How to increase revs?

[Kraker_Jax]

Would having something done to the crank help increase the revs? Also haveing all the internals balanced and what not? I'm not asking about a stock setup. I'm asking if I took the LD crank and put it in my new block, what could/would need to be done so I would be able to rev it higher than the normal high. I know changing the cam out just moves the power band correct? I'm just trying to plan things out for the future. I want to go make sure I don't take any short cuts on this build. Went to a meet last night and a bunch of people loved the car, they asked what I had in it and I said stock and they sighed. "No V-8???" Me- "|-|3LL no!" But back to my question, what all could/should be done to achieve this goal?

[karay240]

Before we get started on how to in crease revs, I'd like to know why and how much do you want to increase the redline. Also, whether or not it's going to be a street car is a key point in building a motor.

 

That being said, I think you're on the right track w/ balancing the bottom-end. The main ingredient to high revs that actually make power is headwork, headwork, and headwork. No matter how balanced the bottom-end is, unless you've got the airflow to support those revs, going past red-line is going to be pointless.

 

If this car is going to be driven primarily as a street car, I would probably keep the redline at the stock level. With any OEM motor, there are improvements you can make to bump up the power throughout the rev range; however, once you have done everything you can, then you are going to have to "just move the power band" around to make more power at high RPM.

 

It is possible to make over 300 naturally aspirate horsepower from the L series motors, and the redline will be high, but it will be a PITA to drive on the streets, due to the lack of low-end torque.

 

Anyway, back to your question. In order to make more revs that count, you will need WELL DESIGNED AND EXECUTED head work (porting/polish and a very tight combustion chamber), a high lift cam, bigger carbs, and a very good header. (oh, I'm not sure of the braking point of the stock pistons and rods, so if anyone has any insight, that'd be great--I'd be safe and change those out, too.)

 

Before you spend a dime on the motor, look up all of the stuff you think you'll need to acomplish your goals. Then multiply that number by 1.5. That will probably be closer to the amount that you'll be spending. I'm not advocating that you should go w/ a different motor. I just want you to know what you'd be getting yourself into for the HP you'll be getting out.

 

I think that pretty much covers it, but it's early in the morning (for me, anyway), and I'm tired. If I failed to include some blatantly obvious point, I'm sorry.

 

 

Kenny

http://www.rbmotoring.com

[Kraker_Jax]

Thanks for the reply!!! I'll have to thank you, as you're the first person that didn't act as if I was a complete idiot. I'd like this car to be streetable yes, but I'll be leaning more towards going straight down the track. I'm not planning on making a complete stroker actually, just throwing in the LD crank for good measure. I'll be putting a turbo on the block and if I get a larger turbo down the line that takes longer to spool up, I'd prefer not to have to change the internals once again. I'd be getting forged pistons from somewhere and I was wondering if you had an insight on where to get some forged rods maybe? I'm sure theres someone that makes these, but I have yet to find one in my searching. I know head work is a must to make the most out of the turbo, but on the combustion chamber. You can/should only go so far on your CR correct? I would have to stay somewhere around 9:1 yes? I know this block is going to take alot of planning, and I have patience on things that I really want to do right the first time, and this is one of those things! Thanks for the help and any other replys would be great also! Thank you again for helping an newb out!

[zuhow]

I'd say Kenny gave you good advice, but make you best estimate and multiply by 3 not 1.5.

 

You need to decide now if you want to turbo it or not. If you want to turbo it, and you're going with the stroker crank be prepared to spend some serious cash. Personally, thats what I wanted to do, but I couldn't find a LD crank for a good price and decided that that money would be better spent on turbo and fuel upgrades.

 

You will need to look into better valve springs, check out Top End Performance, they sell a real nice engine rebuild package. You can chose the bore/ stroke/CR for whatever you happen to want. $1900 for just about everything (parts only).

 

Ask yourself why you want to increase the rev limit. The loads on parts go up really fast as you spin it faster, you'll have to pay for that strength.

 

Don't worry about forged rods, the stockers are good, just have them balanced and polished.

[Guest JAMIE T]

L6 is a fine engine for sure. I loved mine. To get your crank and bottom end up to the task of supporting high rpm head flow you can do the following:

 

Lighten the crank by knife edging the counter weights. Choose lightweight pistons and rods. Use absolutely the highest quality connecting rods you can afford. Nothing kills connecting rods like RPM. Have the assembly well balanced with a lightweight flywheel and SFI approved harmonic balancer.

[Pyro]

It would help if you gave more car information. What car do you have?

Also, what kind of rpms do you want to do? 7K is about the limit for the L28.

 

Be careful to not waste your money building up the engine block too much. Performance rods, cranks, and pistons can really add up! The stock Z block can handle at least 6500 rpms and 350 hp without any problems. It is the cam, valve springs, head, intake, and exhaust the makes the engine rev. All the block has to do is stay together.

 

For non-turbo: Rebuild a L28 block to stock specs with flat top pistons, add a N47 head for 10:1 cr, buy a stage 3 cam kit and a complete exhaust kit (header and 2.5" pipe) from MSA. Then you need to install a set of webers or SU's because the stock efi isn't good for much over 5500. It will rev to 6500 but I'm sure power will be dropping off. Or you can spend big bucks on a custom intake and aftermarket efi system. If you are going to build a stroker, then use a P90 or P79 head. MSA also sells stroker kits.

