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Chevy 355 engine

3K views 11 replies 3 participants last post by  64nailhead 
#1 ·
I have a 355 with a lunati voodoo cam (10120703) 268 duration 489 lift, holley 4160 600 cfm, wieand intake 8004, my problems is when I first crank my engine I can hear the cam cutting up sounds good but after driving or getting warmed up my cam is not as pronounced I also noticed after driving if I wait 30 minutes or so and try to crank it its harder to crank I have to hold the gas to the floor any help would be appreciated
 
#2 ·
Well first thing is first that is a pretty decent performance cam as I run lunati voodoo hydraulic roller cams in both of my builds. To start off with you are using the holley 1850 or 80457 vacuum secondary correct? Just asking as sometimes someone can say a 4160 and its a typo and can be a 4150. That will make a difference in trying to help but that might come later.

When you first start your engine up on a cold start the cam sound will be a little rougher at first as the engine warms up as the carburetor does not work as efficient till its good and warm which is why you can not adjust a carb if a engine is cold. Before giving any other suggestions is your timing correct as incorrect timing will make all kinds of issues and adjust your carb will not fix it.

Also I got my stuff all set up really well and on the occasion on a hot start with my holley I sometimes have to give it a small shot but not a whole shot it just depends but most of the time I don't. Also are you running your choke all the time? I have mine off during the summer months.

You should be running at least 16 degrees initial timing and if your running vacuum advance on timed port on the side of the metering block you might want to try to run it on full manifold as it will add extra timing at idle.Initial timing and the mechanical advance needs to be set up to work with your build. Let us know about that then we can move forward.

Also with that intake you need to make sure your running a plate like I posted below or you may run into a vacuum leak since your running a square bore carb on a spread bore intake that takes both bolt patterns.

http://www.summitracing.com/parts/edl-2732/overview/
 
#3 · (Edited)
Yea it's a 1850-9 not sure on timing I took it to a shop and had it set I don't have a timing light don't know a lot about setting it I know should learn how to :spank: and I never use my choke because it usually fires right up but until after driving and letting it sit 30 mins or so my spark plugs where black and sooty I dropped two sizes from 65 to 63 they're better than before but still a lil sooty should I go down another 2 I put up some pics, so the plate would go under my carb adapter ?

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#4 ·
Yea it's a 1850-9 not sure on timing I took it to a shop and had it set I don't have a timing light don't know a lot about setting it I know should learn how to :spank: and I never use my choke because it usually fires right up but until after driving and letting it sit 30 mins or so my spark plugs where black and sooty I dropped two sizes from 65 to 63 they're better than before but still a lil sooty should I go down another 2 I put up some pics, so the plate would go under my carb adapter ?

View attachment 241786

View attachment 241794 View attachment 241778
Plugs look oily. Are the valve cover gaskets leaking?

Trying to tune without knowing the timing is the equivalent of marriage without sex - what's the point? Buy a timing light and vacuum gauge and do some reading about timing.

Sounds to me like the bulk of your issue is timing, but it's hard to tell without knowing the base and centrifugal timing.
 
#5 ·
I had a valve cover leak, I got a vacuum gauge I usually take it somewhere and have the time set guess but my distributor hold down tab keep coming loose I ordered another one from jegs hadn't got it yet guess i'm a tight wad with certain things hate to buy one use it one time then it sit on shelf waste maybe i'll try rent one or find a non expensive one any recommendations for timing light brand
 
#6 ·
Amazon.com: INNOVA 3555 Advance Timing Light: Automotive

Something like this will work just fine for DIY'er. Might be able to find one locally as well. This an essential tool for the hotrodding community as far as i'm concerned.

Regarding the distributor hold down loosening, you can most likely bend your old one back or grab one from a junkyard. The stock ones are much more durable than the aftermarket chrome cheapies IMO. Also, they don't need to tightened crazily. Snug to kinda tight is plenty tight enough for the hold down.
 
#7 ·
Before you can even attempt your timing needs to be verified in order to rule that out as a issue as timing is very critical when it comes to tuning carb. If your harmonic balancer does not have timing marks on it you can make your own timing tape and as far as setting your timing is just as simple as turning the distributor counter clockwise to advance it and clockwise to retard the timing. Also you need to verify that your top dead center mark is accurate as well as GM used three different tdc marks over the years.

Setting up your mechanical timing is pretty easy as well as all you will need is a hei advance tuning kit which comes with a spring assortment and weights and it will allow you to have your timing in quicker or later depending on what your engine needs. Also since you have a vacuum gauge you need to see how much vacuum you have at idle and if an automatic transmission then also see how much vacuum you have in gear. If your vacuum is low enough in gear it can cause the power valve to open and cause extra fuel at idle.

Also on that carb its very lean out of the box on the idle/transition circuit and does not tune well without having to open up the throttle blades to much which can also cause fuel to be pulled from the transfer slot underneath the butterfly's on the front. That carb is calibrated by holley and on any cam with more then 220@50 or more it needs to be recalibrated with a richer idle fuel curve cause the bigger cams need a richer mixture at idle in order for it to run right cause of the overlap and reversion the cam overlap itself. I had to modify my 600 vacuum holley to run on my 272/280 219/227 @50 515/530 voodoo hydraulic roller cam in order for it to run right and good.

I won't get into any detail about that as you really need to know your holley inside and out on how each circuit works with the other and also on what to look for as doing this advance tuning is more critical then just swapping out jets and adjusting mixture screws etc.The timing is the very first thing that needs checked and known and then you can then post back and we can take it from there. I posted some links below that might help some so you can have more knowledge and know what to ask others and hopefully we can get you in the ball park.

http://www.crankshaftcoalition.com/wiki/How_to_make_a_timing_tape

http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

Carburetor Tuning the Scientific Way
 
#8 ·
Also another help would be if you were to ditch the rear metering plate and convert it to a metering block and below is a link that has everything needed to do so and is way cheaper then summit and its only a little over $30 bucks with shipping and this will allow you to have jets in the rear which will come into play when tuning things.

The 600 holley is jetted in the front out of box with 65 jets and the rear metering plate is equivalent to a 66 jet size which is actually on the very lean side of things as on my holley I have mine jetted 65 primary and 73 secondary. There is normally a 6 to 8 size difference on jetting from the primary compared to the secondary as the secondary side does not have a power valve on all the street carbs holley makes.

METERING BLOCK CONVERSION WITH TRANSFER TUBE
 
#9 ·
Also on timing lights there is two different kind and the dial back timing light is what was posted above and they are ok but sometimes they don't read as accurate as a non dial back type especially on msd boxes if your running one by chance. Below is the timing light I use and that thing is always worked well for me since I have degree markings on my balancer.

http://www.summitracing.com/parts/ino-3551/overview/
 
#11 ·
I run 16 degrees initial timing on both of my small block chevy's and I run vacuum advance which I have set to a limit of 12 to 14 degrees and run it on full manifold which gives me extra timing at idle so with initial being about 16 and with vacuum advance I have around 30 degrees. Always set your initial timing with the vacuum advance disconnected also while checking your mechanical advance as well.

On my mechanical advance I have around 15 degrees and all in about 3000 to 3500 rpm. With 16 initial plus 12 from vacuum advance and 15 mechanical I have a total of 43 degrees while cruising. It will vary depending on the springs you use on your mechanical advance curve and I also use an adjustable vacuum advance canister.
 
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