Street porting a 1.9 big valve head

[tekenaar]

Originally Posted by RallyBob I uncovered some more ancient documents yesterday. One of which was a flow comparison test of one of my 1.5 litre big valve heads, and then the effect of placing various intake manifolds on the head to see how much airflow was retricted by the intakes. The results are kind of old (1993) so I don't have any current 'welded/ported' stock intake flow test data, but I did test a bone-stock 1974 intake and then a mildly ported stock intake (I think you have this one in your possession now Gary). I only performed the flow test at .450" valve lift, to simulate a performance street camshaft at peak lift, and no carburetors were bolted to any intakes either, just a radiused (clay) transition was used. *1968 1.5 head, 1.85" Manley valve, street ported, bare port only: 115 cfm *stock 1974 intake manifold: 92 cfm *mild street-ported intake manifold, enlarged for 38 DGAS: 104 cfm *Cannon downdraft intake manifold for Holley 2-bbl: 93.5 cfm *Cannon 'long' DSD intake, 40 mm opening: 100 cfm *Cannon 'long' DSD intake, ported/welded, enlarged to 45 mm: 120 cfm *Irmscher 'short' DSD, 40 mm opening: 110 cfm *Dergo DSD intake, 40 mm opening: 107.5 cfm *Magnoletsi DSD intake, 40 mm opening: 112.5 cfm *TWM intake, 45 mm opening: 114 cfm Hopefully this info will be helpful to someone. Bob

Interesting 40/45 Cannon comparison . . . now you've REALLY got me curious about my Steinmetz 48SSD! Hmmm . . .

[N61WP]

Well, this might be a totally stupid question, like I've never done that before....but what is enough flow? I mean, I know it depends on displacement and compression ratio for what is needed, but I have to assume at some point the curve starts to go the other way once flow passes a certain point and velocity drops. Is this measurable?

Jc

[RallyBob]

Originally Posted by N61WP Well, this might be a totally stupid question, like I've never done that before....but what is enough flow? I mean, I know it depends on displacement and compression ratio for what is needed, but I have to assume at some point the curve starts to go the other way once flow passes a certain point and velocity drops. Is this measurable? Jc

If you cannot support the additional airflow with appropriate camshaft choice and compression, as well as induction and exhaust, then there is certainly a point when you might have 'too much'.

So putting a fully ported big-valve 2.4 head on a 1.9 block with a Solex and a stock hydraulic camshaft won't gain you much.

But as far as the potential for a drop in velocity, it is more a matter of port size than port flow. If you can gain flow but not lose velocity, then by all means go for it! Porting is easy, but porting effectively is not always so simple.

I like bigger valves because the curtain area is so high (more exposed valve seat area at low lift). In conjunction with modest porting, the big valve head can actually make a fantastic street head where you have no loss of power or torque...only gains throughout the powerband. Now for racing, you will want even more flow, and at some point you'll need more port volume...as you said dependent on compression ratio and displacement.

It's also dependent on the required powerband. A larger runner can store more of a charge between cylinder firings and improve VE on a smaller displacement engine too, however the trade-off might be a narrower power band requiring special close ratio transmission gear ratios and accurate induction/exhaust tuning for best results. I've had one Opel racing engine pull 112% VE for a 400 rpm powerband thanks to inertia tuning, most street engines would be lucky to break 85% at any point!

Bob

[RallyBob]

Originally Posted by Hiro very interesting data Bob, thanks! I didn't imagine there was so much difference between the various DSD intakes, what is the shape/length difference between the TWM & your modified Cannon "long"? Hiro

The TWM intakes are about 90 mm long (centerline through inlet runner), while the Cannon intakes are about 120 mm long measured in the same place.

The Cannon intakes have a more pronounced angle as well, they are at the same level as the inlet port for a short distance, then they angle upwards, then they level off again (so they don't angle the sidedrafts too much and upset the floats). When I modify the Cannon intakes, I weld some more material at the center area of the runners, to allow me to port the intakes for a 'straight shot' at the valves.

Bob

[RallyBob]

Originally Posted by tekenaar Interesting 40/45 Cannon comparison . . . now you've REALLY got me curious about my Steinmetz 48SSD! Hmmm . . .

Otto, I've never had one of those in my possession, so I don't know how they flow. If you ever take your car apart for any period of time, maybe we can set up a flow-test.

