criticalx

96 ta lt1 6 speed 3.42 car

lt1
11.5 cr (dome 3.5 cc)*
rods (want to upgrade)
ported heads - a shop around here does it
cc503* - but thinking bout going with cc306 or so
1.6 rr*
stock crank*
port intake
tb stock - or go to 52 ported?

goal is 11 second car

thanks for help

duh

iTrader: (16)

So, before anyone else flames you, I'll tell you what they'll say.

The CR is too low. It's only a little bit higher than stock. Try another full point, or at least half a point. Since you have a porter close to you, they'll say he sucks and doesn't know LTx heads and the engines needs, so go to AI or LE since they're the only ones that anybody in here trusts. They'll also say the cam is ok, but get a custom one from one of the previous guys because they know best what works with their heads.

Now for me personally.... Bring the CR to 12-12.5:1 for pump gas. Do lots if research on your porter. Talk to a lot if his customers and see how well they do. Numbers are good on paper but nothing beats how a car performs at the track. Chances are by this point a 52mm TB will be a bit small. Spend the extra $10 for a 58mm or a few more bucks for a mono blade. Since you're doing pistons, forged would be a good idea. New rods with better cap screws would definitely be an upgrade even over stock rods with arp bolts. Either way, the new bullet should make enough HP to get him to the 11's as long as the rest if the car is up to the task.

96capricemgr

iTrader: (1)

Why a dome and just 11.5:1 that makes no sense.
Proper deck height and head gasket, modest valve reliefs and it will be over that compression without screwing up flame travel with a dome.

Needs 4.10s and a real axle to put them in to get there with a T56.
The intake wont even need to be ported.

Far as the porting "a shop around here does it" may or may not work out for you. "ported" is not the same as ported well.

criticalx

H618CP piston bad Idea? im not sure on compression.. im not sure if they in the hole more than stock..

what best way to get to 12.5 cr?

porting they have a flow bench.. im new to porting thing...

1995 T/A

What's your dads name? I may know him, I live near by.

bowtienut

iTrader: (1)

Don't worry about compression so much and run the 503 cam. As 96 said, being able to launch (without breaking the rear) and drive the 6-spd will be the key more than anything you're doing to the engine. More cam will just make it tougher to get off the line.
11-sec ET is a fairly modest goal if you just put it together right.
Stick with flattops. Milled heads after porting will give you all the compression you need.
Ported intake is not likely to do anything for you.
A stock TB re-bored to 52 mm would be plenty.

criticalx

I told my dad this but he wants more power

96capricemgr

iTrader: (1)

That piston uses a ring that is 30% thicker than stock and best I can tell around 580grams as opposed to I believe 532 for stock. Really headed in the wrong direction with those specs.

The compression ratio published for those must be with a comic book thick head gasket. If you insist on replacing pistons pick a flat top with valve reliefs, deck the block to .005-.010 down and use a .026-.029 head gasket and you will have plenty of compression.

If you think a flowbench is the measure of a head you have an uphill road ahead, flowbench can tell you something BUT at the same time you can make a head flow more on the bench and be slower on track. If the locals are good(based on actual track data) with say the Vortec heads it might be worth a shot if cheap. If they can't prove their experience with a similar head and are going to cost the same as proven options why be the guinea big?

criticalx

so those piston wont work? or wont work good?

HellTeeOne

Take these guys' advice on piston selection. LT1s don't need dome pistons to get the SC number you're looking for, just the right quench/deck height/chamber size.

Find out what your SC # will be, then select a cam with the appropriate intake duration number, adequate lift and a ~110 LSA and you're 90% there. With well-ported LT1 heads, I'd go with quite a bit more cam than the 503. The 306 will work, another decent off-the shelf choice is the 847. Spending an extra few bucks and getting one from one of the 2 well-known vendors is probably your best choice.

Intake doesn't need porting. Stock throttle body will work, just slap an airfoil in it. If you're going to buy another tb just get a 58.

As far as heads, if you can find some of your local shop's work running around on other LTx cars and they've done well, then go for it. However, I won't ever trust a shop's work on these types of heads without having seen other ones they've done first. Conventional small-block Chevy techniques and wisdom do not apply with these heads in several important areas.

Basically shoot for 11.75 compression or better with flat top lightweight pistons, heads from someone who knows LTx stuff extremely well, good cam from LE or Ai, stock intake and throttle body, 30# injectors, long tubes, and a good tune. That's the basic recipe for a ~400rwhp LT1 that will propel an f-body into the 11's with traps speeds approaching 120mph.

Bullit95T/A

This guy is a little cheaper then the top 2 porters and does some quality work.
He has some youtube videos up as well..................http://www.headbytes.com/

96capricemgr

iTrader: (1)

You are kidding right?


OP, the reason you picked those pistons is the missleading compression ratio estimates. stock pistons can get you that compression with decent quench and some head milling and they are somewhere around 5cc reliefs, no dome needed. You put that piston in with 58cc chambers, .035 quench and it is 12.75:1.

Their published numbers would be something like .020 down in the hole with a .049 gasket which due to bad quench might actually detonate at 11.5:1 on pumpgas.

MIll ported heads down to a 54cc chamber, deck the block to .010 down, use a .026 gasket and stock pistons and you would be at 11.75, which I would do rather than what you were looking at, have the block decked the mains maybe hones, the rods resized with ARPs and give it hell.

criticalx

my brother building a 95 trans am and done has piston on rods ready to go in motor. how can u make them work?
I thought he researched this

1994Z28Lt1

iTrader: (1)

They will work just fine its just not an optimal setup, heavier pistons increases rotating mass which is not helpful for making power. Thicker ring packs create more drag (more heat, less horsepower)

They will go right in and be just fine its just not an optimal setup when you can easily go to lighter pistons and thinner or equal ring packs and not give up ring sealing

96capricemgr

iTrader: (1)

How about you pay attention to the fact these are a dome and compression is going to get out of control if he makes any attempt at decent quench.

criticalx

his gonna use .049 quench head gaskets

96capricemgr

iTrader: (1)

Quench should be down near .035 for detonation resistance on a NA motor. That is deck height and gasket combined.

criticalx

thanks for help

criticalx

Ok.. After some talking I got him to do it yalls way.. so stock piston on new scat I beam rod? He don't like the stock rods.. gonna check piston height when we tear it down.. what's the ideal dynamic compression for the cc503 ?

cardo0

Zero deck the block and use a real gasket. Using a thinner head gasket with an increase in compression is a dumb azz idea. If u deck the block anyways then use a zero deck and use a normal compressed height gasket (0.038" to 0.049"). Remember to get the block surface finish 25 to 50 roughness for the aluminum heads.

Finish your heads first then measure chambers so u can solve compression ratio for different piston sizes. Once u nail your compression ratio u can select your camshaft.

cardo