camarojoe

I've always believed that a hydra-rev kit, whether it's AFR or ISKY another brand, is a must when you plan on spinning your hyd. roller equipped sbc past 6200 rpms. I just took my blown up motor in to a reputable race engine builder to get torn down. One of the first things he said after noticing how good the heads looked was about the rev kit. He said that with todays spring technology that these kits aren't nescissary when you use the correct valve spring. He called the rev kits 70's technology, which I thought was funny. He said that he's seen engines lose 30-40 hp after adding them. He then explained that the addtional weight of the kit is just extra weight added to the lifter and that it is bad on the valves. Of course I've read a bunch of articles on the rev kits and they say how engines are able to spin higher without valve float, because the springs aren't collapsing the lifters. Then I have two examples that I thought of about rev kits, one is pro, one is possible a con.

The first is the GMHTP Thunderchicken project car, which I guess was sold recently for around 17,000. Anyway when MTI rebuilt that 396, they kept everything pretty much the same, the cam was a little different, but not enough to explain why they lost 30hp. Then I saw that they added the rev kit, which was their only major change. MTI dynoed and tried to duplicate everything as it was when the dynoed the engine on its first build. This may or may not prove my engine guy's point about rev kits costing hp. It is interesting to think about though.

The second example that I think is a positive for the rev kits is the PHR Engine Masters Challenge. Joe Sherman used the ISKY rev kit with his ported AFR 190's and a mild 234/234 cam to win the challenge, I think it was a 364ci sbc. He did make 604hp with this engine, which explains itself with that kind of hp #.

What do you guys think about these rev kits and the theories about how they work?

MrDude_1

weight on the VALVE eh?


i always thought that the point of it was that it pushed down on the lifter without putting even more stress on the valve....

camarojoe

The rev kit relieves or dampens the pressure on the hyd. lifter plunger so that the lifter is more efficient when the valves come open. The lifters are more effective then because they can take the abuse that an aggressive cam/ spring combo needs. This is the theory of a how a rev kit works, right? I'd like to know who agrees with, Dave, the guy who thinks the rev kits are a load of huey.

Jed

I seem to remember that TRAXION was running a rev kit on his car. Check the archives or send him a msg.

camarojoe

Yeah, I remember that Traxion's been running the AFR kit for some time. Hopefully he will post his thoughts about it here. I'm going to talk to Dave later today, or whenever he calls me to tell me the fate of my engine. I'll try to get in a few words about his opinion on the rev kit.

383backinblack

rev kits are a great idea for road racing cars, or circle track cars that spend a long time wound out at high RPM.....other than that it makes working on the motor a pain in the a** and doesnt offer a huge benefit

MrDude_1

i disagree....


with one, you can run lighter valvesprings, and reduce stress on the valvetrain as a whole.... even if you dont see a power increase in normal street driving, its better for the valvetrain then running badass springs all the time....


plus on the weekends you can still rev the **** out of it

383backinblack

it doesn't allow you to use lighter valve springs, it allows you to use the spec'd valve springs for the cam and not have to add more spring pressure to properly control the valves at high RPM.

....otherwise you could crush a lifter.....the other option is using a solid cam, or higher quality lifters, like the comp cams pro magnum series hydraulic lifters.

in almost every case, you shold NEVER use a lighter spring than the cam specs for.....

because the rev kit can add pressure to the lifter, and thereby follow the cam lobes with more stability.

it CANNOT control the rest of the valvetrain, as it provides NO more pressure on the valves themselves.....

just the lifters, and could lead to slow/irregular opening/closing and possibly bouncing the valves off the seats at closing.

92 zzz28

My new engine has the AFR Rev kit on it and so far, 1 day, its fine. I am tuning of course, but I actually forgot about it until I saw this post. Right now, I only think my situation has improved, both in power and rev capability. I know the HSR is going to really help my rev abilities, but the engine runs silky smooth to 6000. Thats as far as I have taken her so far...

I used Rev kit on an old drag engine with hydraulic roller cam and I also forgot about it until the tear down. In my experience, they work great, so well that I forget they are even there...

