[eric32]

Hello guys I am making a new post here and apologize for the long post as some know I have been having an issue with my 350 Dart shp build that I can't figure out what the problem is and I am thinking that the camshaft I have just might not be working for some reason with this build as everything else has been checked and checks out ok and I can't seem to get a 600 Holley vacuum secondary carb or any carb yet to work right on this build and the others I have tried and it was the same on previous 377 SHP build but slightly different but not by much.Nothing carb wise had been normal working and being able to be adjusted.

It seems to have air and fuel distribution issues and and the fuel is falling out of the mixture and puddling in the intake and some other issues in the combustion process.

I had a Mike Jones custom before the cam and intake swap and any carb I put on it I could get to work with just minor tuning like normal on the previous 377 and it ran fine wtih a victor jr intake and its specs were
276/280 228/[email protected] 510/510 lift 106/112 lobe separation angle 54 degrees overlap seat to seat
Seat to seat IO 32 IC 64 EO 78 EC 22
@50 IO 8 IC 40 EO 54 EC -2

No exhaust heat crossover had ever been used in all my past builds including this one so I know that a carb needs heat in the cold months but I never had this mystery problem I have now in over twenty plus years of small block chevy builds. Even during the warm months I have had the same problem.

I had a 350 build in the past that had 200cc RHS cast iron heads with a high rise dual plane intake with 9:1 compression and below is three cams I had in that build and all three worked just fine without me having the current problem I am having. That build got the cylinder heads changed out to a set of Dart 180cc SHP aluminum heads and had the Lunati voodoo hydraulic 270/278 219/[email protected] 515/530 lift cam as its final one before I sold it in 2018 and went to my 377 which I swapped out that short block to my current 350 build.

I know the cams used with that previous 350 build with the RHS heads then over to the Dart 180cc SHP heads build were not perfect especially the Crane hydraulic roller and could have a slight bit more compression with them but they all ran good still.


I won't post anymore history on that part and hope this post is not confusing and sorry for all the info but I need to know if there is somebody that can look at these cam specs and who has way more knowledge then what I do on them and if you can see anything by the opening and closing specs of them that would indicate a problem of my current grind compared to previous grinds I have used in the past that worked just fine with an almost identical setup. I know the opening and closing events of a camshaft if not grounded right could have a negative effect on how the engine would run.

I know the basic tech such as lobe separation angles and the specs of duration and what I am looking at and also the effects of wider versus tighter lobe angles and the effects of overlap. What I am looking for is a more advanced knowledge of looking at the opening and closing degree numbers and being able to get an idea if something would not work right such as the intake valve being open to long or to little and the same thing in relation with the exhaust opening and closing numbers.

I know things work in relation to the opening and closing points and it can affect certain areas of the cam in relation how it will work with the engine such as the whole combustion process and can effect the engine build.

Current cam Mike Jones custom grind hydraulic roller.
268/272 220/[email protected] 510/510 lift 110/114 lobe separation angle 42 degrees of overlap seat to seat.
Seat to seat IO 24 IC 64 EO 78 EC 14
@50 IO 0 IC 40 E0 50 EC -6

Previous 350 build camshafts used in it.
Lunati voodoo hydraulic roller cam
270/278 219/[email protected] 515/530 lift 106/112 lobe separation angle 50 degrees of overlap seat to seat
Seat to seat IO 29 IC 61 EO 77 EC 21
@50 IO 3.5 IC 35.5 EO 51.5 EC -4.5

Lunati voodoo hydraulic roller cam
262/270 211/[email protected] 500/515 lift 106/112 lobe separation angle 42 degrees overlap seat to seat
Seat to seat IO 25 IC 57 EO 73 EC 17
@50 IO -0.5 IC 31.5 EO 47.5 EC -8.5

Crane power max hydraulic roller
283/291 222/[email protected] 5??/5?? lift (can't remember exact lift) 108/112 lobe separation angle 63 degrees overlap
seat to seat IO 35.5 IC 69.5 EO 81.5 EC 29.5
@50 IO 3 IC 39 EO 51 EC -1

Thanks guys and hope to hear from some of the more knowledgeable guys on here. I have tried looking up stuff on google but I can't find much.

 

[eric32]

I guess this is something that nobody can answer or give some tech advice on and perhaps this thread should be ended and closed. Sorry for any inconvenience and apologies.

