1996 - L31 Vortec Rebuild - Flat tops or Dish stockers? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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  #16 (permalink)  
Old 02-22-2016, 07:52 AM
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Yeah,i would make sure because the only flat top Mahle's in hyper I see are #MAH2243547WR.They show a pin hgt of 1.56",but,then show compression with 64cc heads at 9.4:1. A 4.030 bore flat top with 64cc heads should put you just over 10:1.

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Old 02-22-2016, 08:04 AM
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Quote:
Originally Posted by jokerZ71 View Post
Yeah,i would make sure because the only flat top Mahle's in hyper I see are #MAH2243547WR.They show a pin hgt of 1.56",but,then show compression with 64cc heads at 9.4:1. A 4.030 bore flat top with 64cc heads should put you just over 10:1.
so they are shorter?
is 10:1 good? i cannot remember the stock CR
but anything better is good to me, sorry for the basic questions
i've never took the time to learn much about CR and block height


Quote:
Originally Posted by hcompton View Post
The 350's are pretty simple and hyper pistons work fine. The ones i suggested were the only ones i know of that come in the 1.575 pin height. Im sure others do as well.

Has your block already been bored. It should be bored with the piston in hand. Also the bores should be finished for the type of rings to be used. Thin low tension ring need a different bore than old school thick cast rings. So if the block has been bored for modern style thin ring package you need a piston with that same ring package. Older pistons with thick cast rings will not seat properly into that type of bore.

If the block has not been bored yet then it should be bored with the machine shop measuring the pistons and checking the ring package to give the proper finish on the bore.

Hope this helps.
Not bored yet, it's on the machine shop, now it's depending on which
rings come with the piston set since i plan to buy a ready to go set.
i remember for my L98 i had to tell the machinist the tolerance
and give him an exact number maybe provided by some of you here
back in 2008, hypereutectics were closer to the bore than the old cast
pistons, so i think i will be getting Mahle or SpeedPro with the rings
that comes with it and then i will need exact specs to tell the machinist
what bore to do.
Now i need to decide for sure which pistons should i go with.
Thanks once again for your help.
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Old 02-22-2016, 08:26 AM
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IDK for sure.The listing states 1.56",but,9.4:1 with 64cc heads,which is about stock L31 compression with the 12cc dish pistons.Unless these pistons have some really large releifs,they either have a shorter pin hgt,or,their info is just incorrect.With your cam & 65cc heads you have,you want compression in the 10:1 to 10.5:1 range.
Also,don't let the reply above about cutting the decks scare you from doing so to achieve a proper quench.Most of these newer blocks need the decks cleaned up,especially around the water ports.Having the decks cut to 9.015".or,even 9.010" will not hurt anything,or,effect the strencth of the head bolt threads at all.That is BS.You're talking about .010" to .015".Not even 1/4 of a thread width,or,anymore than using a thicker gasket would effect the thread strength.You don't want to go crazy either by removing a lot,but,.010 to .015" is not gonna hurt you 1 bit.It will allow you use a good gasket & achieve a proper quench.
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Old 02-22-2016, 08:28 AM
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Yes sometimes they list in a generic way but the real specs
are printed on the box. i will ask today
Thanks once again
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Old 02-22-2016, 08:52 AM
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Quote:
Originally Posted by Calderone View Post
Hi guys, we pulled out the engine on the 1996 Yukon.
L31 Vortec SBC, We were doing the top end only but we decided
to go with a full rebuild. We already have some parts for it.

1 - 0912 AFR Heads
2 - LT4 Hotcam
3 - 1.6 Crane Cams Gold Race roller rockers
4 - 3600 Yank Torque Converter.

We already have 1 5/8 headers and other goodies
as the Taylor intake spacer. We want to make the truck
fun to drive, not looking to make it a race truck but closer
to the feel of it.

We are going .30 over, so it will be a 355 but here's the doubt.
Which kind of pistons to run? We are going with Hypereutectic
i rebuild my 87 Vette L98 eight years ago with great success using
Mahle Flat tops and runs really great so i want to repeat the formula.
But i'd rather ask than make a mistake, we still have the black box
and no 411pcm so we might purchase a custom tuned black box for now
and later maybe a fast system so we won't have to worry about tuning
issues.

