Hey guys and gals

I finally pinched enough money together to do some upgrades, the cam I bought just to get car back on the road (MTC-1) over a year ago just isnt working for me. The car runs great but I do get valve float around 4800-51000rpm. I have a buddy that im getting some the camel humps no acc holes but 202 vavles, screw in studs and guide plates for 300 bucks I honestly cant beat the deal, they were used to break kn a 355 race engjne and the car wrecked 1st race of the season.

He has the cam that was in the engine but the powerband is 3000-7000rpm, I told him I would think about cam and looked at some of summits cams and cant beleive the price they are about the same price I paid for the melling cam.

Can summit cams be trusted or are they reboxed and sent out? Any cam you think might work ill list some quick specs

350 +.030 over dished
4 speed no stall needed
Msd pro billet dist
Headman headers full lenth true dual exhaust
Around 4.11 gears or so (teeth not counted jacked up and spin and count method
Weiand stealth intake
600 holley dp but have 750VS sent on shelf

 

I'm not surprised! 51,000 RPM is really spinning!!

Seriously, I've used Summit cam kits in 5 engines now, with no problems whatsoever. After a lot of detective work, I found out they're made by Crane, and Crane is one of the few manufactures that still "Parkerize" their cams. You can read more about Summit cams HERE.

Ed

 

51000rpm is alot but its a chevy though. My fat fingers got the best of me.

I will find out today who makes the cam my buddy has he says it is stamped with several numbers but only knows the rpm range, But for around 100 bucks I can get a ather good summit cam and lifter kit to wake up the engine, the short block is stout so im sure it will hold together but not liking the idea of 7000rpm.

I am leaning towards these 3 cams

http://www.summitracing.com/parts/su...make/chevrolet

http://www.summitracing.com/parts/su...make/chevrolet

http://www.summitracing.com/parts/su...make/chevrolet

 

Get the # off the cam and look it up

If it was floating valves you were having a spring issue or the cam was done by then.

When P.A.W. was around I was young and broke used their house brand (regrinds) with no issues at all they ran pretty good. Summit usually sells decent stuff they put their name on. Love their plug wires unbreakable (boots).

 

This cam is actually all in 4500rpm so valve float at 4800 would be normal

 

All those cams you have listed have a recommended comp ratio. Do you know what your current ratio is and what it will be with the camel hump heads? You may fall short with the dished pistons you mentioned?

 

im just guessing but with 76cc heads and accounting for a possible mill down of heads throughout the years 8:5:1

 

If valve float is the problem then maybe what you need is new valve springs. Or you could try only tightening the rockers 1/2 to 3/4 turn after zero lash (assuming hydraulic lifters).
I've read on this forum that the 1 to 1.5 turns on the rockers acted like a factory rpm limiter causing float after a certain rpm.
All of those cams you listed require a high compression engine. They also have a pretty high rpm power band so with your low compression engine and one of those cams it would be a real dog at low rpms. A 4:11 rear end is a plus for a bigger cam. One of the cams you listed even had a 106 lsa that's tight for a street driven 350.
I see you have a '77. If it's an L-48 with the stock heads then your looking at about 7.7:1 CR. Pistons are 17cc dish pistons if that helps you figure your new CR with the camel hump heads.

 

Are the 76cc head your current heads or the proposed heads? Has the block been decked and what about running a thin gasket. How about running a cam similar to a L46 or a nostalgia hyd. L79?

 

Current heads are 882, the block is a 75-77 truck engine 4 bolt main with basic rebuilder pistons similar to speed pro I have tried adjusting rockers but nothing changes.

I was going to buy edelbrock rpm heads but its not in the cards for me right now maybe after this deployment

 

heads are 291 with porting only on the intake and have been milled down to 62cc
here is the specs on everything that i know so far the heads do not have screw in studs but have new ones that are pressed in not pinned
camshaft is
E-1180-P valve lift 488 303°
234 @ .050
109lsa
link here
http://estore.elginind.com/shoppingC...gh+Performance

what you guys think price wise as far as bolt and go heads just need to be cleaned up have thick grease to prevent rust and look good

 

what exhaust system do you have ?pick a cam to match you intake flow ,and exhaust flow.use good brake in oil.get good valve springs .do a valve seat leak test .

 

Choosing a cam is not an easy task nor should it be guessed at. In order to get in the ball park it's important to know what your compression will be and where you want the power delivered.
To get good torque down low you want good cylinder pressure.

