QuickVet

I have decided to reduce the size of my cam in hopes to run faster quarter mile times and work better on the street. Sounds funny, I know. However, The cam I am currently using is way to large for my small application. I would like any suggestions you may have for my little 350 ci motor. Here is the current setup:

350 CI stock L48 bottom end
Performer RPM dual plane intake
Holley 750
ZZ4 aluminum L98 heads with 1.94 1.50 valves
Lunati bracket master II cam. 246/246 @ .05 with .515/.515 lift
4.10 rear with 3000 stall converter.
most recent dyno numbers 268RWHP 291RWTQ

Im believe the large cam is killing this motor. Although I have run 12.64 at 107 in the quarter mile, I do believe that a smaller cam that produces more torque might really help this car get down the track. When I tell people what is in this 350 ci motor they cant believe it even has vacume and idles/runs. And when I tell them I run 12s with it they look at me like im nuts. Please help me :D

Anyone have any suggestions on a nice cheap Hyd camshaft that I should swap for?

If you would like to see the ugliest dyno in history, please click the picture below. (keep in mind that I am probably closer to 290RWHP and 300RWTQ. This dyno was taken with a tranny that blew up shortly after the dyno was run. After I replaced the tranny I gained 2-3 tenths and 2-3 mph at the track.

1979toy

What is your static compression ratio?

Les

That's a good question...& are you having drivability problems on the street?

Anyway, your ETs are very good for your MPH so you're leaving hard- your pic shows that too. I wish I knew the flow numbers for your heads but I'll take a shot at this anyway. With the smaller valves & ports you may have a slight mismatch w/ your cam but I don't think by an awful lot. I don't know how much you'd gain from a cam swap unless you stepped up w/ the big bucks for a hydraulic roller set up. You have the gears & torque converter to support the cam you have.

Just a thought(& this is what I'm doing w/ the 355 in my Z28)- if money is not a concern, a set of AFR 180 or 195 heads should match up very well w/ your current cam & really pick up some power. The cam in my Z28 is very similar to yours numerically but it's a solid flat tappet- duration 248/255 @ .050 and lift of .503/.518. My compression ratio is 11:1 and AFR ballparks my HP at 465 w/ the rest of my combo- 1.6 rocker arms would add 20-30. My local head guru says 475-485 may even be possible w/ my 1.5 rockers.

I realize that this doesn't exactly answer your question but since you have the drag racing sickness I thought it might be worth a look for you. Good luck, whatever you decide.


[Modified by Les, 5:28 PM 12/28/2003]

SmokedTires

Aaron, try Comp Cams recommendation. I had found a cam that I thought would work really well while playing around with DD2000 and Comp came up with a cam that was very close to that cam based on what I told them which I thought was pretty cool.

Here's a link to their cam recommendation form: http://www.compcams.com/Technical/CamSelection/

QuickVet

Im not exactly sure what "static" means, however my guess for my compression would be around 9.5 or so.

I will talk with comp cams.

What do you guys think about ProTopline 200cc iron lighning heads with the same cam in already using?

I would hate to spend all that money and not go much faster, but if you think I would do much better that way, then a cam swap perhaps that is the answer then. BTW, i dont have any street drivability problems other then not being able to cruise on the highway :smash:

I do plan to convert this car back to a driver, but i can afford to do it yet, and that is gonna have to wait a year or two. Untill then, drag racing it is.

1979toy

You are already going faster than most C3 folks ever dream of going.

I think that in the case of a 406 with a big camshaft the phrase "Bigger is Better" would come into play when looking for cylinder heads. If you are not having driveability problems now then by all means stick with that camshaft. The next place to make power will be the cylinder heads and I would try to locate 210 to 215 c.c. intake port heads to match the rest of your combination. 200 c.c. heads will work fine if you're willing to have the bowls smoothed out before you install them.

QuickVet

I was under the impression that anything larger then 200cc on a 350 would be a dog. dont you need to keep good port volocity for maintain good power?

71coupe

Before you tear it down, do a compression test. You want 175 -180 psi on the cylinders. Anything less means that big cam is bleeding off most of that marginal 9.5:1 c/r.

QuickVet

how do i do that? and where do i get the tool to do it? thanks

z-u-later

:lurk:

Les

You can buy a compression tester at your local speed shop or parts store- not very expensive. Get the kind that screws into your spark plug holes rather than the push in type w/ the rubber end on it. You'll need to warm up your engine, pull all spark plugs out, disconnect the coil, wire or hold your throttle wide open, & screw the guage into a spark plug hole until it's fully seated. Then crank the engine over several times until you get the highest reading for that cylinder. Write down the reading & cylinder # before moving to the next until you've done them all.

The hardest part could be getting the guage seated all the way just because of the cramped quarters but it can be done. If I've left anything out the instructions that come w/ the tester should cover it. Good luck & let us know what you come up with. :cheers:

Oh, and bear in mind that if you change to heads w/ a different chamber size these numbers will change too- but at least this will give you a starting point & let you know more about the health of your engine.

QuickVet

wow, informative.

QuickVet

thanks les
I will pick one up today if i can. I will try to get a reading soon. I will keep ya posted. who knows, maybe i will learn something. :)

gkull

Aren't ZZ4 L98 heads only 58 cc's? I don't have a book to verify that does anybody else know?

My desktop dyno has a list of head flow files it gives the GM-Aluminum-L98 head a max flow cfm flow of only 199 intake and 175 exhaust at .600 lift. Which is about the bottom of the barrel for performance heads.

