JAKE

"Straight Up" can be confusing. It doesn't mean just merely aligning the dots. Most cams come with advance ground in it from the supplier. So to be installed "straight up", the cam would have to be installed in the retarded position equal to the amount of advance ground in at the factory.

With my cam, for instance, it's ground on 113 LSA but when I degreed it in, using the Lobe CenterLine Method, it checked at 108.5, showing the cam had 4.5 degrees of advance ground in at the factory. In order for it to be installed "straight up" I would have had to install it 4.5 degrees in the retard position.

BTW, since there is no 1/2 degree bushing, I would have to choose between a 5 degree OR 4 degree bushing. That would have put the cam within 1/2 degree of being "straight up".

He has to be getting that lift with rocker ratio, like I am (.612/.610). I've never seen a cam with 224/230 at .050 having that much valve lift using a stock, 1.5 ratio, rocker arm. The ramps would be too radical and aggressive for that much lift with such short duration.

According to CompCams, it's better to get your lift with rocker ratio anyway.

Jake

STL94LT1

Jake, both of my cams had 2* advance built in. So, you are technically correct, they weren't installed straight up.

Yes, my 605/622 lift is with a higher rocker ratio (1.6).

biggrizzly

Man - you guys are making me dizzy!!

I have decided to back off this cam decision for a while and give it a lot more thought. After work today I chatted with the guy over at the shop that recommended the cam, and although he still insisted it was a great choice, he did back-peddle somewhat when I was armed with a little bit of knowledge and information. He also agreed that the duration was a bit wide for some applications, but that was what made this grind good. He also pulled back a little by telling me that he recommended the cam believing I had more racing expectations than tooling around town since I had told him that this was not my DD and I only used it on weekends and at club events. Perhaps that could have been construed as such. Anyhow, I feel like I had given him enough information to get me going. As a "Newb" to LT1 hop-ups perhaps my strategy has been all wrong.
I thought that in my first few posts I made it clear what I intended to use this car for, but perhaps that got lost somewhere.

So starting again --- I'd like to finish my project that I started with a car that can be driven on a long trip if desired, (Corvette Events) or vacations to the beach, and can still be run at occasional drag strip events held a couple times a year by my club and get the respect a great C4 ought to get from the faster C5 cars. I would like to be around the 350RWHP level and be able to run mid 12 seconds if that is possible. Being ruled by my financial baroness I can't spend any more money than I can scrape up from paycheck to paycheck and am truly limited on my overall budget to around a couple grand at the most.

I just pulled the other exhaust manifold and am removing the heads either tonight or tomorrow and plan to take them into the machine shop next week. The shop doing the machine work on the heads IS NOT the same people that recommended the Lunati custom grind I started this thread with. They are a long time respected shop in my area. LINK to Website
I what information do I need to take to the machine shop with me on Monday when I take the heads? should I just tell them I want a 12 second Z06 Killer? Only kidding When I talked to the guy at the machine shop yesterday, he was very courteous and answered all my questions, but he really couldn't tell me much until I got the heads in there and we talked about what I want to do. I told him I wanted the heads ported, he said that they do a "street / strip" port job and then you can do an all out performance competition type job depending on your application. I told him I was probably interested in the street/strip version. This is when he told me that they will do bowl work, deshroud the area around the valves, and back cut the valves. This info is found on their website. He told me that a guesstimate cost for the worked heads assembled would be around $800. He said we could talk about cam at that time too. I did not tell him anything about the Lunati custom grind cam, as that was a total after thought.
Anyhow - I'm just rambling again and I need to get out in the garage and try to remove those banjo fittings on the back of the heads!!!
Later

tequilaboy

If this hasn't been mentioned already you may want to check out one of Lloyd Elliot's packages.

http://www.eportworks.com/lt1.html

bobmic93

I remember being very nervous about the cam that my guys wanted me to put in. Started doing a lot of research and learn what I could. We here on the forum are vette enthusiast and can share experiences with h/c's and porters. Who knows best, would be the guy who builds performance cars for a living and sees what works and what doesnt. Who else knows something about cams would be your tuner as he deals with cam specs for a accurate tune.

anesthes

Hrmm. Lets take things one at a time.

'straight up' means just that. If comp grinds the cam at 106 degrees (2 degrees advanced) when installed straight up the intake centerline will be at 106 degrees. If its ground on 108 degrees, thats where it will be. You can advance it with offset bushings, but we're talking about whats actually ground into the cam at 'straight up'.

