Smaller stem valves for 46/40 heads?

[tadd]

I've got a set of core heads that I am going to have new guides, valves and seats cut. A few other posts have mentioned bennifts from smaller (8mm, IIRC) valves like lighter weight (Alternate 906 cam) and better flow (homebrew head porting).

Given that the guides and valves are being replaced anyways, this seems like a very low cost up grade... or just a waste?

I've got two sets of centerlube cams to choose from, a 906 grind and a schrick 'racing' cam. Both are off visting with camgrinder to get actual specs on his camdoctor, but I can see with the schrick wanting as light as possible (less spring rate is good) if it is even close to what John posted in the alternate 906 thread.

I've already slipped far down the slope.

Anyone care to comment?

t

[aws]

Tadd: Unless you have to purchase new valves the 8mm valves do not make a good investment for the performance gains. The flow number increase is minimal and the lighter weight is inconsequential unless you plan to run over 8000 rpm. The 906 cams can be run to 8000 with the stock springs and retainers when shimmed 1mm tighter than stock spec. I have run a small turbo engine to 8800 with that combination with no problems. If I remember the numbers they were 95lbs @ seat and 225lbs over the nose when set at that height. Some people don't like the stock retainers but I never had a problem. With that said I am not comfortable with the stock retainers when the open pressure exceeds 260lbs. aws

[kenikh]

Tadd, if you want to go this route talk to Aaron or Steve. They both have very good solutions - for your 2.8, I think you would benefit from the lighter valves since you want to go to 8K.

AWS, I am building a similar small turbo: a 2.3L. I am only spinning to 8000 RPM, but would be curious to hear more about your experiences: cam specs, compression, intercooling, etc.

Are you still running the little turbo?

[tadd]

Aws:
Thanks for the conformation. It was my understanding that the 906 style ramps were very gentle and could support stock hardware to stupid rpms - it was the schricks that I was concerned about.

Quoting camgrinder: "...Schrick that checked out 272/260 @ .050" with .520"/.500" lift on a 98 lobe center."

That's a lot of lift, so I was thinking that the lighter valve would help alot with the standard Ti retainer. Anyone on pelican used (driven) the schricks? Seems like they would be a higher lift DC80. Yee Har.

Which begs a funny question... most folks are dead set against using Ti for rods due to fatigue problems, but Ti retainers are common if not de rigur. Why the difference?

I'd also like to hear about the turbo -- just don't tell Kenik.

Kenik:
Hey, don't you have 14 other threads right now! Go away and paint something!

[kenikh]

Originally Posted by tadd

Kenik:
Hey, don't you have 14 other threads right now! Go away and paint something!

BLAH BLAH, at least I am laying hands on my car.

I still think that regrinding those Schricks and using the forged rockers would be killer. Knock down the lift a tiny bit, move the lobe spacing out and you'd have something truly wicked. Wait a minute, that's a DC80.

[stownsen914]

I have Elgin 310/296's in my 2.7, and am using stock valve train revving to 7500. I shimmed up the springs to get a little more pressure. Note that I am not sure stock springs would handle Schricks if they have .520 of lift. With my 310/296 shimmed up (I forget exactly how much, but something like .5-1.0 mm), the stock springs are approaching coil bind. 301/296 has something like .490 lift on the intake. You might run into trouble with stock springs and .520 lift. You'd certainly be fine with 906 cams.

Scott

[aws]

