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Can Opeler
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3,937 Posts
Bob I think you just answered my lean and loss of power issue at 5500rpm+ I’ve been scratching my head because even after fixing the leaning issue it’s still sounded and feels horrible at 6k.

Now I’m realizing this issue started after I fixed an oiling issue. I have 4-5bar at high rpm now. Also after these 100mph+ runs my engine almost dies at idle and makes lots of noise for about 15 seconds.

I’m excited to see if the solid lifter cam fixes this.

Autoholic, I sent a set of used solids to Gil and he is having them resurfaced and parkerized. He claims he’s had good luck with that. Piper cams also sells solid lifters.
 

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Super Moderator
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14,562 Posts
Thanks Bob for your insight. That kind of knowledge can make a big difference. I’ll trust your judgement far more than mine on this. Now I need to pursue some new mechanical lifters. I have lash caps and an OR-77 if I wanted to run that cam. Bob, in your head porting experience, is it worth it to pursue another 0.07” of lift for a street engine? That would be the difference between a custom cam I’d pursue and the OR-77 that I already have.
It’s certainly worth it on numerous levels. For one, that Isky cam design dates back to the late 1960’s, early 1970’s. Modern designs will make more power.

The OR-77 has .430” of valve lift. After valve lash, you’re only seeing around .415” of lift at the valve. Barely more than OEM. I’d be looking for .540” lift or so. Subtract the lash and you’re at .525” to .530” true lift.

On a high port head, you could potentially be seeing 20 more cfm of airflow between .415” and .525” lift…of course this depends on what the head flows. But you get the idea.

With a custom grind, you can make the LSA whatever you want it to be. I have had very good luck with 112° LSA on street driven. 2.4/2.5 liter engines.

With moderrn opening and closing ramps, you can get better vacuum and be easier on the valvetrain too, especially on the closing ramps.
 
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So, I checked out Bullet Camshafts’ master list.

This is ballpark what I’d be looking for. 2.4 head has an intake port deficiency (like the 1.9) and yet it likes higher valve lift. Not crazy duration for a 6500 rpm engine.

INTAKE: F277/346 - .538” lift with roller rocker arms (.523” after valve lash), 248° @ .050” duration, 277° advertised duration

EXHAUST: F270/3397 - .528” lift with roller rocker arms (.511” lift after valve lash), 241° @ .050” duration, 270° advertised duration

Grind it on a 112° lobe separation angle (LSA)

These have asymmetrical ramps, closing ramps are gentler to prevent valve bounce.

Anyway, this would take advantage of the 2.4 head’s flow characteristics and be mellow enough for the street.
 

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Just Some Dude in Jersey
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16,261 Posts
Valve cover clearance using poly locks can be an issue with 2.4 valve covers, which I think might be lower than 1.9's. I had to cave in the PCV chamber on my GTX engine in order to get the valve cover to seat. I also encountered an issue when I needed to loosen the Polylocks to check lifters. There's barely clearance to get a 15mm socket on the rocker nuts and then there's an allen screw at the top of the nuts that locks the non-self-locking nuts in place. So, it's really hard to find a way to hold the nut still while loosening the allen screw. I couldn't hold the nut while loosening the allen and this cause the whole nut with allen to turn. I think I had to wedge a screwdriver between the nut and the rocker to stop the nut from turning when I loosened the rest of the Poly's. Since the allen basically locks the nut to the rocker stud, when I tried to loosen the allen it caused the rocker studs to unscrew from the head. Aarrgghh! It's amazing how little force/torque holds the rocker studs in the head. A stripped stud or nut can cause the studs to unscrew. I tossed those Polylocks on my Shelf of Failed Mods.

On the subject of hydraulic lifters, look through PJ's threads to find the one where one of his hydraulics wore through to the internals and caused him a breadown on a trip with his wife. I don't think he ever determined the cause for sure. His best guess is that the lifters weren't hardened properly. Apparently there isn't much "meat" to the lifters between the cam surface and the machined out inner chamber that has the spring. Like only 1/16" of metal.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #105 ·
Thanks Bob. I've never heard of the company. Have you worked with Bullet Cams before? Have they done a CIH cam? I don't know a whole lot about various cam companies aside from who actually has or at least used to produce cams for the CIH. Is there anything I should look out for before sending off a cam blank to someone? I only have one and I don't think they are easy to find now, so I definitely don't want to ruin it. Cams and lifters is definitely an area of Opel knowledge I want to know more about since it's one of the harder areas to really learn without spending a lot of money.

