My motor is a 350 bored .060 over with AFR 195 eliminator heads. Compression is around 10.5-1 the intake is a Weiand team g and it has a 750 mighty demon carb on it. My timing is locked out around 34-35 degrees. My cam was custom ground from cam motion with a .575 .581 lift and 234 238 duration @ .050 with a 108 lobe seperation. I have been trying to get this thing running right for a while now and have been having the same issues. I know this isnt a tech board but I know a good amount of people on this section and know there are some really smart people on here. I have already tried the tech boards with no success and am in a pinch to firgure this things out. So please dont move this or atleast not until I get an answer.

My motor has been really tough to idle before and when you would rev the motor it would want to stall out when it came back down and would also not come back down to an idle quick. I locked out the timing now and it seemed to help some. It will idle pretty good now and not really want to stall but when you rev it it sits at 1500 rpms or so and doesnt want to come back down to an idle like it should without messing with the gas. I checked the vacuum at a few different rpms at 1100 it would bounce a little right around 11 inches. At 1000 rpms vacuum was 10 and at 800-900 it was 8-9 inches. I know it seems a little low but the cam has a 108 lobe seperation so thats why it might be a little low because of the lumpy idle but im not sure. I thought it might be a vacuum leak so I made sure to plug all of the ports on the carb and lock out the timing so thats not a factor and re-do the intake gaskets which were brand new and it still doesnt want to come back down good off of a rev after that. I checked the AFR also to see if that could be a problem and it was 13.6 roughly at 1100 and 14.8 at 800-900 rpms which seems to be fine. The carb has also been taken off of my car and put on my cousins car which is a very similar build and works fine so I doubt its the carb. I have no clue where to go from here the timing is locked out, the AFR doesnt seem that far off, and I just changed the intake gaskets. What could be going on here???? o yea I have also recently changed the plugs and the fuel pressure gauge seems to stay constant at 6 psi all the time. Please help!!!

 

Plain and simple that cam is WAY TOO BIG!! I believe you are going to pull your hair out trying to get that thing to run with that big of cam.

A cam with 224-226 degrees, and ground on a 110-112 would have been a better choice with your heads and compression ratio. And those numbers are the max I would use..IMHO, on a 350.

The cam I ran in my old F Body had just a tad more duration than yours, and was ground on a 114* LSA...and it was in a 436 engine!!! My cam was on the small side for a solid roller, but I did not want the problems you are facing, because at the time the engine went together, I did not know how to tune the EFI, hence the wider LSA, and overall better idle, and street manners.

 

I appreciate the post but I respectfully have to disagree. My heads flow upwards of 280-290 cfm and there are many builds on this site that have even larger if not close to the same specs as me and run just fine. Just dont get how you can say my motor needs a baby cam when it has one of the best set of heads you can buy on it. My cousins build is almost identical to mine and runs great. A cam with 234 238 duration is not even close to that big for a roller set up. There is definitly something up besides having too big of a cam and I am almost positive of that seeing I had the cam custom ground from Cam Motion that gave me those specs, I did not ask for them.

I adjusted the valves using the method of bringing the motor to the #1 compression stroke and adjusting the half that you can and then goign to the #6 compression stroke and adjusting the rest. I have heard from some people that it is fine to do but some say you shouldn't do it on a larger cam. So I am thinking some of the valves may be open or something which is causing a lower vacuum reading and the motor to act like it has a vacuum leak. Does this sound right and has anyone with a larger cam adjusted the valves this way or did you do one cylinder at a time. I am grasping for straws now. Thanks guys!

 

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Yea I definitly dont think its a cam problem. With a 106 lobe seperation what type of vacuum were you making? Just to give me an idea if mine is about right or not. What type of intake did your buddy have? Was it a team g? I was thinking something was up like that or a mis adjusted rocker or something. I just did another set of intake gaskets lol Now I might have to pull it again. I torqued the intake pretty good this time just in case there was a leak do you still think the gasket wouldnt seal it? Thanks for the help! Much appreciated.

 

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Thanks for the reply. I will try to re-adjust the valves first but im not sure if that is going to fix it. Unless the method of adjusting half of the rockers at the #1 compression stroke and the other half at the #6 compression stroke doesnt work with a larger cam then it should be fine because I was pretty careful when adjustign them. If someone can tell me that have done this method wit ha large cam in a SBC that would be appreciated.

I am just confused because even if the intake is a little warped dont you think the gasket would make up for it and when I did the gasket over I smeared with my finger some RTV on the entire gasket(thin layer) which I know some people are against but it still didnt fix the problem and the problem was there without RTV on the enitre gasket before as well. If I take the intake off will it be noticeable with a straight edge if its warped? Thanks again for the help!

