Street porting a 1.9 big valve head

[Paul]

Also, here's a picture of my 1.9 head with 1.72 Intakes. If you look close you can see the deshrouding...

[Paul]

Oh yea one more head modification trick...., don't forget the "Ancient Chinese Secret" ... aka the RallyBob dimples

[CDN OpelNut]

Originally Posted by RallyBob Well, it looks like this will be ending sooner than expected! My deadline date has moved up a few weeks, and my backlog of work is substantial enough that I won't be able to take on any more intake porting or head porting jobs. I need to finish what I've got and then pack up my equipment once more. Thanks again. Bob

Well, with Bob not doing this anymore, I had to find a way to at least provide his instructions to someone else, or getting a guide together so I can do it.

I took the liberty of reproducing the info Bob has provided here into a larger format with large pictures into a pdf document and I've uploaded it here.

A warning - it's 25 pages and full of big pictures.

If Bob objects to my use and posting of his info, this post can be pulled.

[RallyBob]

Originally Posted by CDN OpelNut Well, with Bob not doing this anymore, I had to find a way to at least provide his instructions to someone else, or getting a guide together so I can do it. I took the liberty of reproducing the info Bob has provided here into a larger format with large pictures into a pdf document and I've uploaded it here. A warning - it's 25 pages and full of big pictures. If Bob objects to my use and posting of his info, this post can be pulled.

Nicely done. I certainly don't have any objections to this, in fact, I was initially hoping to have Gary 'lock' this thread after the 9th posting, but it quickly escalated into a Q & A session which kinda diluted my original intents of just having a brief 'how-to' posting. It is certainly easier for a newbie to read your format rather than having to scroll through 150 posts!

Bob

[Gary]

Originally Posted by RallyBob Nicely done. I certainly don't have any objections to this, in fact, I was initially hoping to have Gary 'lock' this thread after the 9th posting, but it quickly escalated into a Q & A session which kinda diluted my original intents of just having a brief 'how-to' posting. It is certainly easier for a newbie to read your format rather than having to scroll through 150 posts! Bob

Ya mean like this: http://www.opelgt.com/forums/opel-en...lications.html

[Paul]

Bob,

In a discussion on the Opel Tuners board, you have explained the port floor shape (or something do with the port floor) is the cause of turbulence which disrupts flow at higher valve lifts (.450 for1.85 valves). Is there anything in the pictures in the beginning of the thread that shows the work you do to eliminate this problem? Or does this phenomena even come into play at the "Street porting" level.

If this issue wasn't addressed, are there any pictures or explanations you can give?

Thanks

[RallyBob]

Originally Posted by Paul In a discussion on the Opel Tuners board, you have explained the port floor shape (or something do with the port floor) is the cause of turbulence which disrupts flow at higher valve lifts (.450 for1.85 valves). Is there anything in the pictures in the beginning of the thread that shows the work you do to eliminate this problem? Or does this phenomena even come into play at the "Street porting" level. If this issue wasn't addressed, are there any pictures or explanations you can give?

I didn't get into it because it generally is the realm of the higher-level prep heads. And the fact that you have to either get it just right, or it's going to be wrong....similar to the 'dimple' theory, random dimples won't help much (or at all) unless you know exactly where to place them. Only the flowbench will show this.

Most street cams have lower valve lift, so the turbulence is not much of a concern. Even a .475" cam has only ~.450" valve lift or so after valve lash. My racing heads keep flowing right up to about .625" lift however, and most of my pure racing cams are using .550" to .570" valve lift since they definitely make more power and more mid-range torque.

For a higher performance street engine or a racing engine, the intake port design is the key to unlocking more power from the engine. And while the floor of the ports need special work to get rid of the turbulence, the roof of the port must be modified in conjunction with the floor or it doesn't work at all. The 'fin' locations are crucial...not for airflow numbers but for airflow direction. I can make heads that flow higher numbers, but they actually produce lower hp than a head that's ported correctly.

That said, I prefer to not show pictures, since too little information is often a bad thing. If a head is incorrectly ported then you're worse off than if you didn't port it at all. So, the reason I only showed the 'mild' level of head prep is because it is pretty fool-proof and hard to mess up. If you're off by say, a 1/16" in any dimension, it really doesn't matter and won't affect power or VE. But if the higher-level heads are ported not-quite-right...they're simply wrong and the head is essentially junk.

