4.3L Cam & Piston Advice

[Volphin]

Hi guys,

I have pulled my old 4.3L from my 19 foot Regal ('89) due to a faulty block. 11 years was a good run for it.

I have done some upgrades over the years, and here is where the engine is to date:

4.3L Normally aspirated, Non Balance Shaft, roller cam.
True Vortec Heads
1:6 Roller tips
1409 Carb with 1485 Cal kit.
2114 Eddy dual plane manifold
SeaKamp SK 4802 (for new engine)

I have a short block in a crate, awaiting installation, but would like to upgrade the cam for a greater, wider torque curve.

The cam in the shortblock is a Melling CCS-38 which remarkably matches the
'91-'93, ZR9/Z79, Syclone/Typhoon cam in specs:
- Lift (I/E) - .351/.386
- Dur @ .050 (I/E) - .179/.195 (.252/262 @ 0.06/rocker ratio)
- IC/LS 108/112

Comp Cams recommended these cams:
Cam 09-412-8
- Lift (I/E) - .334/.334
- Dur @ .050 (I/E) - .260/.266
- IC/LS 108/112
RPM: 1200-4500

Cam 09-415-8
- Lift (I/E) - .334/.334
- Dur @ .050 (I/E) - .266/.270
- IC/LS 108/112
RPM: 1800-5000

Which would you pick and why? Is there another alternative I'm overlooking?

Will probably want to upgrade the pistons as well. Looks like Sealed Power OE type units.
Any recommendations for a slightly higher compression upgrade?

Thanks!

 

[Bondo]

Re: 4.3L Cam & Piston Advice

Hi guys,

I have pulled my old 4.3L from my 19 foot Regal ('89) due to a faulty block. 11 years was a good run for it.

I have done some upgrades over the years, and here is where the engine is to date:

4.3L Normally aspirated, Non Balance Shaft, roller cam.
True Vortec Heads
1:6 Roller tips
1409 Carb with 1485 Cal kit.
2114 Eddy dual plane manifold
SeaKamp SK 4802 (for new engine)

I have a short block in a crate, awaiting installation, but would like to upgrade the cam for a greater, wider torque curve.

The cam in the shortblock is a Melling CCS-38 which remarkably matches the
'91-'93, ZR9/Z79, Syclone/Typhoon cam in specs:
- Lift (I/E) - .351/.386
- Dur @ .050 (I/E) - .179/.195 (.252/262 @ 0.06/rocker ratio)
- IC/LS 108/112

Comp Cams recommended these cams:
Cam 09-412-8
- Lift (I/E) - .334/.334
- Dur @ .050 (I/E) - .260/.266
- IC/LS 108/112
RPM: 1200-4500

Cam 09-415-8
- Lift (I/E) - .334/.334
- Dur @ .050 (I/E) - .266/.270
- IC/LS 108/112
RPM: 1800-5000

Which would you pick and why? Is there another alternative I'm overlooking?

Will probably want to upgrade the pistons as well. Looks like Sealed Power OE type units.
Any recommendations for a slightly higher compression upgrade?

Thanks!

Ayuh,... Use a D-dish, or Inverted Dome Hyper-utec. piston to mirror the Vortec head shape to utilize the maximum Squish factor...
Shoot for 9.5:1 static compression, 'n a quench of .040/ .045"....

Oem pistons suck...

 

[Volphin]

Re: 4.3L Cam & Piston Advice

Ayuh,... Use a D-dish, or Inverted Dome Hyper-utec. piston to mirror the Vortec head shape to utilize the maximum Squish factor...
Shoot for 9.5:1 static compression, 'n a quench of .040/ .045"....

Oem pistons suck...

Like these?
http://www.summitracing.com/parts/uem-kb142-030/media/images/make/chevrolet

 

[Tail_Gunner]

Re: 4.3L Cam & Piston Advice

Comp cams xm 264 ground at 112/lsa is a moderate cam the xm270 @112 is a little hot but a good choice. Those cams are for v8 but comp will grind them for the v6. You will have to replace the spring's for the added lift or have the heads machined. Replacing the spring's and retainer's is a better value and more reliable method....just a opinion

 

[Volphin]

Re: 4.3L Cam & Piston Advice

Comp cams xm 264 ground at 112/lsa is a moderate cam the xm270 @112 is a little hot but a good choice. Those cams are for v8 but comp will grind them for the v6. You will have to replace the spring's for the added lift or have the heads machined. Replacing the spring's and retainer's is a better value and more reliable method....just a opinion

Assuming I went with the XM270, with my 1:6 roller tips, that would put my total lift @ .525/.533 assuming a .030 increase. Would I not be smacking a piston or the valve guide? Stock XM270 is .495/.503...

