A turbo'd car with a CAM question

[blackbombshell95]

now i'm doing my top end swap here soon. as i am getting closer and closer to getting all the parts i need.

now if i use my regrinded cam and install a turbo later will that affect my overall performance?? This is what i am being told.

i'm trying to remember the measurements of the regrind.
oh ya here they are
#1461-- 206/212, .282/.292 lift @112 i'm not sure how of an aggressive regrind it is. i wonder how aggressive it is?

[donk_316]

Im working on some specs for a good turbo grind on a 3400. Ill post what i find as i get deeper. Your cam doesnt look really agressive at all.

[blackbombshell95]

ok. th ink it would hurt my car if i had a turbo setup?

[Froggx]

It doesn't look too agressive, then you realize our ls sucks hard with only 112 degrees. That would introduce more valve overlap than I was comfortable with when I ordered my regrind, which I am planning around a turbo. You have to realize the stock cam is pretty good for boost, I saw somewhere where it supports up to around 6500 rpm well enough with air being forced in Also, your split is backwards. In a turbo motor, it's better to have more duration and lift on the intake side to promote more time for cylinder filling then to keep the exhaust gas velocity up and attempt to avoid reversion with less duration and lift on the exhaust side. I have no idea if that's TOO agressive though, not enough people go for cam regrinds as well as turbos to know what really works and what doesn't.

Of course, this is assuming you're using aluminum heads and you have a hydralic roller camshaft. If this isn't the case, ignore everything I've said about it possibly being too much duration.

[blackbombshell95]

I'm going to be using the 3400 aluminum heads. Once again they will be P&P also with the plenum.

Well, it will be about 4 months before i can touch a turbo for my car. And by then hopefully u will come up with a cam for a turbo 3400. so anyways when I install the turbo i have to go inside and install the bigger injectors anyways.

[dbtk2]

Obviously, you can't get a perfect cam with a regrind, but that cam won't be bad with a turbo, and it will definately be better than stock. It looks very similar to my cam. My cam is .2847 intake/.3027 exhaust lift. 204 intake duration/216 exhaust duration. 112 LSA. It is actually designated as a mild turbo cam. It seems to me like more exhaust duration and lift would be better with a turbo cam, because it will help get the exhaust out of the cylinders to spin the turbo, giving you better spool up. Lower intake duration and lift isn't a big deal, because first off, the intake valve flows better than the exhaust anyways, and second, the turbo is forcing air into their.

But anyways, your cam is pretty mild, and will work just fine for a turbocharged or a N/A engine. Obviously its not optimal for a turbo setup, but its not bad, and the car should run pretty well with this cam without the turbo on it.

Shawn

[Froggx]

Yeah, intake duration really isn't all that important since the turbo is always forcing more air in. However, shorter exhaust duration is better because while it seems like you'd get more air out of the cylinder with longer duration, keep in mind that turbo cams avoid overlap, and with the exhaust stroke going without overlap it means only the exhaust valve will be open, which gives the gas only one place to go, out the exhaust side. Spooling a turbo is about heat and gas velocity, a lot of gas moving slowly will spool a turbo less quickly than less gas at a higher speed.

Those are the specs for the crane h-260 cam, are they not? Keep in mind that this is a nonroller camshaft, and what is mild on those is more aggressive on the roller cams because of ramp speeds and such being so much faster on a roller cam.

Edit: just looked at your sig, it is h-260, I need to learn to read.

[dbtk2]

Yeah, I know it will be more aggessive on a roller camshaft, because the ramp rates will be significantly faster, but it is still a pretty mild cam.

And yes, as you already found out, its a crane h-260. Its too mild for me, so in the spring when I get the car back out, 1.6 rockers are going in... I'm just debating on whether I should only put them on the intake, or if I should put them on both intake and exhaust, I'm thinking both, but I'm not sure, and I can't get a straight answer on what is safe valve lift on stock Gen III heads (as far as valve stem clearance goes, etc..).

Shawn

[blackbombshell95]

thanks for the info guys. shawn let me know about the roller rockers. I am very interested. And actually thanks for bring that up. i plan to do rockers during my topend swap. i just don't know of a good set or a part #. i would really appreciate it


btw with my mild regrind, what kind of gains might i expect. i know its a long shot, but any ideas?

[dbtk2]

I would guess gains of about 20hp or so. Probably another 5-10 with 1.6 roller rockers.

Shawn

[blackbombshell95]

ok. so 1.6 roller rockers. I know what rockers are, sort of understand of how they work. But is 1.6 the size or how much they lift??? maybe you can clear this up for me if you don't mind.

Also Shawn do u have a part number for those roller rockers and know where i can buy them at?

[Froggx]

multiply the lift of the cam lobe by the ratio of the rockers (in this case 1.6) and you have your final valve lift

[blackbombshell95]

are they better rockers than 1.6 for our car? or is that plenty. just trying to get an understanding.

[Froggx]

I have not encountered better rockers, you have decent lift on your cam now so I wouldn't be too worried about anything bigger

[dbtk2]

You don't need anything bigger than 1.6 rockers with that setup, it will provide plenty of valve lift. For instance, the stock valve lift on a '95 3100 is like .408" or .412" IIRC. With that cam and 1.6 rockers you will have ~ .451" intake/.467" exhaust lift.

Personally, I am using the Comp Cams 1.6 rockers because they are significantly cheaper than the Crane Cams ones. However, they are only roller tip, whereas the Crane cams ones are roller fulcrum and roller tip. But, you're using the new 3100 topend aren't you? In that case, you can use the stock rockers off that engine, because the 3100's with factory roller fulcrum rockers and all 3400's have 1.6 rockers. So you might not have to buy any at all if you have a complete engine you are getting your topend swap parts from. If you don't have the rockers from the engine, I have some 1.6 rockers from a '97 3100 if you are interested.

Shawn