Thread: My Chevy 355 has little real power - looking for suggestion on CAM change

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Originally Posted by techinspector1

You need more gear. The 4.10's with the 35" tires are the same thing as running a 3.28 gear with a 28" tire. Install a 5.13 gear.

Too much volume under the carb. If the spacer is not a 4-hole model, lose it.

Too much carb for a torque motor. Borrow a buddies 600 or 650 to try it out.

Too much cam for the compression ratio. Assuming a deck of 0.025" (since you don't know), your static compression ratio is 9.08:1. Swapping in a Crane #113941 (216/228 @ 0.050", intake closes 35 ABDC) and advancing it 4 degrees will give you a dynamic compression ratio of 8.169:1. Since a good strong motor will need a DCR of 8.00:1 to 8.25:1, you'll be right in the ballpark. I'm not saying use this cam and only this cam. I'm just giving you a for-instance of what specs I would buy if I had to buy you a cam. This cam makes power from 1,800 to 5,600 with valve float at 6,200 if you use all the matching hardware from Crane. Use a converter with a stall of 2,000 r's.

At 184 cc's, the heads should work fine for you. Eric thinks they are a little large and I agree with that for a torque motor, but hey, where do you draw the line on cost? Ideally, they'd be 170 but I'd keep 'em.

I agree about the gears. If I had to do it over again, I would do 4.56 in a heartbeat. With 5.13 gears, I wouldn't be able to still drive it to work (would be at too high rpm).

OK, the spacer is easy, that's gone. The carb is reasonable easy too, and makes sense. I think I will go with the Holley truck avenger for all the angles I have to deal with, although I heard some positives about the quadrajet too.

Two more questions then come to mind:
1) what about the intake? There was a suggestion to change it out. That's not the first suggestion I've had to swap it out, but will that really matter?

2) How is degreeing the cam by 4 degrees different than simply advancing the static timing by 4 degrees after the cam is installed?

Thanks for ALL the advice guys. It's very helpful. I can't promise I'll make all the changes ($$), but at least I'll get closer. The engine as is just does not make power where I need it (but it was a GREAT deal, so it's ok).

"1) what about the intake?"

I'd leave it alone for now and change out the cam first. I think you'll find the motor to be refreshingly crisp with the shorter cam. I will enter a vote for the quadrajet. In my opinion, it is the best carburetor ever made and when properly dialed in, is just a tick from being as good as EFI. The tiny little primaries will do a great job of metering fuel for economy and the huge secondaries will cover you for those insane bursts of showmanship you are so well known for.

"2) How is degreeing the cam by 4 degrees different than simply advancing the static timing by 4 degrees after the cam is installed?"

You have cam timing and you have ignition timing. I'm talking about advancing the cam timing by 4 degrees in relation to the crankshaft in order to close the intake valve earlier and match up with your static compression ratio. There are several ways to advance or retard the cam. You can do it with a multi-keyed crank sprocket or with offset dowels in the cam sprocket. IT IS IMPERATIVE THAT YOU DEGREE THE CAM AFTER YOU HAVE ADVANCED/RETARDED THE CAM DURING INSTALLATION. IT IS VERY EASY TO DO IT BACKWARDS AND RETARD THE CAM WHEN YOU ACTUALLY WANTED TO ADVANCE IT.

As a side note, your present DCR is approximately 7.35:1. No wonder you can't spin the tires.

i agree advancing the cam will also help with torque. from what i understand most aftermarket cams produced today are ground 4 degrees advanced. i know that this was true with my Comp Cam. so if you were to advance it say.... another 4 degrees that would be 8 degrees total advance. i have a huge cam in my galaxie .530 lift and .230 @.50 i advanced it 4 degrees and i made a huge difference. the reason i chose such a big cam was b/c i do lots of interstate driving. i can do about 60mph at about 2300rpm and my cam makes powe from 1500-6800 so im right in my power band, and besides i didnt have the money to build a motor that would ever launch that beast of a car hard so i figured i might as well just make it the type of car thats fast from a 60mph roll. the thing is an absolute pig until it gets momentum and then its fast but i will say that the extra 4 degrees advance helped down low. and up high or at a roll with a 3.00 rear end that thing will fly. but a cam like that in you truck just wouldnt make any sense. i know lots of people who build big 4X4's and put huge high reving cams in them, whats the point besides the fact that is sounds cool. my friend had a 383 blazer that he built and i had a .565 lift cam!!!!! (i forgot how much duration but trust me it was insane) he spent a ton of money on the valve train so it would accept all that lift and he had something that was usless for what he wanted to do with it. putting in a huge cm can just kill performance as i learned with my galaxie, i had mismatched parts so i ended up having to spend a ton more money to make it how i wanted it. i had to buy intake (which isnt cheap for an FE), headers and im saving for a set of edelbrock heads. ohh yah and all this stuff id going on a 406 block but for now i have the 352 in it so i can drive it. but anyway thats just my 2 cents
thanks
Tyler

