287 or 782 head on GLHS?

[tvanlant]

I am going to the head area now in search for more power in my 87 GLHS. What should I go with? I've heard that 287 or G-heads make more horsepower while the 782 swirl heads make more torque. Either head, I will be doing slight porting and a 3-angle valve job to improve power.

Now... the 287 head drops compression by .5, so that would make it 7.6:1 compression. Won't that be WAY too low? Of course I could run more boost, but I'm still running the stock Garret and won't be upgrading the turbo for quite some time.

My goal is to run 12.50s with drag radials. Here is my setup to make it easier to answer my question:

87 GLHS
Forged Venolias & T2 rods
A555/A520 hybrid trans
MP logic Stage II
Small Spearco Front Mount
+20% injectors, AFPR, 255 pump
88 TBI cam, 52mm TB
Ported Exhaust mani, 2.5" dp & straight thru exhaust

I almost bought an 85 287 head, but then I read about the compression drop and I'm scared the car will be a dog without the turbo spooled, and I'm worried I won't gain that much from it due to the stock turbo being run at 20psi as it is with the 782 head.

Any comments appreciated,
Thanks

[GLHSKEN]

It's a 2.2L, Stay swirl head.

[SMPerformance]

It's a 2.2L, Stay swirl head.

+1:thumb:

[GLHS592]

Ken, Stephane, can you explain please?

I'm running a G head and I like it. Running one with turbo II style pistons will lower your compression ratio, therefore, you can run more boost. It does seem to make for hard starting conditions. I had that problem with the stock electronics and the SDS.

[glhs875]

Ken, Stephane, can you explain please?

I'm running a G head and I like it. Running one with turbo II style pistons will lower your compression ratio, therefore, you can run more boost. It does seem to make for hard starting conditions. I had that problem with the stock electronics and the SDS.

Either head can made to run just fine. And by my calculations, a G head with T2 style pistons works out to around 7.9 to 1 compression. and WILL NOT cause a starting problem. That's the compression ratio I had in my Daytona. It ran great in all areas up to 26psi on pump gas with stock 88 electronics.

[GLHS592]

WILL NOT cause a starting problem.

I've messed around with the SDS's starting values and cannot figure it out. Maybe you can help me out one day. :)

[glhs875]

I've messed around with the SDS's starting values and cannot figure it out. Maybe you can help me out one day. :)

If I had to guess it probably needs to be richened up during engine cold condotions. An engine needs alot more fuel when cold to run properly.

[GLHSKEN]

The 2.2 was calibrated for that head. The stock compression is fine for 20-30 psi boost and is not really a factor in running it that high. The 2.2L also likes that bottom end grunt especially combined with the 2 piece intake. I've never had an issue with the higher RPM hp, gaining 23-26mph in the last 1/8. The cars seem to "wake" up at over 16psi with the swirl head.

Staying with a stock turbo and a front mount, You will be limited to about 270-280 whp. With full slicks, a 12.5 is possible, it will be aweful tough with DR's

[GLHS592]

The cars seem to "wake" up at over 16psi with the swirl head.

With the "G" head on my old engine, it woke up too at > 16 psi. I haven't had my new engine over 16 psi yet. ;)

[GLHSKEN]

I was running a swirl head at 8.5:1 compression. Throttle response was great. Went up 5% grades in vacuum... Faulty electronics/ injectors cost me that engine.

[glhs875]

My car woke up as well above 16psi with the G head. My first gear boost limit was 15psi, which was still more than DR's could handle. Then it went to 26psi for the second stage of boost. The car would go ballistic and break the DR's loose at around 40MPH in 2nd gear with the auto trans. when the 26psi would hit. I loved it!!

[SMPerformance]

Ken, Stephane, can you explain please?


In test done on the engine Dyno a swirl head will produce more hp at high boost

On my 8 valve engines I saw 55hp gain between a 445g head and 782 swirl same boost level
Engine was allot less prone to detonation hence you can go with a more aggressive timing

A Swirl head will reduce the combustion pressure variation, due "in theory" to a more consistent gas mix near the plug when firing. This giving a more efficient combustion.

It was also proven that the action of the swirling gasses during ignition helps speed flame propagation thus providing a higher resistance to détonation and a quicker pressure rise at the early stages of the combustion process.

Better controlled combustion means the potential to produce greater torque and the quicker burn promoted by swirl increases the détonation limit.

[GLHS592]

Interesting. Thanks!

[glhs875]

In test done on the engine Dyno a swirl head will produce more hp at high boost

On my 8 valve engines I saw 55hp gain between a 445g head and 782 swirl same boost level
Engine was allot less prone to detonation hence you can go with a more aggressive timing

A Swirl head will reduce the combustion pressure variation, due "in theory" to a more consistent gas mix near the plug when firing. This giving a more efficient combustion.

