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HP gain running 1.6 vs 1.5 rockers

 
JTH55
V-6 Camaros rule!
Posts: 32
Joined: 11/12
Posted: 12/26/12 08:29 PM

Here is the engine in question 421 sbc 4.155 bore by 3.85 stroke with good internals heads are dart iron eagle 215cc runners with mild porting done.the cam is a solid roller. lift is 576/582 dur.248/254 with 110 lobe sep. intake is vic jr. with 800 cfm.carb just some mild port matching also .comp with heads is 10.5 to 1. what would be the power increase if rockers were upgraded to 1.6 from 1.5 and some real port work done .in other words is it worth it.will the gains be noticeable.thanx for any and all input. jerry  

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 12/27/12 09:46 AM

The rocker arms will not give you any great gains, maybe 1%.
Port work on the other hand can give substantial gains if done properly. In the range of 5-10%.
One of my BB632s had big chief heads from a pro stock motor. These heads had extensive work done to them, as far as filling in port areas to improve flow and moving the intake port. I sold the engine to a friend and he changed the heads to Dart big chiefs. My car ran 5.0s in the 1/8th and his ran 5.9s. My car was a few hundred pounds lighter which would account for some of it but not 9 tenths. It just shows that the right head work can give big gains.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

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76Skylark
Big Block power for the win
Posts: 868
Joined: 12/11
Posted: 12/27/12 03:45 PM

Or you can look at it like this.... Take it apart send out the heads/Intake, If you know some one, it may cost less than 750-1000 dollars. put it back togeather and on the street you may say wow "I feel that", Or Not. It sounds like a Bad A__ motor as is.but you May have a better retirement Plan than I do. Hell It's only Money. If you are like Me, I AM ONLY TRYING TO IMPRESS MYSELF. and you are there. I am building a Drag Car but every Penny has to show Results,but I'm not good as a Gambler. Dave's car was a purpose built racer He spent Big Money and got Big results. Speed cost's Money   How Fast you wanna Go.  

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skyeking
I mow my lawn and find Chevys
Posts: 2738
Joined: 08/09
Posted: 12/27/12 04:43 PM

Hi there,
  Agent 632 says it ALL.
  Rule of thumb also says that
  the larger the cam, the less gain
  with the 1.6 rockers.
  Hi there Agent 76!!! All the best
  to all of the people..  
skyeking

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BuzzLOL
I have an SS396 tatoo
Posts: 380
Joined: 12/10
Posted: 12/27/12 06:37 PM

.. X 4... the 1.6 rockers prolly not noticable in the seat of the pants, maybe on the strip or dyno... porting could be noticable, depending on what is already done... and what more is done... and how well it is done... I assume the Dart iron Eagle heads are similar to the World MoTown heads with ports designed by head porting guru/instructor (the late) Joe Mondello ('Dr. Oldsmobile')...

.. 1.7 rockers may be more noticable...  

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 12/28/12 08:43 AM

I forgot to mention that my friend, the one I sold the engine to, put the biggest intake port size heads he could find and even on a 632 they were too big. This is what caused his car to be so much slower than mine. Those heads he put on were ported too. Mine were 440 cfm on the intake side I think his were over 500 cfm. It also shows that bigger is not always better and sometimes a lot worse.
Even with a 150 shot of nitrous he could not match my times on motor.
Here is a picture of the motor in my friends car.
MVC 027S 1  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

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76Skylark
Big Block power for the win
Posts: 868
Joined: 12/11
Posted: 12/28/12 12:22 PM

Icon Quoteskyeking:
Hi there,
  Agent 632 says it ALL.
  Rule of thumb also says that
  the larger the cam, the less gain
  with the 1.6 rockers.
  Hi there Agent 76!!! All the best
  to all of the people..


Master Noel,  If you don't already know,The Best of everything Are my thoughts for you in the New Year, Carry On Brother,The Rest of ya.......Well  Same to you to.  

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skyeking
I mow my lawn and find Chevys
Posts: 2738
Joined: 08/09
Posted: 12/28/12 04:50 PM

Hi there Agent76,
 Are you good for a Lark in 2013??
 Master??? Of What may I ask.
 If you can't be good then be careful.
 Every success to you in the New Year.  
skyeking

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JTH55
V-6 Camaros rule!
Posts: 32
Joined: 11/12
Posted: 12/29/12 12:50 PM

thanx guys for the  input.dave 632 that motor u posted looks all busness.reason I posted is because I havnt bolted the heads on yet and thought if the gains were really noticeable I would have them worked over.by the way what head gasket thickness do u like on a engine like this .039-.041?this motor will see both weekend trac time and street use.any HP guesstimates?  

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BuzzLOL
I have an SS396 tatoo
Posts: 380
Joined: 12/10
Posted: 12/31/12 12:32 AM

.. Head gasket thickness depends on piston to deck (quench) distance... do a search for engine quench and read up on it...  

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JTH55
V-6 Camaros rule!
Posts: 32
Joined: 11/12
Posted: 01/01/13 06:13 PM

sorry buzz forgot to say that piston is .005 in the hole at TDC .this whole deal fell into my lap and just looking for some experienced gearhead advice to avoid any problems.these are custom made JE pistons.  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 01/01/13 07:16 PM

JTH55

If the JE pistons have any dome of even 1/16" to 1/8" with the 1.6 they will hit the valves. You need .080 on intake and .100 exhaust for a Steel rod.
These are clearnces for Aluminum Rods .100 on intake and .120 exhaust.

More rocker arm ratio only give you more lift.

Quick way to figure that out. Your given stock rock arm ratio for a SBC is 1.5.
FOR EXAMPLE ONLY: your cam has .450 lift. Divide your stock RR of 1.5 into .450=.300 X New RR of 1.6=.480. You have increased the lift by .030 Hope that helps.

Bob  

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BuzzLOL
I have an SS396 tatoo
Posts: 380
Joined: 12/10
Posted: 01/01/13 09:06 PM

.. Any gasket from .025" to .041" should work OK... always need to assemble one rod/piston assembly to crank and install cam and 1 pair of lifters and verify valve-piston clearance... have you run this engine yet? Should be ~550+HP already... that's a big, not very streetable cam...  

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JTH55
V-6 Camaros rule!
Posts: 32
Joined: 11/12
Posted: 01/03/13 03:44 PM

yea buzz I know it is going to be on the edge for what is considered to be streetable.i personally have not ran the motor .the guy that had it before me ran it on the street and at the track in a 2700 lb fox body mustang. for whatever reason the car was sold and engines heads/intake/carb were taken off.which is where I came in .couldn't pass up the deal so out comes the 406 and in goes the 421.gonna keep the 406 in storage. this motor has less than 100 miles on it and just a few passes on it can look at pistons and cylinder walls to see not much wear at all.so to sum it all up just want to put the dart215cc heads and my vic.jr with the 800 avs carb and see how she runs.still given the converter a lot of thought cam doesn't come on till 3000.  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 01/03/13 08:36 PM

JTH55
He was smart. There are a lot more of those small block chevys, that make the Fox body's run strong. Its funny the guys that did this always complained about the heads cracking, because of the 2 exhaust ports together, but they did it anyway.

Bob  

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