One last cam question. Would your advice for cam specs change a little if I planned to retard the timing? What if variable valve timing would eventually be used, with a total of 10° in variation from ≤5° advanced to ≤5° retard? One thing I really want to try to resurrect is VariCam. I think I can improve the design and make it reliable. The CIH is also the perfect engine to use for it, since the dizzy is driven off of the crank and not the cam shaft. Pretty much every V8 that ever used it had issues with the device messing up the ignition but that won't impact the CIH. Whether or not I wind up finding a way to make it work is unknown right now but my Opel GT is to also serve as an engineering sandbox.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #106 ·
Valve cover clearance using poly locks can be an issue with 2.4 valve covers, which I think might be lower than 1.9's.
I'll be using the aluminum Opel valve cover. I want my 2.4 to look like a regular 1.9 until you look closer at it.

On the subject of hydraulic lifters, look through PJ's threads to find the one where one of his hydraulics wore through to the internals and caused him a breadown on a trip with his wife.
I read his 2.4 build thread but I haven't read that. I think I just need to accept that I might have to adjust the valve lash a few times over the course of enjoying the car.
 

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Registered
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I stopped playing with hydraulics on anything other than very mild cams years ago.

In the 1980’s, my friend John tried just about every damn cam combination C & R had back in the day. Solids, hydraulics, mild, medium, full race.

The hydraulics were fine in town, but at higher sustained loads and rpms they pumped up. This lifted the valves off the seats and created a misfire. On one particular highway “test run” it ran so badly when we got off the highway we were running essentially on one cylinder.

Parked the car, let the lifters bleed down, and then they were fine to drive around again. But basically you couldn’t use WOT at highway speeds without this happening every time.

Fast forward to the 1990’s and I was doing a lot of dyno work on Opels.

One particular engine I dyno’d for a friend was a 10.5:1 compression 2.2 liter with a big valve heavily ported 2.0 head. It had dual 45 DCOE Webers. The cam was .480” lift, 244° @ .050”, 284° advertised duration, with hydraulic lifters. We broke in the cam, made a quick pull and rejetted. Another pull and adjusted timing plus another jet change. Third pull was for the money. At around 6500 rpms it fell on its face. We went to 7500 and that was that. Power plummeted. It made 183 hp.

Same deal, lifters were pumping up something fierce. Clattering away and misfiring after the pull.

Anyway, we ended up switching to solid lifters and a different cam. Installed the old standby F306 Cam Techniques cam. On paper, not far off the hydraulic cam. .459” lift, 246 @ .050” duration, 288° advertised duration.

It idled immensely better. It revved better, up to 8200 on the dyno. It also made 214 hp.

I will use hydraulics on a street engine that doesn’t rev at all. I’ll go up to about 220°-225° @ .050”, and that’s about it. The biggest cam I’ve successfully run with hydraulics (long term) was an old H310 cam which was .465” lift and 224° @ .050”. I used it in my street car for evaluation and ended up selling it to Otto Bartsch. I believe he still has it in one of his GT’s.
So to sum it up, Hydraulic for mild street that doesn’t rev at all. Just cruising and occasional "dropping the hammer''.
Solid lifters for all else.
I just recently purchased an Iskey cam 412 lift, 256 duration, Hydraulic lifters, Matched to the cam, now that it has been run in. Any pointers? problems? Thanks.
 

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Valve cover clearance using poly locks can be an issue with 2.4 valve covers, which I think might be lower than 1.9's. I had to cave in the PCV chamber on my GTX engine in order to get the valve cover to seat. I also encountered an issue when I needed to loosen the Polylocks to check lifters. There's barely clearance to get a 15mm socket on the rocker nuts and then there's an allen screw at the top of the nuts that locks the non-self-locking nuts in place. So, it's really hard to find a way to hold the nut still while loosening the allen screw. I couldn't hold the nut while loosening the allen and this cause the whole nut with allen to turn. I think I had to wedge a screwdriver between the nut and the rocker to stop the nut from turning when I loosened the rest of the Poly's. Since the allen basically locks the nut to the rocker stud, when I tried to loosen the allen it caused the rocker studs to unscrew from the head. Aarrgghh! It's amazing how little force/torque holds the rocker studs in the head. A stripped stud or nut can cause the studs to unscrew. I tossed those Polylocks on my Shelf of Failed Mods.
I bought RennSport PolyLock rocker nuts from Edelschmiede:
and they worked very well. I do not have a 2.4 valve cover, so I cannot comment on that fitment, but Edelschmiede mentions a possible clearance problem. I have read that some PolyLock nuts are too tall for the GT aluminum valve cover, but I did not have clearance issues.