It was also proven that the action of the swirling gasses during ignition helps speed flame propagation thus providing a higher resistance to détonation and a quicker pressure rise at the early stages of the combustion process.

Better controlled combustion means the potential to produce greater torque and the quicker burn promoted by swirl increases the détonation limit.

Iam not disputing your findings, but then how come I was able to run 6 to 8 more degrees in timing with a G head vs. a Swirl before having detonation problems. Everything was the same, intercooler, octane, compression ratio,car, trans.,etc. From what I have found is that a swirl head, at least on gasoline, needs timing values about the same as a pentroof type head, which is alot less than an open chamber or bathub type head which has slower burn qualities. And we noticed the same thing on another car as well.

[JDAWG]

In test done on the engine Dyno a swirl head will produce more hp at high boost

On my 8 valve engines I saw 55hp gain between a 445g head and 782 swirl same boost level
Engine was allot less prone to detonation hence you can go with a more aggressive timing

A Swirl head will reduce the combustion pressure variation, due "in theory" to a more consistent gas mix near the plug when firing. This giving a more efficient combustion.

It was also proven that the action of the swirling gasses during ignition helps speed flame propagation thus providing a higher resistance to détonation and a quicker pressure rise at the early stages of the combustion process.

Better controlled combustion means the potential to produce greater torque and the quicker burn promoted by swirl increases the détonation limit.
Was this a stock head or ported? Were the valves back cut? Interesting stuff. I thought when the swirl head was ported you lose the "swirl".

[Marcus86GLHS]

87 GLHS
Forged Venolias & T2 rods
A555/A520 hybrid trans
MP logic Stage II
Small Spearco Front Mount
+20% injectors, AFPR, 255 pump
88 TBI cam, 52mm TB
Ported Exhaust mani, 2.5" dp & straight thru exhaust


throw in a MBC, set the boost for 20-22 psi, and with slicks (not DR's) that looks like a 12.5-something car right there provided you can keep your race weight around 2,500.


KEN: so do the glhs cars come stock with 782 swirl heads?

[SMPerformance]

Was this a stock head or ported? Were the valves back cut? Interesting stuff. I thought when the swirl head was ported you lose the "swirl".

both where ported heads

P.S I ran 10.27 @ 136mph with a stock unported stock valve swirl head

I had put on a stocker after burning a valve seat just to finished the race

the same boost with a ported head the car ran 9,30 all day @ 145+mph

[GLHSKEN]

KEN: so do the glhs cars come stock with 782 swirl heads?

Yes, all 86 and up cars do.

[JDAWG]

both where ported heads

P.S I ran 10.27 @ 136mph with a stock unported stock valve swirl head

I had put on a stocker after burning a valve seat just to finished the race

the same boost with a ported head the car ran 9,30 all day @ 145+mph
you are da man!

[tvanlant]

Thanks for all the input. I am currently running 18-20 psi with a MBC, and I plan to keep it that way since I'm using the stock T3. There are really good arguments both ways, but I think I'm going to stay with a swirl head for the bottom end grunt as Ken was explaining.

Next question is.. how much can I expect to gain in terms of horsepower and track numbers by self porting my swirl head and backcutting the vavles, on my particular setup?

[JuXsA]

What SMP says is gospel:D

[glhs875]

What SMP says is gospel:D

While Iam sure Stephane & SMP knows alot of things I don't, I'm having to disagree on the ignition advance statement of a G head vs. Swirl. All I know is if I were to dial in the max amont of timing a G head could tolerate, then make no other changes but to a swirl head, and then give the engine more ignition advance, I'd be blowing pistons out the oilpan.

[GLHSKEN]

I wonder what the case would be with equal compression ratios.

No one's word is gospel, from both these guys we are learning a lot. This is one of the better discussions I've seen recently.

[glhs875]

I wonder what the case would be with equal compression ratios.

No one's word is gospel, from both these guys we are learning a lot. This is one of the better discussions I've seen recently.

Stephane may have different results. On my 87GLHS (stock 86 electronics = 27degrees total timing @ full boost with the 12 degree base included), with the bone stock stock swirl head on 93 octane @ 18 psi with an auto trans. It would ping like crazy after the shift into 3rd gear. I had to retard the timing about 6 degrees from the base of 12 to get it to stop, and if it was real hot outside it would still ping some. Then I put a bone stock G head on, it did fine up to 18psi, but anything over that had some detonation, but wasn't as harsh. That was with the base timing @ 10degrees instead of 6degrees with the swirl. I used 85 T1 pistons with the G head to keep the compression the same as the swirl head had. The same compression ratio leveled the playing field some, but there was still a noticable difference in timing needed and tolerated between the two. Kevin Davis had similar results with his car. And Iam not saying that the swirl head needing less timing is a bad thing. Actually it's a good thing, it means the combustion process is alot more efficient. But detonation can sneek up alot sooner with the swirl if not watched. At least that's what I found.

