383 Vortec/TBI Build Thread

[Daveo91Burb]

Zip disc would be better, with a bucket of water right there to keep cooling it. Faster and less heat than grinding.

Or, a bottoming tap.

I ended up going with an ARP stud - worked perfect.

 

[Daveo91Burb]

How is your deck height?

I think it's just a hair under 9.015. I was able to slide a .006, but not .007, feeler gauge between the top of piston at TDC (got exactly at TDC with a dial gauge) and a straight edge held across the deck. 3.75/2 + 5.7 + 1.433 + .006 = 9.014. With those numbers plus my head gasket numbers I'm getting 9.48:1 CR.

 

[shiftpro]

I think it's just a hair under 9.015. I was able to slide a .006, but not .007, feeler gauge between the top of piston at TDC (got exactly at TDC with a dial gauge) and a straight edge held across the deck. 3.75/2 + 5.7 + 1.433 + .006 = 9.014. With those numbers plus my head gasket numbers I'm getting 9.48:1 CR.

Previous post: ARP stud... brilliant. You're a stud too.

Deck height... Well at least you checked. IMO you're leaving efficiency on the table. Of course it means assembling the engine, at least crank and one piston to check it, then back to the machine shop. I'm not saying your engine will be a dog.

As I recently mentioned in another post, I've become an absolute maniac about deck height. It's my newest obsession. The last half dozen years two of my buddies rebuilt 454s and decked the **** out of them. Total obvious seat of the pants difference in basically stock engines. This mod, I would imagine, would be even more pronounced in a built engine. And of course to be fair, mods on a BBC are much more 'in yer face' than sbc.

Just curious Dave, how did you come across your head chamber's cc's? Spec list?

 

[shiftpro]

Oh and thanks Dave for posting the awesome pics. Eye candy makes me happy.

 

[Honky Kong jr]

Oh and thanks Dave for posting the awesome pics. Eye candy makes me happy.

Here is some more........

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[Daveo91Burb]

Previous post: ARP stud... brilliant. You're a stud too.

Deck height... Well at least you checked. IMO you're leaving efficiency on the table. Of course it means assembling the engine, at least crank and one piston to check it, then back to the machine shop. I'm not saying your engine will be a dog.

As I recently mentioned in another post, I've become an absolute maniac about deck height. It's my newest obsession. The last half dozen years two of my buddies rebuilt 454s and decked the **** out of them. Total obvious seat of the pants difference in basically stock engines. This mod, I would imagine, would be even more pronounced in a built engine. And of course to be fair, mods on a BBC are much more 'in yer face' than sbc.

Just curious Dave, how did you come across your head chamber's cc's? Spec list?

Funny...I'm actually concerned the other way, i.e. too much CR. This is a 3/4 ton 4x4 that I want to be able to tow with, 9.5:1 is the upper limit of what I want, even with vortecs. If you wade through this thread you'll see that I actually switched pistons mid way through the build. The speed pros I had before would have given me 10:1 or even higher. Also buried in this thread is the fact that I switched machinists mid way through the build. Leads into your next question.... Lots of problems with this first guy, but one of the big ones is he insisted the vortecs were 67cc, not 64cc. I knew better but didn't argue. (mistake!) He ordered the speed pros, but didn't cc the chambers until afterwards. At this time he started flaking out on me and eventually went and got all my **** from him and paid for work he had done. (His machine work was still good, thankfully). Brought it to a new machinist, good rep, and he had to balance, do some more honing, install press-fit wrist pins, freeze plugs, cam bearings, etc. At this time I decided those pistons were just too much and bought the KB 135s I'm using now. Vortecs are supposed to be 64cc and that's eventually what he told me they were. I'm sure they're not exactly 64, but probably pretty close.

