My 3.4 IRON HEAD Build

[GEARS]

OK guys, I give you full rights to flame me for not swapping to aluminum heads, lol, but it after all is a truck, and I really want to keep the TBI look, and have a roots blower.... No need to tell me how much more powerful your turbo 3400 is I just wanna do something completely unique in its own class.

Here is the deal, 1986 S10 with a Blown TBI {Fe} Head 3.4.

1) Right now it sits with a GMPP HT3.4 bottom end...

2) I am in the process of adding heavily ported and cleaned up iron heads (the ones that came with the crate), with shaved valve guides for clearance, and cut for viton seals on all 12.

3) Valvetrain is getting completely re-worked... Crane H-272-2 cam, with Comp Cams 1.6:1 roller rockers, and Comp 983-KIT for valve springs, locks, and retainers. This combo will yield me a 0.484" lift on the intake and a 0.512 lift on the exhaust with safe margins in relation to coil bind and spring pressure.

4) Cloyes Double Roller Timing Chain FTW!

5) Serpentine belt swap, and run the blower with a ASP 2.5" 8-rib pulley.

6) Water/Alky Injection to protect the guts of the motor!

7) Holley 400 cfm TBI run on a home-tuned 1228062 ecm off of the original 2.8 TBI code, using Moates stuff and TunerPro.

Headman LONGTUBE headers, with no cat, custom y-pipe, and a 2.5" flowmaster delta 50


I am hoping to pull about 6 psi out of it, which with that cam, and a good tune, and water injection, I should have a really customized 3.4 that can hopefully put down some reliable power...


Lots of pics to come, and this thing should be on the road by the new year!! If anyone has any input or tips for me along my journey of building this thing, feel free to comment!!!!


CHEERS

[2.8/3400 1985 Camaro]

You don't need water/alcohol injection on 6 psi of boost.

[Superdave]

the Crane H272-2 cam is not a boost cam at all, you'd be far better off with either the Crane or Comp 260 grinds.. or something custom from Delta.



Seems like a cool build though.

[GEARS]

The thing I liked about the H-272-2 cam is that it drops my dynamic compression ratio because of the valve overlap, AND gives me a higher lift than if I use the current H-260-2..

This is not a good idea??

[2.8/3400 1985 Camaro]

From my understanding, its a poor cam choice due to the wide LSA, which actually gives you less overlap than say a 110 LSA cam, which is what the 260/260 is, the 272, does have comparatively more exhaust duration though, but I believe you only particularly want more exhaust duration than intake when turbocharging.

[Superdave]

the wider LSA actually works in it's favor to lessen the overlap but it's still got too much. IIRC it's around 50 degrees. You really want to be 30 or even lower.

The less boost you blow out the exhaust valve during overlap the better. Boost cams typically have LSA's in the 113-114 range and run a little higher lift with less duration just to get rid of as much overlap as possible.


The good news is that you could probably get a custom ground one for about the same price.

[GEARS]

I see, well then I'll just stick with the current H-260-2. Plus with the 1.6:1 ratio rockers the lift will be 0.455" Intake and 0.484" Exhaust. LSA is 112* and I calculated valve overlap to be 42*, which is better than the H-272-2's 54*.

Then I oughta just keep the current Crane springs, retainers, and locks as they are!

Thanks for the input guys!!