kenikhl: The Turbo engine was a long time ago, 66x90 (2.5) with stock 2.2 rods before you could get good aftermarket rod bolts. I used 2.7 RS pistons that were 7.5/1 compression with the short stroke crank. The first version of this engine I tried the Chrysler TO-3 turbos, but put several airboxes in orbit when it sneezed (backfired), so I used the two 280ZX turbos that gave me 18lbs of backpressure at 15 lbs of boost. It had 2.4 heads ported to 40mm and early S mag stacks and throttle bodies. It used early S cams which are close to the 935 cams (which I did not know when I built the engine) I used a mechanical injection pump with a diaphram to control the mixture on boost (too hard to control the mixture) I then went to a Buick Park Avenue 3.8 Delco Crankfire with Mass Air flow Sensor with sequential injection, (changed the firing order). but I had to burn a chip every time I changed the mixture. About that time Alex started Electramotive and I ordered one of his first twin plug TEC-I units. It made close to 450RWHP at 8400 @ 15lbs of boost and over that at 18lbs but I was scared to run it that high because it wanted to run over 9000. It seems to me that the engines that you put the least amount of money in always run the best ( maybe its because we expect so little from those efforts) and this one fits that description. I ran that combination for years. The first engine went for 40 hours and the only problem was it blew the CE head gasket out of the head groove and it started to leak when the head came back down and pinched the gasket ( wastegate hose blew off going down the straight and the boost went over 25lbs) Bob Holcomb at Motorsport Design taught me about Ni-Resist headgaskets and the second engine went over 60 hours. In 8 years of racing I can count on one hand the number of times I was passed on the straight with that little engine. (once a ex-NASCAR making 850HP)
Tadd: I run the Ti retainers because of strength, not weight, they will support more than 300lbs over the nose with no problems. That number sucks horsepower but is cheap insurance when (not IF) mistakes are made. I would not be running those kind of numbers on a street engine. The stock springs run into coil bind at around 490/500 lift. I have not used Shrick thought Bob At Motorsport Design has suggested it several times. One last suggestion, the 70.4 stroke 2.7 crank can be run to 8000 but not over with out breaking or the flywheel coming off, ask me how I know this. The factory modified the crank with a wider rod throw radius and tried differant flywheel retension methods to mitigate those problems but eventually went to the narrower 3.0 rod and thicker cheeks and 9 bolt flywheel of the 3.0 engine. If you plan to run over 8000 talk to Dave at Marine or Bryan at Pauter to make a new crank.
aws

[tadd]

Aws:
Wow, that thing sounds really awesome. Nothing like a turbo for adiabatic efficiency! Your gonna make Kenik have a pavlovian response.

I know about the nasty crank harmonic with the 70.4 crank. The idea I'll be trying is some Ti rods from crower. They are 340g (vs 720g stock steel) each (95g reciprocating, 250g rotating) along with Ti pins that shave about 20 more grams (75 vs 95). I'm also adding a fidanza flywheel with 5.5" tilton clutch. The theme was to shave mass to move the nasty harmonic even with the stock 70.4 mm crank. If it don't work out, then I'll regrind a 66 for SC journals and Ti pankles. Maybe twin turbo too? It's only money, right?

[kenikh]

Originally Posted by aws

kenikhl: The Turbo engine was a long time ago, 66x90 (2.5) with stock 2.2 rods before you could get good aftermarket rod bolts. I used 2.7 RS pistons that were 7.5/1 compression with the short stroke crank. The first version of this engine I tried the Chrysler TO-3 turbos, but put several airboxes in orbit when it sneezed (backfired), so I used the two 280ZX turbos that gave me 18lbs of backpressure at 15 lbs of boost. It had 2.4 heads ported to 40mm and early S mag stacks and throttle bodies. It used early S cams which are close to the 935 cams (which I did not know when I built the engine) I used a mechanical injection pump with a diaphram to control the mixture on boost (too hard to control the mixture) I then went to a Buick Park Avenue 3.8 Delco Crankfire with Mass Air flow Sensor with sequential injection, (changed the firing order). but I had to burn a chip every time I changed the mixture. About that time Alex started Electramotive and I ordered one of his first twin plug TEC-I units. It made close to 450RWHP at 8400 @ 15lbs of boost and over that at 18lbs but I was scared to run it that high because it wanted to run over 9000.

Intriguing info! I had considered using RS P/C on a 66mm for this exact reason. Finally decided to go custom since I wanted to run much higher static CR and smaller piston diameter. I went with 85mm JEs in Nickie cylinders and massaged the 9.5:1 spec pistons to 8.9:1 when cc'ed against my heads. I'll be running knock control and water/methanol injection. I am blown away that you were able to adapt the Buick EFI. Amazing.

Which airbox did you use? A custom unit or modified stock? I ask because I am also using '69S mag stacks and was planning on modding the stock airbox for boost. I assume you plugged the air bleed screws to hold boost...did you run into any issues with boost leak from the MFI throttle shafts?

Those early S cams were pretty radical for boost, but aren't terribly far off of the 935 grind. I am using these cams:

Custom Dougherty turbo cams: GT2 intake with the DC43 exh on a 108 lobe center (@ .050” Duration=248I/242E, lift .485”I/.484”E, 108 lobe centers)

As far as the MFI pump, I am toying with the same idea and was planning on using a computer controlled solenoid on the barometer actuator to control fuel trim on boost. Did you use a factory unit or build your own?

My hat is off to you - a very pioneering endeavor.
Thanks for the input!

