1965 Plymouth Slant Six Engine

Spring is in the air. You're probably more than ready for another season of racing or cruising ... but is your hot rod? We're here to help with your parts questions, tuning problems, and combination conundrums. I'll answer as many questions in the pages of Pit Stop as space permits. If you have quality digital photos of the car, engine, or part in question (no smaller than 1600x1200 pixels, but larger is always better), we may throw them in as well. When e-mailing, don't forget to include "Pit Stop" in the subject line, and put your real full name and hometown or military unit, base, or ship in the message body. -Marlan Davis

Turbo Slant Six
We are building a '65 Plymouth Slant Six engine with a turbo. The engine builders in the Portland, Oregon, area either tell us that the compression ratio should be 8:1 or that you can run up to 11:1. We have invested a considerable amount of labor and money in this project. Previously, without a turbo, the car ran in the mid-11s at 112 mph at the local track.

The new turbo engine will have Hilborn fuel-injection, a custom billet Crower crankshaft (one of five made), special aluminum connecting rods, Venolia pistons, an MSD crank-trigger ignition, a Weaver dry-sump oil system, and a copper head gasket. The block has stainless steel O-rings installed and oversized ARP studs. The turbo is from Turbonetics with a Spearco intercooler.

Although a serious Chrysler Slant Six may sound slightly offbeat to today's rodders, this engine actually has quite a performance pedigree dating back to the early '60s and the factory-produced Hyper Pak option. This injected Slant Six-powered dragster was shot by Eric Rickman back in October 1962 on a residential street in Los Angeles.

We'll be using a custom-ground mechanical flat-tappet Crane Cam ground on a 108-degree lobe-separation angle that uses the following lobe profiles:Intake Lobe
Grind: F280/3994
Duration (0.020-inch tappet lift): 316 degrees
Duration (0.050-inch tappet lift): 280 degrees
Duration (0.200-inch tappet lift): 189 degrees
Valve lift (1.6:1 rocker ratio): 0.639 inch

Exhaust Lobe
Grind: F276/3934
Duration (0.020-inch tappet lift): 312 degrees
Duration (0.050-inch tappet lift): 276 degrees
Duration (0.200-inch tappet lift): 184 degrees
Valve lift (1.6:1 rocker ratio): 0.620 inch

The boost will be 12-15 psi with an estimated 546hp output. The body has a full Morrison frame, a four-link rear, a strut frontend, and a Lenco five-speed with a Ram clutch.

With all your resources and knowledge, could you please help us or point us in the right direction?Dave MuellerThe Slanted CrewKelso, WA

I checked with noted drag-race and Bonneville turbocharged engine builder Ken Duttweiler on this one. Duttweiler says that modern technology has invalidated a lot of old-school engine-combo practices. "Your cam thinking is obsolete," maintains Duttweiler. "At 15 psi boost and the 550hp level, you would only need about 230 degrees at 0.050-inch tappet lift."

Although the cam overall needs to be a lot shorter, the exhaust side still should be at least 10 degrees longer than the intake-not shorter as in your projected profile. Although at one time running a shorter-duration exhaust lobe was standard practice to help the turbo spool up quicker, today's new-generation turbos , with their advanced lightweight impellers, no longer require this crutch. On the other hand, "a longer exhaust lobe generally enhances engine rpm capability. It helps get the spent gases out of the head." More specifically, Duttweiler calls for 0.050 duration numbers of 230 degrees on the intake, and about 238 degrees at 0.050 on the exhaust side.