Roller or flat tappet?

Hey i wanted to know from anyone out there who has done a tbi build or know someone that has done it. I have a 94 non roller 350 chevy truck engine it has been bored 40 over and the heads have a 3 angle valve job. Now i am about to start on the assembly and i was thinking of going with a roller set-up i know about the retro-fit roller lifters what i dont know is, is there a special cam i need i know about the computer as well so i know i cant go too radical. So iguess my question(s) is/are:

1. Is it worth it to go roller? What can i gain

2. I am going to use my factory heads and just work them and top them off with some comp. cams silver 1.6 ratio rocker arms or should i go with the regular rocker arms or will the comps give me more out of my heads.

3. As Far as performance what should i expect just a ruff estimate

I guess what i am asking for is some advice i want to keep the efi and get good solid performance out of the motor and i am taking any and all suggestions so help me out if you can. Thanx

actually im pretty sure that your block is a roller block, if the lifter bores are taller and machined flat along with three raised bolt bosses for a lifter spider in the lifter galley then you wont have to "retro-fit" in a roller

but really i think for the money the roller in this situation is not worth it, low lift rollers actually have to have more seat duration for the same amount of lift as a flat tappet to keep side loads of the lifters low to increase lifter tappet life, a roller cam will reduce friction and improve mileage but since your talking about having to increase seat duration by 10 degrees for the same amount of lift if it is in the .450 range then that negatively effects mileage, so in theory if the cam's lifts are low and are the same the mileage should be close to the same and even if the roller was slightly better it wouldnt be worth the $600 if you ask me to make it a roller.

comp cams sells cams for the computerized engines specifically, i myself dont know why if they have wider LDA's to decrease overlap so MAP sensors arent screwed up or what but maybe someone else can help you with this question

I cant seem to find the need for a higher ratio rocker, they increase power if the engine is undercammed or if it needs help ridding exhaust but if it is a daily driver they will increase valve guide wear and depending on how big you cam they increase overlap area and may have a slight negative impact on mileage, roller rockers arent cheap and arent worth that much power, only if your lift is over .500 will rollers be required to help in keeping wear down for a street engine, if your keeping lift down for a daily driver type engine then prep a good set of stamped steel rockers and id call it good

im sorry i dont know much about the EFI of the pickup if the stock tune can be used or something has to be done to tune for the increased airflow, hopefully someone else can help

you arent giving anywhere close to enough specs for a HP/TQ estimate, even for my out-dated dyno software your number of specs are still way short

This is a well traveled road. Let’s start with the heads these are swirl port 14102191 or 14102193 castings. Take a look and check this out. These are low compression heads of about 74 to 76 cc in the chamber combined with a full dish piston. This makes a rather lazy chamber in terms of squish and quench. You really need to get compression and agitation up. The heads can be milled .030/.040 which will add about half a ratio. This helps compression but does nothing for squish and quench. A digression into squish and quench, these are two processes of developing mechanical octane into the engine discovered by Sir Harry Ricardo back in the 1920s and reported in his monstrous 2 volume works “The High Speed Internal Combustion Engine”. To make both squish and quench effective the piston should close to within .040 to .080 inch of the head’s step. This cannot happen with a full dish piston, you need either a flat top or “D” dish piston. The selection will be based upon the volume needed to maintain a livable compression ratio for the fuel you want to use. The concepts of compression and squish/quench need to be separated. While a relation ship exists, these are different functions that would prefer different engineering solutions. The factory mixed these functions because of economics not engineering. They use a full dish piston that can be put into the left or right bank cylinders. This doubles the production quantity you can get off a set of tooling and cuts the cost of part numbering and tracking/cataloging in half. This decision has nothing to do with giving you more power, better fuel economy or lower emissions. In simple terms more compression nets better power and improved fuel economy. The down side is that more compression also nets more nitrogen oxide (NOx) pollutants.   Squish and quench are functions that happen as the piston closes thru Top Dead Center (TDC). Squish happens first and before ignition. As the piston closes toward TDC the mixture is trapped between the piston and the squish/quench step of the head. The mixture is ejected from this area toward the sparkplug giving the mixture one really good last stir. The resulting turbulence causes the mixture to burn faster and more completely, this produces more energy and reduces fuel consumption by not throwing unburnt fuel out the exhaust. It also lowers unburnt hydrocarbon (HC) and carbon monoxide (CO) pollutants. The quench function occurs as the burn speeds across the chamber gathering temperature as it goes. If the temperature is unrestricted at some point the combination of temperature and pressure become sufficient that the mixture ahead of the flame front explodes, thus detonation occurs. The quench function of the piston and the head’s step being very close together results in an area of high surface area to volume. This cools the late burn mixture and keeps it from exploding ahead of the flame front. This is good by preventing power loss through detonation. It also helps hold NOx emissions down as these form at higher temps, but adds to HC and CO emissions by slowing or stopping the chemical reactions of the late cycle burn. Unfortunately this is an evil that has to be lived with.

