LS3 Carbed build

[CGT]

Nice numbers for a hydraulic cam, im not tuned in on ls stuff, what type of average intake runner and head csa dose it have
Tom

Big . Its 4 inch at the plenum...about 3 inch at the manifold exit...2.86 at the throat.

[paulzig]

Or,.... put the heads/intake/cam etc on 400 plus cubes and lower the rpm. LOL

What about less camshaft?

Lower comp, small cam which peaks around 6000-6200 carry to 7000 RPM might make a good daily driver

it would take an extremely small cam to get Chad's 378 to peak at 6000-6200 rpm. I did a 408 ls with ported cathedral port heads, 2.02"/1.56" valves, 243/258/110 cam with .625" lift. sv intake, 4150 carb. It made peak HP at 6000-6200 rpm. The induction trac is the number one thing that determines where an engine makes peak at.

Randy

Considering the stock cam pulls an LS3 close to that 6000RPM, you might have a hard time trying to make it RPM a lot less than what it is, so its a funny thing most of the time you struggle to go up in RPM not down

[zums]

Nice numbers for a hydraulic cam, im not tuned in on ls stuff, what type of average intake runner and head csa dose it have
Tom

Big . Its 4 inch at the plenum...about 3 inch at the manifold exit...2.86 at the throat.

Didnt read thru the whole thread, just checked out page 1, is it still alky or gas, those csa's would make more sense if its still alcohol, its a little monster
Tom

[CGT]

Nice numbers for a hydraulic cam, im not tuned in on ls stuff, what type of average intake runner and head csa dose it have
Tom

Big . Its 4 inch at the plenum...about 3 inch at the manifold exit...2.86 at the throat.

Didnt read thru the whole thread, just checked out page 1, is it still alky or gas, those csa's would make more sense if its still alcohol, its a little monster
Tom

It was dynoed on C12

[zums]

Big . Its 4 inch at the plenum...about 3 inch at the manifold exit...2.86 at the throat.

Didnt read thru the whole thread, just checked out page 1, is it still alky or gas, those csa's would make more sense if its still alcohol, its a little monster
Tom

It was dynoed on C12

What made you go that big for that cube and rpm with a carb
Tom

[CGT]

Didnt read thru the whole thread, just checked out page 1, is it still alky or gas, those csa's would make more sense if its still alcohol, its a little monster
Tom

It was dynoed on C12

What made you go that big for that cube and rpm with a carb
Tom

It really wasnt a clean sheet deal. Original goal was to see what could be done using as many stock parts as possible. I had a 6.2 ls3 core. The heads are bigger than this stock. They have been epoxied down some and will probably get epoxied up more and the intake manifold could use some also.

Stock valves have been turned down smaller, stock crank, rods, valves, rockers, lifters...i built it just for dyno testing so it may end up with a solid roller, better connecting rods , crank and more rpm.....more epoxy, or more stroke to bring the rpm range down...not sure yet

[zums]

It was dynoed on C12

What made you go that big for that cube and rpm with a carb
Tom

It really wasnt a clean sheet deal. Original goal was to see what could be done using as many stock parts as possible. I had a 6.2 ls3 core. The heads are bigger than this stock. They have been epoxied down some and will probably get epoxied up more and the intake manifold could use some also.

Stock valves have been turned down smaller, stock crank, rods, valves, rockers, lifters...i built it just for dyno testing so it may end up with a solid roller, better connecting rods , crank and more rpm.....more epoxy, or more stroke to bring the rpm range down...not sure yet

I can respect that, nice job
Tom

[CGT]

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Back to work.....

[steve316]

Chad this post makes me want to have you build a ls for me.

[CGT]

Chad this post makes me want to have you build a ls for me.

Well your the retired one! You might want to reconsider that....I have some weird oil pressure deal going on with this thing when under vacuum....trying to figure that out and get back on the dyno.

[MadBill]

...t....I have some weird oil pressure deal going on with this thing when under vacuum....trying to figure that out and get back on the dyno.

One apparent weirdness is that with a wet sump, the gauge reading psi will drop by 1/2 the "Hg. of pan vacuum, however the operating pressure differential between the pan and bearings will remain the same. In other words, if you enclosed the gauge in a sealed plexi box plumbed to the pan, the gauge would then not be affected by pan vacuum.

[202ci EH]

...t....I have some weird oil pressure deal going on with this thing when under vacuum....trying to figure that out and get back on the dyno.