So I tend to not disclose that specific info so as to not lead anyone down that path, and I don't have any photos of these heads posted as a result. If an Opel owner ports their head based on my photos and messes it up, then suddenly I'm the a**hole because my head porting designs suck! Even though it wasn't me who did the work...and they were merely guessing and trying to emulate my work from a photo. There are a few internet photos of some of my 'trick' heads that have been posted, but fortunately for me the details are not that well exposed. And information such as 'how much material to remove from where' are not disclosed either.

As you know, I'm pretty darn open here about my experiences with Opels, and I post a lot of tech stuff and share photos of things that work well to make power based on my 22 years of tinkering with them. The headwork is just very difficult at that level to copy, plus I invested a lot of money (I bought a flowbench), and time (about 3 years) to get to the 'breakthrough' that allowed the heads to work well for power production. To ask someone to replicate it accurately without a flowbench or the experience of porting hundreds of Opel heads is asking a lot. So I just posted the techniques to prepare a safe alternative for a street head, since that's what 98% of us are building here. That's not to say the racing heads don't work on the street, they actually work very well. But they're tough to reproduce for most people.

Bob

[oppositelock]

I can appreciate Bob's point of view and warnings on this. He's put in the time and figured this all out and knows what works. It's not simply a matter of grinding as much metal away as possible, that I found out the hard way. Years ago I spent many hundreds of dollars to have a big valve, big port head built. I didn't know who Bob was back then or any other experienced Opel tuners for that matter so I had to rely on the usual V8 machine shop guys. The guy who ported my head (who came recommended by a friend both Bob and I know) went hog wild. They certainly were big ports, you could stick your head in there. And they couldn't use something easy like Chevy valves, they were Toyota Landcruiser or something like that because my friend was always thinking up weird stuff like that. So I bolt the head on the car with anticipation of the impending rocketship it's about to become. I fire it up and the tailpipe starts spewing out white smoke. The guy had gone through a water jacket. Oh great, I just spent $1000 on a doorstop. I take it back to the guy and he says we can just JB Weld it. Um yeah, I don't think so. I took it to another friend, a V8 machine shop guy, and he says he can fix it. He sends it out to have it cast iron welded. Apparently they cook it in an oven and weld it with some special rod. Unfortunately things moved around when they heated it up and the number 1 cam journal went out of line with the other journals. You can't put a cam back into it. Now it's REALLY a doorstop. Even if it did work it probably wouldn't flow worth a crap anyway.

That was a long time ago. Live and learn. So yeah, the moral is don't be too ambitious if you don't know what you're doing. And just because someone charges a lot doesn't mean they know what they're doing.

We're very lucky Bob is sharing his knowledge with us. Especially since he's not doing outside work anymore. Information is money these days and he's giving it to us for free. It's not like there are that many people (in this country, anyway) that have that much knowledge and experience tuning Opels.

[Gordy]

Question??
My 1.9 L head is at the machine shop and is having 1.85 sbc intakes and 1.5 sbc exhaust valves installed. The shop is a little worried that if they cut the exhaust seats the extra needed to install the hardened seats that they may be getting awfully close to some water jackets. Should I forget the hardened seats and play it safe or is there enough meat on the head to cut out the extra to allow for hardened seats to be installed with this valve combination? Thanks, Gordy

[GTJIM]

The exhaust valve seats used for Opel heads are 'thin' ones that go into shallower machined recesses.
One of your main problems is going to be the too big 1.85" intake valve touching the outer edge of the exhaust seat ....
Is this a "street" motor or a "racing" motor? If the former you must have the exhaust seats and will be better off with 1.75" intakes to get everything to fit and last the necessary miles. A race motor does far less miles than a street motor and is torn down more regularly to check valve seating etc. so you can go a bit closer to the "edge".
Bigger ain't necessarily better on the street!

[RallyBob]

I found some info last night that I thought might be informative. It was my original flow chart from my first series of Opel CIH flow tests when I bought my flowbench. Dated October 20th, 1991! I baselined a stock Opel head then flowed a 'Level 2' ported head, which back then was simply my way of saying '1.72"/1.50" Chevy valves with street porting'. Thought it might be interesting for you to see why I always harp on getting the intake ports to flow well on Opels, and why 1.85" intake valves are a better choice, even for modest street use.

