how do you I know when you swap the intake manifold it changes the rpm but what determines the redline :confused: thanks

 

Your red line is determined by a number of things including what materials your crank and pistons are made of and what type of cam you are running (hydraulic, solid, roller). Those items or combination of items determine how high you can safely spin the engine (RPM) without the engine self-destructing (what can happen when you exceed your red-line). Changing the intake manifold may allow you to make more power at a higher RPM but that alone does not change your red line.

As a general rule of thumb:

1. cast pistons, nodular-iron crank, stock rods/rod-bolts and a hydraulic cam will put your redline around 5,000-5,500 RPM

2. hypereutectic or forged pistons, up-graded rod-bolts and solid lifter cam will bring your red line to 6,200-6,700 RPM

3. forged pistons, H-beam rods, factory forged crank, 4-bolt block, roller cam and ported heads will take you safely to 7,200-7,500
RPM. Although the heads have nothing to do with red line, they do allow the engine to "breath" at those high numbers.

4. After-market block, after-market high end crank, H-beam or aluminum rods, altered oiling system, roller cam with light-weight valve train pieces, stud-girdle, fully ported heads, multi-carbs, etc. = 8,000+ redline.

As I said above, my 4 examples are rather generic as the quality of the engine parts can vary from Mfg. to Mfg.

Deen

 

:thumbs: :cheers:

 

:iagree: The weak link in mine has always been the rocker arms :banghead:

 

from your comment above it sounds like i beam rods cant cut it above 6000 rpm and you must use the oil slinging h beam rod :D :cheers:

 

Corkvette1,

Actually there are quality aftermarket I-beams forged from 4340 material with over-sized ARP bolts that are just as good or maybe even better than H-beams. I was just trying to keep my "generalized" answer from getting too complicated.

Deen :seeya

 

I've always found cams and valve train to be the limitation. So if your motor is balanced and blue printed with forged internals. (No stock motors)

H-Roller lifters motor Less than 6500 rpm

H-Flat lifters Less than 7500 rpm

Solid -Flat lifters Less than 8500 rpm

Solid rollers 9000+ rpm

I have only personally run the upper three classes of lifters. Normally your cams hp and Tq drop off so much before "RedLine" That your wasting your time even attempting to rev your motor that fast.

 

:lurk: Cool from the sounds of things, my motor should redline between 8000 & 9000 rpms :D That means that I should be safe shifting at around 7000 :steering:

 

Smoked tires with your good internal parts you'll have no problem. This past weekend I never hit my 7500 rev limiter, but I did run it way over 7000 in the second two gears all afternoon.

 

Does a higher max-RPM generally equate to longer engine life if you don't use it? E.g. if you're tricked out and safe to 8000 RPM, but you only ever rev to 6500 or so, will the safety margin be worthwhile?

How does forced induction affect these limits, or is that a whole new topic?

Lastly, comments on a splayed 4-bolt created from a factory 2bolt block, as compared to a factory 4bolt block?

-Chris