383backinblack

at one time when i was still learning, i actually contacted comp cams and asked them about rev kits,

i also talked to AFR last year, to see if their rev kit was anything special compared to others,

and they all told me the same thing, its not going to make your car faster, and it really has no major benefit on a drag car.

they are pro's, and they make the rev kits.....my money is that they know what they're talkin about.

is it gonna hurt you? no, but you dont need it

my engine revs up to 6200-6300 rpm no problem, with no rev kit...and its a STROKER with a very, very agressive cam

camarojoe

I didn't recieve a phone call today. So I'm still wondering what happened to my engine. Anyway, I'm still left wondering why my engine dude insists he's seen rev kits take away 30 peak hp from some engines after being installed.

383backnblack, I agree w/ what AFR said about the kit. I'm just wondering why someone lost power after adding the kit. My engine was pulling strong to 6700rpm so I wonder if this kit is nescissary for this kind of rpm with a hyd cam, or if I'd be okay w/o it. I didn't tell the engine guy how high I spin the motor, maybe he thinks I shift at 6000rpm and that's why he said the rev kit is useless. I'll get his opinions on the kit straightened out tomorrow, and I'll post them.

MrDude_1

well, if the cam or heads arnt made to flow enough air at a higher RPM, you wont see any gains from reving the engine higher.... you will appear to loose power as you are on the downside of the curve......



but if everything was made to spin higher, using the rev kit only helps with power.

fb305svs

Well, i have a rev kit, and i added it to my list of parts for a couple reasons beyond the recommendation of the RACE engine builder for a bunch of local top points cars.

1. It DOES increase the power band, it is a known fact that double spring, stainless steel valved, chrome moly retainored valve trains are heavy and WILL float at 6k tops with a decent sized hydrolic roller cam.

2. The rev kit makes a great adition to ANY motor, drag or otherwise to increase DURABILITY. The likelyness that an over rev damages your motor is far lessened in the valvetrain area with the adition of the rev kit since it takes all the extra strain of forcing the lifter back down the back end of the cam lobe to keep the valve down.

3. The Purpose as stated by others already is to allow the use of an appropriate spring for any specific HR cam, with out having to go to a solid setup due to the fact that hydrolic lifters can only take so much spring rate and seat pressure.

4. HP increase claims are not worth going by. They get there numbers by comparing the amount of hp AFTER the peak of the curve. A few hp can be found with the addition of a rev kit, but DEFINATLY NOT lost. The rev kit works to improve valve float, which is a lot lower than most of you think in your motors. Only until you have heard your motor on an engine dyno where you have the intake air ducting nearby will you understand when valve float occures. Its loud, and very noticable with a carbed motor and no filter.


Take a look at the pics of my motor below...





Specs on the motor- Comp Cams XR288 cam, ZZ3 shortblock, untouched, trickflow 64cc, CNC chamber 23 * assembled heads, victor jr intake, holley 670 street avenger carb, hooker LT headers...

Here's the dyno chart right from the engine dyno- notice how long the peak hp hangs on and does not drop off. The motor was over shot purposely to 7200rpm to check for valve float, and around 7000 was where we started to hear it come in.

a/f ratio was an even 12:1 tuned conservative... less than 5hp could have been gained by leaning it out, so it wasnt even tried.



Hope this helps you guys, if your building a hydrolic roller motor, be prepared to spend the cash for the insurance, not the hp. the XR288 cam is quite honestly possibly the biggest cam you can run with these heads and a zz3 bottom end... piston to valve clearences were just above minimums with 1.5 rockers.

specs on the cam- 236/242 dur @ 050, 520/540 lift, 110 lsa... yes it idles lumpy and is marginal on producing enough vacum for brakes, but my car does ok, and stops fine, and drives great... not sure where people get all huffy about driveability, but it drives great and i only have 342 gears in the car.

BTW, track times coming oct 3rd!