 

[Tail_Gunner]

Re: 4.3L Cam & Piston Advice

Assuming I went with the XM270, with my 1:6 roller tips, that would put my total lift @ .525/.533 assuming a .030 increase. Would I not be smacking a piston or the valve guide? Stock XM270 is .495/.503...

http://www.s10planet.com/forum/showthread.php?t=14790&

You can identify your head and rocker info in that link and all that is required. It is your choice to use ls6 springs or comp's behive's...The behives are going to give you more seat pressure.

http://www.pacificp.com/forum/viewtopic.php?t=8710&postdays=0&postorder=asc&start=0

A very detailed thread showing the exact process along with the spefic retainer's and parts.

http://www.carcraft.com/techarticles/vortec_valve_spring_upgrade/

And a over view of the entire process. Note you will have to drill out your push rod guides to accomidate the increased lift.

 

[Volphin]

Re: 4.3L Cam & Piston Advice

4.3L Rocker Swapping 101

You can identify your head and rocker info in that link and all that is required. It is your choice to use ls6 springs or comp's behive's...The behives are going to give you more seat pressure.

GM Performance :: View topic - LT4 Hotcam in L31

A very detailed thread showing the exact process along with the spefic retainer's and parts.

Valve Spring Upgrade - Beehive Valvesprings for the Vortec V8 - Car Craft Magazine

And a over view of the entire process. Note you will have to drill out your push rod guides to accomidate the increased lift.

Thanks for the handy links!
The heads are Vortecs, and I have already had them drilled and retapped for proper height Threaded studs. The pushrod clearance has also been drilled out on these heads. The springs are on my list. I just wish I knew how that cam will perform. I don't want a dog on the lake. Do you think it is too much lift?

 

[Tail_Gunner]

Re: 4.3L Cam & Piston Advice

You bring up a good point ...a dog on the lake. We all boat differently some put around never really getting on plane...other's scream around at WOT 24/7. For myself i rarely put around or run at wot....well maybe a little. It's a 2 minute warm up and i am off on plane. I primarily run between 3000 and 3700. However i do run @ 4000 and above for a bit...thrill seeking and i boat on a long large river.....30-40 miles is not a uncommon trip..10-15 is average for a day.

The 270 works very well in my case..my tub does not even begin to work until 1500 rpm (wake speed) and that was the factory cam. I notice no uncomfortable surge or bad driving manner's around the dock or jumping on plane.... but the 4.3 does act like a two stroke now much more midrange punch.

I guess if your running around a small lake and doing a bunch of idleing the 270 might not fit and reversion could be a factor do you ilde around for more than 30 minute's. The 270 will not make your boat a dog and if you put around a lot it would be a good ideal to check your exhasut for reversion just to be on the safe side...The 270 is a mild mild cam in the engine world and just a tiny bit edggy in marine..

Google smog cam's you will find they have no overlap...and conform to epa stds a very convient stradgey for automotive and marine aka water reversion its one in the same. They are a very old cam design..but then so is your engine tech much as done to improve performance. Little side note XM cam have very agressive ramp rate's they open very fast and close fast that is why i choose the xm for myself as many other's have.

 

[Volphin]

Re: 4.3L Cam & Piston Advice

You bring up a good point ...a dog on the lake. We all boat differently some put around never really getting on plane...other's scream around at WOT 24/7. For myself i rarely put around or run at wot....well maybe a little. It's a 2 minute warm up and i am off on plane. I primarily run between 3000 and 3700. However i do run @ 4000 and above for a bit...thrill seeking and i boat on a long large river.....30-40 miles is not a uncommon trip..10-15 is average for a day.

The 270 works very well in my case..my tub does not even begin to work until 1500 rpm (wake speed) and that was the factory cam. I notice no uncomfortable surge or bad driving manner's around the dock or jumping on plane.... but the 4.3 does act like a two stroke now much more midrange punch.

I guess if your running around a small lake and doing a bunch of idleing the 270 might not fit and reversion could be a factor do you ilde around for more than 30 minute's. The 270 will not make your boat a dog and if you put around a lot it would be a good ideal to check your exhasut for reversion just to be on the safe side...The 270 is a mild mild cam in the engine world and just a tiny bit edggy in marine..

