bnoon

The cam has been a nice overall gain, but knowing full well that better cams could be had used for the same that this one was new, I'd have chosen a different route that's for sure. The cam runs fine with an idle just a bit on the lopey side, but not nearly as wild as some were making it out to be when I first told you which one I had chosen. She still pulls enough vacuum to run the power brakes, which actually surprised me quite a bit. The one thing it needs now is a full tune job to maximize any gains on top of what's already been provided (as any big cam jump would). It will also help the rich idle that I've had to temporarily compensate for until my chip burning equipment gets here. All in all it was a good experience overall, aside from tearing the timing cover gasket and waiting until the next day to go get another one to finish the installation today.

Just FYI, the summit cam specs are:

280/280 single profile advertised duration

224/224 @ .050

.465/.465 lift

114' lobe separation

kevinc

Congrats on the install, but if you want to get into how fine it runs post a timeslip or dyno graph...

NastyL98_T/A

That's a little cam. It's not nearly as outrageous as some of the cams we're putting in cars at the shop. Anyway, who told you it was too big?

Ions91Z28

Yea, that's a pretty small cam, not to mention pretty wide LSA. Should be fine in terms of vacuum. I don't see anything at all large about that cam, but congrats on it working.

bnoon

They were saying that the wide lobe separation would be to much for the computer to handle and that it would idle like a Pro-stock dragster. Do a search by my user name and Summit 1104 and I'll bet it comes up. By the standards I was used to, the wide separation and long duration just gives it a wider power band. I chose the low lift along with tha combination since this was mostly just a preventative maintenance swap for the timing gears while I was changing the water pump out (might as well have since I was in there). The stock almost 100,000 miles heads were left untouched as was the stock bottom end (since the car holds good pressure and doesn't leak or burn oil to badly for a "beater")

As for the car running fine, it ran a 15.6 according to the G-tech prior and now runs a 15.4. The two tenths improvement is hardly anything to be proud of because of the tuning needed to bring the combination to it's true potential. At this point, there's something to be said for not loosing any time, especially since I did the SLP runners and P&P on the plenum and base at the same time, which alone would have netted equal or better gains than adding a cam into the mix. I was just happy that I didn't lose anything.

No dyno numbers yet because there isn't a dyno within 3 hours of here... but, we are supposedly having a shop open up this summer with one. I'll be waiting to tune until then for the most part, but getting used to making changes with the tuner until then so that I can at least turn on the fans at a lower temp with the lower stat I used...

For now, the attention turns to installing the stereo and painting the flakey hood and roof...

ImportsRsloths

Sounds pretty mean......!!!

Jim85IROC

iTrader: (2)

I'm not sure who was giving you flack, but a 114lsa isn't a problem for a TPI computer. the wider the better as far as the computer is concerned. You can even run down to a 112lsa without any sort of big issues. My TPI car has a 112lsa.

I assume this is a 350, right?

bnoon

Are you sure, the wider the better? Stock is like a 109 lobe separation, isn't it? The 114 is on the edge of giving up the vacuum because of the overlap, but it still gives enough for the power assist brakes anyway.

This is a 305 TPI, so it is a bit more radical that the same cam would be on a larger small block, but it's still not as bad as some of the people said in this thread.

Jim85IROC

iTrader: (2)

The "peanut" cam had an LSA of 109*, but that cam was so pathetic that it didn't matter. The duration was so short and the lift was so small that there was still virtually no overlap between the intake and exhaust valves.

The better cam (i.e. L98 cam, and also used in the 85 LB9 and 5-speed LB9s) had either a 114.5* or 117* LSA depending on year.

The overlap of the intake & exhaust valves is what the real issue is, but this is most often a result of the LSA when comparing cams of SIMILAR lift and duration.

