F54 L28 bottom end rev limit?

[thehelix112]

Seems to me you can have both response and control depending on your definitions. Reponsiveness to me is a measure of the time between an input and a response from the engine/car, while control is a measure of how well/finitely you can adjust something.

It would appear hard to have control without response however as good response means you are less likely to overshoot an input adjustment.

But anyway John, WRT to your point, perhaps you are implying that at higher rpms the air is moving much faster and hence the response is that much faster simply because everything is happening faster? Better response leading to better control.

I think control can be achieved at any RPM given adequate response and throttle travel. Given the choice between a slightly more difficult to control engine and one which requires rebuilding twice as often, I know which I'll be going with.

Dave

[ZSaint]

Gavin, I'm no expert but drilling the rockers to loose valve train mass sounds like premature failure to me! I understand that some engine builders will smooth, polish and balance the rockers....but drilling holes in a high stressed member seem questionable. Phred will likely add to this, based on his experience.

P.S. If you paint the rockers RED, it will improve your HP 50%!!!

I havd had a bit of experience in 'lightening' Datsun rockers. I think there are some pics in the Datsun "How to Hot Rod..." book. You want the weight as light as possible without creating a weak link. Stress relieving the rockers by lightening, polishing and shot peening is the way to go. I have never heard of anyone 'drilling' a rocker arm assembly. Sounds like creating a weak point to me!

[ZSaint]

Gawd... I remember when Phred was just learning about L6 engines. I built the first torque plate for the L6 in 1977 and it is still at Hatch's Engine Service!! He built a couple for me and they were pretty good. We had a limit of 7600-7800 in those days because of the harmonics in the L28 crankshaft. The large diameter dampner was the answer. Prior to Datsun Comp providing that baby, 7200 was the max before the flywheel fell off! Ol' Phred has learned a lot over the years, yes he has!! I think I paid for most of his education, however!

[ZSaint]

Read my first post. It did not go through the first time, at first!

[Phred]

Eric,

Unfortunately, I'm a long way from retired, just tired. Yes, I still build SCCA engines. So far this year, a T-2 350Z, GT-4 L-16, and an odd rally Z-22 w/L-18 head. Also a Baja 1000 302 Ford, a couple of Gaerte Midget engines, and a full 360 V-8 Gaerte sprint engine. For about eight years I did Cosworth, F-F, & S-2000. Now, its nice to have lots of different things to do.

Gav240Z,

I'm with ZSaint, polish and shot peen, (not the contact pad) Lightening the pivot end is a waist of time, concentrate on the valve end. No drilling. I will also be trying one of the new hi-tech cam/rocker coatings on my own 3 liter later this year. So I won't know how, or if, it effects the L-engines for a while.

Phred

[thehelix112]

Hey Phred,

I realise you're a busy man and probably sick of this but I still have some questions.

Do you have any issues with blowing head gaskets between #5 and #6? If so, what was the solution? A fellow here in Melbourne (RPMZ) has had his head drilled and uses an external water manifold to ensure correct coolant supply (I think?).

Also, what was the HP achieved from the SCCA turbo L28s and at what rpm/boost? Around the 600hp mark as noted in various books?

Many thanks,

Dave

[Phred]

Hi Dave,

There is no more of a risk of blowing a gasket between 5&6 than there is in any other cyl. Just make sure the basics are covered. Perfectly flat deck surfaces, and quality fasteners, properly installed. As far as external water lines, it should not be nessesary. At least we havn't found it is needed on NA 300hp L-6's. Having said that, I have seen other engines that were modified in this way to help coolant flow around the back cylinders of hot engines. Many USAC midget engines have external lines to ensure an even distribution of coolant. These engines run over 15:1 compression on alcohol. Bottom line, if you think you have a problem with uneven cooling, modifications may be in order. Also, Redline has a product called "water wetter", which really works. It allows the water to flow easily around tight restricted areas inside the engine, eliminating air pockets, and thereby reducing coolant temp.

The most common way of sealing high compression/turbo/supercharged head gaskets is "o" ringing. It is most effective when used with a solid copper gasket, but can be used with standard gaskets if the wire is located properly. The "o" ring in this case is a .041 stainless wire. A .028/.030 deep groove is cut in the block around the cylinder bore. Then the wire is installed, which protrudes about .012. This protruding wire creates a sealing groove in the fire ring of the head gasket. (the metal edge of the head gasket around the cyl. bore,) When used with a solid copper gasket, a reciever groove must be cut in the head where the wire will push the displaced gasket into. This creates a stepped edge seal, and will hold mega pressure. For instance, this method is used to seal many blown alcolhol drag race engines. I use this this method on L-6, and L-4, high compression road race engines (around 13.8:1) as well as other types.