Will .030 over Mahle Flat top pistons work on my build?
or should i go with the stock dished pistons that they sell specifically
for 1996-2002 Vortec engines?

Thanks in advance.
Never, ever round dish stockers. The dish occupies too much area under the squish/quench step of the head. This greatly reduces the needed affects of these functions and causes the engine to be more detonation prone than necessary. Either use a flat top or a D dish if tweeking the compression ratio is necessary. These type pistons off the maximum squish/quench function in the case of the D dish (cup) the flat top's advantage is retained by the step while the overall compression ratio is established by the selection of the dish volume which is wholly contained under the valve pocket.

Bogie
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  #21 (permalink)  
Old 02-22-2016, 09:38 AM
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I think you're on to a really good build here & is good combo if put together well,getting the compression,quench,etc engineered in.The 2 problems I can see are,as you know,the fuel injection system can't supply adequate fueling for the cam/head potential & that 3600 stall convertor is gonna be way too much for the cam,especially in this heavy vehicle.A 2200 to 2500 stall would fit a lot better & not risk overheating.
Another member here recently used a 3000 stall with this cam in a Camaro with an L31 & he was really displeased with the effects.I don't think you will like it either in the vehicle this is going in.
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Old 02-22-2016, 09:47 AM
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i picked that converter based on other people using it on vortec trucks as well
but we'll see, we can always change it down the way and sell the 3600.
Our eyes are on the intake/fuel system as well, we'll see how it goes
and if we are not pleased we can buy some bigger spider (they sell high volume spiders now) or simply go with those selftuning systems pointed
before which i think are the best thing ever.
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Old 02-22-2016, 09:58 AM
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Do you have link for the upgraded higher volume spider.I would like to look into that myself.I wasn't aware of that.
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Old 02-22-2016, 10:09 AM
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Yes you can order them in three sizes, they are pricey but maybe worth
the $$$$

Last year we got the upgraded one (non poppets) but stock size

Here are the ones i've been looking for:

62 lbs/hr. $ 899
GM V8 High Performance 62 lbs Vortec Spider Assembly 1996 2002 CP 10722 62 8 | eBay

48 lbs/hr. $ 799
GM V8 High Performance 48 lbs Vortec Spider Assembly 1996 2002 CP 10722 48 8 | eBay

36 lbs/hr. $ 699
GM V8 High Performance 36 lbs Vortec Spider Assembly 1996 2002 CP 10722 36 8 | eBay

Company site is AUS Injection : Racing Fuel Injectors Service Cleaning New Replacement
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Old 02-22-2016, 10:46 AM
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Quote:
Originally Posted by hcompton View Post
You will at least need the 36 lbs but im thinking the next size up will be needed to make sure you can tune around any flat spots and be able to go rich if you need to. The cost of that thing is pretty high for such a problematic system. I dont think i would spend that money in a system that may not last or be worth the effort. Since in the end its not really a great system to begin with and has proven itself a pretty big problem.
True, when we upgrade intake/fuel system we will go for a selftuning
system no question asked, i know that the poor plastic intake
won't give us what we need but we'll try it out for now and
save up some $$$ and get the new system, we might be surprised
and the invested $$ will totally worth it by the seat of the pants speedometer
which is what i love the most

