IronOutlaw

iTrader: (4)

I am planning out my 355 and about to start buying parts. Goal is to have a fast street car. It will not be a dd and will see some strip time. Id like to run 11s on motor and make over 400rwhp NA. I am going to eventually spray the car with a 100-150 shot.

Parts list (I know its not complete yet)-Its pretty much the Ellwein budget build. Ive talked to some local racers and they have had great results with both scat and mahle.

Trickflow 21 Degree Cast Heads as cast
AI valvetrain kit
Scat 6" Pro comp rods with 7/16" bolts-26000716
Mahle powerpak pistons-SBC250030f05
Stock Crank
ARP Hardware everywhere
Melling standard Volume high pressure oil pump
Stock oil pan
42# injectors
Walbro 255 pump
Electric Water pump
Double roller timing set
Stock computer with opti

Questions-


What kind of compression should I shoot for? 12.0:1 is what I was thinking. Im going to be running 93 octane all the time. Can I achieve this with the heads and pistons I have picked out? I dont quite understand "Quench" and Im not sure how far I need to have the block decked.

Will the stock intake be a restriction? Would it be worth letting AI Port the intake and go with a 58mm throttlebody, or should I keep it stock and go with a 52mm?

What kind of RPMs will this bottom end be able to handle? Would it be safe to shift at around 6500-6800 rpms? I know shift points depends on the cam I get, but I know I will need more RPMs to make the power I want with a 355 than I would with a 383.

Anyone running the FICINJECTOR rebuilt 42 pounders? They are very cheap compared to other brands Ive looked at. I know 42 is kind of big but I want room to grow.
http://fuelinjectorconnection.com/sh...d&productId=35


Will the stock 2 bolt mains be safe at this power level or should I go with 4 bolt splayed mains? I know where a corvette 4 bolt block is I may use but Im not sure what the guy wants for it.


I know these questions are elementary, and I should be asking my engine builder some of these, but Im not sure who Im going to get to build it yet. Ive thought about bolting it together with the help of a friend but Im not sure I want to undergo that yet with my skill level. I want to start buying parts now so I can keep interest in the project. Im bad about setting a goal and then quitting.

I want to go ahead and buy the rods/pistons/heads soon so Im more worried about compression and Piston to valve clearence than anything right now.


AND I HAVE DECIDED 100% ON THE HEADS. PLEASE DONT TELL ME TO GO WITH AFRS, AI PORTED STOCKERS, OR LE PORTED STOCKERS.

Camaroking1996

Port the intake and get a 58 mm throttle body. What kind of cam are you going with?

IronOutlaw

iTrader: (4)

Im not sure yet. Its going to be a hydraulic roller, and Im going to let AI spec it.

Camaroking1996

That bottem end will hold well over 400hp and your build sounds good so far.

TravisMcGill2000

iTrader: (2)

12.1 compression will be perfect. Id also get intake ported and use 58mm tb. What thickness head gaskets you gona run. Need to know that to find the quench. The bottem end will handle your power goals.

IronOutlaw

iTrader: (4)

I have no idea on headgaskets. Ive been playing with Summits compression calculator and gave up. Basically I need help deciding which piston and headgasket I need to make around 12.0:1 compression. Should I have the block decked or keep the stock deck height? What did you go with on your original 355?

merim123

iTrader: (11)

I like this calculator here http://www.kb-silvolite.com/calc.php?action=comp

I'm at 11.75:1 compression on my 355.

My inputs for the site:
head cc =53
piston cc(dish +/dome -)= 5
head gasket (felpro 1074) =.039
head gasket bore =4.10
bore =4.03
deck =.006
stroke =3.48

97 6speed z

Your original post asked a lot of questions, and your've already received several good answers above, soooooooo ....... I'll just concentrate on clearing up two (2) specific issues for you, namely, static compression ratio and quench.

Item 1 - Quench

Without going into ALL the details, on your build you want to aim for a .039" - .040" quench distance. The easiest way to do this is to zero block the block and use the Felpro head gasket which is .039" compressed thickness. Notice I said aim for that .039" - .040" quench range because you need some latitude in adjusting both deck height and head gasket thickness to achive the static compression ratio you're after also! To get your quench "in the range" I just gave you, remember your total quench distance is just the sum of how far you pistons are "in the hole" plus your head gasket compressed thickness, got it? For example, using a .026" compressed thickness head gasket with having your pistons .013" in the hole ..... will also give you a .039" quench. On your build DO NOT go lower than .035"/.036" quench!!!

