High Compression 2.8

[rvbilly]

2.8 High Compression

Thanks so much, I`m gonna check it out right now, Bill..

[torq455]

adding 1.6 rockers won't change duration much, espically at .050 where it matters. it wont change the power band like a much larger cam. trust me, i have them. same power band, just more power. you can't put a 4.3 TB on a 2.8 intake. the most you can go is 62mm safely. the 4.3 is 70mm. look at it this way--the LS6 puts out about 430 HP at 6500rpm. it's TB is 75mm and we are adding two more cylinders that are bigger than ours. the guys at TPIS performance told my dad not to waste money on a bigger TB, even with a few mods. as you can see, 70mm on a 2.8 is a waste of time. remember, bigger isn't always better, unless you are planning on boosting and running the 2.8 to 8000+rpm!

[ignoreance]

What Cam Do you have I thought you had the 252H ? Now I'm lookin at the rest of the post and its something other than the 252H? cus those specs are not a comp cam 252H The below figures are based off the 252H

Thats crap that it can't change the duration. take 206/252= percent of duration at .050 right yes you get .81746 for a round off. Then .81746/1.5=.54497 then times that by 1.6 new ratio changing it to .87196 then take and times that back by the total duration 252 and you get a duration of 219.7 hmmmm thats a pretty damn good duration... thats why ratios work. Thats the vantage point of changing the top rockers on a stock camshaft. The one he choose has a fare duration compared to stock. I wouldn't have gone with a square cam (meaning same duration intake and exhaust) myself but thats what he has chosen.

The reason that comp cam is nice it takes it from 252 to 206 right to the point meaning its going to be a real sharp curve the ramp of the cam goes quick. Not like my Crower cam which also has its benefits with 283 but takes all the way to 204 to get to 050. That means you can run quite a bit more compression on it cuss its soft lead in and out and that can bleed off compression. The exhaust is a bit more aggressive on mine with a number of 286 and 214 at .050 .

This engine your dealing with Throttle Body Injection TBI. Its not the same as your MPFI.... So READ and then advice. TBI uses two 43mm Butterflies with the injectors above that. He knows what he is talking about

on the stock manifold and TBI. We have two 1.325 openings one for each side of the engine the Holly or 4.3 TBI increases the size to 1.68 on each venture. This is an IRON HEAD engine... NOT ALUMINUM HEAD. Thats why we take our intake manifolds out two 43mm holes or Standard 1.68

[rvbilly]

2.8 High Compression.

Hi Ignorance , The Comp Cam I had I returned it to my machine shop where I bought it and put the credit against my machine work , I have recently got a cam being ground for me by a well known local company, they are grinding me a 204 Intake 216 Exhaust @ .050 - .435 Intake .450 Exhaust lift for 1.5 Ratio rockers with a 111 LSA and a 107 Intake centerline , almost like the 3.4 Crate motor cam , this will wake up the motor even more than the Comp 252, with roller rockers this cam provides high torque and a better HP. I think 455 Torq was confused on the TBI , Betterthanyou is even offering a bored out 2.8 to 4.3 intake here on the site now, I know it will allow a big improvement on the airflow , I don`t know if I`m going to use 1.5 or 1.6 roller rockers yet, with 1.6 rockers it would yield me .464 and .480 lift with that cam , I don`t really want that much lift , there will only be .038 Quench on my motor and the heads will have a 47 cc chamberso I want too leave room for the valves, I`m still hoping for 175 Hp and about 180 Torque outa this thing , ( flywheel ) Do you know if the 3.4 oil pump with the larger 3/4 in pickup will fit in my S10 pil pan, I haven`t checked that possability out yet , thanks Bill.. got a new avitar done today of my little beast , body is in great condition with all factory options available for $ 500 Canadian...

[rvbilly]

2.8 High Compression

Hi again , I just tryed your Duration math with the new cam and == 1.6 rockers should yield me about 217.6 Intake and 230.4 Exhaust that would make the cam usable between 3000 - 6500 RPM, I think that`s way to radicle for my liking , I think the 1.5 roller rockers would be my best choice , what do ya think ? Bill..

[ignoreance]

Get your toy/transportation running. The rockers can be changed out in about 4 hours. The oil pick up fit in my trooper But I have a 4x4 I guess it depends on the pan you have I think they make two 3/4 pick ups probably one for a camaro and the other for the 4x4 S-10 The pick up that I got with my crate motor was cool. I bought a 3.1 for 800 to the house I couldn't ask for much more I change out the camshaft and stuck 1.5 Crane full rollers on it.

I'm Not sure About the Pick up. Maybe someone else can answer.

I know the cam I picked is small but I got the same issues as you. I want to pass smog. As far as numbers Stock we have 120 and 150. The cam you picked should be good for about 10 and 10 the intake manifold is the real bottle neck opening it up to a new world above 3k rpm's there is probably another 10hp there the torque might stay level but it depends on how you do your intake/Manifold if you really want to open it up you can remove the center divider and make it a single Plane manifold. Headers for the RWD going to get maybe 10hp 7tq then its really put the rest in what type exhaust you run back I would go Dual if you can all the way back and do a H pipe with that small of a motor you could stick with 1 3/4-2" Duals run two cats and emissions will never be and issue. With the Duals you could look at another 7 and 7. Not If but when you decide to go to the 1.5s or 1.6s rollers there is gains there too, like 3hp on the 1.5 rollers and probably about 10-13 on the 1.6s
So I would put you about 165hp and 180tq then its up to tuning and you could gain another 5-7hp and maybe 3-5tq

I want to buy another manifold and drill holes and weld mounts for port injection and try and go all the way to the 454 TBI and strip the injectors off the top of the TB. But thats money and time and both of which I am lacking


Go with the 1.5s for now if you don't like it switch to the 1.6s