Stock 1.9 head with 1.57" intake valves and 1.34" exhaust valves

Intake port:..... Exhaust port:
.100" - 28 cfm..... 23 cfm
.150" - 44 cfm..... 33 cfm
.200" - 59 cfm..... 42 cfm
.250" - 72 cfm..... 51 cfm
.300" - 81 cfm..... 55 cfm
.350" - 85 cfm..... 59 cfm
.400" - 86 cfm..... 62 cfm - 72% exhaust flow @ stock lift
.425" - 87 cfm..... 63 cfm
.450" - 87 cfm..... 63 cfm
.475" - 88 cfm..... 64 cfm
.500" - 88 cfm..... 64 cfm
.525" - 89 cfm..... 65 cfm

You'll note the bare exhaust port flows 72% of the bare intake port's flow, which is a little on the low side but fully acceptable. When the exhaust manifold is added however, the exhaust flow increases about 4 cfm. When the intake manifold is added, the intake flow is reduced by about 12 cfm. At this point the proportion is closer to 89% through the system, but this does not include the restrictive Solex carb.

Now, here is the street ported head with 1.72"/1.50" valves:

Intake port:..... Exhaust port:
.100" - 31 cfm..... 31 cfm
.150" - 49 cfm..... 48 cfm
.200" - 64 cfm..... 60 cfm
.250" - 77 cfm..... 70 cfm
.300" - 88 cfm..... 77 cfm
.350" - 95 cfm..... 88 cfm
.400" - 105 cfm..... 92 cfm - 87% exhaust flow @ stock lift!
.425" - 107 cfm..... 93 cfm
.450" - 111 cfm..... 95 cfm
.475" - 112 cfm..... 97 cfm
.500" - 105 cfm..... 97 cfm
.525" - 102 cfm..... 98 cfm

Note how easily the exhaust port responds to increased valve size and mild porting. At .425" lift, the exhaust flow improved 30 cfm from stock. That's 48%! But the intake port flow only increased 20 cfm, or 23%. Also note that by .475" lift, the intake port was all done making decent flow, and in fact gets worse at higher lift. What the chart does not show is the extreme turbulence encountered at the higher lifts, which absolutely kill (reduce)power at higher rpms. It takes some very trick intake port work to get around these problems on the 1.9 heads.

I thought this would make for some interesting documentation for those looking at prepping their own heads.

Bob

[jordan]

Great information bob! I'm glad you found that, I was curious as to how different configurations compared.

[Hiro]

Originally Posted by RallyBob I found some info last night that I thought might be informative. It was my original flow chart from my first series of Opel CIH flow tests when I bought my flowbench. Dated October 20th, 1991! I baselined a stock Opel head then flowed a 'Level 2' ported head, which back then was simply my way of saying '1.72"/1.50" Chevy valves with street porting'. Thought it might be interesting for you to see why I always harp on getting the intake ports to flow well on Opels, and why 1.85" intake valves are a better choice, even for modest street use. Stock 1.9 head with 1.57" intake valves and 1.34" exhaust valves Intake port:..... Exhaust port: .100" - 28 cfm..... 23 cfm .150" - 44 cfm..... 33 cfm .200" - 59 cfm..... 42 cfm .250" - 72 cfm..... 51 cfm .300" - 81 cfm..... 55 cfm .350" - 85 cfm..... 59 cfm .400" - 86 cfm..... 62 cfm - 72% exhaust flow @ stock lift .425" - 87 cfm..... 63 cfm .450" - 87 cfm..... 63 cfm .475" - 88 cfm..... 64 cfm .500" - 88 cfm..... 64 cfm .525" - 89 cfm..... 65 cfm You'll note the bare exhaust port flows 72% of the bare intake port's flow, which is a little on the low side but fully acceptable. When the exhaust manifold is added however, the exhaust flow increases about 4 cfm. When the intake manifold is added, the intake flow is reduced by about 12 cfm. At this point the proportion is closer to 89% through the system, but this does not include the restrictive Solex carb. Now, here is the street ported head with 1.72"/1.50" valves: Intake port:..... Exhaust port: .100" - 31 cfm..... 31 cfm .150" - 49 cfm..... 48 cfm .200" - 64 cfm..... 60 cfm .250" - 77 cfm..... 70 cfm .300" - 88 cfm..... 77 cfm .350" - 95 cfm..... 88 cfm .400" - 105 cfm..... 92 cfm - 87% exhaust flow @ stock lift! .425" - 107 cfm..... 93 cfm .450" - 111 cfm..... 95 cfm .475" - 112 cfm..... 97 cfm .500" - 105 cfm..... 97 cfm .525" - 102 cfm..... 98 cfm Note how easily the exhaust port responds to increased valve size and mild porting. At .425" lift, the exhaust flow improved 30 cfm from stock. That's 48%! But the intake port flow only increased 20 cfm, or 23%. Also note that by .475" lift, the intake port was all done making decent flow, and in fact gets worse at higher lift. What the chart does not show is the extreme turbulence encountered at the higher lifts, which absolutely kill (reduce)power at higher rpms. It takes some very trick intake port work to get around these problems on the 1.9 heads. I thought this would make for some interesting documentation for those looking at prepping their own heads. Bob