i cannot think of a good reason that they chose that weak plastic upper intake cover design
apart of maybe weight savings? everytime we take it apart we fear of breaking it somehow
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Old 02-22-2016, 11:40 AM
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With the combo of parts you have,I see you making in the 400 to maybe 430 HP. IMO,36 lb/hr injectors will be too much for that setup & will likely make tuning a PITA,especially at idle & lower rpm operation.Somewhere around 29 lb/hr would be more suited for this.With the stock intake,probably closer to 25/26 lb/hr.
Those units are most likely the same as a stock unit,but,have had the regulator adjusted for more than the 65 psi used for stock units.The higher psi can cause the poppets to stick & the mini jectors on the newer units to leak as well.I can't see paying $899 for these units.After the injectors,the intake itself becomes the bottleneck.It will never supply enough air to feed any motor needing 36 lb/hr of fuel.Your spacer will only help slightly.
The most I've seen out of 1 of these setups put down approx. 360 HP at the rear wheels & he almost melted the upper intake doing so.
FWIW,you could piece together either a Ramjet system,or,a ProFloXT & use your pcm,distributer,etc for around $1200,maybe less if you shop smart,or,can fab some stuff yourself.
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Old 02-22-2016, 01:03 PM
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Is your Honda an 8 cylinder engine? How much HP does this Honda supposedly have?For an N/A engine,you need .50 lbs of fuel per hour for every HP produced. A higher compression well built motor can get by with .45 lb/hr. A 400 HP 8 cylinder engine will run very well with 25 lb/hr injectors,or,even 29 lb/hr for safety sake,but,going too large causes many tuning problems. 36 lb/hr injectors in the OP's build will cause him nitemares in tuning,especially since the regulator is sandwiched between the upper/lower intake,so,adjusting fuel psi is a big deal & not easily done.
Do you even read the links that you posts here before doing so?
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Old 02-22-2016, 06:12 PM
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The OP is not likely to be making 450 HP. Closer to 400.I said 25 lb/hr injectors would work.29 lb/hr to be safe which is very close to your 20% over.Funny how you chose 450 HP to justify your 36 lb/hr recommendation. The Ramjet 350 uses 22 lb/hr injectors for it's 350 HP rating & still runs pig rich throughout it's rpm range.By your math those injectors would only supply 281 HP.Do you really think GM would cut fueling that close on a warranted crate engine.There's more to tuning than simply setting duty cycle to xx%.Duty cycle is dependent upon rpm, pulse width, psi.
As for my tuning g experience, no I don't have a buttload of hands on & it's pretty much limited to GM controllers prior to the 0411, which can be fairly limited.Aftermarket ecu's offer better control but i have no experience there.But, I do have enough to realize that you have very little, if any, yourself.I mean it took 4 hrs to search google & offer the above response.lol.
As for the recommendation of installing another regulator in the return line of the vortec spider....evidently you also know very little about it as well, or, you would realize how stupid that would be.For 1, the poppets will begin to lock up after approx 75 psi. They won't open, at least not reliably below 58 psi.The regulator is basically built in to rear of the spider & operates at approx 65 psi.So do your math again at 65 psi & see what you come up with.

Last edited by jokerZ71; 02-22-2016 at 06:28 PM.
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Old 02-23-2016, 12:14 AM
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Quote:
Originally Posted by jokerZ71 View Post
Speed Pro #H631CP is also a good piston for your build if the Mahle's your looking at don't come thru.Just stay away from Speed Pro H345's.The H631 is about the same price as the Mahles at $160 per set.
i really think we'll be getting H631CP30 for the extra compression.
Found a great kit with rings and pins
Chevy SBC 350 Flat Top Pistons Moly Rings Kit 030 355 | eBay

But it shows 64cc = 9.77
Compression Ratios w/ Stock Deck Height (9.025"):


Brand Speed Pro
Part Number H631CP30
Bore 4.030"
Piston Style Flat Top with Two Valve Reliefs
Piston Material Hypereutectic Aluminum
Compression Distance 1.560"
Piston Head Volume - 5.00 cc
Wrist Pin Style Press-Fit or Floating
Pin Diameter 0.928"
Piston Ring Thickness 5/64" x 5/64" x 3/16"
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Old 02-23-2016, 04:44 AM
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I think that compression calculation is assuming 9.025" deck & a .041" gasket which is what normally comes with rebuild kits.I've used these before & know they have a 1.56" pin hgt.With proper quench distance in the .040" range, you will be at approx 10.2:1.
With your 65cc heads & .026" gasket, you'll be at a dead on 10:1 with a quench of .051".Not ideal, but, it'll work.If you cut the decks to 9.015" & use the same gasket, your looking at 10.24:1 & a quench of .041".

Last edited by jokerZ71; 02-23-2016 at 04:56 AM.
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