 

[ExcellenceAuto]

Is this the same issue as the other post? Something about it runs really good except when you let your foot off the accelerator, something happens? Sorry, I kinda remember reading that post...
What exactly is the problem again?

 

[eric32]

Yes it is and from day one when I put this camshaft that I had custom grounded and installed in my previous 377 with the air gap intake and then I had nothing but problems with any carb wanting to work on it since day one and after a year and a half I have not been able to get much time working on it as one problem after another has plagued me having to get other things fixed that took away from that.

The first cam and victor jr intake in the 377 build which was slightly bigger ran like fuel injection and any carb I stuck on it regardless of it being my 650 vacuum secodary Holley or 600 and my double pumper carbs I could always adjust them and tweak the idle circuit and it worked fine like it normally does.

Then the problem from the 377 cam intake swap only got worse when I swapped the 377 short block out for the 350 short block and the same symptoms only increased and no matter what I do or change the calibration on the carb and only by changing out the spacers can I get some difference in how it runs but it is not letting me getting any adjustment out of the idle mixture screws and be able to kill the engine and it idles off the idle mixture screws and that is even with the idle speed screw backed nearly all the way back and no transfer slot exposure.

It runs funny and when driving its smooth for the most part but once you let off the throttle and as soon as the throttle blades close to where it would be on idle it studders every time for a second and a half and then smooths back out like a big temporary swing up or down in the air fuel ratio till it stabilize. I finally got it to not studder while driving and finally got it to get a meager 1/8 of an inch of an adjustment on the idle mixture screws and at 1/8 a turn out it will now studder in gear but open it up to a half turn out then it smooths out. But in park its richer and will studder off and and is a very soggy feeling to it. The throttle snap sounds not to bad but not the best either but not as bad as it was while I messed with it last week.

I am waiting for some warmer weather which might have to wait till March if I can get to at least 50 degree weather and I have a different blase plate I am going to try as the one I have been using the transfer slot is about .400 up form the base plate and takes over a 1 and a 1/2 turns just to get a .020 transfer slot exposure and this is an older base plate Holley used on the early model 600 vacuum secondary 1850 and 80457 models. The pcv port goes into the side of the base plate on the passenger side and then when Holley changed them to a new design they have a longer transfer slot machined in them and I can turn the idle screw only 3/4 of a turn to show .020 transfer slot.

To me in theory with the longer transfer slot on the newer base plate it gives me an easier range to get the right setting and also a broader range of its use across the throttle travel in comparison to the older version as I know the transfer slot is critical in the operation of the carb in more way I can word here. On the older builds I used the 600 Holley vacuum secondary or the 670 street avenger which use the same base plates they always had the newer design base plate where the pcv port was moved to the rear and a longer transfer slot and its always worked in the past.

I don't know that if the longer transfer slot is playing a culprit in this or not but I used the same base plate on all three 600 carbs I built to try on this and had the same problems across the board. I leaned it out back to stock and in the past it would allow me a broad range on a mild build like this to adjust the mixture screws no problem.

I have used two different metering blocks and new power valves and gaskets and tested them in my power valve tester tool and its all been good. I am wondering even though on the older base plate the transfer slot is not showing that with the larger more amount of throttle blade opening allowing so much air through the primary throttle blades that somehow its still creating enough velocity to be pulling fuel from the transfer slot somehow causing my idle mixture screws to not respond but I don't know.

Or in a weird way this cam wants an even leaner idle circuit compared to all my previous builds with near identical cam sizes as this. Even my Father who has built performance motors for nearly 50 years has never seen anything like this and has even stumped and he builds everything from Detroit to Japanese stuff and has done work on building late model dirt track cars and built carbs and engines for many people from factory and hot rod builds and really knows a lot and everything we have checked over a fine tooth comb I have not been able to find the reason yet.

I have another 600 I am putting together and using the other base plate this time with the longer transfer slot and see if that one little difference between the older base plate versus the new one. That is the only difference between the older carbs I used to compared to the newer design ones as I looked over every dang part on it and measured everything and found out that is the difference.