Steve

camarojoe

Thanks a lot guys for the opinions guys. I posted what happened to my engine in the tpi forum, if you're interested. I didn't talk to Dave about the rev kit deal, it's the least of my worries right now. Anyway when I do I'll take him a print out of all this info to use against him. I'm going to wait until I get all my parts back first though.

fb305svs, thanks for all the info. I really do agree with ya.

89gta383

iTrader: (5)

Rev kits are good. I have one, and Brett went back and forth taking out and installing the kit in the 91Z. Don't know what he was thinking though.

Gumby

I am just gonna throw in 2 cents...

Just form the pics that rev kits makes 100% complete sense.
It should not even be a rev kit but part of a normal valve train.

Why did GM skimp on them parts???

Matt

MrDude_1

bacause in production, bing "good enough" is cheaper.


i agree though... having one set of springs control teh lifter and another control teh valve is a great idea.

383backinblack

because its not necessary in 999 out of 1000 applications....no production v8 from any of the big three ever had a rev kit.

basically because its dumb to use parts you dont need

MrDude_1

lol...
you dont need a oil cooler either.

doesnt mean that it cant help prolong the life of your oil and help the engine.

they shouldnt put them on there.. you dont NEED them.. and its dumb to use parts you dont need


im sure them not using a rev kit in production had nothing to do with the fact that:

• they never used a agressive cam in production
• they are not concerned about valve float at high RPM in production
• saving $5 a car times several thousand cars saves alot of money
• they dont care if it slightly increases the life of the engine with a agressive cam that they didnt put in there.
• the same amount of people will still buy their cars, with or without it.
  

fact is, factorys dont make hot rods. they dont even make the best car they can. they make what they can sell for profit. thats it.

if you dont want one, dont put one in your motor, if you have a valid reason not to do it, let us know. but dont just say "the factory didnt do it so it must suck".. thats a idiots responce. you arnt a idiot are you?

MrDude_1

before anyone mentions my first bullet point...


they never made a agressive ROLLER cam in production.

383backinblack

ya so like i said....if you dont need it, why put one on?

MrDude_1

put in a more agressive cam and spin the motor some more and you will see the benift of it.


i doubt anyone that tears into a motor enough to add one still uses the stock cam.

383backinblack

it really depends on what your doing.....i plan on getting up into the 7000rpm range next season....but im going to do it by using a solid cam to build more power, not a rev kit,

you will find very very very few engines with rev kits at a drag strip, and its not beacause everyone is an idiot...there are better ways to accomplish the same goal in that type of racing.

in circle track or road racing where you maintain 6000 or better rpm for loooong periods, a rev kit is a great idea to get, and maintain valve control without enormous spring pressure....if you really want to run a hydraulic cam

MrDude_1

uuuh, thats a race car.


solid cams on street cars suck..... i know if i put a soild cam in my car, i would be adjusting the lifters twice a week.... 3 times if i go for a drive on the weekend.

i agree there are other ways to accomplish the same goal IN RACING.

but we're talking hyd cams, in cars that see some(perhaps alot of ) street duty.



its just a way to get around a compermise some engines have to normally take. kinda like how i can now put 4.10s in my rear and still get great gas miliage because of the T56.... the compermise used to be hwy gears and MPG or performance gears and gallons per min ( ) ... now thats nolonger a issue.



basicly im saying, if you can use it, do so...it has been shown to help when its not "needed" in some cases...

i could put it on my friggen L03 in the vert and it would help some when i overrev it. -- but its not "needed"

but im sure it wont help much in a soild roller cam race motor... -- but its not "needed"


so what im getting at is it can be helpful without being needed.

383backinblack

well sure,

but you cant say that a rev kit, which is normally a "race car" part is fine, but you cant use a solid cam which is a "race part" on the street

most good solid cam and valvetrain setups can go thousands of miles without getting out of adjustment....there are plenty of them running around on the street.

usually if you check the lash when you change your oil, its still almost perfect

92 zzz28

You are right about solid cams having a place on the street. Some people, like yourself and me, would not have a problem adjusting the valves ever so often. Then you have the people who don't know what that means!! They just want a car they can drive and not have to do much maintainence other than routine things, oil, tune up, etc.

