dual plug heads to a 81 turbo

keepinitril · Sep 6, 2010

Im not into the turbo coupe yet, but Im stoked because we have a dual plug head at the shop.

81 is the cutoff for the historic (or histaric) class and I was going to find a pace car and throw the dual plug head on there.

BUT im curious what all is needed to make it work out. It looks like I need a DIS for it to work,
but I'd would rather see what others have done

Red_LX · Sep 7, 2010

People have used the dual plug head and either blocked the intake side set of plug holes or just left old plugs in there that weren't hooked up....otherwise, if you actually want the dual plug you might as well start with a complete DIS engine and build it up with turbo internals. There's really no gain in going to a DIS head.

Jax Rhapsody · Sep 14, 2010

Unless he has an early dual-plug that had two dizzy's. With megasquirt you probably could have some advantages. Especially with changing the firing orders.

bhuff30 · Sep 16, 2010

Jax Rhapsody said:
Unless he has an early dual-plug that had two dizzy's.

Don't think I've seen that before. Any pictures?

65ShelbyClone · Dec 27, 2010

A dual-distributor 2.3? That's a new one.

There's not much special about the dual-plug head over an oval- or d-port casting and definitely nothing to be gained if only one set of plugs is used.

Delray Dude · Dec 28, 2010

Even if one side is dead (plug wise) one would gain the use of the roller cam assembley if the old head were not.

mustang_matt · Dec 28, 2010

dont bother with the dual plug head. I built a turbo 89 stang a few years ago, and the dual power heads just doesn't flow as good as the turbo heads.. problem is alot of the turbo heads are cracked now. I used the stock head off the 89 4 popper. but the combustion cambers are smaller on the n/a heads so you can run into detonation problems if you run to much boost. you will really need to watch your timing. BUT really just dont waste your time on a dual plug head.
@65shelbyclone it wasn't a dual distributor it was a coil pack setup. with a dual drive control module.

65ShelbyClone · Dec 29, 2010

Delray Dude said:
Even if one side is dead (plug wise) one would gain the use of the roller cam assembley if the old head were not.

It would be a lot easier to just put the roller setup in an earlier head.

mustang_matt said:
@65shelbyclone it wasn't a dual distributor it was a coil pack setup. with a dual drive control module.

I am familiar with the EDIS system. I had never heard it called "two distributors" before.

zonker · Dec 29, 2010

+1

the dual plug head has probably the worst port flow of any of the 2.3 heads, and with it's closed chamber it's gonna raise the compression ratio.

as for the dis issue, u can use a 8 plug head on a 4 plug car with distributor without issue, other than leaving the intake plugs unused.

hmm. u could always open up the combustion chamber then cc them. that would take care of the CR issue.

and a little porting around the valve guide area will help flow...

so i guess if you're up for the labor of reworking the head a little thaen yes, it will work dandy.

Delray Dude · Dec 29, 2010

65ShelbyClone said:
It would be a lot easier to just put the roller setup in an earlier head.

Very true and good point.

Delray Dude · Dec 29, 2010

zonker said:
+1

the dual plug head has probably the worst port flow of any of the 2.3 heads, and with it's closed chamber it's gonna raise the compression ratio.

as for the dis issue, u can use a 8 plug head on a 4 plug car with distributor without issue, other than leaving the intake plugs unused.

hmm. u could always open up the combustion chamber then cc them. that would take care of the CR issue.

and a little porting around the valve guide area will help flow...

so i guess if you're up for the labor of reworking the head a little thaen yes, it will work dandy.

I can see the possible need to improve the port flow, but why bother with the compression ratio? I understand stock turbos came with lower compression, but raising the the ratio a tad wouldn't really matter in my opinion. If one was worried about too much boost due to a higher compression ration, then they can always regulate wastegate to achieve the desired boost - and well, if one was going to this much trouble, you would think they would already have an adjustable controller.

But then again, with as many lima engines out there - it's probably cheaper to just swap over the roller cam stuff onto the 4 plug head and do a small clean up on it and run with that.

65ShelbyClone · Dec 29, 2010

The higher compression is going to make ping a bigger concern around boost onset and also necessitate less peak boost. Generally speaking, less compression and more boost will make more power with a given fuel octane at the expense of thermal efficiency. Everything is a trade.

Delray Dude · Dec 29, 2010

65ShelbyClone said:
The higher compression is going to make ping a bigger concern around boost onset and also necessitate less peak boost. Generally speaking, less compression and more boost will make more power with a given fuel octane at the expense of thermal efficiency. Everything is a trade.

Ok, makes sense. I know enough about turbos to be dangerous but not enough to be leathal...

KhanTyranitar · Apr 25, 2011

Delray Dude said:
Even if one side is dead (plug wise) one would gain the use of the roller cam assembley if the old head were not.

Why not just use the roller cam, it will work with the old head.

65ShelbyClone · Apr 26, 2011

Why use a stock roller cam at all?

KhanTyranitar · Apr 27, 2011

Because the roller cam is considered an upgrade replacement to the previous cams. It can be used without any tuning modifications.

65ShelbyClone · Apr 27, 2011

It's not an upgrade as far as the profile is concerned. It's a straight-across trade at best and the Ranger cam actually pulls the power spread downward. That's why no tuning is required.

KhanTyranitar · Apr 28, 2011

The roller cam holds certain valves open longer, and opens and closes them more gradually, resulting in an increase in low end torque and fuel economy, while still keeping the top end power. Trust me, the roller cam is an upgrade. It also runs quieter and puts less stress on the lifters.

65ShelbyClone · Apr 28, 2011

There sure are a lot of complaints that it signs off early and needs to be retarded several degrees for "keeping the top end power."

I'm not saying it's a bad cam and it may even be worth a few ft-lbs down low, but I wouldn't suggest that anyone go looking for one thinking it's a fabulous upgrade...because it's not fabulous. I would say keep the followers, sell the cam, and put the proceeds toward a better profile.

KhanTyranitar · Apr 29, 2011

Maybe so, often the "loss of top end" is compared tot eh low end. The top end with the roller cam is the same as the old cam, but you get more low end.

I guess they way to sum up though, is the 8 plug head is not needed, and adds a lot of complexity to your project, and the roller cam doesn't offer significant benefits. For what you can save versus swapping and modifying an 8 plug head, you could buy a nicer cam with more lift.

dual plug heads to a 81 turbo

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