Side By Side Cylinder Head Comparisons/ RallyBob's Performance Suggestions

[RallyBob]

You can't use Opel valve seals! The Opel valves are 9 mm, Chevy valves are 11/32. You need new guides, new valves, new seals, you SHOULD install exhaust seats, and you'll need new springs, retainers, and valve locks. Otherwise it won't work out.

If you are installing larger valves, you have to cut the seats before you can unshroud the chamber. I use old dummy valves installed in the head to prevent seat or valve damage while grinding. Cc'ing is overrated. Not necessary on a street engine. Other than for calculating true compression ratio, it serves no purpose for 95% of the enthusiasts out there.

I never built the blower engine. Too many distractions! I built the 2.4 shortblock, ran it in naturally aspirated form for a while, then tore it down to inspect for wear ( I always do this when building new concept engines). I had the block re-honed, and wrapped it in plastic,where it sits to this day. Some day I'll built the blower intake and put it together. I'm thinking it would go great in my Kadett wagon. Imagine 250+ hp in a 2000 lb grandma car?

I think you'd better invest in longer connecting rods with that 305 Chevy pistoned engine you're thinking about. The piston will be about .210" below deck! Probably about 5.5:1 compression or so! Maybe try a 5.2" Ford 2.3 Pinto rod. Narrow the rod by .0065" per side (.013" total) to fit the Opel crank, and now the piston will be only about .050" below deck.

Bob

On larger valves and torque. Going to just larger valves with proper unshrouding and no other changes, what happens to torque at the low and mid range rpm? I found older message in the yahoo groups saying the larger valves help torque because of larger surface area. I don't understand exactly what that means. I thought the larger valves, without any other mods, like increased compression ratio or cam changes, would decrease velocity in general. Or is it that the Opel 1.9 just needs the bigger valves to help achieve better balance, by making up for the poor intake?

Thanks,
Alan

You said to use a Pontiac 400 spring about 1.44" diameter. I'm looking at a ordering some good springs and was wondering what the range of size and IH is. I've found a lot of 1.46" springs that i figure will probably have no problem working, but what installed height do you recommend? I don't want to order something too tall that will not work well or just plain be too tall to fit.

And just to verify I want to use a standard length sbc 1.72/1.50 valve, chevy retainers and locks, 11/32" guides and of course hard seat inserts... then after the machining is when I'll want to unshroud and port/polish.

Have you used screw-in studs like on a sbc? I'm pondering this one since my head will be in the machine shop soon. I'll have to take a look again, but I think I could get away with 3/8" studs, use the opel fulcrums and a chevy nut to keep everything together. I don't remember if the fulcrum is like a chevy where it is separate from the nut, or if it is large enough to fit over the stud without being drilled out.

Thanks

Dan

[RallyBob]

Okay, this gets confusing. I don't give out particular part numbers because the parts I use these days tend to be a bit pricier than some people are willing to pay. I don't believe in scraping the bottom of the barrel, even for Chevy parts. Here's a general guideline however.

But to try to answer your questions, I use standard length small block Chevy valves. Retainers are critical to establish spring height. A flat retainer will require a shorter spring than a high-step retainer. I tend to go for a +.080" or +.100" height retainer. When the spring seats are machined for the larger spring diameter, the exhaust spring seat is usually the correct height as it is, but the intake must be milled about .055" (don't take this as gospel, the machinist must establish this...there are variances from year to year and it also depends on valve seat depth). At this point, the spring installed height should be about 1.625" - 1.675".

Depending on camshaft choice, spring pressure should be around 100 - 115 lbs on the seat. Do not exceed 125 lbs, stock rockers will break like china at this point! Open pressure will vary as well with spring choice and valve lift, but stay below 250 for a street engine. I used to run 240 lbs with a .430" lift, 242 @ .050" duration camshaft, and valve float occurred at 8400 with this combo. Should be more than adequate for the street.

Opels have screw-in studs already. You can't use Chevy studs for two reasons. One, the flange from the Chevy stud may interfere with the Opel rocker arm. Two, the Opel stud is drilled for oil flow to feed the rocker arm. If you use a Chevy stud, you stop the flow of oil to the rockers. The rocker will burn up in about 3 to 5 miles. I've had the oil galleys plug up before, it will destroy the entire head. Not pretty.

Bob

Thanks for the info. out of curiosity, what springs do you use? I'm not looking to buy the cheapest stuff out there, I'd rather have quality and spend 50% more for the piece of mind. I'm really looking at the 10 degree titanium comp cams retainers. And since everything wants to come in a set of 16 I'll have a full set for my spare head or extras for my current just in case.

Another thing I've found is its hard to find a stainless steel valve smaller than 1.94 for the intake side. Any source for a 1.72 valve in stainless?

[RallyBob]

generally use Crower 1.25" springs (see, I'm already going against what I told you), and their 1.25" 7 degree titanium retainers. 10 degree are unnecessary for the street, we've run them to almost 10k rpms with no problems. You can buy these is sets of 8 by the way. These springs/retainers are lighter than 1.45" springs, so they reduce the unsprung weight a little. Also are very reasonably priced.

You can either do what I used to do, which is buy the 1.94" valves and turn them down to the required size, or order them from Manley. They will make them any size, turn-around is very fast. I prefer the undercut stem (Pro-flow?), they flow better and are a little lighter.


Bob

Does it compromise the valve at all turning it down? I guess you could potentially go with any size valve you wanted if that is the case, turn them down to say a 1.78 to get a happy medium between the 1.72 and 1.84.

