TD 427 Tall Gen V TBI Modification

[ccj8008]

Not much in the forum regarding the tall truck blocks, 366 & 427. Most are Gen IV engines. I have a 1991 Gen V sitting in front of a 6 speed manual trans in a Kodiak truck. This had factory TBI. It was converted to propane by the previous owner. This required a 'Super Fix' unit from MSD to deal with the computer.

I want to convert to dual fuel, LPG/gas. I am figuring on an intake manifold change and carb + new distributor. Typically, intakes are exchangeable between Gen IV and Gen V. Can anyone confirm this is still the case for the tall blocks? I can get a Gen IV intake off Ebay.

Distributor- I have heard tall blocks use a different distributor to make up a .400" height difference. Any recommendations for swapping out the TBI distributor?

 

[375 H&H]

I have an older truck 427. it works fine with standard distributers, but I have also read of others that required the tall deck distributers. I would assume that they were made both ways over the years.

 

[paratrooper307]

The intakes should fit, also I believe there are adapter spacers you can use to make conventional standard deck intakes fit on a tall deck block. This may be desirable as the selection of TD manifolds is limited. If you want to use a standard distributor, you will need a TD intake though, otherwise you have to use a longer distributor or one with a slip collar.

The reason you don't see much about them is they are generally not considered especially desirable for performance. That is probably not the most fair assessment, but that is common perception. They are less common than standard big blocks, some parts don't interchange, and they were chiefly used as workhorse truck engines. Long on toughness and reliability, performance was secondary. The factory heads on them are junk from a performance perspective, but most BBC heads will fit, although I think some late model heads require modification. The good news is that TD blocks come with a strong crank and can be bored and stroked for some good cubes The four-ring pistons aren't intended for high rpm operation, but that is of little concern in a truck.

 

[454Sub]

They also use a taller piston skirt, and more rings to stabilize the piston and prevent it from rocking in the bore. Honestly everyone thinks that the tall deck 427 is the same as the old 427, it is not, nor is it even in the same ballgame. Is the tall deck a bad motor.... no, is it worth building over a cheaper, more easily assessable, not to mention more cubes standard 454, also no.

Now, they can be built into something that would function perfectly fine in a truck style platform, so what your doing is perfectly acceptable abeit an odd way of doing it. MSD and ACCEL offer several adjustable dizzys for BBCs that could be made to work.

 

[diesel4me]

The older tall deck motors used a reverse rotation distributor when they came factory with timing gears,rather than a chain...you can swap in a cam from the "regular" big blocks and use a timing chain though...I think the tall deck distributors in the older motors were "special"length,but I have seen later HEI's adapted to them..

I have a book that has more details on the differences,but its been a long time since I have read it...if you need to know more specifics I can dig it up and see if it has the answers..but it "stops" around the late 80's,anything newer it wont have any info on..

 

[ccj8008]

Intake

The 366 and 427 both appear to have dual thermostats in the intake manifold. I assume this is for enhanced cooling, so I want to keep this feature rather than using the spacers to adapt a standard block intake manifold. Looks like my carb choices may be limited to square bore?

Of interest, the bellhousing for the 6 speed is massive so it would be interesting to know the clutch diameter.

Guess I will go ahead and buy the Gen IV TD intake and an MSD distributor specified for tall decks and make the swap. Thanks for the comments and suggestions.

 

[beags86]

The 366 and 427 both appear to have dual thermostats in the intake manifold. I assume this is for enhanced cooling, so I want to keep this feature rather than using the spacers to adapt a standard block intake manifold.

Time to wake up the zombie thread.

The dual thermostats where for being loaded or pulling. The first thermostat (lower temp) will open and operate like normal. Then once you put a load on the engine (pulling or hauling a load) the secondary thermostat will open (higher temp) and allow more coolant flow.