod.:flipoff2::flipoff2: I am not going to put a v8 in my samurai!!!

the CPI heads and cam are suposed to be better than the TBI stuff, the blocks and cranks are suposed to be the same.

I've looked at the possibility of useing an EATON m90 supercharger on a CPI lower, I like those blowers:evil: and changeing the igintion to fire off the crank with a DSI ignition would solve the distibutor problem:goofball:

I have a TBI... only mod is a throttle body spacer, and a custom exhaust, they seemed to waken up the throttle response and gets a bit better fuel ecomomy. For what I do its a great motor but I won't be wasting any money on it when most modern GM's like the 5.3 are damn near as light as the 4.3 with nearly twice the HP, and to think I have one taking space and collecting dust on the floor:shaking:

This 4.3 will be going into a 98 4 door Tracker so a small block isnt even close to happening...LOL I have a complete MSD ignition system already billet disty, CPI coil pack, digital 6 box. I also have a set of hooker super comps for it. There are many cams available and even a supercharger if someone is interested in those. I will be at least doing the full valvetrain swap just not sure which cam yet. I will be runnning roller rockers which will cause their own issues with valve cover clearance.

Sounds like a cool project, Keep us posted on what you end up using and what power you squeeze out of it, I love the 6's but have room for the 8:D

Intake, high flow exhaust, custom PCM tune, throttle body spacer, underdrive pullies they all add up. I didn't notice them so much as I put them on, but when I drove an identical stock vehicle, it felt like a slug.

Anyone considered using this cam?http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=564&sb=2 It is being reccomended to me for use with a suoercharger. I am a little concerned about apowerband starting at 2000 rpm. Has anyone used this cam and how do you like it? Thanks Jim

are you trying to build a 500hp 4.3?:laughing:

the CPI cam is about as aggressive a profile that you would want to go even with a supercharger, the 4.3 I pulled out of a 95 gmc safari was still running and was all wheel drive. that van weighed 6000lbs, it was quick but I don't know what the gear ratio was, it had a 4l60e trans. instead of a cam you would be better off getting a set of vortec 96 and later heads and modifying that CPI intake to bolt up to them. the CPI intakes flow quite a bit more air than the 95 and earlier heads can even handle. a cam isn't going to do much good unless you run the vortec heads. those heads flow as good as the gm performace parts heads at half the price.

the cy/ty guys are getting some big power gains running the vortec 96 and later heads:evil::beer::evil:

Mine's a Vortec, but I have a cat back exhaust and tune. Still very slow and underpowered though.

wynjammer makes a small boost supercharger for the 4.3 cpi. Thants about all you can do for boost, they say that the cpi injector itself can't won't stand up to much pressure.

are you trying to build a 500hp 4.3?:laughing:



yea 500+ :D

Anyone considered using this cam?http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=564&sb=2 It is being reccomended to me for use with a suoercharger. I am a little concerned about apowerband starting at 2000 rpm. Has anyone used this cam and how do you like it? Thanks Jim

video of that exact cam with a powerdyne pullied for 7psi HERE (http://s-seriesforum.com/albums/vidios/Boosted_Thrills_12_63_104.wmv)

not sure how well it would work in an offroad application. dont expect much power below 2500rpm. it pulls like a SOB at 4000rpm.

i have since switched to a 60mm turbo and droped down to a 3.42 gear out back (28"tire). i found the limit of 48LB injectors:D

i can and do daily drive the truck weather permitting. after i get my cut down holley stealth ram intake on im gonna try a smaller cam. less duration more lift

im more than happy with my stock 4.3 Hp and Torque geared to 5.13s with 38s its all i need ??

why is it that you think you need more power ?? or is it the "just cause" factor ?

