TBI or carb questions

[87TBIguy]

I know there I many threads out there discussing this, but ive got a few questions of my own. So ive got an 87 tbi 350/built 700r4, used a a mud/ trail rig. The tbi 350 had done me well all summer, until it grenade this weekend. Spun #4 rod bearing. Gonna be picking up an older carbed 4 bolt main 350 for 100 bucks. Needs a rebuild obviously, will be doing all the work myself aside from lower end machining. Ill be able to do 3 angle valve job and all other work myself.

My question is should I switch over to carb and build it that way. (Id like to do a Rv/ torque cam, possibly hyper pistons and different rods with a dual plane intake. ) or put the tbi setup on this older engine with an adapter? If so how is it possible to keep the tbi with a built engine.

Also any other suggestions for more power/ torque?, already have long tubes

 

[Jims86]

I know there I many threads out there discussing this, but ive got a few questions of my own. So ive got an 87 tbi 350/built 700r4, used a a mud/ trail rig. The tbi 350 had done me well all summer, until it grenade this weekend. Spun #4 rod bearing. Gonna be picking up an older carbed 4 bolt main 350 for 100 bucks. Needs a rebuild obviously, will be doing all the work myself aside from lower end machining. Ill be able to do 3 angle valve job and all other work myself.

My question is should I switch over to carb and build it that way. (Id like to do a Rv/ torque cam, possibly hyper pistons and different rods with a dual plane intake. ) or put the tbi setup on this older engine with an adapter? If so how is it possible to keep the tbi with a built engine.

Also any other suggestions for more power/ torque?, already have long tubes

If you are going to do a lot of off road, you would be better off doing a stock rebuild, with the stock cam. TBI will not respond well to a cam thats too far from stock.
You would be better off with rebuilding the 4 bolt bottom end, and using the heads and intake from the TBI engine....Those are worth 300 ft lbs tq from the factory.
The older engines were only around 165 hp, and 265-70 ft lbs, smogger heads, and keep in mind, a carb wont do as well with the cold up there, and any high angles you may encounter. also, keep in mind, unless that 4 bolt engine is 86 or newer, you are going to need a different flywheel and starter....hopefully it will come with all that.

 

[87TBIguy]

Thanks for the reply. I was thinking about going with Comp Xtreme 4X4 #12-239-3 1300-5600 rpm 218/226 dur @ 50 .462 .480 lift
and if I go carbed I was thinking of going with a q-jet or offroad avenger, just from what I have read/ heard of working well. Also thinking of a dual plane intake. I can get an MSD HEI dist, for about 130 as well. Just wanting to put out a little more power than previously.

 

[87TBIguy]

Also I don't drive the truck in the winter. But still not sure what direction I want to go with this. If I run the tbi heads and intake on the older block I will bump up my compression ratio, correct?

 

[Swims350]

only if the older heads have bigger then 64cc chambers.

I'd go carb forget the tbi crap. you have to get a chip made for any cam other then stock computer compatible, and maybe anything else serious.

I'd just check out the carb heads you have, compare them to the tbi ones, and go from there.

If it were me, carb setup period and then I'd run old school heads to avoid issues with the 4 center bolts.

I have an 88 tbi truck right now that's going to carb with a set of 305 old school heads.

 

[87TBIguy]

if I go with the old school heads, carb setup I will have to get different accessories too right because old school heads down have all the bolt holes on the end of the head? Also what would I do about alt wiring? and coolant temp/ oil pressure. have the gauge cluster with oil pressure, volt gauge, fuel, coolant temp, what about wiring for these?

 

[Jims86]

Thanks for the reply. I was thinking about going with Comp Xtreme 4X4 #12-239-3 1300-5600 rpm 218/226 dur @ 50 .462 .480 lift
and if I go carbed I was thinking of going with a q-jet or offroad avenger, just from what I have read/ heard of working well. Also thinking of a dual plane intake. I can get an MSD HEI dist, for about 130 as well. Just wanting to put out a little more power than previously.

