HEAD vs HEAD 2.2 turbo = stock vs Ed Peters

[Dr. Johny Dodge]

in my "limited' builds of the past I never got much more than a MP/DC lm or smec a 314 cam and a little help with things here and there

I had 6 85 G head motors in as many years and Idono , 4 or 5 later motors with the FB head

never got clean plugs out of a FB head yet - always very black and ugly

my G head motors always gave me nice clean very lightly tan coloured plugs (almost dusty looking)- includeing the one rebuilt 85 motor with the 86 style dish (which drove with no notable difference)

(I was doing this way back before A/F widebands .. or web sites lol)

I did have one FB head that ran reasonably clean .. for about three weeks
it was the 86 LW rod motor with a large can TII conversion that didn't work so well as the wastegate would not open (non rebuilt used motor)
that ran on overboost shutdown until it broke - that head ended up still clean, with pink and white valves but no notable piston top damage - something died deeper inside it

of my 3 or 4 LW rod motors that was the only one that failed - all my 85's spun the rod bearings in 6 months
and my one & only roller cam motor failed in the valve train it seems

10 years after it died , a "new cryco parts counter 2.5" / TII conversion in an 87 shelby z I bought , I pulled the head to find a chunk of piston top from below the exhaust valve , stuck in the valve , a roller follower sitting between the springs and a lifter that would not compress ten years after it had last run - all the other lifters would compress but that one wouldn't budge even when smacked with my framing hammer on the bench vice
- that ran for the two years I had it and the time the guy I bought it from had it with the stock TII tuning
that head did not run cleanly either

I have to say I do find posts saying don't even start a 2.5 with a 2.2 LM funny as hell though

I've read that tuning a 2.5 with a G head can be an issue - I'd think maybe it has to do with the very large piston dish vs the G head chamber and the much smaller dish of the 84/5 motors

that large dish , small rim edge also makes me think the 2.5 piston might be weaker above the top ring too

but back to the heads..

I have a couple of questions with regard to the G head
I've read the port roof as it enters the valve bowel is ever so slightly higher in a 655 head - true ?
- measureable ?
I have a 655 head and this "ported" G head I just got so I don't have o-e ports to compare

and , at the manifold surface , exactly what is inside the head just above the intake bolts and the top row of exhaust studs ?

meaning what would I be drilling into if I were to raise the intake bolts by the difference in port height of the regular port vs the 655 port

I was planing to mod the intake for a 655 head so adding weld behind the valve cover rail wouldn't be a streach , thus putting the 655 modded intake on the small port G head with the height differance now being at the top .. and bolt bungs on the intake that still haven't been tampered with so they might not break off

and again for the top row of exhaust studs ? - with the intent to take the downward hook at the opening of the exhaust port , plus some away

I will not be useing the stock exhaust manifold that imediately turns the exhaust flow downward so I don't need the head to be the early start to that change in flow direction

I look at the exhaust ports and see the same change in direction my 460 ford exhaust ports had
- the floors of the 460 port are ramped down so much the bottom of the port looks more like a suggestion of a port

the fix is a Trick Flow head - they raise the stock 460 ex port 3/8 inch

I guess I ask from the viewpoint of a couple of gone over the hill big block . raised port dodge / ford projects and little chance of scoring one of those isma heads lol

I do however already have everything to build an isma valve /pt/beehive/S60 cam, G head

and as I think of it , can I fix the cam center - due to a lack of caps on both the heads I got last week by machining it to take bearing shells ?

if so I have a pair of semi ported heads .. if not , a nice thump in the scrap bin ..

[Force Fed Mopar]

in my "limited' builds of the past I never got much more than a MP/DC lm or smec a 314 cam and a little help with things here and there

I had 6 85 G head motors in as many years and Idono , 4 or 5 later motors with the FB head

never got clean plugs out of a FB head yet - always very black and ugly

See, I've never gotten a dirty plug out of a swirl head, unless it was oil fouling from a guide/seal issue. But, every one I've had has been run on either a factory swirl cal, or based on a factory swirl cal.

[thedon809]

Somewhat related. I was told it was better to run a swirl head with this style piston, is that true? I plan on cleaning up the ports and deshrouding the valves a little bit.

[GLHS60]

That looks like a swirl piston.

Many high boost types run a G head on that style to lower the compression ratio.

Thanks
Randy

[thedon809]

That looks like a swirl piston.

Many high boost types run a G head on that style to lower the compression ratio.

Thanks
Randy

Since all my heads are borderline junk I was trying to figure out which would be best. Overall goal is 350whp with an hy35 or he341.

[GLHS60]

Weight of the car and its use has some bearing on which head in my opinion.

G head looses a bit of "off idle" response so you would be softer off the line.

