LT5 coming together...FINALLY!

[Paul Workman]

Tiz been a long but enlightening road, starting the year before last with what turned out to be a secondary fuel pump failure, then a blemished exhaust valve (did NOT appear to be burnt; got several of us doing the bit), to porting the heads. (Much(!) second-guessing in that regard, "fer sher") Marc H marked a guide line in my heads in the combustion chamber in order to relieve the valves a bit more.

And, now the end is in site.

The plenum retains the internal splitter between the runners, tho shortened 1" and left quite sharp so as to not create a disturbance (pressure wave) as air enters the IHs. (better velocity that-a-way) You can roll a 36mm ball thru the primary IH runners. However, the ball will stick on the nub of a boss that remains in the secondary runner.

The "vacuum" and tumble created by the bosses is retained with an expansion of the chamber below the injectors - that bowl area - and the theme is carried into the heads.

At this point, and before I went on to complete the head porting, my top end P&P to head port matching differs from some in a couple ways: Instead of simply tapering the head opening about 1/2" or so on the primary side, I extended the IH outlet (36.x mm) diameter into the (primary) head runner to the depth of the secondary throttle plate centerline before blending into a taper that ended at the base of the valve guides. (The convention of the FBI seems to be of the opinion that wee doan need no steeenking secondary throttle plates!)

In hind-site, I wish I had the chance to have dyno'ed the preliminary result before continuing with the head porting. The performance was an awesome improvement - much more than the 30 or so hp gains I've experienced in other projects! (Mebby someone will try it and share the results?)

In the end, the head porting dimensions will be follow pretty closely to those I used as a reference; engines that are well documented and putting out 500+ hp (with dyno power curves that are essentially FLAT from 6000 to 7000+ rpm w/ NO loss of torque on the low end!!). Couple that with some magic cam timing numbers retrieved from a Mason jar in Pete's back yard, it should bring a tear or two to a few unsuspecting mopes!

Damn...Is it spring yet??? Can't wait!!

P.