Be very careful trying to screw in a compression tester. I personally don't mess with them because I would have to remove my headers to gain enough clearance to thread it in the spark plug hole. Also the thought of taking a chance of cross threading a head or inducing metal shavings into cylinder scares me.
**************************************** *********************************

To answer your question about 200cc ProtopLine heads and reduce your cam to a Comp Cams XE274.

I had a 355 ci in my Vette - I was always trying to get it to run better. I started with the L-82 four bolt strong block and had it bored .030 over and installed flat top KB Hyper pistons which makes about 10.7 compression with 64 cc heads.

I started with fully ported 186 casting double humps probably around 180 cc and 2.02/1.60 valves. I used a Crane PowerMax 278 cam and it ran really nice with 1.6 roller tip rockers Weiand Excelerator single plane and Edelbrock 750 carb 1 3/4 headers into true dual without cats. Very consistant high 12.70's with TH350 and 3.55 rear gears I think it was a B&M hole shot TC 2500 rpm. Made good power out to 6500 rpm, but you could shift at 7000 if you felt like it. That motor was probably a true 400 hp and trannies/rearends/u-joints began to fail quite often

My next change was heads only to GM over the counter 292 heads fully ported 2.055/1.6 @200 cc. That's when I first noticed that the car just didn't run that well under 2000 rpm and I had just filled the tranny full of busted metal for second time even though it was a proffesionally built up th350. that combo with slicks got it down in the 12.40 range. That combo ran really nice to 7000+ rpm. So anyway I installed a 700R4 instead. The 700R4 actually slowed the car down in the 1/4 a couple of tenths. The gearing is wrong on 700R4 and they use more power than a hopped up TH350.

Then 3.55 gearing with 30% overdrive and motor that didn't run well under 2000 rpm wasn't a good match so I installed 4.11 gearing and a 3000 stall 10 inch lockup converter.

Well from one of circle track friends I aquired Dart Iron eagle 230 cc heads with 2.055/1.60 They actually should have had larger valves because the 2.055's were sunk way into the seat. That was overkill. 355 ci can't use that big of heads on the street with a H-flat cam. So I installed a solid roller and within a short period of time the whole short block motor went in the dumpster. I was a little hard on it.

So I bought another flat top piston short block with a CC XE274 cam and went back to the 292 heads with @ 200cc. IMO I don't think that the XE274 cam ran as good as the Crane PowerMax 278 even with my high 10.7 compression. the sound is more radical with a 274 because of the 110 lobe centers and it's ground with 4 degrees of advance to help the low and mid range charge. Maybe my 1.6 rockers made a already hot XE cam too hot for my 355 ci hot rod. I had even moved up to a 3500 stall 9.5 inch lockup TC. You need to go to the http://www.cranecams.com and look at the 278 and compare it to the XE274 specs and make a decision. I would also recommend 200 cc's or less on anything less than 377 ci

I probably drove that 278 crane 50,000+ miles over the years with various heads and setups. That XE 274 short block didn't even last 3-4 months before it had smeared pistons. It wasn't built well and after 20 minutes at high speed it was a basket case. I was testing for Nevada open road racing where you basically drive at @6500 rpm for @90 miles

Les

gkull,

That's a long history of serious engine abuse there! :thumbs:

You're right about the access to the plug holes- I honestly can't remember if I couldn't get it done w/ headers on(it's been too many years since) but I'm running angle plug heads & that may be why I seem to recall doing it w/o pulling the headers. Two reasons that I recommended the screw in type-
1. Once seated it won't leak.
2. The 1st time I did it a buddy brought his tester w/ the rubber end. We did everything right & on the 2nd or 3rd cylinder there must have been just enough cylinder pressure & the right amount of fuel vapor- somehow it lit off & blew his hand back from the head. It wasn't enough to hurt him at all but it scared the crap out of him! After my buddies & I got done laughing at him we saw that the rubber had been done in pretty well.

Now I realize that the odds of this happening are virtually nil but I thought the story was funny. It would definitely be easier to use the rubber style. QuickVet, the rubber type should do you just fine if you're worried about access to the holes.




[Modified by Les, 7:31 PM 12/31/2003]

71coupe

Come on guys, if you can screw in a spark plug, you can screw in an adapter (unless your headers are huge and dump directly in front of the plug hole). Don't buy a cheap 1-piece tester that doesn't have the adapters. Mac tools sells a good tester. Here is the pic:



You just screw in the small adapters by hand, then screw in the hose & click on the gauge.

http://mactools.com/ProductDetails.aspx?ItemNum=CTD300

:cheers:

EDIT-
If your headers are in the way, you might be able to buy one of the shorter adapters, as seen in their deluxe kit in the pic below:








[Modified by 71coupe, 3:19 AM 1/1/2004]

QuickVet

thanks for all the great information. Im gonna pick up one of those compression testers :cheers:

Still trying to decide what route to go. but i will post my results for sure. Since there is no real way to know how much difference any head will make without doing it, im gonna only change on part at a time just to see what it does and keep track of each mod.

gkull

71 coupe - i have the Hooker Super Comp 1 3/4 headers and angle plug heads. There is no way to thread in a C tester. I generally even only use short spark plugs to give the wires more room from the pipes.

Nomad78SA

gkull,
Where can I find a good selection of shorty plugs at?
I think I need to see if I can get to my plug holes to do a compression check again. I am also running Hooker super comp 1 7/8 headers with angled plug heads. The last time I checked them I was running 235 psi. per cylinder but I had the body off so I could manuver around. I have pulled the heads and studded them from the last test so I need to see what is going on.
Neil in Tenn


[Modified by Nomad78SA, 8:31 PM 1/3/2004]

gkull

Nomad78 - Right now I just have Autolite Platinum for 3/4 deep reach plugs. Get on their web sites for the different plug manufactures and they list the shorties for the different thread types.