Pulling g-head

[turbo84voyager]

I have pretty much decided to pull the g-head from my 89 turbo mini. It runs great in cooler weather and upper rpms but the lack of low end torque and having to pull some timing in the hot summer months is not making it much of a screamer with the a/c on around town. I am going to pull a 782 off the shelf and have some porting work done and throw it on swapping the new cam (89 roller) / followers and lifters from the g-head. I am a little disspointed since I spent quite a bit of time on fine tunning a g-head cal for a daily driver but the low end is just not where it should be.

[87ShelbyZ]

Sounds like its not the head, As G heads are know for around 10 percent more torque as it has better breathing chambers... And it should be the other way around better low end lose some top end.. Your in Pa and complaining of the heat?? try living in a desert :lol:

[t3rse]

add more timing

[rbryant]

Does the G head have stock sized combustion chambers? If it does then the lower compression will move the power band up because you will need more boost to make the same power.

At the same time your overall peak power should also be increased as long as you increase the boost because the lower compression will allow for a cooler charge and less detonation.

Almost everyone experiences less low end and more top end power with a G head compared to a swirl head.

-Rich

[turbo84voyager]

The 782 has more bottom end than the g-head.

I'm not complaining about the heat. It was 90 yesterday. The problem we have is our roads are much more hilly which puts more load and more chance of detonation. On perfectly flat roads even in 90 degree days it rarely knocks.

As for adding more timing I have quite a bit of timing, and it runs good, but when its 90 + out it doesn't like all that timing and I get CEL. I have tried tweaking the timing tables for a year now and one runs good one day does not seem to run as good another. On a cool day the van runs great and pulls hard especially over 3 grand. I believe it pulls harder in the upper rpms than the motor with the 782. If it was more of a drag only vehicle I wouldn't even consider changing the head. When I pull timing I get no CEL but I loose power. The problem is I use this as a daily driver which is what makes it more difficult. It needs to start and run good in 0 degree weather but also run good 90+ with A/C.

I have 2 other TD's with 782 heads and both of them have much more low end power even the one with the same hybrid turbo. If the van was a stick or if I had a higher stall converter it wouldn't be that bad. It is not as bad if I drive around town in 2nd. The A/C and hauling people or items in it just make it more noticeable.

[turbovanman²]

You found what I keep preaching, G-heads and Minivan's don't mix. I hated my G-head setup, I just couldn't muster the energy to take it out, then it dropped a valve and my TIII was born. Now, it has top, middle and bottom end, :clap: :partywoot:

[puppet]

Lately a lot of guys are having issues with the bathtub ... what's the deal?

[ShadowFromHell]

I noticed in my shadow vs CSX the csx had much more usable power. The shadow had a G, and the CSX a swirl. I had talked myself out of using the g-head at one point (car has been apart for a while), but plan on trying it again. Ive sunk to much $$ on it since, had it rebuilt, ect.

[turbovanman²]

I'll keep saying this because I can, :p SMP used a swirl head and said the swirl head is better for power.

[turbo84voyager]

I noticed in my shadow vs CSX the csx had much more usable power. The shadow had a G, and the CSX a swirl. I had talked myself out of using the g-head at one point (car has been apart for a while), but plan on trying it again. Ive sunk to much $$ on it since, had it rebuilt, ect.

Useable power is the best way to describe it. It runs great in midrange but dead in lower rpm's which is more important in a heavier minivan.

[My96z]

I love the G head in mine. Moparzrule has taken quite some time with the cal on it for me. Matter of fact, Tyler is doing a +1 G head for me that will be ready when I get back from this shotty place.
Latley the valve keeps falling out on mine if I shut it off hot, and I have to wait till the engine cools down and then rotate it by hand to get it to seat, then pop my roller back on. So I am sure its not sealing well. Then I seen the carnage on Simons van so I parked it. I will swap the fresh Tyler +1 head on it when I get back.

Justin, you have pretty much the same mods as I do and mine has plenty of low end grunt. I regularly shuttle a squad of soldiers around (no back seats) and even pull my bass boat around with it. Never gave me much problems when the cal was pretty good (and I think it could use more tweaking). I expect things to be better accross the board with Tylers head. I am running around 20-ish PSI and I have to feather it to keep it from blowing the tires.

G-head fo' Life!! :D

[Force Fed Mopar]

You try advancing the cam at all? That should bring back some low end.

[contraption22]

Your lack of low end power is consistent with using the G head. But you really should have a higher knock threshold with it as well.

[Juggy]

what are you expecting to spool or make power at? wheres the car doing it currently?

if you have no low end with the G head then keep tweaking the cal, it sounds like you need some more timing advance

i honestly think the problem MOST people are having with their G head cars, is that they dont have a good tune going on, and not getting the full potential of the head.

a 2.5 G head car should have tire smoking low end

[turbo84voyager]

I am using a variation of Moparzrule cal. I just worked out some drive ability issues. If I run the cal with all the timing in it, I can hear what I believe is detonation, but I don't get that much CEL knock, so im not sure what it is. Matt (moparzrule) and I were talking about it at carlisle this weekend. I pulled some timing out of it and it sounded much better. I have been playing with the cal for over a year. It would probably be better with a higher stall converter since it pulls hard 3 grand and up. On the interstate it runs better than my 782 headed 2.5 in my 84 mini.

The whole issue is it is a daily driver with A/C and I have been playing with cals for a year now. I can get a cal that will run great one day but a change in the weather and I get knock so I pull some timing and I loose power. Off the line the A/C is very noticeable while i dont even know its on in my 84 (782). I have a 782 head out getting ported which im sure will flow better than a basically stock G.

[88C/S]

What would water or water/alky injection do for your knock situation.

[Juggy]

r u runnning a CAT sensor??? maybe that can help the change in temperture

[turbovanman²]

What would water or water/alky injection do for your knock situation.

Still really a bandaid, :(



r u runnning a CAT sensor??? maybe that can help the change in temperture

It doesn't really change all that much. I found that out too late otherwise I wouldn't have put it into my TIII. One less wire/sensor/hole to run or make.