As for adjustment, the RennSport PolyLoks are easy to adjust. I simply placed a 12-point 15 mm open end wrench over the nut body, after it was adjusted, to hold it, and tightened the set screw. Far easier to adjust than the self-locking nuts, and never causes the stud to back out. I don't understand HOW that would happen with a PolyLock nut, since the nut turns easily on the stud once the set screw is loosened.
 

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Thanks Bob. I've never heard of the company. Have you worked with Bullet Cams before? Have they done a CIH cam?
They’ve been around forever. Very big name in drag racing and circle track. They bought Ultradyne a few years ago too.

I have not had them grind me any Opel CIH cams (yet). I did make a decision to use them for future cam work based on their reputation and grind selection, which is massive.

That said, I have used their cams before (I know, confusing). Cam Effects had them grind the Opel roller cam blanks 20-ish years ago. They did work very well.



One last cam question. Would your advice for cam specs change a little if I planned to retard the timing? What if variable valve timing would eventually be used, with a total of 10° in variation from ≤5° advanced to ≤5° retard? One thing I really want to try to resurrect is VariCam. I think I can improve the design and make it reliable. The CIH is also the perfect engine to use for it, since the dizzy is driven off of the crank and not the cam shaft. Pretty much every V8 that ever used it had issues with the device messing up the ignition but that won't impact the CIH. Whether or not I wind up finding a way to make it work is unknown right now but my Opel GT is to also serve as an engineering sandbox.
Presuming you are looking to simply expand upon the powerband of whatever cam you have in there, I see no reason to change cam specs. The only potential negative is the increased possibility of piston-to-valve interference. 5° either way is not a ton of variation for performance, but it can certainly affect tolerances. In theory you should increase the power band’s spread about 1250 rpms in either direction.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #110 ·
That said, I have used their cams before (I know, confusing). Cam Effects had them grind the Opel roller cam blanks 20-ish years ago. They did work very well.
Thanks for the details. I’ll contact them when I’m ready for the cam to be ground.


In theory you should increase the power band’s spread about 1250 rpms in either direction.
That was the benefit of a VariCam back in the 60’s. It didn’t really add to your peak numbers but it made it easier to have a wide power band.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #113 · (Edited)
I got the Piper Cams adjustable timing gear in the mail today….
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The Allen bolts use a 5mm Allen wrench. They are torqued down, so I’ll have to find a way to undo them without stripping them. Might want to replace with a star drive bolt?

I’m pleased with buying from Piper Cams, so I might also buy the solid lifters from them.

Today I also dropped off the engine (with crank), cylinder head, Cometic gasket, BHJ honing plate, and head bolts with the machine shop I’m going to use. I forgot the pistons so I’m bringing those later this week. Should be a few weeks before they get to my engine. It’s a little nerve wracking for me, if the block or head is screwed up it would be very difficult to replace them. I’m sure everything will be fine but I knew I’d be uncomfortable leaving something on my project in someone else’s hands.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #114 ·
I'm selling my Isky OR-77H with a set of lifters. Charles said he wanted to buy it, so I'm giving him first dibs on it but if he passes then this is open to whoever wants it.


I'll likely sell an Isky OR-77 cam in the near future as well.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #115 ·
I wish I had figured out what way I was going for my cam like, last week. I have gone back and forth many times over the past several years deciding on solid vs hydraulic lifters. The more I read and looked into it, the more undecided I got. I should have just asked Rally Bob from the beginning on exactly what I should focus on for this type of build. Had I known even last week what my final decision would be, I would have ordered the solid lifters when I bought the adjustable cam sprocket.