I am putting the fine tune on a intercooled paxton blown 4.3 vortec with custom ported heads hand fabbed upper intake [kinda looks like a ram jet]and fuel rails 9/16 ID. 60lb per hour accell injecters, ported lower intake,vette twin throttle valves,TPS and IAC ect. 7.7 to1 molly skirted forged speedpro pistons with plasma molly rings,Eagle H beam rods ,knife edged drilled crank.The cam is a custom lunati hyd. roller Int/.495Exh.505 with 1.6 crane roller rockers, dur is 225I/230E @.050 114LCA jessel belt drive .Boost referenced pressure reg. and a holley pump feeds it.custom PCM piggybacked to a laptop.painless did the harness with two wide band 02,s the distributer only drives the oil pump high volume but not high press. and sends out spark.timing is off of a crank trigger and is also boost referenced.I made my own oil pan with a swinging pick up and crank scraper.it is not in the truck yet so HP is a ? but Im not worried about power.It is going in a 4 runner 4 linked 2.5 fox airs, d60,s 5.38,s sm465/203/205 doubler 39.5 boggers.I,m not trying to brag I,m just proud of thi motor and truck. if someone could tell me how to post pic,s I will sorry I,m not a computer guru I build trucks for a living.Humboldt custom fab and 4wheel drive. Probly more info than you wanted but I hope it helps.

I am putting the fine tune on a intercooled paxton blown 4.3 vortec with custom ported heads hand fabbed upper intake [kinda looks like a ram jet]and fuel rails 9/16 ID. 60lb per hour accell injecters, ported lower intake,vette twin throttle valves,TPS and IAC ect. 7.7 to1 molly skirted forged speedpro pistons with plasma molly rings,Eagle H beam rods ,knife edged drilled crank.The cam is a custom lunati hyd. roller Int/.495Exh.505 with 1.6 crane roller rockers, dur is 225I/230E @.050 114LCA jessel belt drive .Boost referenced pressure reg. and a holley pump feeds it.custom PCM piggybacked to a laptop.painless did the harness with two wide band 02,s the distributer only drives the oil pump high volume but not high press. and sends out spark.timing is off of a crank trigger and is also boost referenced.I made my own oil pan with a swinging pick up and crank scraper.it is not in the truck yet so HP is a ? but Im not worried about power.It is going in a 4 runner 4 linked 2.5 fox airs, d60,s 5.38,s sm465/203/205 doubler 39.5 boggers.I,m not trying to brag I,m just proud of thi motor and truck. if someone could tell me how to post pic,s I will sorry I,m not a computer guru I build trucks for a living.Humboldt custom fab and 4wheel drive. Probly more info than you wanted but I hope it helps.

i can host the pics for you. send me a PM and ill give you my email

hey mike, what crank are you running? heads? sounds like your into that motor some serrious coin:evil:

im more than happy with my stock 4.3 Hp and Torque geared to 5.13s with 38s its all i need ??

why is it that you think you need more power ?? or is it the "just cause" factor ?


my 4.3 is pretty much stock (hypertech, exhaust and K&N system) and it's not enough motor IMO for my setup. it's a great motor, will run damn near forever, and is super reliable, but I wish I had more.

it was more than enough with 4.88s and 37s, but once I switched to (1 tons) 5.38s and 42s I find myself needing much more bottom end grunt. it works well, but doesn't have enough balls for a good hard bump when needed. I still really like the motor, but just wish it had more HP.

that being said, personally I think it's a waste of time to "build" the 4.3 when you can get much more from different motors for less. the 4.3 is an expensive motor to get real HP from.

just my .02


on a positive note, a good friend of mine has the exact same setup as me (same tire/size/gearing), but is running a ford 302 and I can run almost dead even with him when we are racing in the sand. and his rig is much lighter :flipoff2:

When I bought my jeep The guy told me the 4.3 in the jeep was stroked. He said it dynoed at 300 hp. Dont know if its true, It does soud VERY good. The power is there too. I dont have all the details on it. If you want more info I could try and get the specs. He said it was a crate motor he sent off to be built(mapped/blue printed). He may still have the paperwork.

hey mike, what crank are you running? heads? sounds like your into that motor some serrious coin:evil:
Zk16vl The crank is a scatt and the heads are 96 votcec done by Aero head performance in AZ.I have about 11 grand including the electronics and complete fuel system. My good friend has a local machine shop so I did a lot of the work myself.I also own a fab shop so tigging up the oil pan and upper intake plus the blower mount plate I did on a local collages 3 axis CNC machine.remember I live in humboldt ca.LOL

wynjammer makes a small boost supercharger for the 4.3 cpi. Thants about all you can do for boost, they say that the cpi injector itself can't won't stand up to much pressure.