For that matter a Rev Kit can be something that they want for peace of mind when and if they engage in some spirited driving.

For myself, on my newest engine (hyd roller), I put a rev kit in it. Right now the car sees street duty 100% of the time. In a few months, that should drop to about 60-70% of the time, with the rest left to racing and what not. I decided to put in the rev kit because it makes me feel more confident that I won't have any problems when I do run it to high RPMs...

Gumby

Hope it doesn't get into a big pissing contest but...


I think the big problem is GM thinks that a V8 only needs a 6000 rpm red line. I think red line should be around 14000.

It really makes having good gearing fun when you got RPM's to match.


Now they have made mistakes in the past. I hear them old 302 GM's would do 7000+ all day with no problems stock.


Matt

92 zzz28

Yeah they probably would, but they came with a solid cam...

383backinblack

zackly....

there are v8's that rev that high.....but i dont think you or anyone else would wanna pay for one.

TRAXION

Want proof? I'm the proof.

AFR uses WEAK valvesprings on their 190cc heads. In fact, AFR even recommends NOT using these stock valvesprings! Plenty of guys I know experienced valve float @ 5800rpms using the crappy stock AFR valvesprings. Well, I did use the stock valvesprings combined with the Hydrarev. Results (this is a stock L98 bottom end):

Tim

383backinblack

thats why i have comp cams triple springs that match my cam, also from comp cams

Black363IROCZ

I think if you properly adjust your valves the first time, you should have no need for a rev-kit

MrDude_1

you people have entirely missed the point and the application of it.

Black363IROCZ

I don't think there is a point to it. they sell it to "prevent valve float" at high RPMs and supposedly there is a power gain. I'm saying if you adjust your valves properly, you won't have valve float and those gains will be comprable. And as for running lighter valve springs. big deal...

MrDude_1

wrong.

they sell it to prevent lifter float.

92 zzz28

With a hydraulic cam, whether or not the valves are adjusted properly, you ARE going to experience valve float. With solid cams you don't need a rev kit because you can install a very heavy spring with out an negative side effects. Try installing a 500# spring on a hydraulic lifter and see how long they last...THats what the Rev kit is designed to do, apply spring pressure to the lifter body to hold it firmly against the cam. This helps the entire valvetrain stay more stable. Like installing 7/16 rocker studs. Do you need to? No. But it leads to more stability...Thats all the rev kit is doing, ensuring that the lifter stays in contact with the cam at all RPMS, especially the higher ones. It allows the valve springs to then do what they do best, close the valves properly...Just my $.02

91wtROH17's

I am putting the LPE 219 cam with the LTR setup and box stock AFR 190's, Are the valve spring's OK up to 55-5600RPM?? Sorry to go off topic, but you all have me thinking now!!

Black363IROCZ

rofl, you get the douche of the universe award for talking out your ***. move along before you feel the wrath of my "blocked" button.

MrDude_1

prove me wrong.

hell, what else would you expect a spring pushing on the lifter body to be for?

you jackasses want to play semantics meanwhile ignoring the majority of the people on here that could benifit from one when building their engine.

so block me. its not like its going to hurt me any.


http://www.airflowresearch.com/pages/hydra_rev.htm


heres a quote:

and while im not going to search for it, yes with a agressive roller lifter profile on a hyd cam, at high RPM you can literally launch the lifter up far enough that it breaks contact with the cam.



another benifit i see over a stiffer (and heavier) spring at teh valve..

lets pretend that our cam has .500 lift at the lobe. the spring on the lifter only has to move .500 inches to control the lifter. meanwhile the spring is multiplied by the rocker ratio.. typicly 1.5 on SBCs.... so it has to move .750 in my example. thats alot more movement for somthing at high RPM...

overall though, if you want to run some badass heavy springs in your hyd roller motor, go ahead. but for the rest of us street cars running hyd roller lifters that want to rev high with agressive opening and closing ramp cams, without valve float or collapsed lifters, we'll run this...