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The swirl port head has a lot of similarity to the cast iron L-98. It represents a midway step between the earlier SMOG heads and the later fastburn heads like the Vortec, Fastburn, and the LT-1&4. It has a fair chamber where the sparkplug is moved inward, upward, and toward the exhaust valve. This does a lot to improve burn characteristics. It does not include the step side beak, nor the slightly sunk exhaust valve of the later heads which helps provide better control of the mixture within the chamber. These heads include a vane attached to the intake guide to force better swirl from what are rather lazy ports. The swirl is a good thing the method of obtaining it is not. Depending upon your gearing and how you drive there are some things you may want to do, unfortunately it sounds like you already rebuilt the heads so taking the valves out and carving ports may not be the most desirable thing at this point. If you cruise around 2000 rpm and or load the truck heavily all the time, you may want to  just leave the vanes alone for the better low speed swirl they produce. If you want to move the power band up, or the truck runs more like 3000 revs at cruise and or doesn’t carry heavy loads all the time, you can just carve the vane out. This really wakes the engine up over 4000 revs. Certainly porting the intakes will do a lot to induce great swirl by enlarging and raising the port along the cylinder side wall (that’s the wall that commonly divides the intake port pairs. This process would include enlarging the area between the guide and the wall on this same side. On the exhaust side putting a nice streamline shape on the guide and angling the short side radius back a bit helps a lot. On the port wall common to the cylinder wall side it’s good to enlarge this a bit widening the area past the guide and blending this smoothly back to the original shape and size at the manifold face. Streamlining the guide helps the flow to pass it. Cutting the short side radius back helps keep that flow from throttling the long side flow. Enlarging the cylinder wall side of the port wall increases capacity on the side where the major flow is already occurring.

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A roller cam with same/similar timing to your current cam is probably worth 5 to 10 HP up on the top end through friction reduction. The real reason the factory went to a roller cam was not friction reduction but rather to allow the oil companies to reduce zinc based additives which the EPA was mandating. The additives provide “boundary” lubrication for rubbing surfaces like cam lobes to flat tappet lifters. The reduction of this additive in post G level oils risks excessive wear between these parts an issue the SBC already had. Roller rockers fall in the same category, roller 1.5s might add a couple ponies, 1.6s would probably pick up 10 to 15 depending on the cam. Their effectiveness on a 350 goes away as the .050 timing gets above 230 degrees. Roller rockers do take a lot of the binding loads off the valve stem, but whether the added life is justified by the cost, I don’t know. This is a place where your check book should be your guide. The cam you can run is going to be managed by the TBI. TBI needs pretty good manifold vacuum differentials. As the cam gets wilder, idle vacuum is reduced and the differential between idle and WOT vacuum gets too small for the sensors to read closely. Edlebrock seems to think that 195 on the intake and 214 for exhaust is about the limit for TBI to also pass emissions. A cam like this with about 9.5 compression, 1.5 rockers and a custom chip should deliver about 300 horsepower. Comp thinks that a cam like the 252AH-12 is it for TBI and emissions. It bumps the valves at 206 in and 212 out, a little hotter than the Edlebrock. Angle between the lobes is important. More LSA will allow a bit more duration as the long LSA cuts down on overlap which will help vacuum. The Comp cam will push the ponies up to maybe 320 on the engine previously configured.

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This will require a custom chip.

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http://www.fastchip.com/

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http://www.hypertech-inc.com/

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http://www.superchips.com/

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http://www.kcspeed.com/

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http://www.jetchip.com/

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You may want more intake area with a 2 inch bore TBI such as the Holley 502-6, a GM unit from a 454 or have yours bored out  http://www.turbocity.com/

Bogie

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 THe roller cam is definately worth the money. Having done it both ways I can tell you that given identical duration numbers the roller cam will produce more power/ torque. Friction is horse power consumed, i.e. not usefull to make the truck go forward, but wasted entirely.