Originally Posted by techinspector1

"1) what about the intake?"
IT IS IMPERATIVE THAT YOU DEGREE THE CAM AFTER YOU HAVE ADVANCED/RETARDED THE CAM DURING INSTALLATION. IT IS VERY EASY TO DO IT BACKWARDS AND RETARD THE CAM WHEN YOU ACTUALLY WANTED TO ADVANCE IT.

As a side note, your present DCR is approximately 7.35:1. No wonder you can't spin the tires.

Since I have never installed a cam before, I may just leave the cam as not "degreed" and install it straight up to avoid the risks involved. I have heard that degree-ing can work, but only if you really know what you are doing with your setup, and if you don't know 100%, then you shouldn't do it. How imperative is the degree-ing in the sceme of what I am trying to accomplish?

How is the dynamic compression ratio different than normal CR, and how did you calculate that using the information I gave?

Thank you VERY much, this is helping me learn quite a bit. If I were to have 7.35 ratio, it's no wonder I can advance the ignition timing to the moon (not literally, but I can go more than I have now) and get no pinging.

Am I crazy, or does no one make a NEW quadrajet? My brief searches don't show new ones for sale anywhere. If they are so popular (also with the off-road crowd), why don't they make more? Any sources would be useful, I don't want re-man or something I have to spends years tuning. The Holley was pretty close right out of the box, but I have lots of people suggesting q-jet.

Finally, I read somewhere that Qjets were 750 and 795 CFM only, that 600 or 650 quadrajets did not exist? I think I will search here for Quadrajet posts.

"If I were to have 7.35 ratio, it's no wonder I can advance the ignition timing to the moon (not literally, but I can go more than I have now) and get no pinging."

BINGO! This shows me that you are worth teaching!

"How is the dynamic compression ratio different than normal CR, and how did you calculate that using the information I gave?"

Static compression ratio is the comparison of the volume of mixture that is drawn into the motor through the intake valve to fill all available spaces and crevices with the piston at bottom dead center compared to the volume of mixture that it is all compressed into with the piston at top dead center.

Dynamic compression ratio goes a step farther by factoring in the stroke of the motor, the length of the rod and the intake closing point of the cam. The intake closing point is the most important event in the total cycle of cam timing and determines whether you have a motor or you don't.

In the case of your motor, the intake valve is closing about 17 degrees too late to trap the proper amount of mixture to make any power. Although I couldn't find the actual intake closing point of your cam in any of the Lunati information (that's why I use Crane Cams, they give me the info on their website without having to call anybody), I figured that it is about 48 degrees after bottom dead center (ABDC). The cam I suggested for you has a closing point at 35 degrees ABDC, so it will trap more mixture in the cylinder instead of the piston pushing fresh mixture back up the intake tract with the intake valve still open. By advancing the cam another 4 degrees, you will be closing the intake valve at 31 degrees ABDC. That would make the DCR about 8.169:1 and you should be able to see a significant difference in the low rpm performance of your motor.

In order to properly spec a cam for a motor, you don't have to be an Einstein. You just need a few tools and enough intelligence to use them.

The first thing you ABSOLUTELY MUST know is the static compression ratio of the motor. There are online calculators you can use, but I want you to know how to do it yourself. This paper I wrote has had 936 hits since I posted it.....
http://www.streetmachinesoftablerock...opic.php?t=124

Continued on next post.....

Once you've figured the static compression ratio, you can use this handy calculator from KB pistons to figure the dynamic compression ratio....

http://kb-silvolite.com/calc.php?action=comp2

Where it asks for the intake closing point, take the info from the Crane spec page for the cam you're looking at. It will give you the figure at 0.050" tappet lift. Add 15 degrees to that figure and that is what you'll enter into the KB calculator. Crane shows the cam I suggested to have a closing point of 35 degrees ABDC. When I calculated your DCR with that cam, I entered 50 degrees into the calculator.