I once ran the 600 Holley older style version with the side port pcv valve base plate version on a old 350 with the crane hydraulic roller cam listed above and it was just stock settings and it ran fine and that cam had a lot of overlap compred to the others and the stock setting worked with it. But once I gave it back to my Father years back and after I swapped out to the smaller and less overlap lunati voodoo hydraulic roller cams with a newer designed base plate version of the Holley 600 vacuum secondary or the 670 street avenger I could not use the stock settings as on it came out to lean on the stock settings and had to make the idle circuit richer.

The older style one worked just fine on the bigger cam which would require a richer mixture and in theory it would have been to lean. That so far is the only thing I can think of that is the difference between of what I used in the past and the only changes made to them. I got a Quick fuel carb to throw on too after I try a few more things with the Holley but after all this time I have to know what is the problem and no how to fix this problem in the future or help somebody else i it should come up.

I never had a carburetor not operate the mixture screws except with big radical cams which required the idle to expose the transfer slot to much but I corrected that in very short order after just a few changes and adjustments. Thank you so much for replying as I was feeling like nobody was wanting to say anything. I am just trying to see if something with my cam grind is off just a hair from the others as I am having to thing outside the box here as the normal procedures is not working trying to trouble shoot this issue. Thanks again and much appreciated.

 

[BogiesAnnex1]

Did I miss the mention about ignition timing?

The old adage about ‘most carburetor problems are electrical’ holds a lot of sway.

Bogie

 

[eric32]

Yeah bogie I have verified my timing several times and I verified my TDC on my timing tab and balancer even before the timing cover was tuck on and the heads etc. Went through all this stuff before it was build. I have 12 to 16 of initial timing and then with vacuum advance added which is limited with a MSD limiter plate I have an added 14 more degrees at idle with vacuum advance with a total of around 29 degrees. My mechanical advance does not start to advance until 1200 rpm at 2 degrees and is all in around 3000 rpm or a hair over and it times smoothly across the higher rpms and I have around high 48 degrees of timing while cruising rpm with vacuum advance added to mechanical in high vacuum situations.

My timing curve specs I use has been successful on all my past builds even with bigger cams then what I got and with way less vacuum and ran fine.

All ignition stuff has been checked and several times over and with it running the vacuum had been just about one inch from the highest I have had it before but with the problem of unable to be able to adjust the carb normally has been the odd ball problem. It start up nice and healthy and has no struggles and is good running while warming up for the most part and I after the intake swap have gotten some improvement over the air gap I took off.

Still after some adjustments with the carb last week I got it able to finally kill the engine but its in such a very short window that I can get it to to do that. I only have an 1/4 of adjustment on the mixture screws while in drive to where it will studder and at half a turn it will smooth out. I can kill it but I don't have my notes in front of me on the adjustment that I finally found to get me that.

This is the only first time to get it to do that. My plugs are looking better then what they did in the past time but still nowhere good but nothing like when it fouled out in short order.

 

[1979Malibu]

I guess this is something that nobody can answer or give some tech advice on and perhaps this thread should be ended and closed. Sorry for any inconvenience and apologies.

I can shed some light on the lack of replies on that. The amount of context, the number of caveats and just the sheer volume required to even discuss how the basics apply here....makes my head hurt trying to figure out how to put what little I know into a post. I would image the folks that know a lot more than I do thought the same thing.

You touched on something in one of you posts that you should consider here. If I understand you, this is the 2nd engine this cam has been in with tuning problems? I would be interested to see what a degree wheel shows concerning the valve timing events. I've never seen anything that wasn't accurate to the cam card but I have heard many people have. I think a cam in the wrong box could happen pretty easily.

 

[alwill923]

You must degree the cam! I have said this in many posts. You can not trust timing marks.

 

[eric32]

I understand that its a real complex thing to try and explain and that is most likely I can't even find anything on the net to help out with such a lot of information on that subject itself. I have never degreed a camshaft before but that is something I should have done with this and the previous build as I never had any problem in the past with custom grinds but human error can happen and I wonder if after a few more tries I can't get anywhere then I am going to have to tear down the front off this thing and put a degree wheel on and see what the heck is going on with that and at least see what it comes out at.

It just seems something is just way off somewhere even though I had good vacuum readings on the previous builds and it just would never rung right period and regardless of what carb I put on and how I calibrated it there was no change and response from it and timing and all other factors have been exhausted. I do thank you guys for at least trying that this is just a hard thing to really explain and be in a short detail about it as a lot goes into camshaft timing events.