Let's start with the L98 cam. That cam has reasonable lift and duration, and a somewhat wide LSA. As with any cam, the exhaust valve is still closing when the intake valve begins to open. With all other cam specs being equal, if you were to narrow the LSA, there would be a longer period where both valves were open. This can reduce cylinder pressures and cause less vacuum. It also produces a little bit more power. But, when you go back to the peanut cam, even though the LSA is narrow, the duration of the cam is so small, that the exhaust valve is already pretty much closed before the intake valve starts to open. This would be a lot easier to describe if I had a picture to show.

Jim85IROC

iTrader: (2)

Here we go. This will do the trick:
http://auto.howstuffworks.com/engine.htm

Now, look at the animation. You can see the lobes of the camshaft that open the intake and exhaust valves. The radial distance of the peak of those lobes is the LSA. In the animation, you can see that the exhaust valve is completely closed before the intake valve opens. Now... if you give the intake and exhaust valves more duration without making any more changes, both valves will be open longer and you'll wind up with overlap. Likewise, if you don't change the duration but instead you make the LSA more narrow, there will be overlap.

So... getting back to the peanut cam, even though the LSA is narrow, because the duration is so pathetic, neither valve is open for very long, so the narrow LSA is less of a concern.

Clear as mud? If you're still confused, say so and hopefully somebody that can describe it better than me will chime in.

Ed Maher

I never said it wouldn't run, just that it is way too much cam for a stock headed TPI 305. I'd have to say that a 2 tenth improvement from a cam swap in a peanut cam car illustrates that pretty well. I mean, L98 cam 305s average at least a half second to a second faster than the peanut cars.

BTW, your idle problems could easily be reversion problems through the MAF. Don't be too surprised if no amount of tuning clears it up. What's happeneing is air is actually moving in AND out of the MAF when you're idling, completely fudging up the readings.

Jim85IROC

iTrader: (2)

This is on a 305 with stock heads? Yeah, in that case I agree with ed. Way too much cam.

bnoon

The MAF transfer voltages are all within "normal" voltage readings if this is a 0-5V MAF... where idle is somewhere around .8-1V and WOT is around 4.5V and up... Is there a tech article on checking the MAF readings somewhere? I'll be looking for that... Also, on a similar subject... Can someone reccomend a scanner for this car? Cheaper the better...

The other major thing effecting idle is the poor injectors that I have. I cleaned them up, put new pintle caps on, and new O-rings, but fear I made them worse than they were previously by busting off two of the fountain shaped center metal tips while changing the pintle caps. My other injector sets (Bosch sets 24#, 36#, and 42# for Ford vehicles) didn't have such things and I didn't even notice the little buggers until I got to the third one. Salvage yard, here I come... Without the little metal tip, fuel just puddles in the pintle cap on these injectors because the tip is made to fan out the fuel flow though the opening in the pintle cap... major faux pas on my part...

GofasterFirebird

iTrader: (3)

Did you degree it? Maybe they sent you the wrong cam. What is the basis for your "nice overall gain?"

Jim85IROC

iTrader: (2)

It sounds faster.

bnoon

Yes, it is degreed to double check everything, with a new double roller chain and gears, but set straight up. The cam is packaged correctly as an 1104, the duration and lift checked out on the aluminum V-blocks and a dial indicator (using a degree wheel for duration), as best as my eyes could see using those tools anyway.

The basis for being a nice overall gain is because I gained two tenths on my average G-tech runs through the normal "testing grounds" I always use to test at. This is without programming a new chip AND with two broken off metal fountain shaped tips off of the injectors (located under the pintle caps, didn't know they were there when pulling off the old ones until I got to the third injector, DOH!). Those broken tips make it load up really rich under certain throttle/load positions because the fuel puddles in the injector and then on the back side of the intake valve. When the car is dead cold, she runs much better because the extra puddling fuel doesn't load it up quite so bad as it does once it's warmed up.

BTW Jim, it does "sound faster" as well. The wider lobe separation and slightly higher lift gives the exhaust a nice little growl it didn't have before.

Even still, this thing is a pooch. Not fast enough to be fun yet even, but we'll see what the programming and new injectors can do for it in the future.