You know, it just is that simple. You look through the list of cams and pick the characteristics you want from the upper right hand corner of the cam description (Crane), then use the KB calculator to see if you have a match. Try to get the DCR between 8.0:1 and 8.25:1. Any less and you won't have much of a motor and any more than that and you won't be able to run pump gas without detonating. Of course there are exceptions to every rule. If you have a very tight squish, combustion chamber polished, spark plug electrodes de-burred, no overhanging head gasket, no PCV and no EGR, you will be able to get away with more on pump gas.

One more thing about Crane. They will give you the LDA too, although they don't list it that way. Go all the way to the bottom of the cam spec card and add up the two cam timing figures at max lift, then divide by 2. Here's a for-instance.

http://www.cranecams.com/?show=brows...tType=camshaft

This cam reaches max intake lift at 105 degrees AFTER top dead center and max exhaust lift at 115 degrees BEFORE top dead center. Adding the two together gives you 220, then dividing by 2 gives you 110. So, this cam has a lobe displacement angle of 110 degrees. Cams with a higher LDA (112 and up) will make more power higher in the rpm range and will tend to be very smooth at idle, making excellent manifold vacuum. Cams with a shorter LDA (110 and under) will make power lower in the rpm range, but will tend to peak sooner. They will also exhibit a choppy idle and low manifold vacuum. (You will need about 18" of mercury to operate power brakes properly).

You asked if it is necessary to degree the cam in. It's just like anything else. Once you learn how to do it, it's easy. And YES, I would urge you to learn how to do it and to degree this cam in. How else are you going to know that everything is optimized for performance? Go here and click on Degreeing a cam.....the easy way.

http://www.cranecams.com/?show=insta...t%29#Camshafts

OK, I'm out of breath. Any questions?

Thank you very much. I have some reading and work to do.

In order to calculate the CR, there are pieces of information I do not have such as eyebrow volume. Do I simply estimate? I don't want to tear apart the engine to make the decisions on what to buy.

Cool .....

Originally Posted by techinspector1

Once you've figured the static compression ratio, you can use this handy calculator from KB pistons to figure the dynamic compression ratio....

http://kb-silvolite.com/calc.php?action=comp2

Where it asks for the intake closing point, take the info from the Crane spec page for the cam you're looking at. It will give you the figure at 0.050" tappet lift. Add 15 degrees to that figure and that is what you'll enter into the KB calculator. Crane shows the cam I suggested to have a closing point of 35 degrees ABDC. When I calculated your DCR with that cam, I entered 50 degrees into the calculator.

You know, it just is that simple. You look through the list of cams and pick the characteristics you want from the upper right hand corner of the cam description (Crane), then use the KB calculator to see if you have a match. Try to get the DCR between 8.0:1 and 8.25:1. Any less and you won't have much of a motor and any more than that and you won't be able to run pump gas without detonating. Of course there are exceptions to every rule. If you have a very tight squish, combustion chamber polished, spark plug electrodes de-burred, no overhanging head gasket, no PCV and no EGR, you will be able to get away with more on pump gas.

One more thing about Crane. They will give you the LDA too, although they don't list it that way. Go all the way to the bottom of the cam spec card and add up the two cam timing figures at max lift, then divide by 2. Here's a for-instance.

http://www.cranecams.com/?show=brows...tType=camshaft

This cam reaches max intake lift at 105 degrees AFTER top dead center and max exhaust lift at 115 degrees BEFORE top dead center. Adding the two together gives you 220, then dividing by 2 gives you 110. So, this cam has a lobe displacement angle of 110 degrees. Cams with a higher LDA (112 and up) will make more power higher in the rpm range and will tend to be very smooth at idle, making excellent manifold vacuum. Cams with a shorter LDA (110 and under) will make power lower in the rpm range, but will tend to peak sooner. They will also exhibit a choppy idle and low manifold vacuum. (You will need about 18" of mercury to operate power brakes properly).

You asked if it is necessary to degree the cam in. It's just like anything else. Once you learn how to do it, it's easy. And YES, I would urge you to learn how to do it and to degree this cam in. How else are you going to know that everything is optimized for performance? Go here and click on Degreeing a cam.....the easy way.

http://www.cranecams.com/?show=insta...t%29#Camshafts

OK, I'm out of breath. Any questions?

