Vortec Head Retrofit Question

[jjewett444]

HI guys, i thought this was the appropriate section for this thread so here i go.
After searching every forum i can find about what plugs and gap for the vortec heads on a gen.1 block everyone is saying .045 for the average gap. well i have a '75 350 .030 over dish pistons 906 vortec heads performer rpm intake manifold edelbrock 1405 600cfm carb and stock manifolds with true duals. truck only seems to run correctly with .060 gap which is the required for the 96-00 trucks however it is said to be too much gap for non computer hei dizzy. tried with ac delco rapidfire 14 plugs and autolite 605 both at .045 and absolutely no power and misfires.. anyone at all have any real expirence with this setup or reccomendations? thanks in advance

-Jim

 

[vkh]

Hmm, if it seems happy at 60 I'd run it as is for abit and check your plugs, if they're clean after a few checkups I think it's fine. If not you could upgrade your coil and module, there's many brands to do this. Personally I went with a petronix coil and module and got a built in rev limiter for peace of mind. Also maybe check that your timing is where you want it, I somewhat remember vortec heads taking less total timing.

 

[jjewett444]

I have a brand new accel distributor and i am probably going to mess with my mechanical timing since i have the kit and a tach.. static is at 15 and i have roughly 10 deg. on my adjustable vacuum advance. any idea on how far to go with vac advance? it seemed to like when i had about20 deg plus 15 static a little more throttle response it felt like

 

[77 K20]

On the GM HT383 crate motor it uses vortec heads and an older block. They recommended AC delco R44LTS spark plugs gapped at 0.040
10 degrees timing at 650 RPM and 32 degrees total at 4000 RPM. They say to run without vacuum advance though...

 

[jjewett444]

thanks man will look into the plugs.. just checked timing and all i got is a total of 30 degrees all in by 2000 rpm.. should i be better off at 3000? and will using the stiffest springs in my summit kit get me closer to that than the ones that come in the accell distributor?

 

[74 Shortbed]

Move it up to 36*, 2000 is early 2500 is good if the engine can handle it you just have to try it, try one stiffer spring and see what happens, you just have to play with it until you get what you want, or I should say what the engine likes..

 

[jjewett444]

So today after work i pulled off both stock springs and installed from my summit kit, one gold (being the lightest) and 1 black (medium), and no difference. so took out gold and ran 2 black and it changed to 30 deg. at 2500 rpm with vac advance disconnected. took it for a ride and still decent low end probably because of the 1st gear from 700r4 and about the same power as a geo metro with old milwaukee in the tank lol. well i never messed with any jets in the carb but it is a edelbrock 600cfm 1405 manual choke, doesnt pop or anything like it would if lean. crazy thing is that when i pull a wot run it sounds like im flying and it sounds good as hell but i barely move, like literally the same speed as i did with my old worn out smogger 350 with ****** heads.. im absoutley out of ideas on this one here

 

[74 Shortbed]

Move it up to 36* and you'll see a huge difference, and it it'll run cooler..

 

[jjewett444]

ok thanks. how can i do that without bumping up my static? it is at 15-16 now with vac advance plugged and like 30 with vac advance.

 

[74 Shortbed]

You set it without vacuum at this point, don't worry about initial set it at 36* total then check initial, if you have too much then you'll have to remove the limiting bushing.

 

[jjewett444]

how do i set it at 36 though? like i said evem when i plug my vac advance my initial is 15 and my total with no vac advance is around 30 degrees at 2500 rpm. just a little puzzled on how to get it to 36 without setting initial to 21 degree. the truck seems wo run pretty cool now, it seldomly reaches the 195 thermostat point esp here in upstate NY lol

 

[Daveo91Burb]

Going back to the plugs question.....x2 on this:

On the GM HT383 crate motor it uses vortec heads and an older block. They recommended AC delco R44LTS spark plugs gapped at 0.040
10 degrees timing at 650 RPM and 32 degrees total at 4000 RPM. They say to run without vacuum advance though...

The "L" in LTS is for LONG - very important. ("T" is for tapered). Vortec plugs require the longer threaded section. Plugs for older style sbc heads are too short. I didn't check the plugs you're using, they may be correct, but I just thought I'd stress this point. I could see the spark not being deep enough into the combustion chamber, potentially causing misfiring. I believe the mentioned delcos go from a 42 (colder) to 45 (hotter). I run either 44 or 43s in my Vette.

 

[1987 GMC Jimmy]

about the same power as a geo metro

That reminded me of this:

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[jjewett444]

Going back to the plugs question.....x2 on this:



The "L" in LTS is for LONG - very important. ("T" is for tapered). Vortec plugs require the longer threaded section. Plugs for older style sbc heads are too short. I didn't check the plugs you're using, they may be correct, but I just thought I'd stress this point. I could see the spark not being deep enough into the combustion chamber, potentially causing misfiring. I believe the mentioned delcos go from a 42 (colder) to 45 (hotter). I run either 44 or 43s in my Vette.

The plugs i have are ac delco rapidfire #14 which refrences to engines 5.7 350 96-99 vin R. ive also tried autolite 605 which look the same. both long reach and neither will do anything but barley idle if gapped to .045, has to be .060 to run

 

[jjewett444]

You set it without vacuum at this point, don't worry about initial set it at 36* total then check initial, if you have too much then you'll have to remove the limiting bushing.

which limiting bushing do you spaek of? and what do i do if i need to add more?