[aws]

Kenik: The other reason the first set of airboxes went into orbit was that I had custom fabricated a set with the injectors at the top, spraying into the velocity stacks, not realizing that the standoff would blow the raw gas around the airbox causing it to puddle at the bottom of the airbox. The higher backpressure of the smaller TO-3's caused it to backfire, which ignited the pressurized mixture.
No problems with t/body leakage, and the diaphragm I used to run the mixture rich on the MFI had too much travel to adjust the mixture correctly. The Buick set up is when it came alive, which made me realize that with true programmable fuel injection I was going to be able make serious horsepower.
After the frustration of the MFI system I would never use anything but the modern programmable fuel injection.

aws

[stownsen914]

AWS,

That's cool, from reading your post I think I remember seeing a spread in Excellence on your 914 twin turbo a bunch of years ago. Are we talking about the same engine/car?

Scott

[juicersr]

Originally Posted by aws

kenikhl: The Turbo engine was a long time ago, 66x90 (2.5) with stock 2.2 rods before you could get good aftermarket rod bolts. I used 2.7 RS pistons that were 7.5/1 compression with the short stroke crank. The first version of this engine I tried the Chrysler TO-3 turbos, but put several airboxes in orbit when it sneezed (backfired), so I used the two 280ZX turbos that gave me 18lbs of backpressure at 15 lbs of boost. It had 2.4 heads ported to 40mm and early S mag stacks and throttle bodies. It used early S cams which are close to the 935 cams (which I did not know when I built the engine) I used a mechanical injection pump with a diaphram to control the mixture on boost (too hard to control the mixture) I then went to a Buick Park Avenue 3.8 Delco Crankfire with Mass Air flow Sensor with sequential injection, (changed the firing order). but I had to burn a chip every time I changed the mixture. About that time Alex started Electramotive and I ordered one of his first twin plug TEC-I units. It made close to 450RWHP at 8400 @ 15lbs of boost and over that at 18lbs but I was scared to run it that high because it wanted to run over 9000. It seems to me that the engines that you put the least amount of money in always run the best ( maybe its because we expect so little from those efforts) and this one fits that description. I ran that combination for years. The first engine went for 40 hours and the only problem was it blew the CE head gasket out of the head groove and it started to leak when the head came back down and pinched the gasket ( wastegate hose blew off going down the straight and the boost went over 25lbs) Bob Holcomb at Motorsport Design taught me about Ni-Resist headgaskets and the second engine went over 60 hours. In 8 years of racing I can count on one hand the number of times I was passed on the straight with that little engine. (once a ex-NASCAR making 850HP)
Tadd: I run the Ti retainers because of strength, not weight, they will support more than 300lbs over the nose with no problems. That number sucks horsepower but is cheap insurance when (not IF) mistakes are made. I would not be running those kind of numbers on a street engine. The stock springs run into coil bind at around 490/500 lift. I have not used Shrick thought Bob At Motorsport Design has suggested it several times. One last suggestion, the 70.4 stroke 2.7 crank can be run to 8000 but not over with out breaking or the flywheel coming off, ask me how I know this. The factory modified the crank with a wider rod throw radius and tried differant flywheel retension methods to mitigate those problems but eventually went to the narrower 3.0 rod and thicker cheeks and 9 bolt flywheel of the 3.0 engine. If you plan to run over 8000 talk to Dave at Marine or Bryan at Pauter to make a new crank.
aws

Wow, very cool motor.

You wouldn't happen to know Denny Kahler? He ran this car in 1987 at Bonneville with a 2.0 twin turbo based on a 2.0 case that sounds similar to yours, eventually going over 220. I think he is retired out around Phoenix somewhere.



Thread on the car here:
The first 230mph street legal 911 Turbo

[kenikh]

Originally Posted by aws

No problems with t/body leakage, and the diaphragm I used to run the mixture rich on the MFI had too much travel to adjust the mixture correctly. The Buick set up is when it came alive, which made me realize that with true programmable fuel injection I was going to be able make serious horsepower. After the frustration of the MFI system I would never use anything but the modern programmable fuel injection.

Yeah, not a fan of injectors above the butterflies for this reason. Airbox go BOOM!

This is great info that I have been unable to get answers to until now. THANK YOU!

Originally Posted by juicersr

Wow, very cool motor.

You wouldn't happen to know Denny Kahler? He ran this car in 1987 at Bonneville with a 2.0 twin turbo based on a 2.0 case that sounds similar to yours, eventually going over 220. I think he is retired out around Phoenix somewhere.