Impressive demonstration Bob!
Can I please translate this in french & add it to your page on the RROC website?
Hiro

[jeff denton]

That is awesome. My car is gonna absolutely scream with the H head... Someday, maybe...

[RallyBob]

Originally Posted by Hiro Impressive demonstration Bob! Can I please translate this in french & add it to your page on the RROC website? Hiro

Mais oui Hiro!

You may wish to add that this was flowed on a Superflow 110 flowbench, and at 10" (2.54 cm) of water depression. A radiused inlet flange was used, but no intake manifold or exhaust manifold.

Bob

[Hiro]

Originally Posted by RallyBob Mais oui Hiro! You may wish to add that this was flowed on a Superflow 110 flowbench, and at 10" (2.54 cm) of water depression. A radiused inlet flange was used, but no intake manifold or exhaust manifold. Bob

Merci beaucoup Bob!
Yes I will add the experimental conditions you mention,
This is very important for any scientific data,
Also I will plot the flow vs lift,
This way it's even easier to get to the conclusions.
Cheers,
Hiro

[RallyBob]

Small update on this head porting project.

Last week I completed the porting and polishing of the very same head I used for this thread/article. I just wanted to add that I am donating this head to Gary Farias (owner/operator of OpelGT.com).

I bring this to everyone's attention not for my own personal gain, but for the sake of letting people know that Gary's hard work needs to be rewarded. I haven't made any donations to the website for some time and I feel that I'm long overdue. Given the amount of space my (many) posts have taken up here (all at expense to Gary, band width isn't free!), I wanted Gary to know that everything he's done both monetarily and time-wise has been tremendously appreciated by myself and by the many others that visit here every day.

Thank you very much Gary, you're the best

Bob Legere

[Hiro]

Originally Posted by RallyBob Small update on this head porting project. Last week I completed the porting and polishing of the very same head I used for this thread/article. I just wanted to add that I am donating this head to Gary Farias (owner/operator of OpelGT.com). I bring this to everyone's attention not for my own personal gain, but for the sake of letting people know that Gary's hard work needs to be rewarded. I haven't made any donations to the website for some time and I feel that I'm long overdue. Given the amount of space my (many) posts have taken up here (all at expense to Gary, band width isn't free!), I wanted Gary to know that everything he's done both monetarily and time-wise has been tremendously appreciated by myself and by the many others that visit here every day. Thank you very much Gary, you're the best Bob Legere

Bob here I can see again the main trait of your personality,
This I've been fully aware for a very long time.
Now my question is:
How can the international Opel community reward you in a comparable manner?
All my race 2.5 CIH were born following your advices,
If we did not meet on the web in 2002-2003,
I would never be racing vintage trophy races with my little KadettC.
Your input with me is worth several $1,000 in my opinion,
Just by saving super-expensive machining works here in France....
So I have lots of ideas/parts to get shipped to you accross the pond,
But first I wanted to make this clear to you:
You fully deserve it!
Cheers,
Hiro