If you want all your power after say 3000 rpm then you would get the type of cams you are linking to. This kind of power is not all that useful on the street. Starting out with a 4 speed manual you will need plenty of rpm and slip the clutch a bit to get going. Then wait until that magic rpm range is met then you will get the preformance you built it for.
If you want a better down low torque then get a cam something like this.

http://www.compcams.com/Company/CC/c...x?csid=73&sb=2

Notice the intake valve closing point. 60* ABDC. That is when compression starts to take place. Prior to that effectively no compression can take place and no significant cylinder pressure can be achieved.
The cam you linked to looks like the valve events are based on a .050" lift. To convert that to actual intake valve closing take the advertised duration of 303* divide it by 2 then add the intake centerline of 109* and subtract 180. This gives you an intake closing of 80.5* ABDC (ABC). If I am right then that is quite late and will result in little cylinder pressure at lower rpms and little torque until a much higher rpm.
I'm not really one to be giving cam advice but I can tell you what to look for to better achieve your goal.
The real experts have not chimed in yet.
To figure your CR and your DCR try this calculator.
http://www.jeepstrokers.com/calculator/
Notice that you need info like piston dish and gasket thickness to accurately figure CR. Figure out your CR and then choose your cam based on that and figure your DCR, and your desired RPM range in which you want the power. Valve floating is the valves inability to follow the cam profile when returning to the closed position. Spring strength is key to this happening. 35 year old Springs may just be too fatigued to do that.

 

well now with all the help, thanks guys,

I like many others may want to get a curve ahead and not buy parts for the block I have just start from new and know exactly what I purchase to make it all work.

I may just sell the heads I purchsed and buy a newer block IE roller cam.
I leave for deployment in a few months and will have enough money to buy new aluminum heads so its like christmas in the garage when I return and then I can just build build build.

 

I just looked up that cam you got in there now is this it?

http://www.summitracing.com/parts/mel-cl-mtc-1

If it is I can see why it peters out at 4500 or so RPM. It has low duration at .050 and high advertised duration. That means it has a very slow ramp to get the valve open or a low "hydraulic intensity"
That cam would be better suited to a truck or something you want good grunt right off the bottom and low rpms.
It may be slightly better than the stock cam for a L-48 but not much.
It's possible you're not seeing valve float just the limit of the combined parts of that engine. If the exhaust is still stock that's a large restriction or if the intake is stock, another restriction, those heads don't breathe worth a hoot, nor does the stock intake manifold. The engine will only run as good as the most restrictive component allows it to.
I don't know anything about camel hump heads other than they are better than the 882's, however not as good as modern aluminum heads.
You really want to learn about cams and getting that engine running well read these on your deployment.

http://www.amazon.com/David-Vizards-...s=david+vizard


There is only two books don't know why it shows up as three links.

 

When I purchased the cam Its what they had on the shelf and it was peak season for driving in the pacific Northwest and I was inpatient and just grabbed what was on the shelf at the local parts store.

The rest of the car is actually well equipped with msd pro distributor, weiand stealth intake, holley 650 dp ,hedman full lenth headers with true dual exhaust, minimum acc`s power steering pump, alternator. Edelbrock high flow water pump, high rpm flex fan,

It had a high flow edelbrock fuel pump but it started leaking one day so I just changed it with a stock one for the time being.

 

I think you're headed in the right direction with a head change and cam upgrade.
Hard to say what pistons are in there. "Rebuilder" pistons could mean flat top 5cc or 7cc pistons if your lucky, however the compression height may be 1.540 instead of the 1.560 of a stock piston. This means it doesn't go as far up the bore and you get less compression and no real squish band with a stock deck. If the block has been zero decked (common when it's bored .030 over) then you may be ok in the squish band department if you use a .015" shim head gasket.
If it still has the .025" stock deck left on it then your compression will be lower. Best way to find out will to be pull the heads off and see how far down the bore the pistons sit at TDC unless you have some knowledge of what was done to it.
That Flex fan is a big power using device. It does a good job cooling just uses a lot of HP to do it.

 

You may run into a problem mounting your front engine accessories without the mounting bosses and holes in the newer heads. I'd wait on that change and just get a good set of heads from the beginning. With the pistons you have now plus running heads with 64cc chambers and a thin head gasket you will get a decent compression boost for street driving. If you really "cam it up" and run a really high compression you will start to lose the joy of cruising around town. A high-strung engine can really create a labor of love when it comes to Sunday drives, but if that is what you want then it's your car... Just sayin'.

 

I have brackets for non acc hole heads said no worries on that part, I didnt realize that the flex fan uses alot of HP but it does run cool at most 195 on warm days here around 90 at the hottest runnning the car pretty hard. Im going to have heads checked no matter what at machine shop even if I do sell them for peace of mind for the next person, I am going to get that book though it looks like alot of great stuff ti learn always been a hell of mechanic on stock or slight performance upgrades but will nice to learn about the ins and outs of performance building

 

As I am not keen I was told be seller the heads were 2.02 took to machine shop to get mag went good he said valves were 1.94 and 1.6


http://i864.photobucket.com/albums/a...ps6aa435bf.jpg

what do you think