Item 2 - Static Compression Ratio

Since you are planning on both using a 100/150 shot of "spray" down the road, and running 93 octane fuel only, and since we don't yet know the intake closing point of the cam you'll be using ............ aim for a static CR between 12.5 and 13.0. Your biggest problem with determining this lies with the one (1) choice you'll have of the "off the shelf" domed Mahle piston they offer for your build. You see, because you are NOT going with a stroker build, and just boring your stock 350 block .030" over to get your 355 cubes ......... you will need a "domed" piston to get any where near the compression ratio you're looking for ......... assuming that those "as cast" Trickflow 21 degree cylinder heads you're 100% intent on using have say 65cc combustion chambers???

Go to one of the "online" CR calculators, take your cylinder head combustion chamber volume and "domed" piston head volume, and input those numbers assuming a zero deck height and .039" gasket thickness, and ......... if it's any where within the range I gave you above, you should be ......... good to go!

One last thing to consider is that for a cam with longer intake duration, (i.e. a later intake closing point), go with a higher range value for static CR, okay.

Good luck with your build!

IronOutlaw

iTrader: (4)

Thanks for the great advice so far.
So this is what I got...

head cc =54
piston cc(dish +/dome -)= 5
head gasket=.039
head gasket bore =4.10
bore =4.03
deck =0
stroke =3.48

This puts me at 11.79

Its a little lower than I was wanting. Im not sure if you can get the Mahles with a dome. The ones I am looking at are flat tops.

LilJayV10

iTrader: (39)

I have to say there are some really good posts in this thread. Maybe it's a sign tech is getting back to its roots.

Everything I was going to say about quench and compression has already been covered.

One thing that can happen if you run too little quench is the piston can hit the head. As the engine heats up the piston and rod actually grow making them a little longer. Also there can be slight variances in the machining process meaning a rod can be a little longer or a piston is a little taller. Tony Mamo, IMO is one of the smartest people on this site, fell victim to this in his personal build. He was running a tight quench and one of the pistons smacked the head. He took it apart and found out that one piston was a little bit taller than the rest.

Quench, if it hasn't been explained already, is the distance between the top of the piston to the cylinder head. .040 really isn't that much if you think about it.

Now performance wise I don't know if there's a limit to what it can be before it can negate the positive effects.

The better/more quench you have will allow you to run more compression. The reason is the combustion process is more controlled. The a/f mixture and gases are forced into a very small area making everything more efficient.

If you run a lot of compression and not enough quench detonation can occur. This is because you have high cylinder pressure but it's not controlled. The area the a/f mixture and gases are being compressed in a larger area and can randomly ignite.

I built a friends 355 LT1 for his 95 Z earlier this summer. We ended up with about 11.5:1. The block was decked but not zero decked. The pistons were .010 down in the hole and we used .029 victor reinz head gaskets. He went with a factory replacement speed pro piston.

Every block is different and you won't know exactly how much compression you have until it's measured. If you find yourself needing a little more compression you can always have the head milled some and reduce the combustion chambers. I know you are going to spray it and with the thicker deck on the those trick flow heads milling shouldn't be a problem.

IMO, for whatever that's worth see what your compression would be with a flat top piston, zero deck height and a .040 thick head gasket then mess with how many cc's your heads need to be to get your desired compression. they take of .005-.007 for every cc on the head. On my LS1 I used TEA ported 5.3 heads. The chamber work increased the cc of the head to about 64cc. I wanted 59-60cc to get my compression where I wanted so they took off about .025 to get them down.

As always piston to valve clearance should be checked as should pushrod length. Decking the block, heads and using a big cam with different thickness head gaskets will effect pushrod length and PTV clearance.

You might have to disasemble/assemble part of the bottom end several times to check these things but that's the price of doing it the right way and wanting to go fast.

I would definitely have a cam spec'd for you by someone who knows what they are doing. A.I. makes some fast LT1's and should be able to tell you what will work best for you. Keep us updated with what you end up and make a build thread. Always love to see those.