I don't know how much HP the old L-28 turbo engines put out, but 600 sounds reasonable. I was involved in the development of a twin turbo 302 chev for road racing in the early eighties, and it was easy to make 850 HP. The killer was heat. controling both the compressed air temp, and the EGT were the keys to sucsess. Enough for now.

Phred

[thehelix112]

Phred,

Thanks mate. The engine runs with redline water wetter as is, and race 40w oil and will definitely be o-ringed when it comes apart.

Thanks for all your help, will keep you informed of how things go.

Dave

[DAT72z]

On 6/6/2005 at 10:00 PM, Phred said:

Dave,

Ti valves do require special care. But they do not reach a cycle life, and die. They degrade because of the less-than-perfect conditions their subjected to. A steel valve can survive those same conditions simply because the steel alloy is more durable. A pure Ti valve needs a slightly wider seat width than steel, or it will wear abnormally. They also need a nice, straight, honed valve guide bore, or stem wear will result. And, the tips will fail quicker than steel when subjected to valve float. In the past, a hardend lash cap had to be used on the end of the stem, but now most companys offering Ti vaves have a hardend tip manufactured into the stem. There are a couple of high tech companys now offering special treatments that will extend the life of Ti valves. One buzz word used to describe these finishes, is "Diamond Like Coating" or DLC, Very trick stuff. Do a web search for "Casidium". or "Black Diamond" high performance coatings. As far as trying to find the limit where valve float occures, that has been described as being the same as cleaning your gun without unloading. Formula V, Formula Ford, and Sports 2000, are what I call non-leathal engines. They have single springs, and can RPM exceed the springs capability to follow the cam. It can be seen and heard on the dyno. An experienced "ear" can detect it on the track. There are usually no devestating effects, because they use stock cams which have very mild ramps leading onto and off the lobe. When radical lobe profiles are used its much harder for the spring to control the valve. Thats why you need stiffer springs. That's also why some cam manufactures have gone to a asymmetrical lobe profile. The on-ramp is nearly flat, and hammers the valve open. Then, the off-ramp is gradual to allow the valve/spring to follow the lobe closed, and not "float" down. If this float is allowed to continue, such as in a massive over-rev, The valve will bounce on the seat, just when the cam wants to open it again. The spring ossilates, gets confused, and all mayhem can result. I have seen (post mortum) Valve locks spit out, Broken springs, spring seats, valve locks sucked through the retainer, rocker arms broken, or dislodged, and of coarse the final insult, valve hits piston. When engine building reaches this level, its very easy for the "do it yourself builder", to get into very expensive trouble. I think I've use up my space and energy on just one of your questions. I'll try to answer the others tomorrow.

Phred

I know this is an old post.  But I just couldn’t let this slide!  DLC is 1-2 microns thick and it works!  It has the lowest coefficient of friction of ANY Coating!  It’s also nearly indestructible.  It transfer heat, won’t break down and ya!  It will allow the engine to Rev higher and last longer PERIOD.  
 

I’m hunting for DLC coated main bearings now.

[siteunseen]

"Diamond like coating" Good kitchen knives.

 

https://www.google.com/search?q=dlc+coating&client=ms-android-americamovil-us-revc&source=android-home&source=hp&ei=mdcaYtjWM_eawbkPs6asuA8&oq=dlc+co&gs_lcp=ChFtb2JpbGUtZ3dzLXdpei1ocBABGAAyBQgAEIAEMggIABCABBDJAzIFCAAQgAQyBQgAEIAEMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDoRCC4QgAQQsQMQgwEQxwEQ0QM6EQguEIAEELEDEIMBEMcBEKMCOg4ILhCABBCxAxDHARCjAjoICAAQgAQQsQM6CwgAEIAEELEDEIMBOgsILhCABBCxAxCDAToRCC4QgAQQsQMQgwEQxwEQrwE6DgguELEDEIMBEMcBEK8BOgQIABADOgsILhCABBDHARCvAToFCC4QgARQ2AxY7yxg7DxoAXAAeACAAZEBiAHmBZIBAzAuNpgBAKABAbABAA&sclient=mobile-gws-wiz-hp

Edited February 27, 2022 by siteunseen