EG: Very noticeable with an automatic minivan, slightly noticeable with an Omni.

However, the loss in compression ratio is more than compensated for with the fact you can run more boost, all else equal.

For me a G head is the only choice as its less detonation prone than a swirl, all else equal.

If I remember correctly, Shadow, Reeves and Warren all run G heads.

Whats your setup??

Thanks
Randy

[glhs875]

Weight of the car and its use has some bearing on which head in my opinion.

G head looses a bit of "off idle" response so you would be softer off the line.

EG: Very noticeable with an automatic minivan, slightly noticeable with an Omni.

However, the loss in compression ratio is more than compensated for with the fact you can run more boost, all else equal.

For me a G head is the only choice as its less detonation prone than a swirl, all else equal.

If I remember correctly, Shadow, Reeves and Warren all run G heads.

Whats your setup??

Thanks
Randy

This photo is of a late model 5.7 Hemi combustion chamber. Looks similar to a G-head combustion chamber to me! I ran a G-head in my Glhs Charger with an auto. I consider my build as being street/strip, as I would drive it to the drag strip to make runs. My combo could easily pull 1.9's on street radials for the 60' launching under part throttle 3000 RPM to 3500 RPM and with no boost built up, although I could easily build up to at least 15 psi for a launch if I wanted. When the light turned green I would let off the brake pedal and roll into the throttle. My point is if a G-head combo is set up properly, low end response loss if any over a Swirl head is not missed in my opinion.

[thedon809]

Weight of the car and its use has some bearing on which head in my opinion.

G head looses a bit of "off idle" response so you would be softer off the line.

EG: Very noticeable with an automatic minivan, slightly noticeable with an Omni.

However, the loss in compression ratio is more than compensated for with the fact you can run more boost, all else equal.

For me a G head is the only choice as its less detonation prone than a swirl, all else equal.

If I remember correctly, Shadow, Reeves and Warren all run G heads.

Whats your setup??

Thanks
Randy

5 speed omni converted to smec. Phase one is with stock turbo until I learn how to tune and get bugs ironed out. It's a 2.2 with 2 piece, +40, 3bar, boostbutton cal, fmic, shadow 3" swing valve to 3" side exit. I initially had a g head on it and it seemed to run fine. Until the guides like to sink down and I had oil pressure problems.

[Shadow]

Phase one is with stock turbo until I learn how to tune and get bugs ironed out.

Brilliant!

IF I could give any advise, This is what I've been trying to pass on from the beginning.............That you have to learn to Walk Before you Fly!

I hate to say it, but I have not seen One 2.2/2.5 TD come into the shop that was either build by owner or built somewhere else that didn't have issues

Most of the issues; mistakes made while putting it back together from lack of experience Or lack of attention to detail.(or Brutal machine shop work)

Everyone wants to Feel the Boost Sooner rather than later, and this desire leads to more failures than anything. Need to get ducks in a row First, on low boost while monitoring everything before taking the next step.

Unfortunately, very few have the patience for this. So instead they just keep building over and over again, usually making the same mistakes until they give up, giving these mtrs a Bad reputation.

Nice to see that there Are some individuals out there who are Getting it!

[Shadow]

On the G vs FB head debate;

On mild builds (up to 350WHP) we will use either head depending on future goals, but with a little work to combustion chamber and some "clean up" to the ports, the FB works fine at these levels and isn't too much more work than G-head.

It's when you start to look at making 400+WHP that the time/ expense of Properly doing a FB head really makes the choice for you. I have always stuck to just the +1mm valves because the amount of work is at least 50% Less than going Big valve, (again....Properly) and IF it's not done Properly, the +1mm head will out perform the big valve head

Every major build we have done, 2.2 or 2.5 (doesn't matter) has been G-head. It's just Way closer to the goal from the beginning. Swirl is just way more work, and what are you really doing with the swirl? Trying to make it work like a modded G-head.............

I have never seen a significant difference one head vs the other on different weight vehicles, but I do make mtr decisions based on vehicle weight. (2.2 vs 2.5)

On a heavier vehicle, and street driven, I choose the 2.5, but with the understanding, that when it's done, it will act more like a Torky 2.2

[Vigo]

Everyone wants to Feel the Boost Sooner rather than later, and this desire leads to more failures than anything. Need to get ducks in a row First, on low boost while monitoring everything before taking the next step.

I think the age that these cars are at is making the legwork harder and harder before you can get to the fun part. I think i put 10-20 hours of diag/labor into my fuel system on my minivan before i was able to have fun with the boost.

On a heavier vehicle, and street driven, I choose the 2.5, but with the understanding, that when it's done, it will act more like a Torky 2.2

I think 5spd vs auto makes a big difference as well. I.e. on my minivan i have a 2.5 with the cam retarded 6 degrees which is analogous to a 'torquey 2.2' but if the van were auto that low end torque would be sorely missed!