 

[johnsongrass1]

Custom grind or not, I see problems with the chains/gears more than the cam dowel index.
I have two sets on my shelf right now, one is +4 and the other is -3.....Both marked straight up.

Your details are great, your posts are a long read, kinda hard to read actually.
Things to look at beyond the carb, ignition.....Plugs, wires, coil, etc......

 

[eric32]

I used the original timing chain on the 377 build and it ran just fine with the previous cam and intake used with it. I used that timing set on the cam and intake swap deal as well and like stated it never ran right from day one.

I sold the 377 short block with that chain with it. I used another new timing chain for this build and this is one of those learning lessons that I should always degree a camshaft just like when I buy a carb I always take it apart and check everything even before it goes on an engine to check for any errors in manufacturing as you just can't trust a lot nowadays. I got a Cloyes timing billet chain set for my build with the roller thrust bearing.

I agree johnsongrass1 its a hard read and I am sorry as I am not good with words as much as I used to be able to do. I struggle with cognitive skills as since I had a lot of radiation to my head and neck from fighting cancer nearly ten years ago and all the chemotherapy I had shot in my body and the boat load of drugs I had a lot of damage done to my body and at lot I have never recovered from and parts of my body are slowly dying out sad to say with my nervous system.

I try to do the best I can and I had to try and refresh my mind with a lot and re learn some things but as the years have gone on its progressed worse for me and at times I can't even get a correct sentence out when I talk and have to re say things. I have a few more things to try and if not then I am going to have to pull the front timing cover off and check the camshaft degree and buy a wheel.

 

[johnsongrass1]

Sorry about your health....
I'd buy, borrow or steal a known working carb before pulling the covers.
What coil are you using?
What plugs?
What Wires?

 

[eric32]

I am using a large cap HEI distributor and the distributor itself is only three years old and I replaced the control module with a BWD one and the coil is a BWD brand as well that I had from a previous distributor as I had some trouble with a distributor a few years back that the magnetic pickup went bad and I kept the good parts out of it and the distributor I put in the engine in was brand new and I took its coil and control module a year or so back just to check and see if it was ignition related just to rule things out. The wires I am using are premium wires that I got from autozone and are only two years old and still look like new and I checked the resistance and they are pretty much the same the day I got them and read within what is considered a good reading.

I had a set of Jegs performance wires on it before I got these wires on the previous 377 and they worked ok but I got too much RFI noise from them and caused a lot of problems with my radio. I have used the best quality plug wires from Autozone and also Advance auto over the years and never any problems. I had a set of low resistance Summit ones before and just like the Jegs ones they gave me a lot of RFI noise in my radio while trying to play it and stuff. I never did see any performance gain using either one.

i have a brand Holley I am putting on it that has never been used before to rule that out even though the previous ones were like new and very clean and I rebuilt all of them. They had new metering blocks I got from all carbs and a base plate that was nearly new. I am using Autolite 3926 plugs and used also NGK FR4 plugs and also a crappy set of champion rc12yc but they did not last long as they was a colder plug and it was only what I could get at the day I needed them during the whole covid junk the last few years.

I bought me a quick fuel brawler the other day with a four corner idle which gives a way better range of adjustment to try and see how it does. I have to wait for warmer temperatures as I don't have a heated garage and I don't drive my truck in snow. My autolite plugs are seeming to hold up quite a lot better and so far they are not blacking out as bad as the previous NGK plugs which I wonder if they might have been fakes but looked legit.

 

[eric32]

Well guy bottom line I posted on my other post and it is not a camshaft problem by any means. I finally found out my problem and this whole dang time for the last year it was the base plate being the cause of all my problems. All the information is on my other post but this mystery is solved. The older design base plate had a way shorter transfer slot versus the newer design base plate Holley uses on there 600 vacuum secondary carbs models the 1850 and 80457 and 670 street avengers. It worked excellent like I knew it should have and adjusted just fine.

Engine is smooth in park and drive and the throttle opening is nice and clean and a steady 16 inches of vacuum. I had 17 on the 377 but don't know why on this one but I am not worried about it. Its all solved just need to final tune and take it out next week it weather permits and I can do the final tuning of other areas.

Thanks guys for your help.