On his cam, I assumed he was running an XR268 (though his specs don't seem to match that actually, or any cam I can find now that I think about it...weird) which is ground at 108* ICA. So I was pretty much asking "did you install it straight up, or advance/retard it? (what was the ica?)". Sorry for the confusion.

I'm assuming based on your specs you are running the 280XFI HR13 camshaft?

I cannot find the spec card, but usually comp grinds them on 106 or 108 degrees. If your degreeing it at 108.5 I'm guessing its ground on 108 and your timing set is slightly off. (mine was off by 1 degree advanced).

Now i'm confused about what your saying about 'straight up' being 4.5 degrees retarded on your cam, which is at 108.5 degrees.. The lobe seperation angle has absolutely nothing to do with the intake lobe centerline. Or are you suggesting SBC 'stock' intake centerlines are 113 degrees? I've always known stock to be 108 degrees. ?

As far as the lift goes, the cam I thought he was running has .330/.335 tappet lift, so even with 1.6 rockers thats .528/.536 so I don't know what cam he is running... (but i'd like to know).

And the reason I asked how his cam was installed is, because as we all know, advancing a cam tends to move the powerband up a hair. Though comp claims the cam I thought he was running does infact make power to 5800. *shrug*.

-- Joe

anesthes

So they were both installed at 106* ? Whats the part # and grind number of your cams? I'm curious now, and am going to lose sleep over this.

This is the kind of tech stuff I love hashing over with guys. Engine math keeps ya thinking.

-- Joe

anesthes

To put things very simple, heres how it works:

We need to know the specs of your shortblock.
We need to know the final head volume after any work is done.
We need to know what gear ratio your going with
We need to know what RPM RANGE you want to drive the car in
We need to know what type of octane you will be using.

With most of that answered, we can 'help you' (not tell you) what will work, and what won't. Operating range + DCR are VERY important. A 9:1 motor with the wrong cam will detonate quicker than a 10.5:1 motor with the right cam. The suggestions you got today were more of "this works for what you want".

When I built my motor I went with a big cam and was considering shifting at 6500+ at the track. But the car is miserable to drive on the street AND the DCR is soo low it makes almost now power below the cams operating range. It was a bad decision on my part. If I had another half point or so of compression (static), which would bring the DCR up, and was running 3.73 or 4.11 gears the cam would be PERFECT. But if I shave the heads any more I won't have a combustion chamber. haha.

-- Joe

STL94LT1

I will look up my cam card tomorrow. Both of the cams were custom grinds.

anesthes

Ohhhhh.. Ok. That answers that.. See I got confused cuz you suggested one cam, but then you listed your specs and I was like "wtf??" Cuz they were way different. My bad!

-- Joe

STL94LT1

Sorry about the confusion.

-Mike

SK.LT1

I am currently running this cam and it works great.My car is a `96 LT-1 automatic with the stock 3.07 rear end,AFR 180 pre elimintor heads,and shorty headers going into stock exhaust.With this set up,it pulls very strong and fast to about 6300 rpms, and has very good street manners,idles at just about 850.Hope this helps.

anesthes

Hrmm.. It pulls until 6300?

-- Joe

mseven

I'm guessing that the idea there was that because a motor will rev to 63-64 that it's making power.... Mine will rev.to 63+,the cam is done around 6k., The only reason I can see to push it to 62 at that point is for the drop in rpm 1-2 shift based on ratio in an a-4.

anesthes

Perhaps. A dyno sheet would help us see whats really going on with his car. I'm sticking to what I've observed over the years, that generally sub 230 degree cams operate below 6000 rpm. There are some slight differences due to tappet type (hydraulic roller vs flat tappet vs solid) and ramp designs, and how advanced the cam is. But still..

-- Joe

mseven

In general I agree w/your statement/opinion. The best I have seen w/less cam, that were well documented 350's (using the HC on a dyno-jet) had made max. power at 62k.

vettin_it

Ok so ive seen the hot cam suggested and also the comp 268XFI.

the duration on both is very similar with exhaust a little lower for the comp cam.
But the lift is way more on the comp cam 0.570/0.565 compared to 0.492/0.492
So what kind of effect would that have????

BADDUCK

Hotcam total lift with 1.6 rockers is .525/.525

vettin_it

could I run the 268XFI with 1.6 rockers and still be streetable? that sounds like a lot of lift to me!

STL94LT1

Joe, I tuned another forum member's (Topload) LT1. He iwas running AFR 190 heads and the lower lift 218/224 cam. His dyno sheet looks almost exactly like mine, still making power over 6k.