Roller rockers are also one of the cheaper ways to reduce friction. They are also not that expensive any more. 1.6 or 1.5 to one saves the same amount of friction but get the right cam and use 1.5 to 1 rockers if you can. They are easier on your rocker studs.

Don't forget, If you really want to be happy with your project have the computer custom tuned to your application.

The real benefit of a roller is to get the valve off the seat quicker vs. a flat tappet.  Any power gain comes primarily through enhanced valve timing not a reduction in friction (which is negligible).  A fair comparison between a roller and tappet cam with identical duration is nearly impossible because in all likelyhood the roller will have less lobe intensity (valve opening is quicker) and greater total valve lift.

While it's true roller rockers reduce friction, their benefit is in the form of heat reduction (less friction) not inertia reduction.  Again, any power gain through the use of rollers vs. traditional rockers is negligible.  Their true intention is to be used in high-rpm or endurance mills.  Beware of those advertisement claiming +30hp gains by swapping in 1.5 rollers in lieu of OEM 1.5 rockers. 

Caveat Emptor.

Valves that are on the seat do not allow much airflow. the faster you get them of the better! It takes a roller cam OR more duration to do that. Roller cams offer more time / distance of the seat for the same duration, No ifs ands or buts.

JCharlieM is correct a fair comparison between roller cams and flat tappet cams isn't possible. THERE IS NO comparison, rollers ARE better. Find a true high performance car without them.

Any reduction in friction comes at a price. Roller rockers reduce  the side loading of your valves against their guides as well as the friction points on the rockers themselves. Their smoother operation is also easier on the hydrualic lifter internals. Roller rockers are cheap. Roller camshaft bearings are not, yet.

rockers are a good buy. roller cambearings probably not.

"Find a true high performance car without them."

Hmm.  Should first-gen Z/28s, LT-1 'Vettes, Boss Mustangs, Hemi Cudas, 6-pack 440 Roadrunners and LS6 Chevelles not apply?  Heck, I have a 600hp n/a itsy-bitsy small-block Chevelle in my garage with a flat tappet stick.  Does the 11.20 e.t. not qualify as high performance?...  Perhaps not.

Peace.  

Valves that are on the seat do not allow much airflow. the faster you get them off the better! It takes a roller cam OR more duration to do that. Roller cams offer more time / distance of the seat for the same duration, No ifs ands or buts.

more duration to do that, uh no, it takes lifter acceleration to do that, which with lower valve lifts hydraulic rollers have less lift for the same amount of duration than a flat tappet due to increased acceleration for a roller means more side-loads which is not good for long term reliability, as david vizard would state it, "rollers are acceleration limited, and flat tappets are velocity limited. Due to this reason it would of been smarter for low-performance vehicles that GM still use a flat tappet, but they were forced to use roller tappets because zinc being taken out of oils, not to gain power, because as i remember Charles saying (oh yeah and i believe what he says and you should too) that the power increase from reduction in friction with roller lifters is minor and can be negated

JCharlieM is correct a fair comparison between roller cams and flat tappet cams isn't possible. THERE IS NO comparison, rollers ARE better. Find a true high performance car without them.

you listen to way too much hype! check out these engines, here, PHR's engine master competition includes in the rules flat tappet cams, naturally aspirated, 470 cube limit, pump gas, ect and they're making 700+ HP with high and flat torque curves, and if you want to look for even more horsepower (but not as good of a torque curve) look at nextel cup cars with 830 HP i believe they're saying now. Of course at the high end of the scale, like blazing fast times, lift over .750 rollers are better and the only way in extreme situations but it's not like flat tappets are totally useless anymore as you try to put across!

Roller rockers are cheap

when did something that costs at least $200 and gains 5 HP on a mild engine become cheap!

rockers are a good buy. roller cambearings probably not.

if you ask me roller rockers arent a good buy for a street engine with under or around .500 lift, steadily over .500 lift yes they are, but if we'are talking about good buys we arent talking about race engines because then high dollar items start to become necessities anyway, yes roller cam bearings arent usually a good buy for a street engine unless your talking about 460 fords,  thank god this is a CHEVY mag board, hehe

JCharlieM is correct a fair comparison between roller cams and flat tappet cams isn't possible. THERE IS NO comparison, rollers ARE better. Find a true high performance car without them.