[87csx2.4]

Yes I definately needed to run a more aggressive timing curve with the g-head than the swirl.I was able to run more boost on pump gas with the g-head probably because of the lower compression.I was under the impression that the swirl head didnt need the timing because of its fast burn characteristics and being more efficient.I know that trying to run the swirl head on my setup with the g-head total timing at say 18 psi would always knock like crazy when the car stalled into peak torque.I have noticed with this new pent style roof head on the 2.4 it needs even less ignition advance than the swirl did,quite a bit less it really suprised me.Everyone's setup is different when you are doing what I am doing,trying to make a 3200# car go fast is a whole different ball of wax than say an omni.:D

[boost geek]

I find that on my 87 s.c., the swirl head pings quite a bit at only 6 psi, t1. I ran my 86 s.c. with a 287 G head up to 17 psi, with stock daytona intercooler, GLHS stage 2 logic modual, T2 injectors, and no extra fuel without detonation issues. I'm gonna try the G head on my 87 soon, hopefully by spring.

[SMPerformance]

While Iam sure Stephane & SMP knows alot of things I don't, I'm having to disagree on the ignition advance statement of a G head vs. Swirl. All I know is if I were to dial in the max amont of timing a G head could tolerate, then make no other changes but to a swirl head, and then give the engine more ignition advance, I'd be blowing pistons out the oilpan.

next time i'll try to explain better lol :D I always forget most of you are running stock electronics

first you never run the same base timing between a g head and swirl head

when I say agressive timing,was the way we pull back timing degree vs lbs of boost

when I did the test i just didnt replace the heads and did a dyno pulls
I was pulling timing .70 degree of timing per lbs of boost with the g head with the correct A/F ratio

when we switch to a swirl I needed to corrected the fuel map and I was pulling timing .50 degree of timing per lbs of boost less pull on timing = more agressive timing per psi boost

and also dont forget the compression ratio will play games on you

26 psi x .70 =18.2 degree retard G-head

26 psi x.50 = 13 degree retard swirl

P.S I didnt say the swirl needed more timing i said you can run more agressive timing

[GLHSKEN]

I find that on my 87 s.c., the swirl head pings quite a bit at only 6 psi, t1. I ran my 86 s.c. with a 287 G head up to 17 psi, with stock daytona intercooler, GLHS stage 2 logic modual, T2 injectors, and no extra fuel without detonation issues. I'm gonna try the G head on my 87 soon, hopefully by spring.

If you are pingint on 6psi boost, you need to address the root problem.

[glhs875]

next time i'll try to explain better lol :D I always forget most of you are running stock electronics

first you never run the same base timing between a g head and swirl head

when I say agressive timing,was the way we pull back timing degree vs lbs of boost

when I did the test i just didnt replace the heads and did a dyno pulls
I was pulling timing .70 degree of timing per lbs of boost with the g head with the correct A/F ratio

when we switch to a swirl I needed to corrected the fuel map and I was pulling timing .50 degree of timing per lbs of boost less pull on timing = more agressive timing per psi boost

and also dont forget the compression ratio will play games on you

26 psi x .70 =18.2 degree retard G-head

26 psi x.50 = 13 degree retard swirl

P.S I didnt say the swirl needed more timing i said you can run more agressive timing

Thanks, for explaining that better. So you started from a lower base timing setting with the swirl head. I have found that a G head really likes to have some ignition advance put back in after the peak torque range. With the timing being retarded for boost, that is one area where a swirl or fastburn head has it on a non fastburn head. On a non fastburn head the piston tends to outrun the flametravel more in the upper rpm's. If you didn't do that when you dynoed the G, then that could of made back some HP in the upper RPM's.

[87csx2.4]

next time i'll try to explain better lol :D I always forget most of you are running stock electronics

first you never run the same base timing between a g head and swirl head

when I say agressive timing,was the way we pull back timing degree vs lbs of boost

when I did the test i just didnt replace the heads and did a dyno pulls
I was pulling timing .70 degree of timing per lbs of boost with the g head with the correct A/F ratio

when we switch to a swirl I needed to corrected the fuel map and I was pulling timing .50 degree of timing per lbs of boost less pull on timing = more agressive timing per psi boost

and also dont forget the compression ratio will play games on you

26 psi x .70 =18.2 degree retard G-head

26 psi x.50 = 13 degree retard swirl

P.S I didnt say the swirl needed more timing i said you can run more agressive timingGotcha some good info.:thumb:

