armybyrd

iTrader: (4)

My engine is almost ready at the machine shop- 70s 350 they bored .030 over and decked the head surface as well as cleaned everything up. I'm using the stock crank and rods though it will have new flattop pistons. I already have a pair of vortec heads with ls6 springs and comp cams roller tip rockers. Intake will Be An Edelbrock Performer And A Quadrajet On top. I was sold on the comp cams xe274 but the guy working on my engine said I should go with a lunati voodoo since they've had problems with the comp cams and I just did a search online and have heard of a few ppl having issues with them. Should I be second guessing this cam? I've got a rather large bill for the machine work and would hate for the cam to ruin the engine. Also I haven't decided on what head gasket to use and I'm not sure where my comp ratio will be though I figured the flattop pistons would be better than the factory dished.

Night rider327

iTrader: (13)

Can't pick a cam until you know your true compression ratio.

Can't pick a head gasket until you know your true deck height and how far in the bore the pistons sit at TDC.

Stock deck height is 9.025"
Stock piston compression height is 1.560"

This left the piston .025" down in the bore at TDC.. With that you use a .015" to .018" head gasket to get the perfect quench height. You want your quench height (top of piston at TDC to bottom of head counting the gasket) to be in the .040" to .045" range

Aftermarket 350 pistons ranges from 1.455" to 1.568" compression height. Need to know what yours is.

Also the term "flat top" is not close enough. 4 VR flat tops can range from 2.5cc to 7.00cc

Do you have your piston brand and part #. If so that would make this much easier.

Also do you know how much the machine shop milled/decked off the block?

2005Impalla

I love comp cams I have never had a problem with them. I would not blame a cam failure on the cam if your not using the recommended components with it though. If I went with a comp cam I would buy the whole cam kit. I think the performer intake is a little mild for the cam choice and your probably going to have to do a little modding to the Q jet to get it to idle proper. If it were me I would go with the 268 cam. Comp cams shows it as having 4.5" more vacuum at idle compared to the 274 which would be easier to get to idle good with the Q jet.

armybyrd

iTrader: (4)

Pistons are 7 cc. Pn345nps. (Sterling) the machine shop told me re balancing wasn't needed since the new pistons weigh the same or about the same as the stock ones.
Deck is about 10 down. This is what the machine shop told me, I told them I'm using the vortec heads and I'm waiting for them to recommend a head gasket.

Night rider327

iTrader: (13)

I don't show a PA 345 nps piston.

I see a 345NP (or STL-345NP) as a cast piston listed and a H345NCP (or STL-H345NCP) as a Hypereutectic piston, and a H345NP as a Hypereutectic

Also that number does not show it's a .030" over piston.

With sterling/speed pro/sealed power there should be 2 digits at the end of part # to show over size.

Like your 345nps would be a 4.000" bore.. 345nps30 would be for 4.030" bore.

But anyway what I see shows the..
345np at 1.540" CH
and the others at 1.560" CH

armybyrd

iTrader: (4)

They said my cr will be 9.9222 with a .38 thickness gasket. Not sure if I wrote that all down correctly.

armybyrd

iTrader: (4)

That was auto correct. It's PN. Also they are the cast pistons. I'll have to ask again for clarification on the piston part number.

Night rider327

iTrader: (13)

Yeah the 345np has a short compression height and puts the pistons .020" further down the bore than stock.

Those with a stock deck will be .045" in hole.

I think you said they removed .010" off the decks, this will leave the pistons .035" in the bore.

The thinnest gaskets you can get is .015". This will give you .050" quench.

armybyrd

iTrader: (4)

I didn't understand everything the guy told me to be honest and If I could do it over I would've gone with a different machine shop with better customer service. As for the deck all he said was they took 10 off. Is this enough info to decide on a head gasket and get a good idea of where my compression ratio will be?

Night rider327

iTrader: (13)

Did the shop pick the parts or did you? Those 1.540" pistons are hurting you for sure.

"took 10 off" would mean the milled .010" off the decks.

This will give you a 9.015" deck height.. Your 1.540" pistons though will still be sitting down in the bores .035"

You need the fel pro #1094 head gaskets. They are .015" thick. Your quench is still gonna be way over target range but it's not gonna hurt the engine, just not the best.

Vortec heads are listed as 64cc chambers but every one (stock 062/906 castings) I have CC'ed has been in the 62/63cc range.

My info shows the 345np30 pistons as 5.00cc

So 5cc pistons, 62cc heads = 10.378:1
6cc pistons 62cc heads = 10.259:1
7cc pistons, 62cc heads = 10.142:1

I'm not a big fan of comp cams camshafts really but they aint bad now. Years ago they did have some batches go out that was not heat treated/hardened right.

I just like the lobe profiles of the lunati voodoo and some of the howards cams myself.