I do have a rough-cast Opel Parts and Service SSD intake. It was apparently an intake they designed and had cast for Mantapart...and then Mantapart didn't buy them even after contracting them. So they sold them directly to their own Opel customers instead. Just before Tom Thevenin decided to retire, he sent me a list of misc parts he was looking to unload, and one of these items was an as-cast SSD intake they made. It was never even machined, just a raw casting. So I bought it, and drilled/tapped it to fit, but never tested it. I suppose at some time I'll have on throw it on my flowbench, but unfortunately the 1.5 litre 'test head' I used for these other flow tests is currently on loan to a friend of mine. I'd rather use that head to bolt the intake to because any variation will skew results.

Bob

[Hiro]

Originally Posted by RallyBob The TWM intakes are about 90 mm long (centerline through inlet runner), while the Cannon intakes are about 120 mm long measured in the same place. The Cannon intakes have a more pronounced angle as well, they are at the same level as the inlet port for a short distance, then they angle upwards, then they level off again (so they don't angle the sidedrafts too much and upset the floats). When I modify the Cannon intakes, I weld some more material at the center area of the runners, to allow me to port the intakes for a 'straight shot' at the valves. Bob

I see now,
very interesting for my next upgrade, thanks!
I was planning to go for home-made throttle bodies,
alternatives being should I use modified DCOE with their manifolds,
or motorcycle bodies with home-made ones.
I guess the second option will allow for a better "direct shoot at the valve",
moreover the head is a 2.2 so maybe I can play a little bit with the angle to benefit from the raised port design.
Hiro

[RallyBob]

Originally Posted by Hiro I see now, very interesting for my next upgrade, thanks! I was planning to go for home-made throttle bodies, alternatives being should I use modified DCOE with their manifolds, or motorcycle bodies with home-made ones. I guess the second option will allow for a better "direct shoot at the valve", moreover the head is a 2.2 so maybe I can play a little bit with the angle to benefit from the raised port design. Hiro

If you decide to use home-made inlets with a 2.2/2.4 head, then here is another option I intend to use.

http://static.summitracing.com/globa...m-227700_w.jpg

Two of these will work nicely on the raised-port Opel heads! Standard version for 305/350 Tuned-Port GM engine has twin 48 mm throttle plates, with the center divider nearly the same width as the 2.2 inlet ports. Straight shot to the valves! These you can get off Ebay for fairly cheap (you need two units). Now, for Bonneville I will buy two of these Summit units, as they are 52 mm each...perfect for 10,000 rpms! They also have twin 58 mm available, but that might only work with a 2.7 litre/roller cam engine!

Bob

[anastosmotors]

Hi Bob
I have a local machine shop do the porting on my racing cylinder head.
what additional to the street porting should i do for racing.
The car is SCCA FP, high compression pistons with stock sice valves.
35 mm exhaust and 42 mm intake manley custom valves

Pete

[RallyBob]

Originally Posted by anastosmotors Hi Bob I have a local machine shop do the porting on my racing cylinder head. what additional to the street porting should i do for racing. The car is SCCA FP, high compression pistons with stock sice valves. 35 mm exhaust and 42 mm intake manley custom valves Pete

Pete, the porting for a racing head (especially FP) is completely different from street porting. And the intake manifolds are arguably more important than the head! They must be ported as a set, but the gains are huge. I don't have any photos to show you how to port an FP head, and even if I did, you'd have to see it in person, a photo doesn't really tell you everything. Roger Wilson still has my prototype FP head, he used that as a pattern for Stan Czacki's original GT head (the same car now owned by Ken Alderson).

[RallyBob]

Originally Posted by Hiro I guess the second option will allow for a better "direct shoot at the valve", moreover the head is a 2.2 so maybe I can play a little bit with the angle to benefit from the raised port design. Hiro

Hiro, I did this exactly for a 2.2 sheet-metal intake manifold I built a few years ago. I measured the port roof angle, and matched the inlet runners to this angle. You can see here how much it goes 'up' compared to a normal EFI inlet.