Also make you get it balanced. That makes a difference in how smooth the engine runs and revs.

I would also consider getting a set of rods. 4340's or similar should be fine with your power level.

joelster

You can run into piston-to-valve clearance issues by running a large camshaft that has a lot of duration, or have it ground really tight on a 106 lsa, or have the pistons without nearly enough valve relief, or install the camshaft too far advanced/retarded. Generally the camshaft can be made quite large duration wise, and if you spread it out enough on a 112 -114 you won't have any problems. I ran the xfi468 on my 350 and it was 242/248 on a 114, and had a ton of room (over .100" both), and that was with the stock shortblock with those tny valve notches in the pistons. It is something that you will have to measure once you pick out your camshaft. Don't let ptv clearance scare you out of the proper camshaft. The pistons can always be notched and the cam timing can always be moved a few degrees to open it up.

97 6speed z

IronOutlaw, the two (2) excellent posts to your questions supplied by LilJayV10 and Joelster should have all your questions answered now.

If that CR calculator shows your potential build at 11.79:1 using the Mahle flat top pistons, (as you indicated), then milling right around .020"/.025" off those heads should put you right in the 12.5 to 13.0 CR range!

(I had no idea the "as cast" combustion chamber volumes on those 21 degree Trickflow heads ....... were only 54cc.)

Again, Good Luck! with your build, and DO keep us posted.

IronOutlaw

iTrader: (4)

Thanks guys. I have learned ALOT today. Im glad I could get so much information and not one negative comment or argument started.
Having the heads milled to 52cc should put me around 12.1 which is exactly where Id like to be at.

One more new question, who all is running the Felpro 1074s with spray? They are very cheap compared to other gaskets.


Looks like Im gonna have to get the check book out and start ordering parts.

Advanced Induction

iTrader: (2)

I like the TFS castings, but our CNC'd GM head is an improvement over the as cast head in every tangible way. By the time you modified the as cast TFS head to compete, you'd have more $ in them, even if you bought new GM LT1 heads as a base vs. sending in a used set. Of course you can always upgrade later to a better head. Good luck with your project!

LilJayV10

iTrader: (39)

Good to see A.I. in here.

IronOutlaw

iTrader: (4)

Thanks guys. I do understand that as cast the Trickflows do not compare to your CNC GM heads. Do you guys have any track/dyno numbers from your CNC Trickflows? This is going to be kind of a budget build and I like the option to upgrade these heads for a "big" build in the future.

96capricemgr

iTrader: (1)

For a "big" build later you might endup changing so much you would be just as well off to sell and buy new later.

For example if you do a solid roller later you could easily endup needing longer valves, and different spring seats and retainers are virtually guaranteed. IMO you could get more of your money back out of that later selling functional heads than you would throwing it in the garbage to be replaced or trying to sell that stuff separate used.

IronOutlaw

iTrader: (4)

Ok guys. I have been thinking and then thinking and then thought some more. I want to do this build right the first time. Instead of going with the as cast Trickflows I want to get them ported. Id LOVE to hit over 450rwhp with a 355 if that is possible. It will probably be stretching it though staying Hydraulic roller and using the stock computer with small cubes.

Now that said, the ported version of these heads have 54cc combustion chambers. If I go with the Mahle powerpak pistons, they only come in 5cc reliefs. This will put me under 12:1 compression. Would you guys have anything negative to say about using 4cc relief pistons to bump my compression up to get over 12:1?

Here is what summit offers.

http://www.summitracing.com/search/P...?Ns=Rank%7cAsc

Ive heard mixed stories on the Probe pistons. Have heard great things about Ross and nothing about the Manleys. What do you guys suggest? And also I cant tell the difference in the Ross pistons on that link.

97 6speed z

First off ........ your Summit link (above) is not working. But, regardless of that, I would not lose any sleep about "chasing" 1cc in piston head valve relief volume! Unless you're after "bragging rights" in saying you've built a 12:1 static compression ratio motor ...... I'd go with the Mahle's.

If I'm reading this right your SCR using the 5cc Mahle's would be 11.79:1 instead of the 12:1 you're after, correct? I know you're planning on a 100-150 shot of N2O "down the road" and spray loves compression, but ....... Mahle makes a GREAT forged flat top piston for our LT1 motors.