 

[Daveo91Burb]

Worked on valve train a little more tonight. Want to be sure my pushrods are correct length. This pic leads me to believe I'm good, but not 100% sure lifters are staying locked. I soaked them in oil before I put them in, but not sure if that holds or not. Would it change much if they're not locked? Maybe I should take a couple of valve springs out and replace them with light springs? I know they sell those for that purpose, but I'm wondering if I could just go to the hardware store and find some that are same diameter/length but much lighter? I have a really good hardware store close by......

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[shiftpro]

Funny...I'm actually concerned the other way, i.e. too much CR. This is a 3/4 ton 4x4 that I want to be able to tow with, 9.5:1 is the upper limit of what I want, even with vortecs. If you wade through this thread you'll see that I actually switched pistons mid way through the build. The speed pros I had before would have given me 10:1 or even higher. Also buried in this thread is the fact that I switched machinists mid way through the build. Leads into your next question.... Lots of problems with this first guy, but one of the big ones is he insisted the vortecs were 67cc, not 64cc. I knew better but didn't argue. (mistake!) He ordered the speed pros, but didn't cc the chambers until afterwards. At this time he started flaking out on me and eventually went and got all my **** from him and paid for work he had done. (His machine work was still good, thankfully). Brought it to a new machinist, good rep, and he had to balance, do some more honing, install press-fit wrist pins, freeze plugs, cam bearings, etc. At this time I decided those pistons were just too much and bought the KB 135s I'm using now. Vortecs are supposed to be 64cc and that's eventually what he told me they were. I'm sure they're not exactly 64, but probably pretty close.

I completely agree with your reasoning Dave. I missed the part about you switching pistons and your right about 9.5-1 is about the upper limits on pump gas and still have decent timing advance.
Easier said than done, finding the right pistons to run a zero deck height or more, and keep compression in check. Something I don't think about in my world because as long as I can still get it, I'm all about propane (high octane) and high compression. I just wanted to bring this point to light.
And yeah, many engine builders have high compression egos...

 

[MikeB]

Excellent, thanks. All makes pretty good sense to me. So if the valves pass this clearance test, I won't have to worry about the coil bind?

No, not true! Just because your retainer doesn't hit the seal until .550" lift, that doesn't necessarily mean the spring will not coil bind at the same lift. Best way to check is with a spring in a vice. First, compress the spring to the "installed" height, such as 1.70". Then slowly compress it some more by the amount of valve lift plus approx .050".

I forgot, are those stock Vortec springs and installed at 1.70" height? If so, I have a set in the garage and can check them for you. If not, what are they?

BTW, good job so far!

 

[Daveo91Burb]

No, not true! Just because your retainer doesn't hit the seal until .550" lift, that doesn't necessarily mean the spring will not coil bind at the same lift. Best way to check is with a spring in a vice. First, compress the spring to the "installed" height, such as 1.70". Then slowly compress it some more by the amount of valve lift plus approx .050".

I forgot, are those stock Vortec springs and installed at 1.70" height? If so, I have a set in the garage and can check them for you. If not, what are they?

BTW, good job so far!

Thanks, Mike! Yes, pretty sure they're stock springs. I just went out and measured with the stick part of my calipers - looks pretty darn close to 1.70" height to me. That would be great if you could check for me. I think I'm going to be OK, there is a ton of clearance in between the coils at full valve lift, but I know it needs to be a little more because the lifters probably aren't locked. Best to be safe.

Any thoughts on my pushrod length conundrum? I think I'm going to disassemble a couple of lifters and try to make them solid. Then I can check valve springs and pushrod length.

 

[MikeB]

Regarding pushrod length testing, use a test spring and something that doesn't need a lot of pressure for the roller tips to mark, like Prussian Blue. If your lifters are new, I certainly would not disassemble one. That is a "clean room" procedure, IMO.

I just checked two stock Vortec valve springs that had been used with a mild roller cam for less than 1,000 miles. Max revs they ever saw was probably 4500 RPM. My point being they weren't abused. Measurements on both were within 5# and .005" of each other.