Good choice on carbs, stay away from Edelbrock. Dual plane manifold is the way to go, single is for much higher rpm ranges.
IMO, 1300 is a tad high for power to come in for a truck. I suggest you take a look at the stock vortec L31 roller cam, as well as the HT383 cam from gmpp. if you dont want to go roller, take those specs and call around for a hyd cam that is close. The lower the duration, the lower in the rpm range you will get torque. You will want as much off idle tq as possible.

 

[Jims86]

only if the older heads have bigger then 64cc chambers.

I'd go carb forget the tbi crap. you have to get a chip made for any cam other then stock computer compatible, and maybe anything else serious.

I'd just check out the carb heads you have, compare them to the tbi ones, and go from there.

If it were me, carb setup period and then I'd run old school heads to avoid issues with the 4 center bolts.

I have an 88 tbi truck right now that's going to carb with a set of 305 old school heads.

Chris has had some gremlins show up with his TBI, but if yours is running fine, keep it if you want.
you will need an older manifold style for the heads, most of those pre 87 factory heads were 74cc.
The 87 heads are an improvement over the earlier, but Vortec heads would be my choice...especially with a carb, and the need to purchase another manifold.

 

[Swims350]

old heads have all the right bolts holes in them except for some double hump or camel type, really old like pre 70's those don't have all or any holes in them.

why would the gauges have to be changed? use your old sending units in your tbi 350 or whatever size it is in the other block, heads and intake.

CTS of collant temp sensor for the tbi is in the intake, gauge is in the head usually, put it back there. oil pressure sending units are in back of the block behind the intake, ones for fuel pressure fuel pump cicuit, the other is the gauge, or even sometimes near the oil filter, same for any blocks. Just use what sending units you have in your block now, or buy some for your block year and such and put them in what you want.

I run aftermarkets in mine, much more depdnable and accurate IMO.

Why no love for edelbrock carbs? NOBODY online seems to like them, I could NOT be any happier with them, way too simple to rebuild and only $40 for a rebuild kit, only downsides I ever seen was ppl having issues with the tv cable on 700r4's and then having to run an adapter to fit them on a stock q-jet intake.

I love em, gonna run one on my 88 when I switch it over this spring.

my old man has one on his 84 been on that motor and ran for around 8 or 9 years now trouble free, no rebuild. I got one I rebuilt on my brother in laws monte carlo I used to own, been on there rebuilt for like 6 years now.

 

[87TBIguy]

What else would I do to run the GMPP cam?, as that would be a good option as a do work at a GM dealer. And I know I can use my tbi sensors, your saying just hack up my tbi harness and make that work? Sorry for the ignorance to carbs/ setup, never had a carbed vehicle before and this will be my first performance oriented scb build. Id like to try to use one of the sets of heads I have now dues to cost.

 

[87TBIguy]

Think im gonna go with this rebuild kit, that's why I was gonna go with that cam, some feedback on what items on that list I should get would be awesome

 

[Swims350]

list didn't show up.

as for a gmpp cam I think a summit cam kit would be cheaper.

as to hacking up a harness no need to, you only need power from the stock coil to power an hei type distributor, and that is already in your harness you just have to find it and cut it's end off and use a female type end.

the alternator wiring won't change if you stick with your current alt., starter isd the same, now some wiring from the starter to the junction box with all the fusible links may not be needed once done but they can be unhooked later or something once you know what is needed and what is not.

now fuel pump, this is the biggest concern, you can run a mechanical block mounted cheap pump, like me, leaving the in tank pump in place just unplugging it's relay or fuse or both, NOT at the pump, and run lines to the block mounted pump and such, OR use a bypass type fuel pressure regualtor and run the in tank pump as is with the use of a block off plate that you already have.


honestly if you have tbi and it works companies can burn you a chip for it once you know the exact specs on your cam and heads you use etc. they can do the chip and you can use the tbi setup and be done with it.

 

[87TBIguy]

Hmm just found out the core had a spun bearing...

 

[Driver4r]

turn the crank and get oversized bearings

 

[87TBIguy]

I just so undecided on what to do, got looking at some ls swap threads kinda want to that route. just not so sure financially what the best route would be.