Yes,I have a question.What drew you to northern Wisconsin?

Eric, it was just the time to do something else with my life before someone shovels dirt in my face.

I was working a job I hated and putting up with nagging and unhappiness at home. I had just missed a cancer scare that I have only talked with Dave Severson on this board. December xrays showed a shadow on my lung. Photos the following April showed it had disappeared. I thanked God and my lucky stars and decided to change the way I was living while I still could.

A very dear friend had moved to Wisconsin and offered me to come and stay with her while I get myself sorted out. I accepted. All I brought was my tools and a few clothes.

I have no idea where I'll end up, but will travel to my daughter's to see her in North Carolina this fall, then on to Nicaragua for the winter. I've made a few friends there via Nica forums, so it should be easy enough getting around and finding lodging, etc.

Originally Posted by techinspector1

Eric, it was just the time to do something else with my life before someone shovels dirt in my face.

I was working a job I hated and putting up with nagging and unhappiness at home. I had just missed a cancer scare that I have only talked with Dave Severson on this board. December xrays showed a shadow on my lung. Photos the following April showed it had disappeared. I thanked God and my lucky stars and decided to change the way I was living while I still could.

A very dear friend had moved to Wisconsin and offered me to come and stay with her while I get myself sorted out. I accepted. All I brought was my tools and a few clothes.

I have no idea where I'll end up, but will travel to my daughter's to see her in North Carolina this fall, then on to Nicaragua for the winter. I've made a few friends there via Nica forums, so it should be easy enough getting around and finding lodging, etc.

Richard,Dave is coming down to Boone Iowa for the IMCA supernationals.Hop in the car and come on down.It starts on 4th of Sept. and goes to the 9th.
Five days of dirt track racing.This will help get your mind off things.
A quick story about Rhinelander Wis.
I went up north of there one year to deer hunt.It was about 35 when we left a cold front came in.The temp. dropped from 35 to about 20 very quickly and here came the snow.We had to hike back to the atv's about 2 miles load them in the truck and then drive the trucks out.That was the first and last time I went deer hunting in Wisconsin.I was not prepared that day.

Originally Posted by techinspector1

You asked if it is necessary to degree the cam in. It's just like anything else. Once you learn how to do it, it's easy. And YES, I would urge you to learn how to do it and to degree this cam in. How else are you going to know that everything is optimized for performance?

I agree I need to learn. If the extra 4 degrees makes so much of a difference, why don't they just grind that into the cam (possibly differences between each engine setup)?

Originally Posted by pnut

I agree I need to learn. If the extra 4 degrees makes so much of a difference, why don't they just grind that into the cam (engine differences)?

Comp. cams does on some of their grinds.
What I do on some of the performance engines is "degree" the cam and then start the engine get it broke in or at least get it to operating temp. for a few cyles and then go back and re-degree the cam again.
Most of the chains I have used will loose about two degree' or maybe a little less.

Originally Posted by DennyW

You can buy the pre-stretched sets for 32.95, for small block chevys.

COMP Cams Magnum Double Roller Timing SetsPerformance and reliability for the street.
Building a really high performance street vehicle? COMP Cams Magnum double roller timing sets are built for maximum performance on the street. They have heat-treated, pre-stretched, large-pin, double-row chains for extra strength and reliability. They also have crank sprockets with three keyways, which allow you to set cam timing at 4 degrees advanced, 4 degrees retarded, or normal. In addition, all Magnum double roller timing sets are dynamically balanced for smoother operation.

http://store.summitracing.com/egnsea...1&autoview=sku

What Denny say's is true.
One thing I might add is "crank timing" is not the same as "cam timing" in other words I would check all piston to valve clearance's and re-degree the cam when or if you decide to move the crank sprocket around.

Originally Posted by DennyW

I like to check them both ways. Example: I may advance the crank sprocket 4º. And retard the cam gear 1 to 2º. You can work it, and dial it right in. Get a descent dial indicator, and timing (degree) wheel, and just work it to where you need it. Double check it until all your marks repeat. Instructions come with the degree wheel, and tells you syep by step how to check things out. That, along with the cam specs, and you can do it.

I do the same thing.
When I was drag racing I could move the cam timing one way or another 1/2 a degree at a time on the belt drive.
In other words if I thought my 60 ft times where to slow I might advance the cam 1 degree to make it pull a little harder on the bottom.Well you all get the general idea.