redline and what determines it...

[Camaro Dom]

pretty straight forward... obviously stroke and valve float play a role in what determines an engines redline as well as con-rod strenth... what else is there? i've been told pushrod motors are always doomed to reletively low rpms and making gobs of torque there. can someone clear this up 4 me?

[Arctc Wolf]

Re: redline and what determines it...

rod-stroke ratio and valve float determine rpm. the higher the number, the better for higher rpm. i figured a while back that the honda S2000 2.0 liter motor has a lower rod-stroke ratio than we do, and they run 8000-9000 rpm all the time. with the zzp stroker they broke the crankshaft ar the rod jornal due to machining too much material away from it. the rods were fine. our issues are regarding the valvetrain. you need a cam that can flow at higher rpm's. you also need a valvetrain that can operate with the cam and not cause valve float.

[Den69RS96]

Re: redline and what determines it...

I would say the cam plays the biggest part. The valvetrain plays a big role in determining the redline. Obviously solid lifters can tolerate more rpms than a hydraulic can. Also, the materials used in the valvetrain itself. The lighter the higher the rpms. Also 4340 forged cranks and rods and pistons can tolerate higher rpms much better than cast stuff. The mains are important as well. Gm went to 6 bolt mains on the ls1. Older smaller blocks came with either 2 or 4 bolts. A lot of people convert 2 bolt blocks into splayed 4 bolts using studs to eliminate cap walk at higher rpms. I guess the main thing is that even though you build a short block that can spin to the moon, then main factors are the cam, heads, and intake. Yyou want to match these components together. It really doesn't matter if your cam has .650 lift with a 7000rpm redline if your heads don't flow well over 0.550 lift. Yeah it could run to 7000 rpm but you would be out of the engines powerband that it would be a waste of time.

By the way, Nascar engines are pushrod engines and they run to 9300rpm.

[Mogobs30th]

Re: redline and what determines it...

By the way, Nascar engines are pushrod engines and they run to 9300rpm.

NASCAR engines also have exotiv metals that make up the material of the valvetrain. Chrome Vanadium comes to mind with some parts.

[iGoRa]

Re: redline and what determines it...

.. Yeah it could run to 7000 rpm but you would be out of the engines powerband that it would be a waste of time.

You can patch this with FI no problem.

so say cam, stronger rods and springs should do the trick?

[Den69RS96]

Re: redline and what determines it...

Mogobs30,

I know nascar engines use exotic parts. I was just using that as an example to explain that pushrod engines can be made to rev. I don't consider 9300rpm not being able to rev. Anyway, there are plenty of smallblocks running around in many muscle cars that rev to 6500-7000rpm. The 302 in the 67-69 z28's revs to 6500rpm stock. Of course they had forged cranks and solid lifters, but it can be done without exotic parts. I plan on bringing the 350 in my 69 camaro to 6500rpms when I'm done building the motor. The new cam I bought makes power to 6200-6300 rpm and the Trickflow heads I have are matched to the cam. They flow reasonably well in .400-.500 lift range right around where my cam will have max lift. Right now I'm saving for a forged botom end so I don't shoot a rod through my block.

IgoRa,

How would adding fuel injection patch a mismatched set of heads and cam?
The cam, head, and intake will basically determine the rpm range of the engine. However, the bottom end is what really determines if you can live in that range. A stock cast crank, cast piston, 2 bolt small block will not live a long life regularly revving to 6500rpm. However a forged crank, forged piston 4 bolt small block will easily handle that. FWIW, you should always match your valve springs to the cam just like you should match your compresson ratio to your cam

[black98V6]

Re: redline and what determines it...

just thought I'd throw this in, don't forget about the weight of the rotating assembly. The heavier this is the harder it is to push the RPM, inertia is a *****.

[bluovlh8er]

Re: redline and what determines it...

isnt the stock tach have the red line printed on it? i think that determins it.:banana: :banana: :spank:

[iGoRa]

Re: redline and what determines it...

IgoRa,

How would adding fuel injection patch a mismatched set of heads and cam?
The cam, head, and intake will basically determine the rpm range of the engine. However, the bottom end is what really determines if you can live in that range. A stock cast crank, cast piston, 2 bolt small block will not live a long life regularly revving to 6500rpm. However a forged crank, forged piston 4 bolt small block will easily handle that. FWIW, you should always match your valve springs to the cam just like you should match your compresson ratio to your cam

I meant Forsed Induction.. , sorry