[thedon809]

Think I will go with a swirl and just deshroud the valves a little and smooth the combustion chamber out along with the ports. Nothing too crazy. Have a junk head to practice on. I would like to see what I can accomplish with a stock turbo first once i learn to tune.

[Vigo]

Mid-12s @ ~110 or thereabouts. Plenty fast, the variable being for how long, i suppose.

As i understand it the fastest car with a stock fast burn cylinder head was Lugert's stripped out shadow which went ~11.5. Pat recently said in one of his threads that his shadow ran 12.1s with a completely stock FB top end. So the potential to go fast with near-stock cylinder heads is definitely there. I would hate to think that anyone is discouraged from shooting for quick times over lack of head modifying skills/resources.

[MILKCARTON]

My gutted Shadow went 11.68 @115 with the 2.5 with untouched FB head(88 tbi cam), then it went 11.32 @118 with the same head on an 2.2

[83scamp]

On the G vs FB head debate;

On mild builds (up to 350WHP) we will use either head depending on future goals, but with a little work to combustion chamber and some "clean up" to the ports, the FB works fine at these levels and isn't too much more work than G-head.

It's when you start to look at making 400+WHP that the time/ expense of Properly doing a FB head really makes the choice for you. I have always stuck to just the +1mm valves because the amount of work is at least 50% Less than going Big valve, (again....Properly) and IF it's not done Properly, the +1mm head will out perform the big valve head

Every major build we have done, 2.2 or 2.5 (doesn't matter) has been G-head. It's just Way closer to the goal from the beginning. Swirl is just way more work, and what are you really doing with the swirl? Trying to make it work like a modded G-head.............

I have never seen a significant difference one head vs the other on different weight vehicles, but I do make mtr decisions based on vehicle weight. (2.2 vs 2.5)

On a heavier vehicle, and street driven, I choose the 2.5, but with the understanding, that when it's done, it will act more like a Torky 2.2

Rob, this has got me very curious. I've had several folks suggest that I put turbo exhaust valves in my ported G head that is currently on the N/A 2.2 in my Scamp, and run that on the 2.5 turbo motor I'm building this winter. From what you are saying, it sound like a good idea. I'm not going for extreme hp here, my goal is about 300 hp. Now, one issue I am concerned about, I had the head cut .015" originally to get the compression up for the N/A motor. Do you see any issue with that in a turbo application? I do have a stock FB head sitting here as well. I just bought +1mm valves for it, and was planning on sending it to the machine shop after the first of the year. But I could be persuaded to change direction... Where is a good source for +1mm valves for a G head? My current head has stock valves that have been back cut.

I'm thinking along the same lines as you are. I'm building the motor for 20 psi, but plan to start at stock levels and tune from there. This is going to be a street cruiser/weekend fun machine, not a drag racer. I just want to be able to really screw with the mustang/camaro guys and ricer wanna-bees...

I'd love to hear your thoughts on a propper setup for what I'm planning.

[glhs875]

My gutted Shadow went 11.68 @115 with the 2.5 with untouched FB head(88 tbi cam), then it went 11.32 @118 with the same head on an 2.2

That's impressive! Any spray involved with those times!

[MILKCARTON]

That's impressive! Any spray involved with those times!

Yes, 80 shot, and it weighs 2330 with me in it, there are too many variables for a stock head record statement IMO...


I would really like to have a nice head, and would pay good $ for one, FB or G

[Vigo]

there are too many variables for a stock head record statement IMO...

Well nitrous is definitely a big variable...

I just wanted to get it out there that the choice of heads is not so much a limit as a tuning preference, at least up until high power like ~400hp as Shadow suggested where i could see the proper tuning window being so narrow that you would always take the head that was easier to make live, given that they have similar flow potential anyway.

[MILKCARTON]

Well nitrous is definitely a big variable...

I just wanted to get it out there that the choice of heads is not so much a limit as a tuning preference, at least up until high power like ~400hp as Shadow suggested where i could see the proper tuning window being so narrow that you would always take the head that was easier to make live, given that they have similar flow potential anyway.

I agree totally, hopefully now I will actually be able to tune once the van is together ,the shadow never was.....

[Pat]

Mid-12s @ ~110 or thereabouts. Plenty fast, the variable being for how long, i suppose.

As i understand it the fastest car with a stock fast burn cylinder head was Lugert's stripped out shadow which went ~11.5. Pat recently said in one of his threads that his shadow ran 12.1s with a completely stock FB top end. So the potential to go fast with near-stock cylinder heads is definitely there. I would hate to think that anyone is discouraged from shooting for quick times over lack of head modifying skills/resources.

11.75. :-)