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Old 10-12-2010, 11:09 AM
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chevy 350 rev limits

Hi,
Just run in my rebuilt engine,I put recircled rods in(standard rod bolts though),comp cam 280 magnum(480 480 lift) 600 vac sec holley,rpm intake and 186 camelhumps,flat tops and valve springs to match cam.Rotating assembly was balanced.
Using a mallory dualpoint dizzy.
Started to push the engine a bit now seems to have lots of low down torque and pulls strong to about 5000rpm then fades off! Have just bought a 650 double pumper and thought I'd drop that on,see if that would make it pull a bit more.
Do you think the heads are the limiting factor now? What would the safe rpm limit be with standard rods and bolts?
Any thoughts guys?

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Last edited by dave350v8; 10-12-2010 at 11:17 AM.
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Old 10-12-2010, 11:49 AM
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Quote:
Originally Posted by dave350v8
Hi,
Just run in my rebuilt engine,I put recircled rods in(standard rod bolts though),comp cam 280 magnum(480 480 lift) 600 vac sec holley,rpm intake and 186 camelhumps,flat tops and valve springs to match cam.Rotating assembly was balanced.
Using a mallory dualpoint dizzy.
Started to push the engine a bit now seems to have lots of low down torque and pulls strong to about 5000rpm then fades off! Have just bought a 650 double pumper and thought I'd drop that on,see if that would make it pull a bit more.
Do you think the heads are the limiting factor now? What would the safe rpm limit be with standard rods and bolts?
Any thoughts guys?
Could be several things, but what is the valve spring seat and open pressures?
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Old 10-12-2010, 12:16 PM
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Quote:
Originally Posted by dave350v8
Hi,
Just run in my rebuilt engine,I put recircled rods in(standard rod bolts though),comp cam 280 magnum(480 480 lift) 600 vac sec holley,rpm intake and 186 camelhumps,flat tops and valve springs to match cam.Rotating assembly was balanced.
Using a mallory dualpoint dizzy.
Started to push the engine a bit now seems to have lots of low down torque and pulls strong to about 5000rpm then fades off! Have just bought a 650 double pumper and thought I'd drop that on,see if that would make it pull a bit more.
Do you think the heads are the limiting factor now? What would the safe rpm limit be with standard rods and bolts?
Any thoughts guys?
Not enough carb, that combo would take a 750 Holley without issue. The 186 is a nice head but is obsolete by todays standards and certainly isn't set up with the hardened exhaust seats that are needed with unleaded fuels. There are better modern choices the L31 Vortec being a popular selection among many OEM and aftermarket choices.

Mallory dual point or anything with points is also obsolete by any standard if this isn't needed by a specific racing rule, it ought to go for HEI.

The best intake for a wide RPM range probably is the Edlebrock Performer RPM it holds a good bottom while letting the engine wind till the cows come home.

Why people rebuild stock rods is beyond me. This is the most highly loaded part of an engine, therefore, the most likely to fail, yet people continually cheap this out and put their money into the stereo system or something equally useful. 5000 RPM just might be a good place to red line the engine. Actually the stock rod will take 6000 now and then, but if one of them ever comes loose the engine is just junk. I always considered rods that need to be resized as sending a message that says "scrap me".

Bogie
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Old 10-12-2010, 12:40 PM
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If it were I, I would lose the points as the best place for points is the trash and if they aren`t set up right they too can cause upper RPM headaches. What exhaust system is on the car? as if it`s not free flowing with headers and a low restriction system the back pressure can cause this same problem in the upper RPM area. And as mentioned, lack of fuel can also cause this issue. Another place to check is the valve train. If the springs don`t match the cam then it revability will be limited.
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Old 10-12-2010, 01:53 PM
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Thanks for replies,Im running comp cam valve springs to match cam,using block hugger headers,edelbrock performer rpm manifold,shall I try the 650dp or go 750 vac secondaries? Running a manual 5 speed trans!
Thanks Dave
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Old 10-12-2010, 02:08 PM
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That 650 DP will make a amazing difference over what you are using as a mixer right now. I too just went from a 600 vacuum secondary to a 650 DP and it made all the difference in the world. If you already have it, try it. You will probably need a carb spacer for the rear bowl clearance on the vacuum fitting on that intake. I did.
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Old 10-12-2010, 02:28 PM
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Thanks mate for the tip,will fit it this weekend!
Dave
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Old 10-12-2010, 05:54 PM
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I really want that distributor and those heads man!!! If you upgrade maybe you would sell them to me??? lol j/k, I can find my own dual points distributor someday...

According to this website on casting numbers, http://www.thedirtforum.com/castings.htm

the 186 could be 1.94 or 2.02 intake valve size. If they are 1.94, I would say you might just be running out of breath at 5000 rpm. Did you try changing the cam degree any?