I have just purchased from Piper Cams a set of solid lifters for the CIH. With shipping, these cost £162.06 and that is roughly $214. Yes, you can find a set a tad cheaper on eBay but I know who made these. I'd rather buy a product from an established manufacturer. I could have saved some money on shipping if I had bought these lifters with the cam sprocket. Piper Cams does have CIH cams and valve springs, I'm just not using them for those parts.


The next major parts I need to order are valves and valve springs. I'm looking for advice on this. Should I stick with 9mm valve stems or should I go with 7mm valve stems? Considering the high lift I will use for the cam grind, should I use a single valve spring setup or a dual valve spring setup? Krause does have a complete 7mm valve stem option that provides the springs, retainers, keepers, valve seals, bronze valve guides, and valves. I'd want to replace the aluminum retainers in that kit with stronger ones to be safe but it does look like a decent option for 559 euros. I just don't know if it's worth it to pursue the skinnier valve stem option for this engine. Figuring out valves and valve stems is the last major component to this build. Everything else that I need to buy is gaskets, seals, bearings, and hardware.

There are a few engineering projects that I need to figure out as well, but those projects are one-off parts that I'll design and then create. I'll share more about those projects when I start working on them.
 

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Pedal Smasher
1973 Opel GT
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3,157 Posts
Discussion Starter · #116 ·
The solid lifters from Piper Cans finally arrived today. DHL seems to be backed up right now.
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The machine shop also called me today about the engine. They wanted to get more info about what it came out of so they could look up some specs. I took that as a good sign, my engine is starting to be worked on and they are doing some homework on it. They will clean the engine, deck the block and cylinder head, bore the block, fit the pistons, and check the mains / crank that it is in good working order. I don’t anticipate any of this being tasks that would require specific Opel knowledge, so any competent engine machinist should be fine. None of the assembly side is being handled by them, so as long as they don’t remove too much material everything should be fine.
 

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Opeler
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The solid lifters from Piper Cans finally arrived today. DHL seems to be backed up right now.
View attachment 442874 View attachment 442875

The machine shop also called me today about the engine. They wanted to get more info about what it came out of so they could look up some specs. I took that as a good sign, my engine is starting to be worked on and they are doing some homework on it. They will clean the engine, deck the block and cylinder head, bore the block, fit the pistons, and check the mains / crank that it is in good working order. I don’t anticipate any of this being tasks that would require specific Opel knowledge, so any competent engine machinist should be fine. None of the assembly side is being handled by them, so as long as they don’t remove too much material everything should be fine.
After going through a rebuild a few years ago, I wish I had spoken with @guyopel first. He’s been doing it himself and others for years and could have helped me and the shop with some tips and tricks. I touched base with him after the fact and it could have changed my build for the better if I did it beforehand.
 

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Not sure what your plan is but slow down before ordering parts. I have seen solid lifters of that style fail and ground the camshaft lobs off. Photos of some of the failures.
I run factory solid lifters and for my supplies I send my best old lifters to have them resurfaced. You can also have hydraulic lifters rebuilt and base resurfaced.
On my photo # 6493 I note that the rocker arm ball does not fit and because of that all rocker arms were damaged that I inspected.
I use correct length Chevrolet V8 valves and bronze guides in my work. Opel stock valves are 9 mm dia. and heavier than the Chevrolet valves I use.
I have used single springs (beehive) and dual springs. The alloy spring retainers should work for you.
Machine shop is going to need to know what your spring height is going to be and what to do with your exhaust rotators (Are you going to use them? or a spacer) and how deep to cut your intake spring seats.
Your camshaft and other work should work together. Do not leave Horse power on the table because you tried to match and add to what someone else did. Plan for your build save money.
John
 

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Pedal Smasher
1973 Opel GT
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Discussion Starter · #119 · (Edited)
I have seen solid lifters of that style fail and ground the camshaft lobs off.
Well, the first things that come to my mind if the cam lobes get wiped out is that incorrect springs were used or proper break-in procedure wasn't done.

rocker arm ball does not fit and because of that all rocker arms were damaged that I inspected.
I have Harland Sharp roller rockers and lash caps to go with these lifters. So, that particular issue should be eliminated since I won't be using any ball bearings. I also have flat top inserts that were meant for hydraulic lifters, but I could see them being used in solid lifters if I machine the tops off.
 

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1. Springs and break-in was not the issue. Failure shown was from multiple people and different engine builds so it is a pattern.
 
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