randomarrival

I installed the Pertronix Ignitor III to replace the points ignition on my W30 and I started with the default setting at 5500 and then bumped it up to 6200 and it's hitting it fairly easily. Any suggestions on what I should set the rev limiter to? Should I be concerned that it's revving that high?

Everything is stock.

Thanks!

Rickman48

Means your top-end says 'yes' - it'll rev,
but unless you've modified the bottom-end, you don't want to hear it say 'NO', unless you've a diaper on it.
5500 should be just fine!

randomarrival

I'm not sure I get this...

Currently the rev limiter is set to 6200 and it seems to be kicking in about midway through 2nd gear (automatic).

Rickman48

What does you tach say??

randomarrival

Hahaha, the tach stops working properly about 3.5k

Rickman48

Then I'd wait 'til you get the tach straightened out, and put the 5500 back in, just to be safe.
Last thing you want to hear is a rod knock!

randomarrival

I really just wanted to make sure it shouldn't be rolling into that high of rpms - if it's not hitting the limiter then I probably need to check the fuel supply next. Sounds like I may be chasing the wrong problem.

Is there any data out there on the original motor performance, not sure exactly what that'd be.

randomarrival

Driving this weekend it became significantly apparent that it was fuel supply issue - replaced the fuel pump today and we're back in business. Going to roll the rev limiter setting back down to 5500.

Thanks for the help here, still a learning process for me.

allyolds68

I don't know what your engine specs are but most "street" BBO's are making max torque at under 4500 RPM's and max HP at or just under 5000 RPM's . Are you sure you want to set it at 5500? I just picked up an MSD 6AL analog that I'm putting a 4900 chip in to start.

I posted a similar question about what my max RPM should be with mine because I was pretty sure my tach was wrong. It was routinely spinning to 5500 RPM's and the consensus was my tach was way off.

randomarrival

I'm sure someone else can clarify what's reasonable. Going off the original specs it looks like max HP is at 5200 (unless I'm referencing the wrong documentation).

allyolds68

I know my compression ratio after a rebuild is well below 10.5:1 . If you still have the stock engine with F heads your CR is probably a true 10.5:1

This is what I'm running.

1970 455 out of a 442 4 speed car
No A/C
PS
PB
6 blade fan with full shroud
Single core aluminum radiator
Stock large valve E-heads with stock valve train
Holley 6497 spreadbore which I think is a 650
Stock points distributer
Edelbrock Performer intake
Stock air cleaner
Speed Pro SPE 369P + .030 over
Comp Cams DE 42-208-4
Muncie M-20
3.42 posi rear

Here are the comments regarding my questions on spinning to 5500

http://www.realoldspower.com/phpBB2/...ighlight=build

oldcutlass

This is the RPM that the engine reaches max HP, after that the HP declines as the RPM increases. And soon after that valves start to float.

MDchanic

The top curve:



- Eric

oldcutlass

Nice chart Eric.

MDchanic

'T'weren't me - You can thank GM.

- Eric

oldcutlass

It better explains what I was talking about. Depending on mods and individual engine spec's would depend on max peak HP and a rev limiter setting.

TripDeuces

In drag racing you typically shift 500 rpm past the HP peak. Depending on which chart you use the max would be 5700 for your application.
Personally, I'd leave the 5500 rpm limit in there and don't tempt fate. Shift it at 5300-5400 and enjoy it. It's not a small block, don't treat it like one unless you plan to spend money for new parts sooner then later.

bccan

If I'm not mistaken that peak rpm was measured w/ open exhaust (possibly headers), no accessories, etc. I would think a stock exhaust would drop HP & RPM peaks lower. Don't know what you're running in those respects.

Std Disclaimer - "I've been wrong before & this may be no exception."

I wouldn't set any higher than 5500 unless you have mods that will help it make power any higher & have no worries regarding part failure or valve float.

z11375ss

See what your car runs while shifting at that high rpm and then see what it runs shifting at 5000. I bet it isn't much of a difference. You're going to scatter that thing if you keep revving it like that. My .02.

rustyroger

Rods have the job of pushing pistons up and down the bores. The rod bolts have to cope with a tension load on the intake stroke, rods have a compression load the rest of the time which doesn't load the rod bolts. This is over simplifying a bit but a good rule of thumb.
It follows the primary enemies of rod bolts are heavy pistons and high rpms, there is little to gain and lots to lose allowing the engine to rev much past peak power. Use a quality timing light to set your rev limiter at a few hundreds past peak power speed and help your engine live longer.

Roger.

MN71W30

You could calculate your RPM being that it's a stick and you know the tire dia size and gear ratio. Find a formula and plug in the numbers. It should get you close.

Run to Rund

I know an NHRA stock racer with a 455 who shifts at 5500. Some rev limiters begin to affect the engine 200-400 rpm below the set point. I definitely wouldn't take a stock 455 bottom end over 5500.

z11375ss

I have the 5200 rpm pill in my MSD. I'm taking no chances. With a 3.73 that # comes up pretty damn fast!

Rickman48

z11375ss - and what're you going through the traps at, rpm wise??

z11375ss

Haven't run the car yet. Too fresh last year. Weak M-20. Now TKO 600. Weak link taken care of. I'll let you know.