tbi to carb swap trouble !!

[chevysmallblock]

hey everyone i have a few issues going on here that i cant seem to resolve, ill give you the run down first i bought a 78 k10 a few years ago someone had swapped a drive train out of a 87 burban into it so it was tbi 350/700r4, now it ran and drove ok but i wanted to swap it back to how it should have been so i did all the swap, intake,distributor, carb, fuel psi regulator, and tore the ecm out,... and i also put a cam in it (not the one i wanted) but it is a .466 .487 lift cam it idles really lopey (also i noticed it said 2500 stall converter)(i have stock converter in it still) but my main issue is when i put her in gear it stalls out on me... ive tried messing with the timing 4,6,8,10,12,14 degrees, nothing helped its idling a about 850rpm, prior to all of this the trans was fine.. im pretty lost and i adjusted my idle mixture with a vacuum gauge its only reading about 15 psi.. some help would really be appreciated , thank you in advance

 

[SkinnyG]

Your stock converter is the problem.

What's your cam specs/duration?

I tried to run a stock converter with my cam (231°@.050, .470" 108LSA), but it would drop 500rpm going into gear. Idled about 12-13" in park, and 8" in gear. Cam company recommended 2500 stall. I bought one. It's SO much better.

And then you'll want gears to go with it.

 

[chevysmallblock]

not sure on the duration its the summit kit sum-1105

 

[rich weyand]

That cam requires 9.5:1 compression ratio. Did you change the heads or pistons as well?

 

[chevysmallblock]

well its a 78 block and pistons with 87 tbi heads, see the problem was someone fat finged that part number at summit i wanted i believe 1104 not 1105 and i noticed all of this AFTER i bolted it all back together, engine runs awsome, has impressive response from idle, and lopes good at idle in park or neutral...

 

[Georgeb]

What intake did you use on those 87 tbi heads. I was contemplating using 87 TBI heads on my 78 block because I have the heads and they are good but I want to run my Q-jet but I know the center bolts are different. I thought about oogling the holes.

 

[chevysmallblock]

summit sells them it was just a cheap intake i cant remember what brand, they just come with little bushings that change how the bolt goes in

 

[RangRayy]

Did you change out your springs? I was always under the impression tbi swirl port heads couldn't handle much lift with stock equipment.

 

[chevysmallblock]

stock springs, there not binding tho

 

[SkinnyG]

Yup - that cam (224°/234°@050) will totally NOT like the stock converter, and even less so if you have not bumped the compression as well. They say 9.5:1 minimum, I would shoot for definitely 10:1 or more (I am 10.9:1 on my 350).

Probably sounds pretty cool though!!

 

[68post]

You need a much smaller and a better brand of cam in my opinion. Besides the fact that the TBI heads will severely choke the engine at 4,000 and higher.

 

[SkinnyG]

Oh, yeah. ^^^^ that would be the best fix, truthfully.

 

[chevysmallblock]

Well guys after all this, i played with the timing, swapped my carb out with a known good one, idles nice and lopey, in and out of gear, runs great! truck will never see over 4k anyways, bottom end is still there surprisingly, still spins 33s with no problem with out power braking it lol thanks you for all of your input!

 

[83kid]

What intake did you use on those 87 tbi heads. I was contemplating using 87 TBI heads on my 78 block because I have the heads and they are good but I want to run my Q-jet but I know the center bolts are different. I thought about oogling the holes.

Do NOT oogle the holes. Idiot who had my truck before me did, and it will blow the intake manifold gasket soon enough, already has once before i decided to buy the right intake.
Edelbrock part number 2104, preformer intake, canted center holes to make it work

You will leak oil and coolant if you use a different intake

 

[Georgeb]

Do NOT oogle the holes. Idiot who had my truck before me did, and it will blow the intake manifold gasket soon enough, already has once before i decided to buy the right intake.
Edelbrock part number 2104, preformer intake, canted center holes to make it work

You will leak oil and coolant if you use a different intake

Thanks for the advice. I have decided to stick with my 1978 heads and just have them refreshed.