Google smog cam's you will find they have no overlap...and conform to epa stds a very convient stradgey for automotive and marine aka water reversion its one in the same. They are a very old cam design..but then so is your engine tech much as done to improve performance. Little side note XM cam have very agressive ramp rate's they open very fast and close fast that is why i choose the xm for myself as many other's have.

Looks like we boat about the same... I don't even plane until 3K with current prop. Cruising RPMs run 3500-4250. She will turn 5300 if I let her. That was new with the Vortec heads. LOL

So which of the XM270s did you go with?

 

[Tail_Gunner]

Re: 4.3L Cam & Piston Advice

COMP Cams: Search

COMP Cams: Xtreme Marine?, XM270HR <br> Good Mid-Range, Excellent Response, Noticeable Idle

 

[Bondo]

Re: 4.3L Cam & Piston Advice

Looks like we boat about the same... I don't even plane until 3K with current prop. Cruising RPMs run 3500-4250. She will turn 5300 if I let her. That was new with the Vortec heads. LOL

So which of the XM270s did you go with?

Ayuh,.... Ya need more prop,....

Hi guys,
I have pulled my old 4.3L from my 19 foot Regal ('89) due to a faulty block. 11 years was a good run for it.
I have a short block in a crate, awaiting installation, but would like to upgrade the cam for a greater, wider torque curve.

Will probably want to upgrade the pistons as well. Looks like Sealed Power OE type units.
Any recommendations for a slightly higher compression upgrade?

You've got a ready to run motor, 'n yer gonna swap pistons,..?? w

What's in it now,..?? The Oem dished,..?? how far down the hole,..??

 

[Volphin]

Re: 4.3L Cam & Piston Advice

Ayuh,.... Ya need more prop,....



You've got a ready to run motor, 'n yer gonna swap pistons,..?? w

What's in it now,..?? The Oem dished,..?? how far down the hole,..??

Looks like Speed Pro Double relief pistons... they match the old block. Have not unpacked it yet and taken a mic to it.

 

[Volphin]

Re: 4.3L Cam & Piston Advice

Update: Got a chance to dig into the specifics.
The original pistons were Sealed Power 423NP (Dish with 4 valve reliefs, 0cc).
The new short block pistons are also Federal Mogul Sealed Power 345NPS (Flat Top with 4 valve reliefs, -5cc).

According to my calcs:
Bore: 4.030
Stroke: 3.48
Head Gasket Thickness: .039
Deck Height: .040
Piston Volume: -5cc
Vortec Combustion Chamber: 64cc

Exactly 10.63:1 Static Compression.

This is up from the original 10.03:1 with the 0cc pistons... (which ran very, very well!).

 

[Volphin]

Found something interesting on my build...

Found something interesting on my build...

I think I need to replace my pistons and deck the block on my 4.3L build.

Here's why:

The original pistons were Sealed Power 423NP (Dish with 4 valve reliefs, 0cc).
The new short block pistons are also Federal Mogul Sealed Power 345NPS (Flat Top with 4 valve reliefs, -5cc).
The original pistons were Sealed Power 423NP (Dish with 4 valve reliefs, 0cc).

According to my calcs:
Bore: 4.030
Stroke: 3.48 (BUT this figure is WRONG! The 345NPS piston stroke is 3.540 compression distance, not the stock 3.560 so the actual stroke is 3.46 right?)
Head Gasket Thickness: .039
Deck Height: .040
Piston Volume: -5cc
Vortec Combustion Chamber: 64cc

This puts me way out of the optimal quench huh?

 

[Tail_Gunner]

Re: Found something interesting on my build...

Re: Found something interesting on my build...

Try to keep this in one thread

 

[Volphin]

Re: Found something interesting on my build...

Re: Found something interesting on my build...

Try to keep this in one thread

Sorry about that! You're right.

 

[Tail_Gunner]

Re: 4.3L Cam & Piston Advice

http://forums.iboats.com/non-repair...cruiser-4-3l-need-advice-please-587005-2.html

Follow that thread a bit and you will realize you need a machinist. a few hundred now will save you a lot later.The proper equipment is vital

 

[Volphin]

Re: 4.3L Cam & Piston Advice

Well after a day on the phone to a few of my buds in the perf marine engine business, and some time on the phone with Federal Mogul, I have determined that their written specs on the 345NP piston are incorrect. It is a true flat head, 4 valve reliefs. That makes it a +5cc unit, not a -5cc piston as written by Federal Mogul. That puts me at a perfect 9.5:1 Geeez... I really wish these manufacturers would check their work ONCE in a while. It would have saved me a week of searching out the true spec.