 

If you want to go turbo, you need to do it from the start. Buy a complete turbo engine and ecu. Rebuild the engine and turbo to stock specs and install it in your car along with the turbo ecu. Install an IC and turn the boost up to 10 psi. Then later, upgrade the turbo, upgrade the cam, upgrade to an aftermarket efi, and turn up the boost. Stay away from stroker turbo setups because it is almost impossible to get the compression low enough to use pump gas and a decent amount of boost.

[Clifton]

Mechanically the stroke/piston speed is the main limting factor on RPMs. Making power there is up to you. An LD28 stroke would give you just over 4133 fpm at 7500 rpm. Stock L28 at 7500 is under 4000 fpm. I run up to 7500 with a 79mm storke on an unbalanced motor with cast pistons. You should either run an aftermarket damper or new stock one.

[Kraker_Jax]

Currently I have a '76 280. I recently bought a F54 block from Thumper on here. It's only the block as I am going to be building it up. Would it be just as well for me to just upgrade the pistons and rods and leave the stroke as is? I plan on something similar to what you suggested pyro. I was going to build up the internals and then PnP the head that I put on it. After that have everything stock. When I get up to that, I was going to upgrade the intake mani, and then the ecu and get all the electrical set up. Then get a nice big IC and turn up the boost. For last I was going to save the turbo to upgrade. I was just wondering if the stroked crank would be worth it? And if I would need to up the revs to have a better performing engine.

[Pyro]

This is a summary of what I wrote earlier:

 

Don't worry about the block. Just rebuild it to stock specs using a high quality machine shop. It will be fine. Just use a good balancer.

 

Are you planning to drag race the car every weekend? If this is a street/strip car then spend you money on the stuff that bolts to the block (heads, cam, carbs, etc)

 

Strokers are difficult to turbo charge because the compression will be too high due to the small combustion chambers that are used on L28 engines. So you need to make a choice: turbo L28 or stroker with big cam.

 

Don't try to build a high compression turbo. Stick with the stock 7.4:1 cr turbo compression and turn up the boost. If you don't turbo charge, use between 10:1 cr and 11:1 cr and a cam over 240 degrees duration at 0.050" lift.

 

Don't go crazy with fancy block parts. A big cam with a good valve train setup, high compression, headers, 2.5" exhaust, with a good intake setup is all you need to make high rpm power.

 

AGAIN, The block doesn't make the engine rev! It is the stuff on the block that makes it rev. The block just needs to stay together and the stocK L28 will handle a bunch of rpms. I say 6500 easily but 7K still should be no problem for short durations even with the stock cast pistons!

 

Forget the block and start planning for the all the other stuff! (head, cam, valve train, exhaust system, intake system, fuel system, clutch, transmission, rear end, etc.)

[AK-Z]

Don't you need to use KA (or SR) connecting rods? You DON"T want your piston and valves to EVER touch (obviously) putting stock c/r on a stroker crank is bound to go wrong. Also with a strocker setup the head gasket also contributes to how much compression it will make. Personally I wouldn't turbo any engine with a compression higher than at most 8.5:1. Getting a turbo setup to work reliably with a stroker would cost to much time and money. Although it would work if you went he cheap route, but not for very long.

 

I know the first thing to go would be the harmonic balancer if it wasn't balanced properly. low rpms would be fine if it wasn't balanced but at the upper rpms is when all the fun starts and thing start breaking.

[Guest Mesverrum]

Im a little surprised nobody has mentioned it but a pretty common way to raise revs if you are really serious about it is just to destroke the engine some. Im not an expert on the l engines by any means but it seems to me that if you really wanted to you could take the shorter stroke crank from an l24 and mate it to your l28 pistons and have something like a bored out l26.

 

i cant remember for sure but i thought it went from l24, added stroke to become the l26 and then stroked and bored to make the l28.

 

Depending on what your intended purpose is this would probably help you boost your revs if you were going for some kind of high hp n/a setup where you were really concerned with peak hp over everything else. If a honda 1.6 liter can rev to 9k and make 300 hp then im sure you could accomplish something respectable with at least a full liter extra. might even have enough torque to move your car as well.

[SleeperZ]

Im a little surprised nobody has mentioned it but a pretty common way to raise revs if you are really serious about it is just to destroke the engine some. Im not an expert on the l engines by any means but it seems to me that if you really wanted to you could take the shorter stroke crank from an l24 and mate it to your l28 pistons and have something like a bored out l26.

 

i cant remember for sure but i thought it went from l24' date=' added stroke to become the l26 and then stroked and bored to make the l28.

 

Depending on what your intended purpose is this would probably help you boost your revs if you were going for some kind of high hp n/a setup where you were really concerned with peak hp over everything else. If a honda 1.6 liter can rev to 9k and make 300 hp then im sure you could accomplish something respectable with at least a full liter extra. might even have enough torque to move your car as well.[/quote']You may gain redline capability with de-stroking it, but you will lose more torque, and power as a result. Destroking is usually only used when you must limit yourself to a certain displacement, so you move your powerband up to compensate.

[v8260]

you could get a lighter flywheel or shave your original one.