TBITrucker

I am hoping you guys can help me out with this not exactly third gen project.

I am building up a TBI motor for my 3/4 ton truck and can use some cam and tuning advise. This motor was originaly intended for my car but it now has to go in the truck, wich is OK since I really want a 383 for the car anyway. I'm hoping this will get me into chip tuning so if I do get the 383 I will be able to tune it right.

I have an 85 305 H/O motor from a Monte Carlo SS that I want to make TBI for my truck. I need help picking a cam and advise on making it work. I will be using a 4bbl intake with a TBI adapter, World Products 305 S/R torker heads, edlebrock smog headers, heated O2. Turbo city bored out TBI, Truck torque converter, Gibson performance exhaust, MSD 6EZ ignition, open element air cleaner, High flow cat and an adjustable fuel pressure regulator. I have the stock 305 injectors for the TBI and a new fuel pump was just installed on the truck.

The truck is an 88 with an LO3 that is shot ( 2 dead cyl) anyway it looks identical to my car so I figured what I do here can be aplied to the car.

I do have a cam but i'm not sure if it is right for this it is a comp cams x4250 h truck cam the other number is 249-12-231-2

Any way with all that info out there I can really use the help finding the right cam and more importantly advice on how to make it all work.

dimented24x7

iTrader: (2)

That cams fairly good for a truck when paired with a smaller dual plane manifold. It should make a decent ammount of torque down low.
----------
Also, with some mild work, the HO heads can likely outflow the S/R's, if you want to save some money. Even in stock form with a basic rebuild (new valves/seals, screw in studs, springs, etc) they'd be alright.

TBITrucker

OK now you got me with the heads.

The World I have were used less than a year so they are in great shape.

The 416's I have came on the H/O motor and only have 20 or 30 k miles on them so they too are in real good shape.

Having said that do you think I should try porting the 416's myself?
I have no experiance with this so I don't know how good my work would be but do you think a first timer could make them flow better than the worlds?

If so I could sell the worlds and make up some money for the tuning equipment I will need.

By the way will I be OK with the stock injectors and stock fuel pump?

dimented24x7

iTrader: (2)

If you have both then the S/Rs will flow a little more in their present form then the 416's and may take more lift. If you want to save time, then you could just put the S/Rs on as-is. If you want to experiment with porting, then you could work on the 416's and try those. Porting heads is time consuming, though. I just went through my vortecs and blended the bowls and shaved/streamlined the valve guides and even that took about 6-8 hours of work. Expect to spend several weekends on a good port job.

TBITrucker

How would 1.6 ratio rocker arms work with this setup. I am speaking specifically about the $80 summit stamped steel ones. (they are really the only ones that fit my budget).

How would they affect the computer?

Would they change the power band of the cam?

Do I need to buy different pushrods?

what kind of power increase would I see?

Would it be a worth while investment? or should that money go somewhere else?

I have searched the all the threads I could , even some old posts I have made and I am still confused about the voodoo of 1.6!!

dimented24x7

iTrader: (2)

The 1.6 ratio rockers just add a little more lift. The duration remains essentially unchanged. They'll add a little more lift, and maybe 10 HP or so if the heads can flow better at higher lift. Those stamped steel ones are probably pretty flimsy like the stock ones, and with the higher spring pressures you'd need for the cam, they probably wouldn't manage to maintain the 1.6 ratio, anyway. Id say if you where to spend some money, porting and undercut valves would be better bang for the buck.

As for installation, you'd need to widen the guide slot and the pushrods may or may not need to be replaced.

TBITrucker

Thanks

I will probably just go with some head work then


Will the stock (brand new) TBI fuel pump and 305 injectors be OK? or do I need to get larger injectors and or different fuel pump?

dimented24x7

iTrader: (2)

Youll definatly want 350 injectors at least. You can use the current pump, but it limits your fuel pressure to 12 PSI or so.

TBITrucker

Thanks a million dimented24x7 for you help with all this, it is really helping me a lot!

What size 350 injectors would I need? I see there are at least 3 lb per hour ratings for the 350 45, 50, 55 lb/hr. maybee more?

What would be best for this setup?

dimented24x7

iTrader: (2)

The 55's would be alright. The other option is to put in a larger fuel pump and increase the fuel pressure. The latter would probabaly be the better option in the long run. These injectors work fine at MPFI pressures.

Fast355

iTrader: (2)

Stock 4.3s have 46 and 55# injectors depending on what it was in
Stock 305s have 55# injectors
Stock 350s have 61, 65, 68, 74# injectors depending on what it was in.