One apparent weirdness is that with a wet sump, the gauge reading psi will drop by 1/2 the "Hg. of pan vacuum, however the operating pressure differential between the pan and bearings will remain the same. In other words, if you enclosed the gauge in a sealed plexi box plumbed to the pan, the gauge would then not be affected by pan vacuum.

True, sounds more like CGT's seeing a windage or cavitation problem though

Can't complain about the results thus far, stout regardless of the stock parts. How's the valve train looking so far with that much lift? Did you pull some duration out of it at all?

Also, any reasoning behind keeping the ls3 sprung chain guide? Stability or?? We normally remove them and fit the ls2 chain block as they tend to fail with high mileage.

[CGT]

One apparent weirdness is that with a wet sump, the gauge reading psi will drop by 1/2 the "Hg. of pan vacuum, however the operating pressure differential between the pan and bearings will remain the same. In other words, if you enclosed the gauge in a sealed plexi box plumbed to the pan, the gauge would then not be affected by pan vacuum.

True, sounds more like CGT's seeing a windage or cavitation problem though

Screenshot (40).png

Exactly
This screenshot shows the difference in pressure with and without vacuum, so yeah they're is more going on than just a conversion or reference. The good news is that upon inspection it doesn't appear that the cavitation has damaged anything. But I really do need to get it resolved or improved significantly.

Can't complain about the results thus far, stout regardless of the stock parts. How's the valve train looking so far with that much lift?

Well it sounds flawless, as far as how it looks not sure. 30 or so dyno pulls...didn't pull the valve covers, still haven't I made a couple pulls to 7700 which inherently gets passed up by a bit and everything sounds real nice up there.

Did you pull some duration out of it at all?

No. The cam I ordered this week is 4 degrees bigger on each side, spread the LSA a couple degrees, and used a slightly more aggressive exhaust lobe. So...bottom line, once I finally go solid roller I will have some weird-ass one-off hydraulic rollers laying around that will be good for nothing else. They don't really have enough lobe lift to be reground into good solid rollers without getting into the base circle too hard , and too much lobe lift for most street stuff.

I think a solid roller for this engine would look quite a bit different than this hydraulic. To get a hydraulic roller somewhat happy in a deal like this, it seems you have to accept some penalties...excessive seat duration and much slower lobe speed or just a couple this engine has for sure, but I'm learning as I go.

Also, any reasoning behind keeping the ls3 sprung chain guide? Stability or?? We normally remove them and fit the ls2 chain block as they tend to fail with high mileage.

Hard headedness . I work at a fairly large Chevy dealer, been in the business for a long time. I think I've seen 1...maybe 2 of these chain guides laying in the bottom of the oil pan. They were on very high mileage, ill maintained stuff. I'm not saying they don't or haven't failed outside of that.

I've put them on quite a few things(opposite of what is conventionally done)... which is what you stated..remove the tensioner and replace with the LS2 style damper . I haven't been bit....knock on wood.

Sometimes the internet tends to make epidemics out of incidents that are relatively isolated in the grand scheme of things. I like the idea of keeping the chain tight for accuracy and getting rid of some (noise) in the vicinity of the cam sensor.

GM put enough trust in the tensioner to place it on the LS9 equipped cars, and ALL of the new Gen V based engines are equipped with one, which is able to be retrofitted back to the Gen IV based stuff best I can tell. Cloyes is the manufacturer of the new tensioner, part# 12630107. When this one breaks on my engine I'll reconsider the use of it.

[randy331]

I think a solid roller for this engine would look quite a bit different than this hydraulic. To get a hydraulic roller somewhat happy in a deal like this, it seems you have to accept some penalties...excessive seat duration and much slower lobe speed or just a couple this engine has for sure, but I'm learning as I go.

I think it'd be interesting to do some oil pressure testing on a hyd roller set up like this one. One with some rpm and some lift.
See if more pressure makes more power cause of having a hyd lifter.

I've seen less oil pressure/volume make more power on solid lifter cam stuff, but haven't done any testing on hyd lifter stuff.
Kinda wonder if the extra pressure would stabilize the lifter enough to more than offset the pumping losses of the extra pressure???

All we need is for you to invest in an external oil pump set up and we can get to testing this idea !!!

Randy

[CGT]

All we need is for you to invest in an external oil pump set up and we can get to testing this idea !!!

Ive been looking at them!....but not for hydraulic lifter testing.