Screw that small boost crap go big or go home!:flipoff2:

was that a custom crank? do you have part#? is it even or odd fire?

I'm guessing odd fire to be strong enough to be in the 500+hp range.:evil:

also are you worried about oiling? or does part of that 11grand include a gm performance block?

and I'm very familiar with humbolt:smokin:

my 4.3 is pretty much stock (hypertech, exhaust and K&N system) and it's not enough motor IMO for my setup. it's a great motor, will run damn near forever, and is super reliable, but I wish I had more.

it was more than enough with 4.88s and 37s, but once I switched to (1 tons) 5.38s and 42s I find myself needing much more bottom end grunt. it works well, but doesn't have enough balls for a good hard bump when needed. I still really like the motor, but just wish it had more HP.

that being said, personally I think it's a waste of time to "build" the 4.3 when you can get much more from different motors for less. the 4.3 is an expensive motor to get real HP from.

just my .02


on a positive note, a good friend of mine has the exact same setup as me (same tire/size/gearing), but is running a ford 302 and I can run almost dead even with him when we are racing in the sand. and his rig is much lighter :flipoff2:

I,ll put my 4.3 against any smilar or even larger displacement motor you want. you just have to use the right parts and they all need to work togother. I recently finished a 3950cc corvair motor with a blow through turbo A ct 20 at 16 psi it made 414 HP on sunoco blue on a dyno! its in a chenowa sand rail. A lot of people have called BS on those numbers until I take them for a ride. By the way It,s for sale if anyone likes to play in the sand box!

was that a custom crank? do you have part#? is it even or odd fire?

I'm guessing odd fire to be strong enough to be in the 500+hp range.:evil:

also are you worried about oiling? or does part of that 11grand include a gm performance block?

and I'm very familiar with humbolt:smokin:
Scatt custom ground the forging, odd fire Full radiused jurnals and half grooved main bearings plus a mellings high volume but not high press. pump w the custom pan and swinging pick up also the crank has scatts own oil holes kinda scooped looking at the oil outtlet. if I have any oilling probs I have a 3 stage dry sump ready to go. I build a lot of stock car motors for the local tracs. The block is the weak link its a stock vortec with the bottom 3rd filled with hard block.and I am useing a mezzier electic water pump.This is a customer /friends motor build and I cant twist arms, but id have gone after market block. I dont know about 500HP I,m more about torque and driveability when I need it.Oddly enough localy I,m known as ram man As Im kinda known for some outrages dodges. I used to be at Eliete enginering in portland OR. And my crown jewel is a 638 inch Aries twin plug hemi,Intercooled with twin 80mm Garrett turbos with twin 105lb per hour Enderley injecters per cyl. full custom banks Timeing and fuel management controls.It made 3800HP on alcohol at 40 psi and had more boost avalible.The dyno brake would not hold the motor under 4000 rpm it made so much torque/.It went in a offshore race boat.[glad to hear your familiar with humboldt!] nice to chat with someone that is not just what I call a computer racer, you obviusly know your stuff also! peace from the humboldt nation.

with the parts your claiming:), if it doesn't make 500 then tune that thing a bit more. I know about tourqe, but the parts your useing your gonna have some high rpm horse power. the only limiting factor is the lifters, its gonna start to fall at 5800rpm.

lets see some pics, I love eye candy:evil:

I,ll put my 4.3 against any smilar or even larger displacement motor you want. you just have to use the right parts and they all need to work togother. I recently finished a 3950cc corvair motor with a blow through turbo A ct 20 at 16 psi it made 414 HP on sunoco blue on a dyno! its in a chenowa sand rail. A lot of people have called BS on those numbers until I take them for a ride. By the way It,s for sale if anyone likes to play in the sand box!

point is, for half the money you can have more HP from most other SBCs ;)