I know of this car and have researched it. Very cool car!!!

[kenikh]

AWS, one more question: How did you mount the EFI injectors for the Buick EFI system? Did you create spacer blocks or did you actually get EFI injectors to work in the MFI injector holes in MFI heads?

[aws]

Scott: That twin turbo 914 that was in Excellence magazine was my car. Denny Kahler was kind enough to point me in the direction of using the diaphragm to control the mixture of the MFI pump on my first effort. But we both recognized that he had time to adjust it on fly at Bonneville and I needed it for road racing. If he is retired in the Phoenix area I would like to know where because I would chase him down to see him. That 2.0 car was a bullet.

The first turbo 2.5 I built used 2.4 MFI heads that I opened the MFI injector holes up to accept electronic injectors and hand made the fuel rails,using the MFI throttle bodies, the later engine had custom manifolds with injector bosses. I also went to CIS throttle bodies on the airbox at that time, only using the mag MFI stacks. The reason was I went to 41mm port size, the MFI throttle bodies were too small.

aws

[kenikh]

Originally Posted by aws

The first turbo 2.5 I built used 2.4 MFI heads that I opened the MFI injector holes up to accept electronic injectors and hand made the fuel rails,using the MFI throttle bodies, the later engine had custom manifolds with injector bosses. I also went to CIS throttle bodies on the airbox at that time, only using the mag MFI stacks. The reason was I went to 41mm port size, the MFI throttle bodies were too small.

aws

aws -

This thread is proving to be a bit of a Rosetta's Stone for me. So many questions have already been answered, but you just hit another one: EFI injectors in opened up MFI injector holes. I have wanted to do this, but concerns of heat soak killing injectors have held me back. Did you observe any heat soak issues? If not, this option would make my life MUCH easier.

Thanks again.

[aws]

Kenikl: The original engine used square cut o-rings off of a early VW application to seal the injector to the stock MFI threaded hole in the head. This had a tenancy to create a vacuum leak, so I enlarged the hole to seat the injector deeper, still using the early VW square cut o-ring. when I did this there were no specs for the injectors, so I had to figure out the horsepower per cylinder and then call the manufacture for the injector delivery rate.
On a later 2.7RS engine I built for the street, I had to go to injection because the 46mm Webers would not go through emissions. This engine ran for years in Arizona with the injectors mounted directly to the head held in place by a billet fuel rail with no heat soak issues (vapor lock, injector failure, etc) That particular engine was hard to program because of the lack of vacuum signal, so I tapped all the intake manifolds and built a box to amplify the vacuum signal for the MAP sensor to get better drivability. The throttle bodies were ported to 38mm and the early S cams wouldn't generate a strong enough vacuum signal until after 2500RPM, so the off idle response was sluggish. Alex finally solved the problem by making the TPS authority adjustable at given RPM's on his MAP based systems, allowing me to use throttle position for the lower RPM and a MAP signal at higher RPM when the vacuum picked up.

aws

[kenikh]

Again, thanks so much. I have been looking for answers for years to these questions from someone who has actually tried it. A frosty beverage of your choosing is waiting next time I am in Phoenix or you come to Seattle.

Cheers!

[kenikh]

aws, another clarifying question...you ran MAF only with no TPS, correct? I am planning on running a MegaSquirt 3 using sequential injection and blended alpha-n (from a TPS), cutting over to a MAF/MAP at a set RPM, which will help at low RPM to manage lack of vacuum/pressure signal. Did you run an O2 sensor to modify fuel trim, as well? If so, I assume it was a single O2 sensor downstream from the turbo?

What was your experience on low RPM throttle response on your setup? If TPS is not needed, would love to hear more about how you set up your system, what sensors you used and what the inputs were used for. No need to reinvent the wheel if something works!

Thanks!

[aws]

Kenik: The original set up was Buick Park avenue 3.8 MAF with no TPS. When I switched to Electramotive it was a MAP system with adjustable TPS authority to make the off idle response better. If memory serves me I used 2300 rpms for the break point to use more MAP versus TPS. I did not use a closed loop system because I felt the response was too slow for a race car. I did use a O-2 to modify the fuel curve, but this was before wide-band and it would only give a general idea as to what was going on. Throttle response on the 914 was mediocre at best due to back pressure and volume of the intake track, it was, however much better than my street 930 at the time!!

aws