I wish I had a mallory dual point dizzy, I think they are cool.

Last edited by Dirty Biker; 10-12-2010 at 06:21 PM.
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Old 10-12-2010, 07:10 PM
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Quote:
Originally Posted by oldbogie
Not enough carb, that combo would take a 750 Holley without issue. The 186 is a nice head but is obsolete by todays standards and certainly isn't set up with the hardened exhaust seats that are needed with unleaded fuels. There are better modern choices the L31 Vortec being a popular selection among many OEM and aftermarket choices.

Mallory dual point or anything with points is also obsolete by any standard if this isn't needed by a specific racing rule, it ought to go for HEI.

The best intake for a wide RPM range probably is the Edlebrock Performer RPM it holds a good bottom while letting the engine wind till the cows come home.

Why people rebuild stock rods is beyond me. This is the most highly loaded part of an engine, therefore, the most likely to fail, yet people continually cheap this out and put their money into the stereo system or something equally useful. 5000 RPM just might be a good place to red line the engine. Actually the stock rod will take 6000 now and then, but if one of them ever comes loose the engine is just junk. I always considered rods that need to be resized as sending a message that says "scrap me".

Bogie
X2 with Bogie on this. You change that carb and distributer to HEI. It will come alive.


Cole
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Old 10-13-2010, 06:19 AM
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Quote:
Originally Posted by DoubleVision
If it were I, I would lose the points as the best place for points is the trash and if they aren`t set up right they too can cause upper RPM headaches. What exhaust system is on the car? as if it`s not free flowing with headers and a low restriction system the back pressure can cause this same problem in the upper RPM area. And as mentioned, lack of fuel can also cause this issue. Another place to check is the valve train. If the springs don`t match the cam then it revability will be limited.
x-2 on this. a stock exhaust will choke down an engines rpm ability. as an example, my 72 ventura came with a 307 that with factory exhaust would only turn 4400 rpms. when i put in a jegs header-back exhaust kit, i was able to get almost 5000 rpms out of it. i noticed that when i pulled the old "y" pipe assembly out that where the pipes were joined on a 2" pipe that it was choked down even smaller due to the way they put it together.
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Old 10-13-2010, 06:41 AM
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Good advice

The posts are spot on. The 650 dp will be dandy with the 5sp on this so long as the rear gears aren't to tall. The HEI is a must unless you are just trying to be retro cool And I must admit they are very retro shiek... Just not as reliable.

I second the advice.....be careful with your stock rods! Try not to wait till the nose drops before you shift And don't miss shift to often with the 5sp or you may need some kitty litter for clean up.

Overall sounds like a fun engine.
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Old 10-13-2010, 03:00 PM
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just learning how to set the points on a dual point setup would give me an excuse to use my yardsale find old school engine test meter and let me learn more about engines at the same time. My dad talked about them(dual point setups) when I was young befor he discovered subaru and the merits of twin turbo. I want to refresh his memmory when I get down to FLA to see him. You know, let him know that the old pushrod engines can still deliver a big bang for the buck...
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Old 10-13-2010, 06:50 PM
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The HEI and the 650 DP will certainly help. For that matter, properly calibrated points could as well. Points "back in the day" came with a variety of available spring pressures. Pure racing apps required higher pressure springs to keep the rubbing block in contact with the distributor cam. My first Accel dual point had such spring pressure that the blocks were shot in 500 miles. But above all, remember Ol Bogie's advice. 5000 RPM might be a good redline for this engine anyway, particularly with the stock rod bolts.

Pat
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Old 10-13-2010, 07:53 PM
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I would agree that the carb and the ignition is the choke point. Those heads should work pretty well, they're old technology but when they were new they were the good stuff.

I run a pertronix module in my hei and a mallory coil cap. Runs good to 6500 rpm.
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Old 10-13-2010, 09:52 PM
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Quote:
Originally Posted by Dirty Biker
I really want that distributor and those heads man!!! If you upgrade maybe you would sell them to me??? lol j/k, I can find my own dual points distributor someday...

According to this website on casting numbers, http://www.thedirtforum.com/castings.htm

the 186 could be 1.94 or 2.02 intake valve size. If they are 1.94, I would say you might just be running out of breath at 5000 rpm. Did you try changing the cam degree any?

I wish I had a mallory dual point dizzy, I think they are cool.

Its not running out of breath, I ran 186's last season up to 6900 rpm and it never seemed to be struggling for air. They're isn't a considerable flow difference between the 2.02 and 1.94's.

Points distributors arn't good past 5000 in my opinon.

Go HEI, bigger carb, and maybe a bit more timing.
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