Bob

[Hiro]

Originally Posted by RallyBob If you decide to use home-made inlets with a 2.2/2.4 head, then here is another option I intend to use. http://static.summitracing.com/globa...m-227700_w.jpg Two of these will work nicely on the raised-port Opel heads! Standard version for 305/350 Tuned-Port GM engine has twin 48 mm throttle plates, with the center divider nearly the same width as the 2.2 inlet ports. Straight shot to the valves! These you can get off Ebay for fairly cheap (you need two units). Now, for Bonneville I will buy two of these Summit units, as they are 52 mm each...perfect for 10,000 rpms! They also have twin 58 mm available, but that might only work with a 2.7 litre/roller cam engine! Bob

that's a very nice idea Bob!
not so expensive & much bigger than my motorcycle stuffs,
again using US parts is the way to go for our old CIH...
cheers,
Hiro

[Hiro]

Originally Posted by RallyBob Pete, the porting for a racing head (especially FP) is completely different from street porting. And the intake manifolds are arguably more important than the head! They must be ported as a set, but the gains are huge. I don't have any photos to show you how to port an FP head, and even if I did, you'd have to see it in person, a photo doesn't really tell you everything. Roger Wilson still has my prototype FP head, he used that as a pattern for Stan Czacki's original GT head (the same car now owned by Ken Alderson).

(side question, sorry)
what are the FP race specs?
Hiro

[Hiro]

Originally Posted by RallyBob Hiro, I did this exactly for a 2.2 sheet-metal intake manifold I built a few years ago. I measured the port roof angle, and matched the inlet runners to this angle. You can see here how much it goes 'up' compared to a normal EFI inlet. Bob

yes I remember this manifold you've built Bob,
I want to mimic this but you know my poor fabrication skill...
my design will be much simplier just to fit the single motorcycle bodies,
hum... more news this winter I guess!
cheers,
Hiro

[RallyBob]

Originally Posted by Hiro (side question, sorry) what are the FP race specs? Hiro

It is a classification for circuit racing here, call Production. 'F' is where the Opel fits in, based on the standard model's capabilities (like old FIA Group 2, Group 4, etc). Rules are here.
Basically, the head can be upgraded with any valve springs, and retainers, and porting work. Valve head diameters must be standard size, but the stem diameter and material may change (so 6 mm titanium is okay!). This of course limits total power capability. Page 52 and 53 of the rules show the Opel-specific limitations, which include a minimum weight, track width, wheel width, valve sizes, induction restriction, and brake sizes. It is basically a class to provide racing for older cars, but newer cars are being added all the time. Unlike our 'GT' classes, complete tube-frame cars are not allowed in Production class.

Bob

[RallyBob]

Originally Posted by Hiro yes I remember this manifold you've built Bob, I want to mimic this but you know my poor fabrication skill... my design will be much simplier just to fit the single motorcycle bodies, hum... more news this winter I guess! cheers, Hiro

Maybe this is an option? This is four motorcycle TB's (Suzuki GSX-R 1000), adapted with silicone hoses to a car engine. I realize the Opel design (siamezed inlet runners) makes this more difficult, but perhaps by cutting down a standard EFI inlet, then welding 4 short aluminium tubes about 75 mm from the inlet flange, you can do the same thing? These TB's are often $150 for a full set of four on ebay as well.

Bob

[Hiro]

Originally Posted by RallyBob It is a classification for circuit racing here, call Production. 'F' is where the Opel fits in, based on the standard model's capabilities (like old FIA Group 2, Group 4, etc). Rules are here. Basically, the head can be upgraded with any valve springs, and retainers, and porting work. Valve head diameters must be standard size, but the stem diameter and material may change (so 6 mm titanium is okay!). This of course limits total power capability. Page 52 and 53 of the rules show the Opel-specific limitations, which include a minimum weight, track width, wheel width, valve sizes, induction restriction, and brake sizes. It is basically a class to provide racing for older cars, but newer cars are being added all the time. Unlike our 'GT' classes, complete tube-frame cars are not allowed in Production class. Bob

apparently quite close to our "vintage group1" regulation here in France,
a difficult & sometime expensive challenge for engine builders!
Hiro

[Hiro]

Originally Posted by RallyBob Maybe this is an option? This is four motorcycle TB's (Suzuki GSX-R 1000), adapted with silicone hoses to a car engine. I realize the Opel design (siamezed inlet runners) makes this more difficult, but perhaps by cutting down a standard EFI inlet, then welding 4 short aluminium tubes about 75 mm from the inlet flange, you can do the same thing? These TB's are often $150 for a full set of four on ebay as well. Bob

yes this is good enough for me!
my R6 TB are fitted with hose adaptors anyway,
I will probably start tinkering with an old 22E manifold as raw material.
Hiro

[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