bill_lee_3

First off, I've done some searching, but can't seem to find the right information.
I was given a 283 that I'm building for a project. I'm putting vortec heads from an 88 305 and also the tpi setup from the 88 305. I am wanting to put a different cam in it tho. I called lunati and they recomended the 60100 cam, which has a lift of 437/454, duration of 250/256, @.50 207/213. I am wanting a bit of a lopey idle. Will this give it to me? He also told me that I might have to clearance the head because the lift is over 450.
I know a bunch of people are going to tell me to ditch the 283 and get a 350, but I already have one. I want to build the 283 for my s10. It has less of a stroke and is faster revving. Plus, it is different. I'm not looking for a whole lot of power, just something that is streetable.
Any help would be great.
Thanks.
Just let me know if you need any more information.

Rolling Thunder

Hard to say. Its not a crazy radical cam but it is a small motor which tends to be effected more by big cams. The biggest factor is the overlap and the amount of overlap is a function of the lobe separation angle which isnt listed. Course even with that it would only be a guess and a guess based on what we thing you think is a bit of a lopey idle. The thing is the cam specs that would give it that kind of idle dont really go along with something that would be particularly streetable especially since its such a small motor as there less tolerant to big cams than larger motors.

watajob

iTrader: (29)

The bore of a 305 is smaller than a 283 so I don't think valve/wall interference will be an issue at those lift levels. And, heads from an 88 will not be vortecs but probably swirl ports.

Rolling Thunder

I dont believe hes talking about valve to cylinder clearance hes talking about the cylinder head themselves accommodating such lift which with vortec heads .454 is pushing it without any machine work. Although you do bring up a good point no vortec heads in 88 lol.

bill_lee_3

What is the difference between vortec heads and swirl port heads?
I decided to go with a different cam. specs- Advertised Duration 262/272, Lift .420/.442, Duration at 050 204/214, 112 lobe seperation.
From what I have read, that should be fine.
Please help me out.
Thanks, Bill

Rolling Thunder

Personally i think to highly of that cam. Reason being note how much of a difference there is between the advertised and at .050 duration there is. What this means is the cams ramp rate will be very lazy. Why is this important? Obviously the further open the valve is the more it will flow to a certain point. Because of this you want that valve to open as fast as possible to give you the greatest "area under the curve." That cams ramp rate is kinda lazy which means it will open slower than a more aggressive cam. The difference between vortecs and swirl ports is like night and day beyond the fact they both go on small block chevys. A vortec heads valves are angled differently than your typical sbc head which because of this better design flows much better for a given port size. Swirl ports on the other hand are designed with the classic design angle and also features ribs that try to promote a swirling effect on the intake gasses and does it fairly effectively to create better low end torque and economy. Problem is the dont flow particularly well at all in there stock form as again they are geared twords low end torque and economy. Wouldnt be bad for a tame street motor but with that cam it is a complete miss match. Youve got a cam designed to perform well in the high RPMs and heads that are designed to perform well in the low RPMs. Although logically it would seem that the two would kinda balance each other out but on to the contrary it just means it will do nothing well. The low end torque and economy will be sacrificed due to the cam that doesn't perform well int the low RPMs. Then in the high RPMs when the cam would really start to take off it cant because the heads dont flow enough to allow it to take advantage of the radical cam leading to poor high end performance. Further more that cam has no overlap and wont give you that nice choppy idle because the lobe separation angle is so wide.

bill_lee_3

I think I might have found a better set of heads. They are casting number 14014416. They are from a 85/86 305. The combustion chamber is real close to those of the 283, 60cc for the 283 vs. 58cc for these.
I know I will have to alter the intake to accept these heads, but that isn't hard. On that note, I was talking to a buddy of mine who recently had a 383 built for him. The engine builder never uses the center 2 bolts on both sides of the intake, he always just silicones them up. I am not to sure of this, but he has ran the **** out of this motor and nothing has happened. Any feedback on this?
I have checked some of the flow numbers on these heads and they aren't bad, especially with a mild port/polish job.
Let me know what ya think.

ploegi

They put those bolt holes there for a reason. I would be far more likely to trust the GM engineers decision to put them there, rather that some guy, engine builder or no. To me, that just sounds like someone that is half-assing the job.

bill_lee_3

That is kinda what I was thinking.
Does anybody know where to get the adapters so the bolts will sit flush on the intake when redrilled?

Chevy86 IROC-Z

iTrader: (17)

STOP!!!!!
Sorry for yelling. If you get a cam that is lopey, you'll run into ECM problems. The ECM is programmed right? So if the sensors sense a bad vacuum, the ECM will begin to try to fix the vacuum problem by sending false currents to lets say the fuel injectors, the electronically controlled dizzy. I dont know if you can have a custom PROM burnt to such modifications. Notice that most lopey cars are carbed. This is because they lack an ECM. The ECM plays a huge roll in managing fuel on our EFI systems to where as in a crabed system there is the mechanical fuel pump that is driven soley by the camshaft. I would call a DYNO shop to see if there is room for a custom PROM. If you visit Summit Racing on the net, choose any cam and towards the bottom you see whether or not it is "computer controlled," meaning if it falls within the ECM's specs.

Orr89RocZ

iTrader: (20)

Cam is fine for the 283..get it on a 110-112 lsa and it will be fine. Similar in spec to the L98/LB9 cams but much more aggressive ramp rate. On that 283, should peak near 5000rpm with TPI. Should be a good motor, similar to the 305 TPI cars but maybe abit less power due to less cubes. May go withthe comp cams 212/218 and get abit more lope to it. Should still work good with stock TPI and make decent power. ECM will need tuned regardless. Keep it MAF sensor and it will be easier to tune for this setup. Wont take much change from stock 305 TPI chip to get it to run ok.

As far as heads go, vortecs make more power than the other 2 if you get the intake for vortec heads. Else, run the 305 heads, get them cleaned up and machined for fresh springs that can handle lift. 1.6 rocker that cam and let it eat if the piston/valve clearance is ok.