Question about heat x-over / pinging / 383

[Jaysick]

Hi there everyone!
Ive got a little bit of a problem with my 383 in my 70 charger pinging and im hoping some of you guys may have some insight into it.

The heat x-overs were obviously causing problems with the fuel.  I live in San Diego so it gets hot enough for me to notice the effect on my fuel.  Car would sputter and die on hot days when i wasnt on the freeway.   A insulator between the intake and carb fixed that right up so I didnt feel I needed to pull the intake off and put a valleypan with x-overs blocked.   Ive had the car since 2011 and have slowly been building it up.  It had a stock distributor but non-stock cam (lift 443in 465ex dur 214in 224ex) nothing too crazy.   Its bored .40 over and has a compression ratio of 10:1.  I would put a bottle of octane booster in it every fill up to keep the pinging down at high throttle (mostly when kickdown engaged) but recently put in a pro-billet MSD.  Currently ive found it seems to like a timing of 18-36 all in @2k.
Runs fantastic!  Until it starts to heat up...   After it gets to about 180 or so (on a hot day), when I accelerate hard it still pings and the hotter outside the worse it gets.   Not when the temp is down on a cool day but only when hot.   All my gauges are aftermarket and sending units are new as well.  I have Be Cool radiator and dual electric fan setup and dont have any overheat problems.
Im wondering if I need to block those x-overs or if it may be another problem...    I have recently found that I have oil in my radiator but not the other way around.   Car doesnt overheat and runs good other than the problem I mentioned.
Ill have to create another post about my oil in radiator problem as I just found that out this weekend and put some bars leak in it and seems to be ok.    I suspect a blown head gasket (I dont think mopar 383s have water jackets in the intake?)

Anyways, what do you guys think?  Can unblocked crossovers cause this?

Everyone here is so helpful and i'm really grateful for all the excellent advise ive got since joining this forum!

[Dino]

Well until someone else comes along with some excellent advice, you'll have to settle for me.   

A lean condition can cause pinging, as do hot plugs among others so first things first:
Which plugs are you running and what do they look like?
Which carb?  Does it have a power valve?  Any idea on the A/F ratio? 
How much vacuum are you pulling at idle?  Are you running vacuum advance?  Ported or full?

I had hot start issues when I got my car but I've never had any problem during driving.  If you loosen the intake manifold bolts you can carefully slide a thin metal plate over the crossover to try it out but I'd check the other stuff first.  Oil in the rad is probably the first thing that needs solving here.

Oh and 180 is actually pretty low, how high does it get on a really scorching day?

[Jaysick]

Thanks Dino I really appreciate the reply!
Im using Champion RJ12YC plugs.  I havent looked at them since I changed the distributor and plugs out a couple weeks ago but I will this weekend when I check the compression.
Im using an Edelbrock 1412 800CFM.   I feel like this may be a little big?  I was thinking about getting a jet kit and try different ones out which sounds like what you are suggesting?   I loaned out my vacuum tester a couple years ago and I guess im gonna need a new one...  Not really sure what the A/F is supposed to be, Ive only adjusted the idle mix with the two screws in the front.  The distributor I put in doesnt have a Vac advance.

Ill have to try sticking a little plate in to block it off.   Ive been looking all over for someone who says that can be done but couldnt really find any evidence of that so I havent tried it.   Scared I wont be able to seal it back up well enough to prevent a vac leak.   I have a 351c motor that for some reason was ridiculously tough for me to seal up the intake leak free so ive been a little chicken to try something like you're suggesting  
Since I think I have a blown head gasket I guess its coming off anyways..

It gets up to 190 before the fans kick on but if its really hot driving in traffic it may get to 200 before it starts going down but that hasnt happened lately.  If its really hot and traffic is bad ill switch the fans on early to give it a head start.
180 gives no pings on a cool day but 180 on a hot day for some reason causes pinging (only when the kickdown is engaged)  and as the temp creeps up it will start pinging just from hard acceleration.

Thanks again for taking the time to read my post offering up your advice.  Super grateful!
Steve

[Dino]

There is always the risk of not getting it sealed up again when you stick the plate in, although a thin bead of permatex ultra copper would take care of that easily.  I only suggested it in case you really didn't want to remove the intake but it really is the best way to go.  I doubt it's the source of your problem though but if you don't need a choke then by all means block it off.

An 800 cfm is pretty big for a 383 and may be part of the problem.  Would you happen to have access to a smaller carb just to test before you buy a jet kit?  I am not a fan of changing too many things at once because then you still won't know what the fix is.  Do one mod at a time.  I'd start with the carb.

Ideal A/F ratio at idle is 14.6, anything close to that is fine for a stock engine so factor in the cam and it may be off a bit.  This is the vacuum gauge I use: http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

Get some readings on vacuum, A/F if you can, compression, plugs and all that and get back to us.  If you can loan another carb from someone I would definitely try that.  Look for something small like a 600 cfm. 

There's a lot of smart people here who will find the cause of the problem.   

[Jaysick]

Thanks Dino!
I totally agree, one thing at a time so we actually know what the problem is
Ill start with the carb and see what I can come up with and post up here when im done.  My 351 has a 1406 600cfm carb so maybe ill try that out and see how it works.  Nice suggestion on the vac gauge, ill order one up right now.

Thanks again buddy, much appreciated!

[Dino]

Always a pleasure   

I have a 1406 as well, it's going on the 440 tomorrow.

[69wannabe]

With that kind of compression if it is a true 10 to 1 and you are running cast iron heads 36 degrees total advance may be pushing it. I would drop the timing down 2 degrees to 16 initial and 34 total and I would block the heat crossovers with the fel pro intake gasket # 1214. I think thats the number for a 383. I am running about the same compression on my 493 and running cast iron heads running 16 initial and 34 total with a firecore distributor and I have my heat crossovers blocked and I run 93 octane with no octane booster and my engine runs great and no pinging. That 600 carb would be a better carb for the 383 than that 800. I'm running an 850 holley but it's a 493 ci.

[moparnation74]

Oil in the radiator would be the first thing to figure out.

I reside in Texas so I deal with the same hot temps as well.  You said the car runs fine on cool days.  I take it at some point it was tuned on a cool day.  With the new fuels and the ever changing environment, you have to adjust your tune/carb for different seasons sometimes.

[Jaysick]

Thanks 69wannabe and moparnation74 for that input.  Those are all really good points.   Thinking back, its only recently started to get "really hot" and although I cant remember honestly, its possible it was relatively cool during the weekend I stuck that MSD dist in there and adjusted the timing.   I did a lot of things that weekend, adding a trigger box, new dist and such so I was sure it was running great after the long test drive.  Ive had this heat x-over thing nagging me ever since i got the car and keep looking for reasons to plug it... maybe I just just do it already lol.
I kinda thought that 36 total seemed a little much but it seemed to run so good that way (better than ever) at least for a week or so and when its cool out.  Well Ive got some things to keep me busy this weekend so ill get to it.
Ill update once im done.

Again, thanks everyone for your advice and insight!  I read this board constantly and although I dont post much im really grateful for all the help this forum and all its members provide!