Engine wiring question

[DanR]

Ok, for 99% of you, this will probably be a stupid question, but I need some guidance here. I often see engines wired in two ways – from the distributor directly into the valve covers or from the distributor into a location just under the valve covers and, I believe, directly into the engine block. My question is this – is there a hard and fast rule for one method or the other? I seem to see the wiring direct into the valve covers more on drag racing vehicles. I know I could just Google it, but what if I don’t know exactly what type of engine I’m using in a given model? I’m just starting to flirt with the idea of doing some wiring and I want to make sure I get it right. Thanks!!

[Ace-Garageguy]

The drag-racing and production engines you see with the plug wires running into the valve covers are primarily either old Chrysler Corp. "hemi" engines, or racing engines based on that architecture.

Different engine designs place the plugs in different locations for a variety of reasons, so it's always best to research the appearance of the SPECIFIC engine your model represents.

The old "hemi" engines (Chrysler FirePower, DeSoto Firedome, and Dodge Red Ram, plus the later Chrysler 426 Hemi, every racing engine derived from it, and the rare Ardun-Ford flathead conversions) run the spark plugs between the rocker shafts. This requires tubes that the plugs live in, and the wires go to these.

This shot of a 392 cubic inch Chrysler FirePower engine shows the tubes clearly...

...and even though all pushrod hemi engines will be configured like this, some production engines hide the wires in a "loom", like this...

Most non-hemi V8 engines place the plugs below the valve covers, like this smallblock Chevy...

 

 

Edited December 7, 2017 by Ace-Garageguy

[Junkman]

It all depends on the location of the spark plugs. The plug leads always go to the spark plugs.

Edited December 7, 2017 by Junkman

[DanR]

Ok, solid advice guys, but for a 1/25 scale model, sometimes you don't quite know where the spark plugs go (at least I don't). I'm not even shooting for 100% accuracy, I just want the overall appearance to look accurate. I guess for me, the best thing to do will be to just Google it and hope I get it right. Thanks!

[Ace-Garageguy]

2 minutes ago, DanR said:

Ok, solid advice guys, but for a 1/25 scale model, sometimes you don't quite know where the spark plugs go (at least I don't). I'm not even shooting for 100% accuracy, I just want the overall appearance to look accurate. I guess for me, the best thing to do will be to just Google it and hope I get it right. Thanks!

Or just ask here. We'll be happy to help, we appreciate guys who want to get the details right, and after a while, you'll KNOW.  

PS. I added some info to my first post, if you missed it.

[Spex84]

Many older kits lack any indication of spark plug locations, but a quick Google search can sort that out. If it's tricky to see the plug locations in photos of built and installed engines, you can always look for photos of just the heads (ie search "392 Hemi heads) and compare to the kit pieces.

[Casey]

28 minutes ago, DanR said:

Ok, solid advice guys, but for a 1/25 scale model, sometimes you don't quite know where the spark plugs go (at least I don't). I'm not even shooting for 100% accuracy, I just want the overall appearance to look accurate. I guess for me, the best thing to do will be to just Google it and hope I get it right. Thanks!

As Bill said, just ask if you can't tell for sure after a Google search. Some engines have funky plug locations, some are covered my a metal shield, some under a passageway/cover on the cam cover, and so on. It's not universal, but getting the location correct does make a big difference in terms of realism.

[Junkman]

3 hours ago, DanR said:

Ok, solid advice guys, but for a 1/25 scale model, sometimes you don't quite know where the spark plugs go (at least I don't). I'm not even shooting for 100% accuracy, I just want the overall appearance to look accurate. I guess for me, the best thing to do will be to just Google it and hope I get it right. Thanks!

Like Bill said, you have to do your research.

Very few American V8s besides the Mopar Hemis had the sparking plugs in the rocker covers.
Most of them had them in the outer sides of the cylinder heads, but there is a variety of configurations.
This needs to be carefully investigated if you strive for authenticity. So does the firing order, entirely BTW.
The same goes for engines made outside the United States. There are countless different designs.

[blunc]

I suggest doing a google image search of the car/motor you intend to add details to, choose several angles/views that give you a good idea of what you want to add to your build then save those images to your computer for later reference.

If you are unclear after that, someone here can most likely supply more info or pictures.

[Model Carnage]

18 minutes ago, Junkman said:

 

Very few American V8s besides the Mopar Hemis had the sparking plugs in the rocker covers.
 

Let us not excite the FoMoCo gang by leaving out the SOHC 427 and Boss 429

Edited December 8, 2017 by Model Carnage

[MarvinGardens]

Or the McGee DOHC conversion for the BBC!

[Junkman]

Let's start a spark plug placing war!

[Ace-Garageguy]

18 minutes ago, Junkman said:

Let's start a spark plug placing war!

I'll start.

Mickey Thompson hemi heads for the Ford FE engine...

Edited December 8, 2017 by Ace-Garageguy

[Ace-Garageguy]

Mickey Thompson Pontiac hemi heads...

Edited December 8, 2017 by Ace-Garageguy

[Ace-Garageguy]

Babbitt & Lyons smallblock Chebby hemi heads...

 

Edited December 8, 2017 by Ace-Garageguy

[Ace-Garageguy]

Hammerhead hemi heads for a smallblock Ford...

Edited December 8, 2017 by Ace-Garageguy

[Ace-Garageguy]

Aries smallblock Ford hemi heads...

[Ace-Garageguy]

Avenger smallblock Ford and Chevy hemi heads...

[Ace-Garageguy]

Valve cover for the Arias big-block Chevy hemi conversion...

[Ace-Garageguy]

Ford-built 32-valve head setup for the smallblock, though never series produced in significant numbers...

Edited December 8, 2017 by Ace-Garageguy

[1972coronet]

Oldsmobile 455 Hemi , exp

[1972coronet]

GMC's "big block" V6 series have the plugs and wires on the intake-side :

[Jon Haigwood]

Yup , I always google them and then get the correct firing order and rotation direction and where no 1 is located on the distributor cap. If you want.

 

Ford 390

Edited December 8, 2017 by Jon Haigwood

[BigTallDad]

18 minutes ago, Jon Haigwood said:

Yup , I always google them and then get the correct firing order and rotation direction and where no 1 is located on the distributor cap.

Excellent point. All of the previous posts show plug location on the heads, but yours is the first to point out (to me, at least) the firing order on the distributor cap. I've seen far too many "hair part" distributors.

[Ace-Garageguy]

45 minutes ago, Jon Haigwood said:

Yup , I always google them and then get the correct firing order and rotation direction and where no 1 is located on the distributor cap. If you want.

 

24 minutes ago, BigTallDad said:

Excellent point. All of the previous posts show plug location on the heads, but yours is the first to point out (to me, at least) the firing order on the distributor cap. I've seen far too many "hair part" distributors.

Here's another excellent point: in the real world, you can put #1 anywhere on the distributor cap, so long as all the rest of the wires are in the correct relationship to it.

This can be helpful in tight engine swaps, for instance, where you might have a big vacuum advance can that causes a clearance issue. Simply roll the engine to TDC firing (not overlap) on #1 cylinder, rotate the distributor to where it physically fits, start wiring with terminal #1 wherever you want it...maybe to take advantage of the lengths of the plug wires you have.

The POINT is, to be correct on a non-factory setup, the #1 position on the cap as shown on the firing-order references is NOT carved in stone.