how much do you gain with 202s over 188S?

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christineman

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is it true that if you take a pair of J heads that are 188 intakes, that you dont dont gain much power if you punch them out to 202? do y ou pickup 12-20- HP by doing that??

christineman
 
I don't think you will pick up much if anything on the top end and possibly loose bottom end if you don't open the bowl up and clean the ports up to take advantage of it. And like implied above if its a mild build you might not need that bigger valve.

I think mopar put the 2.02 valves in there so they can say their valves are as big as the chevy valves. The bowl and port really need some work to take advantage of it.
 
christineman said:
is it true that if you take a pair of J heads that are 188 intakes, that you dont dont gain much power if you punch them out to 202? do y ou pickup 12-20- HP by doing that??

christineman
Click to expand...

Not unless you do some work to take advantage of them such as a bowl blend at the least.On a stock head its not woth the effort unless the vlaves are sunk,also as was mentioned its combo specific,for example chevy 1.94 +.100 valves are a great option for alot of engines,it just depends.
 
what the others said -- plus if you are not spinning in the higher rpm range-- it just is not worth the bigger valves. Lawrence
 
What about with forced induction? Would the blending still be as important? I just bought a pair of J heads, and I was thinking of going to 2.02's and forced induction.
 
lead69 said:
Not unless you do some work to take advantage of them such as a bowl blend at the least.On a stock head its not woth the effort unless the vlaves are sunk,also as was mentioned its combo specific,for example chevy 1.94 +.100 valves are a great option for alot of engines,it just depends.
Click to expand...

X2
As much as i hate the thoughts of a Chiv valve in there.........my next set of 1.88 WILL get a 194 or a 2.02 cut back to 200.

ou812 tried to tell me to go a 194 or cut back 202" but wanted MY 2.02's!!!!!!:read2: next time:cheers:
 
Theres little gain with a 2.02 valve in a stock unported head. Once you start porting the head, the difference that was only a few cfm starts to get wider. By the time a full port comes into play, they are very worth while.

The loss in velocity is what ou812 is talking about in guiding you (Or anyone) towards a smaller valve. Hi velocity is key in making power. It is more important than a big valve. This defiys the old thinking of bigger is better. Mostly because the old way was easier to do, AKA cheaper. However the bennift of a better working engine, AKA effeciencey..(humm, SP!) is well worth it over the bigger is better thought pattern.

Most people here do not build an engine that simpley skips over the entire power band down low and use converters that flash @ 3500+ RPM's unless there drag racing. In this line of thought, track only, a smaller valve is probably not a good choice, even more so when going on the cheap.

Any builder/head man worth there salt would guide you in this manor like ou812 is trying to do.

Valvebounce, in forced indution, it will matter little since your forcing the air past the valve, under pressure. Build dependent, I would still look at the valve size as a major player in what is going to go on in the engine.
 
When I had my heads done (Iron Ram), they were supposed to go to a 1.92, but screwed up and put in 2.02's. They are ported, but I would rather have stayed at 1.92 for the velocity.
 
If you are force feeding it velocity is a moot point. You are better off with the bigger valve if the port is massaged to handle it.
 
Compression is King! - Like others have stated - depends on the combo.

Put some compression in that motor with a healthy cam, and the 2.02's and it will run!
 
Not trying to hijack the thread, but I ask about the forced induction thing as on a supercharged pushrod inline four that I have, I went from a 37mm inlet, to a 42mm and the peak boost figure didn't decrease. Which was dissapointing. I had thought a bigger hole would pass more charge, and lower the boost.
 
You shuld take the question into the forced induction room. There, you'll likely find people quicker that have been there and done that rather than jumping into this thread with a question that doesn't exactly fit in with the OE posters question.

Also, in that room, there is a person that is in the biz of forced induction, SCDE. You could also ask them directly. There helpful and freindly.
 
64physhy said:
When I had my heads done (Iron Ram), they were supposed to go to a 1.92, but screwed up and put in 2.02's. They are ported, but I would rather have stayed at 1.92 for the velocity.
Click to expand...

If your talking about your stroker, you did right by sticking in 2.02's


a lot of you guys aren't realizing or r forgetting the initial air/volume of the 2.02 with proper bowl shape.

deep port pockets, more coning of the air around the valve and stem,
they also flow more in higher lifts, look at a w2 head sometime.
 
rumblefish360 said:
Theres little gain with a 2.02 valve in a stock unported head. Once you start porting the head, the difference that was only a few cfm starts to get wider. By the time a full port comes into play, they are very worth while.

The loss in velocity is what ou812 is talking about in guiding you (Or anyone) towards a smaller valve. Hi velocity is key in making power. It is more important than a big valve. This defiys the old thinking of bigger is better. Mostly because the old way was easier to do, AKA cheaper. However the bennift of a better working engine, AKA effeciencey..(humm, SP!) is well worth it over the bigger is better thought pattern.

Most people here do not build an engine that simpley skips over the entire power band down low and use converters that flash @ 3500+ RPM's unless there drag racing. In this line of thought, track only, a smaller valve is probably not a good choice, even more so when going on the cheap.

Any builder/head man worth there salt would guide you in this manor like ou812 is trying to do.

Valvebounce, in forced indution, it will matter little since your forcing the air past the valve, under pressure. Build dependent, I would still look at the valve size as a major player in what is going to go on in the engine.
Click to expand...



the valve size is closely related to cid and ''rpm'' if 2.02's do 7000rpm and make power though you only buzz 6000 then....the smaller valve or should I say the right 'matched' valve size-going off of all flowing the same.