I like the 4.3, but it's a huge waste of money to build for real HP IMO

Exactly. Unless you have a serious space constraint, pick up a 5.3 or 6.0 from a late model truck for under $1000 and you're over 300 horse. Do a cam swap and some other minor work and you're over 400 horse for under $2000 easily. Doubt you can build a 400 horse 4.3 for $2000.

yes you can build a SBC v8 for cheep, but its not easy to stuff one in a 4 door tracker (Powerstoken), 4 runner (mechanic mike) or a Samurai (my wheeler). I have built chevy v8's for years, and I am putting a chevy in my Samurai! I know there are lighter v8 engines that will work, but sometimes old school has just a little bit more cool factor:smokin:, I'm not a ford fan, but flathead v8's are cool:grinpimp:

I have dana 44's under my samurai I'm going to run a nv4500 with a dana300 behind the 4.3, I like the gear ratio of the nv4500. I'm building a dailydriver that I can that will be maybe 12 sec quarter mile and wheel any trail I want to go, pure sleeper:flipoff2:

4.3's are expensive so what, the falconer v12 that was based on a SBC was way expensive! does that meen it shouldn't be done? this isn't cheap 4x4 .com, its Pirate 4x4 .com:evil:

If you've got some good info post it:)

4.3 with a small cam, headers and a 125 shot been running or beating the hell out of it for about 3 years

with the parts your claiming:), if it doesn't make 500 then tune that thing a bit more. I know about tourqe, but the parts your useing your gonna have some high rpm horse power. the only limiting factor is the lifters, its gonna start to fall at 5800rpm.

lets see some pics, I love eye candy:evil:
What makes you think the lifters are going to fall at 5800 rpm? If tey do I,ll go solid roller instead of hyd,I only used the so I don,t have to lash the valves every 3000 miles or less. I,ve used the same brand of lifters in several other motors including a 410 stroker dodge that ra 10.80,s at 135 give or take a tenth and a mph or so. the dodge does use a larger diameter lifter but that only makes them heavyer ,more chance of failure and that motor saw a 150 shot of juice every pass /more than 100 before I sold the car and it reved 6800 plus. You are right 500 should be easey but remember it has a factory block that has been hard blocked in the lower 3rd and its not my motor its a paying customer. also a 5.38 gear is going to like a little rpm.and it is just a few key stokes and a couple of pulleys if he wants to push the motor harder! I know its kinda kiddy stuff but if you want some eye candy go to my my space page www.com/likesit1 and check some of those pics. or call 707-445-9615 and tallk to frank camelli about some of my stuff.I buy everthing through him and we have known each othe since I was 19 and has seen about everthing I,ve ever done.I hear what your saying old school is way cool ,I could go get a all aluminium 6.0 ls motor and make 800 to1000 hp but thats not wha thi guy wants and he,s payin the bill

the hydrolic rollers start to have a problem after 5800(the stay pumped up, not enough time to bleed pressure off at that rpm). the last SBC 377 (400 block,350 crank) I built I ran solid roller lifters in it. I never had to adjust the lash, the biggest problem was the erson roller lifters loseing the roller tip(the pin would walk right out the side, POS:mad3:). I would beat the shit out of that motor and it came back for more(8000rpm:eek:) I ripped the teeth off more four speeds and blew up more rearends than I can count, this was all in my 66 Chevelle:evil:

run the solid roller lifters they will hold up fine. I had a 2500 mile round trip from Pleasant Grove,UT to Auburn,CA (raced a neospeed ricer,160 mph just west of Battle Mountian,NV) then to Boise,ID. from Boise back to Pleasant Grove(raced a Porsche 944 west of Twin Falls, 180 mph). the only problem I had after that trip was the Muncie M21 four speed started growling(blew it up 3 weeks later):evil:

nice rail! the last time I was in one we were running 85 up the face of sand mountian at little sahara sand dunes in UT. 2.3 turboed fords are scary fast in a 1100lb rail!