92 zzz28

I know my self and others don't think too much of the "box stock" valve springs AFR uses...I suggest getting the valve springs LPE suggests to use with their cam. I am partial to Comp Cams for valvetrain parts...For a LTR setup, I don't think you will pushing 5500+ very often, if at all , so you may not benefit from a Rev Kit. It wouldn't hurt you any if you did use it, but it really depends mostly on where you are going to be spending the most amount of time, low RPM street or high RPM race...

91wtROH17's

Thank's 92. I will be mainly on the street. I think I have pushed my budget to the max, so I will take it easy on the AFR spring's for a year then change them.

camarojoe

Thanks for the replies, even though this thread is about at the end of it's useful life. I didn't talk to Dave again about the engines he supposedly saw that lost hp w/ a rev kit, there's obviously some info that was ommitted when we talked. He did say that generally he doesn't build engines that rev to the moon and when I asked why Joe Sherman uses rev kits, he said "Joe likes to rev the **** out of his engines". Go Figure. Anyway, I've learned this much, get the right Comp or good brand springs that go w/ your cam, and if you plan on revving the **** out of your engine, get the rev kit for insurances purposes.

Gumby

Check out my all new TV reality show.

PISSING CONTEST

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I think the pics explain it all. That part makes 100% sense to me. Maybe it being a called rev or valve float part is wrong. call it a
" parts GM forgot to put in your engine, so here you go" part.

Just cause it works fine with out it does not mean its not needed.

I got a friend who I can not get into his head that plugs need to be tight. His lawnmower, 4 wheelers, mini bike all have a finger tight plug. Oh he will swear up one side and down the other, star it up and ride wheelies up n down the block to rove you wrong" but still, just cause they run good, doesn't mean its right.

I see just a stupid pissing contest even though the parts look like they belong there. depending on the tiny *** spring inside the lifter is dumb. If your gonna be doing hi R's all the time, a seprate bigger/better spring that controls yout hydrolic lifter, make total sense.


Matt

Black363IROCZ

i run a solid roller. enough out of you.

MrDude_1

you still havent figured out what the HYDRA in hydra rev stands for eh?

TRAXION

... and there ya have it. Anybody who doesn't understand this is just stupid. To combat high RPM problems you need heavy springs to keep the lifter in contact with the cam AND to control the valve. With hydraulic setups you CANNOT just run really stiff spring. It will collapse the lifter. Thus, you can split the spring pressures up so that one spring (hydrarev) is helping with lifter-to-cam contact and the main valvespring can be a lighter spring because now it doesn't have to control as much lifter-to-cam contact because the hydrarev spring is helping that out.

Tim

camarojoe

Tim, that is the best simple description I've read. It states perfectly what I already thought the hydra rev kits were for. What rpm do you think a rev kit is a must for? Or what rpm is it okay to go to when not having a rev kit? I'm assuming that anyone that's deciding to get a hydra rev kit has the correct springs when I say this, not the stock AFR springs.

TRAXION

IMHO, if you have everything setup correctly, than 6500-6700rpms isn't a problem. This ASSumes good lifters, titanium retainers, and reasonable valve weights. I've 'heard' of people getting 7000rpms out of a setup without a hydrarev. I haven't seen this ... but I do think it is possible so long as you use VERY light valvetrain components. The biggest thing that people forget about when selecting a spring is weight of the valves. Nobody ever mentions that. But, it is extremely important. You can hypothetically pick a spring that the cam manufacturer recommends but if you run a really heavy valve then the spring won't control it and you will float THE VALVES. 7000 could probably be attained with some light valves ... like the sodium filled LS1 valves.

I personally like the rev kit for safety - not for performance. If by chance you do break a valvespring then the lifter will not be rocketed out of the bore - and it won't become a nice chunk of steel to bounce around your engine.

Tim

92 zzz28

Good call...I feel the same way...

How much is peace of mind worth when pushing an engine hard everyday...

383backinblack

there are chevy v8s with hydraulic lifters that get up to 7000rpm without the aid of a rev kit....a properly balanced engine with the right combination of valve hardware (no, not titanium locks and retainers) will rev that high with no problems.

it happens every day...if you dont think it does, you arent spending enough time at the the race track