A smaller valve like 1.88 compared to 2.02, you'll notice torque through out, but the 2.02 will make more broader hp/torque.
the engine fights the valve size in a way, low pressure from pulling more than the valve will flow-delay after flow/vacume-inertia pulls the rest.
so not too big but not too small.

I think it's peanuts on the dyno between 1.94 & 2.02

just thinking a loud, gotta go to work now.
 
christineman said:
is it true that if you take a pair of J heads that are 188 intakes, that you dont dont gain much power if you punch them out to 202? do y ou pickup 12-20- HP by doing that??

christineman
Click to expand...

the bowl shape off of the seat needs to be as good or matched as the 1.88's are to compare fairly.

the 2.02 from the factory flowed 20'ish cfm more than the 1.88.
I have tested this to know.

every 5 cfm is worth 10 hp according to most formulas like afr's.

what cubic inch?
what peak rpm?
what carb and cam?

this will make the diff in what to use.


and know that specific heads and their respective port shape will also dictate any increase from a larger valve.

ALSO the velocity gained from the smaller valve will be almost un noticable once you rev over/into the mid of the power band.

how sensitive is your arse dyno?
 
Well,I like when you think outloud, Ha ha ha. Good thoughts and notes. I agree. Mostly, here on the net, alot of this tech talk is splitting hairs and making mountains outta mole hills on the small things that mater little on a street ride.

I like the mention of valve size to engine CID and RPM ability(s). Combined with the engines "Intended purpose(s)" it's not to difficult in most cases to figure out a decent set up, though, theres allways a critic in the crowd.

Also, when most question appear here on the net, there very general and lack info. SUCH GENERAL QUESTIONS GET GENERAL REPLIES, LACK OF INFO LEEDS TO POTENTIAL PROBLEMS THAT COULD HAVE BEEN AVOIDED.

Crap! sorry about the caps!

Have a good day at work!
 
If the 2.02 is done right, not only will the viscosity go up( not down) but it could go too high and cause a choke issue.

I fill that a 2.02 would make more power then 1.88 even in a stock 360 with a stock cam........Why.......
This is how i look at it!

2.02 will flow more air, sooner, then a 1.88. Because there's more "area" at the seat.

The 2.02 flow 20esh more cfm. with out porting. The head will port stall
at the same lift as it did with the 1.88......but will produce more cfm up to that point.

Granted there would be vary little HP gain from a 1.88 to a 2.02 w/"Stock port" head and stock cam.

I really don't fill the 2.02 would loose ANY bottom end torque, ...... Now if you got out of hand, in the bowl blend(opening up instead of cleaned up) You can kill all the bottom end.
ask me how i know.:angry7:
 
Cudafever said:
If the 2.02 is done right, not only will the viscosity go up( not down) but it could go too high and cause a choke issue.

I fill that a 2.02 would make more power then 1.88 even in a stock 360 with a stock cam........Why.......
This is how i look at it!

2.02 will flow more air, sooner, then a 1.88. Because there's more "area" at the seat.

The 2.02 flow 20esh more cfm. with out porting. The head will port stall
at the same lift as it did with the 1.88......but will produce more cfm up to that point.

Granted there would be vary little HP gain from a 1.88 to a 2.02 w/"Stock port" head and stock cam.

I really don't fill the 2.02 would loose ANY bottom end torque, ...... Now if you got out of hand, in the bowl blend(opening up instead of cleaned up) You can kill all the bottom end.
ask me how i know.:angry7:
Click to expand...

Can you please elaborate on what you mean by the term "port stall"?
 
stall=flows no more and begins 'flowing less' at or beyond a given lift
air speed/fps-feet per second-becomes too great = turbulent which disrupts flow, literally causes the air/fuel to no longer hang on/flow with the throat/bowl shape or short turn and takes all air with it, crashing around like cross winds/-eddys.

saturation=will flow no more but hangs on around a certain cfm, or flows the same no matter how much more valve opening there is.

You are better off with saturation than stall cause at least the #'s aren't falling off like with 'port stall'
 
always go with the 2.02 valve, plunge cut and blended even in a very mild 340/360, don't worry about velocity, nobody seems to worry about velocity when they bolt on a ld340 or rpm airgap.
 
1wild&crazyguy said:
stall=flows no more and begins 'flowing less' at or beyond a given lift
air speed/fps-feet per second-becomes too great = turbulent which disrupts flow, literally causes the air/fuel to no longer hang on/flow with the throat/bowl shape or short turn and takes all air with it, crashing around like cross winds/-eddys.

saturation=will flow no more but hangs on around a certain cfm, or flows the same no matter how much more valve opening there is.

You are better off with saturation than stall cause at least the #'s aren't falling off like with 'port stall'
Click to expand...

Thanks Justin!!!
vary good explanation, much better then i would have done. :cheers:
 
EL5DEMON340 said:
always go with the 2.02 valve, plunge cut and blended even in a very mild 340/360, don't worry about velocity, nobody seems to worry about velocity when they bolt on a ld340 or rpm airgap.
Click to expand...

Better velocity with a RPM. Smaller ports, smooth runner bends, taller carb height.

LD340 has gasket sized ports, less carb height and sharper bends.
 
Sometimes you can have too much velocity. Think of what happens filling a water bucket up with a garden hose pointed too close to the bottom.


I put MP 360 heads on my low compression 318. With the 2.02 intakes. Heads were milled just .030 and I used .040 thick head gaskets. Sounds like a bad decision, huh? Motor seemed to make more power everywhere, low-mid and high rpms. No I did not try the 1.88 intake valves first.
 
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