the hydrolic rollers start to have a problem after 5800(the stay pumped up, not enough time to bleed pressure off at that rpm). the last SBC 377 (400 block,350 crank) I built I ran solid roller lifters in it. I never had to adjust the lash, the biggest problem was the erson roller lifters loseing the roller tip(the pin would walk right out the side, POS:mad3:). I would beat the shit out of that motor and it came back for more(8000rpm:eek:) I ripped the teeth off more four speeds and blew up more rearends than I can count, this was all in my 66 Chevelle:evil:

run the solid roller lifters they will hold up fine. I had a 2500 mile round trip from Pleasant Grove,UT to Auburn,CA (raced a neospeed ricer,160 mph just west of Battle Mountian,NV) then to Boise,ID. from Boise back to Pleasant Grove(raced a Porsche 944 west of Twin Falls, 180 mph). the only problem I had after that trip was the Muncie M21 four speed started growling(blew it up 3 weeks later):evil:

nice rail! the last time I was in one we were running 85 up the face of sand mountian at little sahara sand dunes in UT. 2.3 turboed fords are scary fast in a 1100lb rail!
I have never had problems whith any lunatti product they make a side orifice bleed on thiere hyd rolller lifters instead of a oil control valve if you call a spring and flat waffer a valve.If I have any preblems with rpm I called lunatti and they said the will credit me back for the lifers if I go to a solid roller.My partner also named mike woks in the same place I get all my parts though and he has a 377 600hp+ and reves like a mofo. good stroker combo!One question Iv,e Built a lot of sollid lifter roller motors 25 or 30+ most for roundy rounders.And I always ran a studd girdlle to keep from having to lash the valves twice a nite of racing but we were turning them up and down between 4000 and 8200 or so for 100 laps on a 3/8 mile that carries alot of rpm . were you running a stud girdle?that sounds like a lot of miles whith out a lashing! DId you check the other pics of the BB Dodge inthe orange charger add my 70 340 duster with the 410 sroker in it pullin the R/F wheel?Sounds like we both seen a lot of projects come and go and could help each other out! YEA that rail scares the hell out of me I love it, Sorry to sell it but its time for something new.mine is a cuda for the silver state challange or whatever they call it now in nevada. Sounds like we need to get to gether and go play with some toys!

Space and weight are a concern. This is going into a 4 door Tracker. I am not looking for nowhere neqr 500 ponies...LOL Since I am going through the whole engine anyways I see no sence skinping on replacement parts. I would like to get the most reasonable ponies I can reliably. I admit I am not totaly fond of the Wynjammer setup but I know of no other supercharger for the CPI 4.3 and it does look quite KOOL. If only there was a Tunned Port Induction for the 4.3's like used on the Camaro's and Corvette's or Accel's unit. They look Kool too. I happen to like the way the CPI looks and performs stock. It would just be nice to tweak it some. thanks for all the replies. Jim

Space and weight are a concern. This is going into a 4 door Tracker. I am not looking for nowhere neqr 500 ponies...LOL Since I am going through the whole engine anyways I see no sence skinping on replacement parts. I would like to get the most reasonable ponies I can reliably. I admit I am not totaly fond of the Wynjammer setup but I know of no other supercharger for the CPI 4.3 and it does look quite KOOL. If only there was a Tunned Port Induction for the 4.3's like used on the Camaro's and Corvette's or Accel's unit. They look Kool too. I happen to like the way the CPI looks and performs stock. It would just be nice to tweak it some. thanks for all the replies. Jim

Go toS10planet.com there,s some pics of a manifold with mods kind of like the ones I made. Only I cut alot more metal off around the injecters and fuel rails.But it gives you the idea then after sealing all the unneeded holes. I drilled the injecter ports.I fabbed a top like a TPI style and mounted the throttle valve assembly off a vette onto a plate welded to the front of the plenume.I welded aluminium tubes between the lower and upper halfs kinda like tunnel ram only with the throttle valve on the front TPI style. Tubeing comes out of the blower into the intercooler and onto the throttle valve witch incorperates the TPS and IAC.I left the EGR ports but pluged then incase they are needed in the future to get the engine management to work right.Ill post pics when I get the motor back from the dyno in SO Cal.