[GLHS377]

all things else equal, a more effecient combustion chamber will need less ignition advance to get the combustion event to actually start combustion pushing the piston down the bore. too much and you get detonation or at least lost power from fighting the piston before TDC. idealy, the combustion event starts to impart peak pressure 5-10 degrees after TDC. the faster you can complete the combustion event, the less power you loose in the form of declining returns in delta cylinder pressure/cylinder volume. however, the more mean pressure you can exert over more crank degrees is what generates torque, and thence horsepower. starting the ignition event with your A/F and combustion chamber qualites is what ignition timing is determined by. if you can avoid abnormally high peak pressures(and remember that more pressure =more temperature here) but still generate a higher mean pressure, then your engine will make more torque more effeciently over a lower rpm range. creating a quick, high pressure combustion produces an rpm happy engine that is more sensitive to combustion temperature and boost.

now, it's not like we have that much of a choice in the matter, but from what little empirical data we have, it apears that the G head, (as i have expected, with it's significant quench) gets away with less total ignition advance, indicating a more efficient ignition event when under boost. this is exagerated, as IIRC, the G head cars had 4 degrees more advance in the calibrations. to see the actual dynographs with datalogs, we'd be able to at least glimpse into the engine. even though ignition timing is only a portion of the equation, it'd help.

though i run a G head, i have a complete control over engine parameters, and i personally don't think it matters a whole lot on the 8v in a streetcar, as there are bigger fish to fry. most compromises TD owners make, they do it in the name of $$$ anyway, and the swirl head spark curve is more supported in the pretuned calibrations, and it's probably what you already have, so i'd stick with that. the cash you save in tuning will let you buy a properly sized turbo.
but whatever you end up doing, good luck!
-jason

[tvanlant]

Very informative. Lots of information in this post. So.. with my setup, can I expect to gain much from porting a 782 head and backcutting the valves? I'm running 18-20 psi on stock T3.

[tvanlant]

Another thing, I have come across a thread about using a .63 housing on the stock T3 to help it flow a little better. While I have the head off, would this be a worth-while addition? What is involved in swapping the two exhaust housings?

[GLHS377]

since there are no real porting templates for the 8v, i'd stick with ported manifolds. there's some flow to be gained from porting the head, but you should really have someone who can ga-run-tee results do it. you may want to call up chris at turbosunleashed and get a super70 turbo, tho i havent' seen the compressor map for it. you're basically looking for ~320 hp. and your stock tIII compressor doesn't have the mass flow for that. to your injectors won't support that, and once they do, you're going to need some gear variable boost control or traction control. the MP stage II LM has a 2bar map sensor and tables, so you may want to look into a 3bar cal so you don't blow it all up and have to start over. good luck!
-jason

[tvanlant]

I'm not a professional at porting, but I do have my own flow bench, and since 782 heads are everywhere, I figure I'll play around with a couple heads until I can find some horsepower. 320 may be a bit more than I'm looking to get. maybe 280-300. 12.5 et may be a little too much to ask for. Maybe 12.8 on DRs. I'd like a 3 bar and a cal, but I don't have the money.

So.. what do you guys think about adding the .63 housing to my stock turbo while I have the head & turbo off?

[BadAssPerformance]

both where ported heads

Just curious what the I/E CFM were on both of these?

[turbovanman²]

This is an awesome thread, goes up there with the intercooler pipe size thread, :thumb:

[GLHSKEN]

So.. what do you guys think about adding the .63 housing to my stock turbo while I have the head & turbo off?

Honestly, with a stock turbo, I have no clue if it would help/...

[Russ Jerome]

I had a midyear failure in my daily driver 8v Omni, few thing's
I noted when swapping my mildly ported G to bone stock
swirl.

2300# S-60, 2.5 G-head consistant 12.9's.
at 23/24psi boost.

Same turbo,shortblock, cooler ect ran 12.7's
all night at 19psi boost.

That was with pretty new street tires cutting
same 1.9-2.0 short times, kinda ruled out track
condition as I had run at same track LOTs of
times with both setup. Dont recal timing, I usualy
try and bump it up higher every run until knock
light flicker's (Maxxon dual twister in car adjust).

[johnl]

In test done on the engine Dyno a swirl head will produce more hp at high boost

On my 8 valve engines I saw 55hp gain between a 445g head and 782 swirl same boost level
Engine was allot less prone to detonation hence you can go with a more aggressive timing

A Swirl head will reduce the combustion pressure variation, due "in theory" to a more consistent gas mix near the plug when firing. This giving a more efficient combustion.

It was also proven that the action of the swirling gasses during ignition helps speed flame propagation thus providing a higher resistance to détonation and a quicker pressure rise at the early stages of the combustion process.

Better controlled combustion means the potential to produce greater torque and the quicker burn promoted by swirl increases the détonation limit.

Stephane - were these comparisons done with the same pistons? That is, were the piston dish volumes/static compression ratios the same - g vs fast burn?