Not sure what exactly what is in these heads - Nova Tech
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  #1  
Old Jun 2nd, 19, 01:00 PM
Alan71 Alan71 is offline
 
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Default Not sure what exactly what is in these heads

I’m not sure if what I have is good or bad. Comp cam roller tip rockers. Is there any way to tell what kind of cam it has?
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  #2  
Old Jun 2nd, 19, 02:06 PM
Big Dave Big Dave is online now
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Default Re: Not sure what exactly what is in these heads

'191 head is a 1987-'04 74 cc Vortec (center valve cover bolt) head off of a 350 light truck (TBI). It has 1.94" intake and a 1.50" thick flat face valves. It is limited in RPM by port size, valves, and valve springs. '193 heads after 1996 would be a better choice and are sold by Summit already cut for a higher lift cam. The '191 head is limited to 0.470" valve lift before your retainer hits the top of the valve guide boss. Additionally the self guiding push rod slots machined in the head have to be made longer to prevent bending push rods with a higher lift cam. Otherwise those heads are basic smog heads, not performance oriented.

Roller tips are a marketing gimmick. They only cost money, and do not add to performance (by saving parasitic losses due to friction). That is to say the rocker ball on the stud is the major source of power savings as replacing it with a roller rocker can save 14 to 20 in lost horsepower. The trunion bearings in a roller rocker do not have the same level of friction that the rocker ball has in operation.

Yes you can determine what cam you have. You need at least an 11 inch in diameter degree wheel (bigger is better but costs more):

https://www.summitracing.com/parts/s...xoCwgMQAvD_BwE

and a one inch travel dial indicator with a magnetic base:

https://www.harborfreight.com/1-inch...cator-623.html

A piston stop is handy but isn't required to find TDC, and you can break a piston if not used properly.

https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

So with these three cheap tools in your box you can degree any cam you encounter.

Taking the readings you will discover:
true TDC,
Valve lift,
Overlap, and valve duration.

Big Dave
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Old Jun 2nd, 19, 02:56 PM
Alan71 Alan71 is offline
 
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How do you have all this knowledge Dave?
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Old Jun 2nd, 19, 02:59 PM
Alan71 Alan71 is offline
 
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You are very informative and I appreciate all the info
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Old Jun 2nd, 19, 03:09 PM
Big Dave Big Dave is online now
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Default Re: Not sure what exactly what is in these heads

I have been working with and on cars since 1961. Got my mechanical engineering degree because I wanted to build my own cars from the ground up. Owned my own shop (12 bay garage with five lifts) and built engines professionally. Also worked in heavy industry feeding the auto industry parts, so I know what GM wanted and how they worked. 74 now but I'm dying of an incurable disease now. Can't work any more so I share what I learned, till they bury me.
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Old Jun 2nd, 19, 08:33 PM
Alan71 Alan71 is offline
 
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Well I hope you stick around for awhile your knowledge is invaluable.
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Old Jun 3rd, 19, 02:06 PM
Alan71 Alan71 is offline
 
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Default Re: Not sure what exactly what is in these heads

when you say rpm limited, how limited? how do I know or figure out what that limit is?
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Old Jun 3rd, 19, 03:49 PM
Big Dave Big Dave is online now
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Default Re: Not sure what exactly what is in these heads

350 Truck had a rev limiter built into the HEI nodule that was set for 5400 RPM. These engines were built for towing not racing.

Big Dave

Last edited by Big Dave; Jun 3rd, 19 at 04:31 PM. Reason: spleling
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Old Jun 3rd, 19, 04:18 PM
Alan71 Alan71 is offline
 
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Ok thanks
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Old Jun 6th, 19, 11:38 PM
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Default Re: Not sure what exactly what is in these heads

Smaller port heads won't flow air as easily as larger port ones, so the smaller port heads are often used in lower rpm applications, like 4x off-road use.
At a lower rpm, you run the risk of fuel puddling because the air loses too much velocity with a large port head and the fuel will literally fall out of air and pour into the chamber, instead of entering as a mist, like it should.
Fuel, in that form, doesn't burn as easy and you lose power (not to mention, waste fuel).


Elvis
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Old Jun 7th, 19, 12:40 PM
Big Dave Big Dave is online now
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Default Re: Not sure what exactly what is in these heads

Actually liquid gasoline will not burn at all. If you are fast enough, and incredibly stupid, you could put out a burning torch by sticking it completely under the level of gas in a bucket. Gas burns in a very restrictive ratio of gas to air. To rich (too much gas and it won't ignite) too little and it won't support a continuous flame and the fire goes out.

The factory went to EFI not because they wanted to spend four times the amount of money it cost to buy a carburetor, but because they could determine the air to fuel ratio dynamically (a carburetor is pre-set and remains static while running) while the engine was being tested to pass an emission test. A carb goes out of adjustment due to changes in weather (humidity, and atmospheric pressure, as well as inlet temperature)as well as mechanical abuse or neglect. Since GM gets fined if their fleet doesn't meet CAFE regulations they wanted something that guarantees test compliance. After all you are paying the four times difference in cost, not them; so it is a financial no brainer from their perspective.

I continue to run a carb because there is no emission testing (or safety inspection for brakes, turn indicators, brake lights, headlight adjustment, or windsheld wipers) in my Republican run state. In Florida you can run a Top Fuel drag car on the street if you can reach out side the cockpit to make hand signals to indicate turning or stopping. Totally legal because the republican legislature determines noise pollution through a test that is too complex for the police to enforce.

You choose an engine's components based upon not what your hero run's on his car, but depending upon what you want to get your car to do for you. A race car lives on a trailer, it is never driven on the street. A street car can be raced at the track but it will never win competing against a race car that lives on a trailer. By this reasoning there is no such thing as a street strip car. I learned this back in the seventies so I drove a cheap beater on the street and owned the fasted race car in the state because I put my money into the race car. You have to pick what you want, and build accordingly.

If you want a fast street car and beat most comers come test and tune night (no class restrictions) build the biggest displacement engine you can This explains why every street car I have seen runs a 383 SBC. A 383 won't beat a 572 however If and Only If the car owner recognizes that you can have all the power in the world but it does no good to have that power level if you can not apply it to accelerating your car (my second epiphany I learned in the school of hard knocks). A 572 that goes up in smoke at the hit of the throttle won't beat a 383 that hooks and scoots.

Big Dave
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Old Jun 7th, 19, 10:18 PM
Elvis Elvis is offline
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Default Re: Not sure what exactly what is in these heads

Gasoline doesn't burn, but the fumes do.
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  #13  
Old Jun 7th, 19, 10:49 PM
62 NovaWagon 62 NovaWagon is offline
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Default Re: Not sure what exactly what is in these heads

Fumes ignite.
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