The XE274 would be a pretty good size, might be a tad small though for the compression and with out the help of tight quench to fight detonation I think I would go alittle bigger to play it safe.

My cam picks would be...
lunati voodoo 10120704
howards 112601-06
Or comp XE284 (biggest you would want)

I think the performer RPM or summit stage III intake would be a much better match

2005Impalla

If your compression is in the 10:1+ range and your trying to keep the RPMs in the idle to 6,000 RPM range I would pic a cam on a wide LSA and or ICL something in the 112-114 LSA range will keep the cylinder pressure down with a small to medium cam. If your compression is 10:38 I would pic a cam with a 114 LSA it will lower cylinder pressure by closing your intake valve later than a tighter grind would.

armybyrd

iTrader: (4)

I went with the cast pistons since they had them in stock and I don't plan on doing any hard core racing. I hadn't a clue about quench. Should I just scrap those pistons? Of So What Pistons Would Be better?
would a xe274 still be streetable?

armybyrd

iTrader: (4)

Also I got the performer intake since I was planning on using a quadrajet (no rpm intake for spreadbores) but if it would make that much of a difference I could exchange intakes.

86LG4Bird

iTrader: (1)

Correction: wide LSA cams do not keep cylinder pressure down.
LSA has nothing to do with that. IVC does.
You can argue that most "wide" LSA cams are ground with less advance, but any of those cams can be degreed to whatever ICL is desired.
I would never run a 114 LSA cam on a NA setup with 23 deg SBC heads; you're giving up too much power for the same idle/mpg/tuneabilty that you would have with a properly sized cam somewhere around a 110 LSA.
I'd go with something like that Lunati 0704 that Night Rider suggested.

Night rider327

iTrader: (13)

No, I wouldn't scrap those pistons. The quench is not going to kill the engine or cause any major harm, it's just one of those things that can give you "free" help when setting up/building your engine.

GM had wide quench height on it's highest selling crate engines. The ZZ4 has a .076" quench height, same with the 385 fast burn.

Yours is not a max effort engine, so your not giving up a lot with the wide quench, I just like to keep all of mine at .040" to .043" to get any extra help I can.

Just a FYI the H345NP, H345DCP, SUM-17350, pistons would have been a better option to start with. Hyper vs cast, priced close to the same, and all has the 1.560" compression height.

FM uses too close to the same part number and gets people confused. They have like 10 diff pistons with the "345" number.

The XE274 will be streetable but I worry about your cylinder pressure/cranking compression/DCR with your high compression, and pump fuel. You may get spark knock/ping/detonation.

I'm never a fan of "over" camming or carb'ing but sometimes you end up needing bigger to make it work out the best.

I think going up in cam size a tad will be safest bet for you, or use the XE274 and change the way you install/degree it. You can retard the cam by 2-4* and that will change the IVC point and there for have the same effect as a bigger cam.

I really like that lunati voodoo 10120704 cam for this build though, if your heads can handle the .525" lift that is.

armybyrd

iTrader: (4)

From what I've read the ls6 springs should be good for around .544/.555 lift. Can anyone confirm this? Also after some more research I think I'll be better off with a lunati voodoo cam instead of a comp cams.

2005Impalla

I would not run a 114 LSA either but if he tries to run a 106 ICL that comp cams grinds there cams on with almost 10.4: compression I doubt it will run on pump gas.

2005Impalla

And yes a wide LSA will keep cylinder pressure down. Who would install a cam with a 114 LSA 8* advanced? Almost all cams for the SBC are ground 4* Advanced so most cams with 114 LSA will have a 110 ICL. I would install a cam with a 114 LSA straight up so it had a 114 ICL before installing a cam with a 110 LSA -4*

armybyrd

iTrader: (4)

So just to be clear I'm good with the lunati 10120704 assuming my vortecs with ls6 springs can handle the lift? Any ideas on how much power I can expect to make with the performer intake and a Quadrajet?

Night rider327

iTrader: (13)

Yes the lunati 10120704 would be the cam I would use if it was my own engine.

The performer intake will hold you back some, but I see this being a 370 HP / 390 ft lbs torque engine. I think the RPM intake would push it to an easy 385 HP.

I can understand not wanting to re buy parts, budget is a big factor with most of us.

What I would do is mod the intake you have now some. I do this mod to all of my dual plane intakes. Mill the center divider wall out 2" long centered and 1" deep. You can use an angle grinder, die grinder, etc to do this with.

I would also toss on a cheap 1" open carb spacer.

Those two things will help the performer intake to better match your combo.

I can't say about the LS6 spings on the vortec heads. I have never went that route

armybyrd

iTrader: (4)

As always thanks again for all the input. I'll be sure to do the research on my heads.

Night rider327

iTrader: (13)

Your welcome. I'm glad I can help.