Semi Hemi heads

[cdupuy]

[cdupuy]

[mark tucker]

not nessasarly.and what does that have to do with this issue? but the pic of those heads shows little would be required to fix them. my 4 wheeler was a hemi....it isant any more.but it sure is peppy!!!

[gears]

Why am I not seeing photos of anything?
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9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
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[R-Baja]

How about semi hemi heads for an all stock engine except for a 74mm crank?

Stock heads have about a 1.5mm step and 1.5mm deck (top of cylinder to top of piston) That is 3mm or .118". I don't see much squish there.

[modok]

Why lower the compression??? you in mexico??

Cut the step out

[Multi69s]

I personally do not see what all the bad hype about the semi-hemi heads is all about. I really think that most of the talk is from people that have never used them. Yes, some more modern heads may have a more efficient combustion chamber design, but I definitely would not swap out the heads if they performed well for you in the past. In my DD I have a 2110 that has the SH heads. It started life in a sand rail, then was put in a Baja and went to the tip of the Baja Peninsula, then I sort of inherited it when the owner passed away. All of this time it has never given a lick of trouble, and it was actually assembled when GB was still alive, so it has quite a few miles on it. I will be doing a full rebuild on the motor at tax time, but unless there is a major crack in the heads, I will be keeping them.
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[GTV]

The simple fact that you need to give the engine 8-10 degrees more timing to run well means that it's an inefficient chamber design.
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EMPI Power Rules!

[Multi69s]

This is where I disagree and believe that most of the hype is hearsay. My engine is running a German 009, timed at 32 degrees max. Of course some time was used to get it jetted properly (Dual Italian 44s). However, this motor runs like it is fuel injected. It makes good power everywhere in the band, doesn't over heat and gets about 28MPG on the freeway. At least it did before the rings started to go.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[jfats808]

I have semi hemi Tims stg 2 heads set aside for my future turbo FI kit. Originally, I was planning on going with a 2110, but I wasn't able to attain the DH range I was aiming for. Furthermore, I decided on going to make it a 2276. I spoke in depth with Steve on possibilities and even with 94 bore in person this past june and over the phone last couple months. I was unable to get the range of head ccs I wanted for target CR. So, he talked me into doing Semi hemi cut. He went on saying that a couple shops asked him what they could do to stop putting holes in pistons and semi hemi was his answer. This is coming from a skilled head guy and I believe him. Case closed for me.

Here are my heads for a decent close up. 62 ccs and I will be able to run a .050-.055 dh, a 9.1 static and 6.8 dcr with the custom cam I had cut. Im waiting for the Gen4 CB new EFI kit to come out and get the bugs wrung out. He said also that he would only consider doing semi hemi on a turbo. Lastly, when I asked him what idle timing I should start at he said: normal timing, just lock out your max advance at 24. Ill figure out the details when it comes time...

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2276 IDA's 86C 11-1 DD !
2017 48 Trijet DRLA's W125

[Alstrup]

There is no doubt that an engine with SH heads will run. BUT, you cannot make good power and clean emissions with these heads. Its a practical impossibillity. It has been both tested and explained over and over again, and yet they still surface every once in a while. If you want to yank some power out with them, it is nessessary to advance the ignition further, like 4-6 degrees dependant on how much hemi. That alone will aid tremendeously in elevated pumping losses, which again leads to more heat at WOT.

If there is a problem getting enough volume for the CR it is MUCH better to dish the pistons. Then you keep the burn centered, and efficient.

A handfull of people around the Globe that has been fudging with SH for a long time, claims that they have found a shape which is still SH style, but not as Berg Senior advokated, that does not need extra ignition advance to be efficient. I have seen photo´s of them, but never tested a set, so I can´t really say if it is true.

Still, I would dish the pistons any day.

T

[Quokka42]

I have run SH heads and the design certainly does resist detonation. In those days only distributors were available so, although Gene's theory on spark advance was sound, it was better to flycut the heads to obtain even less volume than you would otherwise run to run them optimally. I still think they are a better option for turbo than running ridiculous amounts of deck.
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There has only ever been one man who was perfect, and they nailed Him to a cross.

[madmike]

Doing a similar turbo build as Jon, but a draw threw
I just picked some SH heads 044 ,40x35.5 a cpl.months ago so winter build is the plan
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76 Drag/Street bug 2180cc 'Turbo' 11:85 @113 mph"If I go any faster I'll burn up the Hamster" ,gets 28 mpg. also 10/09/22 11.90 @115 mph
"If I'm ever on Life Support,UNPLUG Me, Then Plug me back In see if that Works"

[Dan Ruddock]

Talked to Joel Mohr about this and as a fan of SH, he said you can run about .5 to almost a full point higher cr than a squish setup. It's all about getting the fuel to burn fast enough without ping and more cr will do that. He said Berg had the right idea but just not enough cr.

The A.C. 911 engine was a open chamber hemi.

For me my past experiences with sh have been Ho Hum but I am going to try again with more cr and see how I like it.

Dan

[modok]

Why do both sides?? Only because it's easier (lazy) yes lazy!! that is the only reason for any hemi head, because it's faster than doing things the better way.

Just take the quench ouf of the plug side.

[rs58rag]

[GTV]

If the hemi head was such a damn good idea Chrysler would still use it with the new hemi. It isn't a true hemi (just marketing!). It also uses twin plugs.
Scroll about half way down:
http://en.wikipedia.org/wiki/Chrysler_Hemi_engine

Twin plug a VW semi hemi, maybe you'll see some favorable results.
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EMPI Power Rules!

[modok]

[rs58rag]

jfats.......I had Tims set up mofoco heads with 40x37 94 bore no step w/ s.h. chambers for 1914 turbo but I didn't remove as much from non-plug side, 59cc (where I wanted it) for 8:1 comp. Ran great and 24* max timing. Next bigger engine will have higher comp. ratio and a lil boost.

[jfats808]

Well you know in samba fashion there are some of us whose doubtful of it. Tbh, I was too....at first. Remember Steve is a HEAD guy. He is adamant of the semi hemi set up. I told him everything about my combo and my intentions. People think I didnt think about dishing.... come on. If course I did. I thought about every angle. I dont care what people think. I never did. Thats the greatest joy of it. Everyone will have their opinions, even i have mine. If it doesnt work for me, ill buy new heads. Simple as that. With my custom vam, im going to pull 9.1 cr with a 6.8 dcr. Im also going to do water intercooling. I just scored je's too from Darren. Im pretty stoked. Lazy? Pfft.
_________________
2276 IDA's 86C 11-1 DD !
2017 48 Trijet DRLA's W125