Just wanted to post a pic of the car and the motor for people to see. At least if it doesnt want to run good it can look good. lol And no I am not trying to lick the windshield in the pic I am pulling it up onto a trailer to get the exhaust done. lol

 

I would adjust the valves one at a time. I use a .002 feeler gauge and then 1/2 turn tighter. I run a pretty large comp hyd roller cam and comp lifters. I shifted at 6800/6900 when I had that engine in the car. With no valve float. That cam and lifter setup has 6 seasons on it, and still in great shape.

 

I dont know if I can help much, but in my 350, Im running a solidflat tappet cam with 600 lift, 261/266dur@.050 on 106 LC. it to is a 10.5 comp. engine with 195 AFR heads. the intake is a Vic. Jr. with a 750 holley. The idle quality is good at 1200 rpm and it pulls 9" of vacuum. It may be just a characteristic of your cam. with that much lift and 108 LC. Try to call cam motion and get their input on the way the car should idle with that cam. Also what size flywheel are you running? is it a lite weight one or heavy. It makes a differece in idle "recovery" when you rev the engine because of less rotating weight to keep the engine running when it drops back down to idle. I use to run a aluminum flywheel AND clutch setup that weighed a total of 16 lbs. the engine had outstanding throttle response but had trouble at idle speeds when being driven in traffic. I constantly had to feather the throttle to keep it running at idle. I have since changed over to a more domestic "heavy" clutch setup and it has helped a lot in the drivability and idle recovery of the car in traffic. just my . good luck with your car.
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I have a stock weight flyhweel and a dual friction center force clutch so I dont think that is the problem seeing it isnt a light weight setup. Using a .002 feeler guage will find zero lash? That would be easier then sitting there and messing with the pushrods by finger if so. I spoke wit hthe guys at Cam motion and thye thought I should have around 12-13 inches of vacuum and I'm making 11 ish so I dunno if its of just a little from there predictions or there is a leak... How much should the gauge bounce and still be fine because the guage was bouncy a little bit? Just not sure if it is do to the lopey idle. Thanks again for the suggestions guys I appreciate the help!

 

I have found that using the .002 feeler gauge works best for me, then 1/2 turn will preload the lifter enough to keep from floating the valves as the lifters pump up. My old 383 with the comp hyd roller ran low 6.40s in the 1/8 turning 6900. My 406 with a larger solid roller only ran 6.17s in the 1/8 with very good air. I have the 383 as a backup engine now. I have found that using the spinning the pushrod method is NOT consistant , and takes longer. With the feeler gauge you can be sure you are on the base of the cam and not on any part of the ramp.

 

that's still a little peanut baby cam in the grand scheme of things ...
the carb is probably just not got the correct parts / adjustments yet ...
Idle air bleeds , powervalve , jetting , throttle plate opening front /rear etc ..
after you get it right it will idle around 1000 probably 6-8 in vacuum ...
it'll need 20 someodd degree timing at idle and low 30's total by 2500-3000 rpm .. how much compression and where the cam IC was installed will vary stuff

 

mine done the same thing, and i was ready to junk the car over it. Turned out my carb was just out of adjustment. I played with the air bleeds, opened the secondaries a little more, and squared up the jetting and squirters then all was well. I doubt your intake would be warped enough to make it leak, good luck. Do you have an msd box?

 

Was the cam degreed, or installed straight up?

 

The cam is installed straight up and I do have an MSD box. The cam is also getting 34-35 degrees timing all the time because I locked the distributor out. I thought it could be the carb but my cousins build is very similar and I slapped my carb on his motor and it worked great. Thats what leads me to believe it is fine. I will definitly take another look at the carb and try some adjusting. Isnt the secondaries only open a certain amount depending upon cam size and idle speed? thanks again for the replies guys!

 

Since it was not degreed, the cam might not ground to the specs on the cam card.

If that's the case, you might not have the cam you think, and would not know it without it being phased..and the engine will never run correct.

Its not common, but it does happen. Cams are ground on sophisticated equipment, by people, who can, and will make mistakes.

Try bypassing the MSD, just to rule out that as a problem.

That's seems like a lot of vacuum Cam Motion thinks you should have, with that cam.

Just my

 

Thanks everyone for all of the help! I think I figured it out finally. Thanks especially to 87 draggta with his suggestion of opening up the secondaries a little more. I thought the carb would be fine because I ran it on my cousin's motor and it worked great but his cam is very similar to mine in lift and duration but its on a 110 or 112 lobe seperation so I think it might be because he has a stronger vacuum signal it ran good but thats just a guess. All I did was open up the secondaries a quarter of a turn and back off the primary idle asjustment until I got it to idle at about 1k rpms and it revs and comes back down to idle now. I need to see if I can get my cousins camera so I can post a video up but I will have to get in touch with him. Thanks again for all the help guys. Now to get the car broken in and everything else fine tuned!

 

Congrats man, similar can make a huge difference. Holleys suck until they are right then they are fine pieces of equipment. I'm glad I could have helped, btw we are waiting on that video.