Viprklr

iTrader: (5)

What actually restricts us from running higher than 5K? Valve springs and possibly rod bolts?

F-Body Demon

iTrader: (1)

My understanding having never hurt a motor, is the valvesprings at 5000 then the rockers 5500 then the bolts 5500. I believe an upgraded system of those three gives you 6500. Im not sure. The only real high rpm engine I ever built went 8500 on a 350 .060 over with solid roller, roller rockers, forged parts, 4 bolt main, rev kit and 2 grand into the heads for springs valves girdle and such....but she screamed like a SOB.

Viprklr

iTrader: (5)

This is what I have:

1.6 ss rockers
AFR Eliminators - springs supposedly good to 6K no rev kit
stock rod bolts

My power peaks at 6500. The car shifts around 5K. I shift it around 5800.

How long "should" I be safe? I have more plans once the engine blows up but I don't want to speed things along either.

F-Body Demon

iTrader: (1)

Keep her out of detonation at high rpm and it should do okay. So long as your not planning on making it live above 5500. Street engine?

Viprklr

iTrader: (5)

I've actually had very few knock counts in the higher rpm/kpa cells. I've been pulling out timing in those areas. S_AUJP_V3.

I built it as a street legal drag car. Most daily driving I let it shift itself. Of course any race becomes a manual shift.

This thing is a blast.

MrDude_1

on a stock motor?

not to be rude, but almost the entire thing..
first theres teh valvetrain... the pushrods suck, the rockers suck and the springs suck.
then on the bottom end, theres the rods.. they arnt exactly the strongest ones GM ever put in a SBC... nor are they balanced all that great.



not to mention the heads dont flow well enough to really feed at high RPM, the intake setup sucks for airflow, and the log manifolds are a real restriction too...

assuming you dont have a 305, about the only thing worth keeping is the block. if you have a 305... replace EVERYTHING.

Viprklr

iTrader: (5)

Mine's a 350 that's nowhere near stock. Check my sig for most of the stuff.

MrDude_1

ah.
i thought you were asking about what stops a stock motor from spinning higher...



assuming you have a well built/balanced shortblock, the primary limitation of most pushrod motors is the valvetrain.
good pushrods, rockers and valvesprings(that match the cam), along with lightest valves you can afford, and spinning up to 6.5-7k isnt generally a problem.... going beyond that, you have to work a bit harder and spend alot more. lol.
all this assumes "the typical street/strip SBC"

jtrescot

I have Edelbrock Victor Jr. cylinder heads, a Comp Cam Magnum solid lifter cam, Scat brand cast crank, and Scat 6.0 I beam rods (nothing fancy, but with cap screws instead of bolts). I rev it past 7000 regularly, and nothing bad has happened yet.

Viprklr

iTrader: (5)

Then it appears that my personal limitation is 6K according to AFR. Good news.

F-Body Demon

iTrader: (1)

Anyone else know this tidbit of info...Scat is also known as Bear ****...haha just jiving ya man.

Viprklr

iTrader: (5)

Pretty much yeah. My bottom end is stock but there is absolutely nothing stock up top.

Viprklr

iTrader: (5)

After revisiting my DD2K table and since I just floated a valve i've decided to upgrade my springs. I need to spin to 7K.

Do you guys think that the occassional burst to 7K with stock rods, rod bolts, and crank will be safe? No other part will be an issue.

Supervisor42

It depends on 2 factors:
1. How good the factory balance is, if the engine has the factory pistons.
2. How much torque it is making above 6K.

If you take stock crank & rods and change the pistons, it's a crapshoot how unbalanced it now is. If it still has the original pistons it should be fine to 6500. Above that it's going to get hairy in a hurry. If it has had the pistons changed and been rebalanced see below.

The second factor deals with how fast the torque drops off as the engine passes 6K. If the cam is mild and the engine is making peak power before 5K the torque level will drop to say 200 ftlbs at 6500. If it had a drag race cam
that peaks at 5500 it could be making 300 ftlbs at 6500. This changes dramatically how much stress the stock rods have to endure above 6500.
This explains why people lose stock bottom ends at 5500 under nitrous when they have run it fine to 6500 N/A.
So, you can see a stock bottom end will survive just fine at 7K if it's only making 75 ftlbs of torque. Which would be where the attached dyno pull would be if it went to 7K.

So in a nutshell, if it's still making enough power to justify spinning it to 7K, the stock bottom end will not survive...

Viprklr

iTrader: (5)

Well I have the factory bottom end. When I rebuilt I put everything back into the same hole from which it came.
According to DD2K my torque peaks at 4000.
At the following RPM's this is what it says for torque:

Peak 4000 - 497
6000 - 426
6500 - 394
7000 - 369

The hp is why I want to spin it that high.
HP numbers:

6000 - 487
6500 - 488
7000 - 493
7500 - 475

My cam is a custom grind Comp Cams XFI 224/230 .566/.570 112lsa. This is WITH 1.6 RR.

Am I going to need to change anything in the bottom end in order to spin to 7K at the track or the occasional street Mustang stompdown?

I plan on getting AFR's hydra-rev kit with a couple of new valves. I'm still researching how fast you can spin the engine with their rev kit though. Hopefully I won't need to replace the springs.

Skoda101

"Am I going to need to change anything in the bottom end in order to spin to 7K at the track or the occasional street Mustang stompdown?"

If every thing left the factory with in spec of what there saposed to be, the only thing I would consider looking at for assurance would be the connecting rod bolts, studed mains. An upgrade to a bigger oil pan would be a wise idea but not neccicary when spenning higher then 6k on a regular basis.

-As for the vavle I don't think a rev kit is naccicary with a rev limit of 7k, find vavle springs with 200lbs seat preasure, use 3/8'x0.65wall push rods they have a freq, which means you won't have much bounce in your disred rpm range. Get titanium intake vavle and the exghust can be steel higher the tempered the better(i'am sure you already knew that ) for retainers,locks they can be titanium but not neccicary for anything lower then 8k

-With those AFR heads, get some quality studs, send you heads off to a porter along with the intake, but if your a diyer, do some searchs on the net for cylinder head fps,csa.

Regards
Skoda