Any reduction in friction comes at a price

IMO-Apples to Oranges=There is very little friction on a flat tappet, if there was a lot of friction the cam would go flat, there is more friction in the roller bearings then a thin film of oil that a flat tappet cam rides on. Rollers have an advantage of increase spring preasure resulting in more aggressive cam profiles and not having the lifter float off the cam at higher rpm. Roller lifters as well as roller cam bearings can handle higher spring loads.

Yes there were many legends of both the race track and the street scene running on flat tappet cams. That was then. Back then making gobs of horse power came with streetabilty compromises that today aren't necessary.

Besides my boss has an LT-1 vette, I'll take hime anytime with the A/C ON.

If you like flat tappet cams, keep using them. Peace

Back then making gobs of horse power came with streetabilty compromises that today aren't necessary.

you think that a flat tappet cam compromises streetability, oh so spending $600 less for the virtually the same power is compromising streetability, i have to disagree, it is true that rollers help mileage some but still not enough for me, and if it is a fairly high performance build mileage usually cant be brought into the equation anyway

I'm adding the rest of my message as this moring I saw it had been truncated:

Edlebrock seems to think that 195 on the intake and 214 for exhaust is about the limit for TBI to also pass emissions. A cam like this with about 9.5 compression, 1.5 rockers and a custom chip should deliver about 300 horsepower. Comp thinks that a cam like the 252AH-12 is it for TBI and emissions. It bumps the valves at 206 in and 212 out, a little hotter than the Edlebrock. Angle between the lobes is important. More LSA will allow a bit more duration as the long LSA cuts down on overlap which will help vacuum. The Comp cam will push the ponies up to maybe 320 on the engine previously configured.

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This will require a custom chip.

> >

http://www.fastchip.com/

> >

http://www.hypertech-inc.com/

> >

http://www.superchips.com/

> >

http://www.kcspeed.com/

> >

http://www.jetchip.com/

> >

You may want more intake area with a 2 inch bore TBI such as the Holley 502-6, a GM unit from a 454 or have yours bored out  http://www.turbocity.com/

> >

Bogie

With fuel injection, modern cam profiles ( both roller and non-roller ), and other friction reduction techniques the factories are producing cars that have pretty good power AND get reasonable mileage!

I try when possible to incorporate these ideas in my buildups so they are more fun to drive passed the gas station. I don't acheive ALL the benifit but I don't have the R&D budget or bills to match them.

I tried two Comp Cams Xtreme energy grinds. The first a flat tappet, With .477/.480" lifts respectively.

The second a roller with .480/.487" lifts. Both running 110 degree LSA and installed on the 106 degree centerline.

The roller produced that lift with less duration and was easier to tune ( that truck does not yet have fuel injection, it would be easier to tune with injection, IMHO ). It lights up all four tires on the back even with 15 psi in the tires, at will. I pulled a chevy II on a car trailer last night and the engine didn't really notice the extra 4000 pounds.

I've done it both ways, I think bol1500's project is a good candidate for the roller. But I won't try to make you buy one.

ACAJOE

Hey Bogie i am greatful for the info. I already have a "super-chip" custom made at the local performance shop here. I guess what i am asking is what should i expect out of this motor and if you had this project which way would you go as i see the the discussion i put up got mixed reviews. I am willing to go either way roller or nonroller it doesnt matter to me but, i dont want to spend gobs of money only to gain a few ponies. I will look in to having my tbi bored out or just buy a bigger one. I am still in the dark with "spuish quench" thing. With it being tbi what kind of pistons should i go for? I know with it being comp-controlled i know my compression needs to be around 9-10.5 inorder to keep the comp happy. Is it wise to mill the heads with the limitations of the comp? Also i know my cam should stay around 210-218 in duration. I am going in circles right now i have this guy that has a set of retro-fit lifters and i am holding him up so i wont be buying something thats not worth it.  help me out i am open to any suggestions and i know i cant build a 400 horse monster now that i have  read and  listened to others but, i want to be able to hold my own along side any mustang or import thanx in advance.  

While I really like roller cams and rockers, in your case I just can’t justify the expense for a warmed up street engine that doesn’t have provisions for the factory roller cam and aftermarket roller cams and especially lifters are really expensive. If you can get a deal on a used set up that’s one thing but new, especially for a mild roller that you require is hardly worth the expense.