[RallyBob]

I've never had a problem with turning them down. And yes, I've experimented with different valve sizes over the years. 1.72, 1.78, 1.80, 1.84, 1.85, 1.88, 1.92, 1.94 and even 1.97 for the intake side. Exhaust side I've done 1.45, 1.50, 1.55, 1.60, 1.625. Depends on cyl. head type, application, engine displacement, bore diameter, etc.


Bob

[RallyBob]

Dan, go to http://www.sivalves.com/ for more info about off-the-shelf stainless valves in odd sizes. They have 1.72, 1.84, 1.88 (for 4.3 Chevy), and even the newer 'Vette sizes with 1.97/ 1.55; with small valve stems. I almost forgot about them, I used to buy a lot from them years ago.

Bob

[2 Fast 4 U]

Originally Posted by RallyBob Hmmm, maybe once I've got the digital camera thing figured out, there's a possibility of creating a "library" of sorts to identify the various heads. Unfortunately, most of the ones I have are already modified, so this defeats the intent of identifying cyl head types easily. But with all the various Opel owners out there, we could perhaps photograph and label the vast selection of heads. 1.5, 1.6, 1.6s, 1.7, 1.9, 1.9h, 2.0, 2.0E, 2.2, 2.4, 2.0 group 1, 2.0 group 2, etc.

don't forget the 1.9 S

[jeff denton]

What is a 1.9S, please? I don't recall hearing of the S before.

[baz]

jeff the 19S is a high comp (9.0/1) from the european market 102 bhp/5400 rpm(gm-test 20)115ft lbs /2800 rpm (gm test 20)

[hrcollinsjr]

Is there a difference in the heads? I believe I have some engines that are marked 1.9S that are low compression.

Harold

[jeff denton]

One of my blocks' serial # starts with *19S, other two start with 19S.
All have different configurations of cast in (raised) logos, one has big square lugs where the motor mounts bolt up. One has a big H just aft of the serial # pad, another has an EB logo there. Two are thick web mains. All came with dished pistons, two had forged rods. One came with a 12 bolt four bearing head, one with a ten bolt four bearing head, one with a ten bolt three bearing head. It's hard telling what their life histories are, all seemed to be quite sad when they got here... The one that came in the Kadett was even tragic. Only thing usable there was the block which was not stock bore size.
I'll have the shop heated up and working tomorrow, will get pics of the two blocks that are candidates for the new race car engine.

[jeff denton]

So the 1.9S is 9 to 1 cr, then what difference is it from a regular 1.9, isn't it 9 to 1 cr also?
In perusing my "new" 1.9H head, (thanks Jim, USA Opels!) I can't really see anything outstanding different about it. Except that maybe the combustion chamber is closer to the deck, know what I mean? It looks like the head has been milled a bunch, the dimples are shallower and the Intake seat is right next to the edge between the chamber and deck. But in measuring the height of the head, from the deck to the valve cover rail, it is actually .015" bigger than a 12 bolt head I have to compare.
I'll try to remember to take my camera to work tomorrow and get some shots up here.
I never did find the spec as to what the chamber's volume should be, I thought I saw it here once but can't find it again. Didn't Bob have them all measured out for us somewhere?
Geez I hope I can make 11 to 1 cr somehow. I just love the smell of 110 octane racing fuel exhaust first thing in the morning...

[2 Fast 4 U]

The 1.9 N is a low compresion engine

[jeff denton]

Here's a few pictures of my "new" head. Notice the 1.9H stamped in the side. The 68 is the year it was built, right?

[Tru-Craft]

Jeff, I'm building a 1969-70 GT head. It has a delta or triangle stamped on the side!?
I could check volume for you, not sure how to accurately check chamber cc's.
Will post a picture of it.
Lyle

[jeff denton]

As far as I know, a 1.9 head is gonna have a combustion chamber volume of 52.1 to 52.6 ccs. This is quoting Bob in another thread. It's gonna vary a bit due to just how far the valves seats are cut in.
I know he had them all listed somewhere. Just can't find it...
The 1.9H is supposed to have a slightly smaller combustion chamber, as I recall it is not as small as the 1.5 or 1.6 but in my situation here I cannot legally run anything but a 1.9 head, or perhaps 1.9H head. The rules just say the head used must be for the block used. I think the H would qualify.

[Tru-Craft]

Originally Posted by jeff denton The 1.9H is supposed to have a slightly smaller combustion chamber, as I recall it is not as small as the 1.5 or 1.6 but in my situation here I cannot legally run anything but a 1.9 head, or perhaps 1.9H head. The rules just say the head used must be for the block used. I think the H would qualify.

Jeff, I have a set of steel stamps, with a 1 and a 9 in it!
The Opel has a power disadvantage to the Mustangs and Pinto's! I would build a 1.5 head. They won't care what you do, until you start kicking there butt's.
The tech guys don't know Opel engines, they won't cc the head, what would they compare it to?
They will just make you add weight to slow you down!!!
They want close racing, it sells tickets!
Lyle

[davegt27]

some people say that a 1.9 head flows better then a 1.5 (1.5 head with 1.9 valves)



you could take a 1.9 head and shave it like crazy to bump up the CR

probably the best thing you could do is petition the rules makers after all a 2.3 mustang or pinto is hardly fair. the only thing that can touch them is one of those 2.2 Dodge

maybe ask for any production head that can bolt up without modification be used. the reason being there are not many factory heads out there and you giving up so much in the displacement category to the 2.3 Ford

Almost every where you go those 2.3 Fords dominate since they managed to get the rules in their favor.

Davegt27

[Gary]

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