75# pressure at 1.700"
210# pressure @ 1.190"

Coil bind height = 1.130"
Lift at coil bind = .570"

Safe height = 1.190" (after .060" safety margin)
Max safe lift = .510"

Here you can see how close the coils are at max safe lift.

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So, you are good to go for up to .510" lift, assuming the retainers don't hit the seals before then. However, I wouldn't go anywhere near that much lift with those springs.

According to GM Performance Parts specs, the same springs are used in the RamJet engine with 1.6 rocker arms, which would net .460"/.481" lift. But I think that is at the ragged edge for springs with such low pressure. I don't remember your cam's lift, but I wouldn't use the springs for anything more than .470", unless you want them to serve as a built-in rev limiter.

I may have mentioned this in an earlier post, but on my Vortec heads I installed LS6 beehive valve springs using CompCams retainers and locks. The combo installs at 1.750" height for .570" max safe lift. Seat pressure @ 1.750" is 198#, pressure @ .500 lift is 295#. Combined with the lighter beehive springs, valve control is significantly better at all RPMs.

Valve springs: GM 12499224
Retainers: Comp 787-16
Locks: Comp 648-16

 

[MikeB]

Deck height... Well at least you checked. IMO you're leaving efficiency on the table.

I disagree. If Dave has a 9.015" deck height + .028" gasket, and D-dish pistons (better quench than full dish), I don't think you can get any better than that. In fact, in his book, John Lingenfelter said .043" quench (.005" + .038") was nice number to shoot for.

 

[shiftpro]

I disagree. If Dave has a 9.015" deck height + .028" gasket, and D-dish pistons (better quench than full dish), I don't think you can get any better than that. In fact, in his book, John Lingenfelter said .043" quench (.005" + .038") was nice number to shoot for.

You're probably right come to think of it.

 

[Daveo91Burb]

So, you are good to go for up to .510" lift, assuming the retainers don't hit the seals before then. However, I wouldn't go anywhere near that much lift with those springs.

According to GM Performance Parts specs, the same springs are used in the RamJet engine with 1.6 rocker arms, which would net .460"/.481" lift. But I think that is at the ragged edge for springs with such low pressure. I don't remember your cam's lift, but I wouldn't use the springs for anything more than .470", unless you want them to serve as a built-in rev limiter.

I may have mentioned this in an earlier post, but on my Vortec heads I installed LS6 beehive valve springs using CompCams retainers and locks. The combo installs at 1.750" height for .570" max safe lift. Seat pressure @ 1.750" is 198#, pressure @ .500 lift is 295#. Combined with the lighter beehive springs, valve control is significantly better at all RPMs.

Valve springs: GM 12499224
Retainers: Comp 787-16
Locks: Comp 648-16

Thanks for checking, Mike. That takes a load off. I'm using the stock L31 cam. With 1.6 rockers I'm coming up with .44 intake/.46 exhaust. Should be good to go there.

Regarding pushrod length testing, use a test spring and something that doesn't need a lot of pressure for the roller tips to mark, like Prussian Blue. If your lifters are new, I certainly would not disassemble one. That is a "clean room" procedure, IMO.

I'm using used L31 lifters. I didn't see your post before I disassembled two of them tonight. I guess I'll just have to make sure they go back together nice and clean. Actually, I may have to disassemble all of them - those two were a bit gunky inside. The good news is by removing the check ball and its cap and spring, and then flipping around the inside cylinder and reinstalling it I ended up with a solid lifter that has the pushrod cup at the right height. I installed those two in one cylinder and was able to check pushrod length and it came out good - mark is right in the middle of valve stem. So I'm pretty comfortable now. Just need to make sure lifters are good, clean, and it working order now.

 

[4WDKC]

Since youre building a 383 a stock vortec cam I would think would be to small. Im planning on doing the head swap on my 350 and I went with a LT1 cam which has just a bit more duration and lift. With a 383 I would think a stock lt4 would be a good one.