Blkmaroman

I just picked up a 509 400 shortblock all put together by the machine shop its standard bore, crank turned, 5.7 rods, but the problem is that the pistons are flatop with 2 valve reliefs. Ive got a set of redone vortec heads that i want to run but i think my compression will be way to high. I can get 76cc heads to drop it, but then id make no more power than just putting together my 350. I could get pistons for 250, have them pressed on for another 50, and then have to get the bottom end rebalanced for another 200. thats just way more then i have to put on it right now. I was wonderig can i bolt it together with the flattops, with stock gaskets, headbolts, and just mix some race gas with my ragular pump gas? thanks

F-BIRD'88

Try it, but use cooler than stock spark plugs (champion RS9YC or RS10YC) and go real easy on the spark advance. Limit it to 29 to 31deg total. Many times that is all the timing a 400 vortec motor needs anyways.
Won't need much % of race gas mix as long as you don't mind doing that.
The motor is going to be "on the edge"

Is modifying the vortec head combustion chamber (opening it up a bit to lower the cr), out of the question. I'm thinking the 68-72cc zone. Can pick up some flow as well.
The vortecs are so superior to a stock 76cc head that it is well worth working with them even if it means more work.



A 70cc modified vortec head with -7cc cc flat tops and a 0 deck height gives you a 10.56:1 cr on a stock bore 400sb. .039" 400 head gasket.
That is do-able with 92-94 octane and the right camshaft, timing and jetting and spark plug heat range.

How about splitting the nessessary cc increase between the head and piston top. take 3cc from the chambers and Machine a shallow 3cc D dish on the pistons. 3cc's of aluminum won't throw off the balance enough to worry about.
Not that hard. Allows you to run proper quench clearacne too.
What pistons do you have now?
What is the assembled piston to deck clearance at TDC?
What cam are you using?
What fuels do you have to work with?

KrisW

iTrader: (5)

I agree with the above about opening up the chambers a bit. It's just more excuse to further unshroud the valves and to work on polishing the chambers. You can buy the cheapie set up from PAW to "cc" the chambers equally. It comes with the graduated beaker and the plexiglass plate to bolt down accross the head while measuring.

I ran L98 heads on my last 400 and that's what I did.. 70cc sounds good but I think I was more like 72 when I was done.

Blkmaroman

The pistons are in the engine and i think the numbers are on the side of the piston, all i can see on the bottom of em is "std" which im assuming is because they are standard bore. Ive been looking at 400 pistons, and they look identical to the keith black Claimer series of pistons, one site listed them at 10.7 to 1 and another set them at 11.4 to 1. ANd ive had my heads milled before i put them on my 350, but i cant remember how much it was. And is opening up the cc's on the head something that i could do, or will a machine shop do it cheaply enough. My car has been down for like a year now, and im ready to get this motor in there, but i dont want to take it back out again to do over. thanks for the replies

Blkmaroman

Oh, and all the pumps here have 93, theres a sunoco up the road that i belive has 94 or maybe higher. And im sure with there being a dragstrip nearby that there is racefuel, but this car is gonna be more street driven than anything, so pump gas would be the best. But worst come to worst, i dont mind mixing some race gas in. And the camshaft is a crane 236i,244e, @.050 so its decent sized.

KrisW

iTrader: (5)

I did mine myself with the kit above. The machine shop will charge you whatever the labor rate is per hour for how many hours they choose to put in. Typically, if you are on a budget this is where you save your money and do it yourself. That's why I got that kit; you want all the chambers to be exactly the same when you are done!

You can do it!

Supervisor42

EVeryone assumes that the block has been zero decked! It hasn't been bored.
Measure the actual deck height since it's already together.
Run the DCR numbers with that cam and the standard deck height with a composition gasket. You'd be surprised.
If the heads have been milled maybe it was just a cleanup. If a "valve job" was done at the same time, the valves may be sunk adding more than the chamber was reduced by milling.
CC the chambers (you can use a piece of window pane glass, vaseline and syringes from any farm/feed store) $8 max.
Most pistons with only 2 valve reliefs have one really BIG one and one normal sized relief. They often measure bigger than the 4 standard ones.
Measure, measure, measure.
Do this before you slap 76cc smogger heads on it, PLEASE!

SteelTownMadDog

iTrader: (2)

No kidding. If a block hasn't even been bored, there's no way someone went through the trouble to "0" deck it. Assume AT LEAST 0.020 deck, but probably closer to .022 to .025.

Also, get big head gaskets. Using the following parameters, this should give you about 10.2:1 ratio which is doable with Sunoco 94;

Deck 0.020
Head Chamber: 64cc
Head Gasket: 4.2" bore, 0.071 comp thickness (Felpro 1144-071)
Piston Volume: -5cc (assumed from 2 valve reliefs)

Blkmaroman

I would love to make to cc a little bigger on the heads, but i dont have the tools to take off metal, and id be so afraid to ruin a good set of heads. If the machine shop can do it cheap enough id rather them do it. Im afraid to even drill my steam holes myself. I was thinking of running a thicker head gasket, but everyone ive talked to told me that would possibly cause more detonation because it would hurt my quench. And the valve reliefs on the pistons are both the same size. My buddy just bought a 89 mustang gt and hes out back doing burnouts by my enginless carLOL. Im really ready to get this thing going.

z28freak84

Hell, If u got access to Sunoco 94, then you are okay anyway. With the vortec combustion chamber you can get away with up to about 11.2:1 on 93-94 octane IF all is CORRECT/PERFECT....Put it together and give it a shot.

You could always convert to E85 too and kick the compression up even higher yet.

Supervisor42

I agree with this. I don't think one will be needed because the block has not been decked.
As for the piston reliefs, I think you're right also. There aren't many standard bore size pistons available. I was thinking about the forged Speed-pro/TRW pistons. Yours are probably the claimer pistons with -5cc. It's common for std size pistons to be an extra .005" down in the hole to stay away from the piston ring ridge at the top of the cylinder in a "slightly used" bore.
Measure the actual deck height. Tools needed: straight edge, feeler gauge, tool to turn the crank, and patience.
I'm assuming this is not going to be a DD since you were thinking about adding race gas. (a 400 in any configuration doesn't make a good DD anyway)
What cam is in it? This has a LOT to do with the actual C/R that the gas will see. It could easily be a 400+ HP combo with gobs of torque on 93 octane.
You will need to recurve the distributor and if it has an A/T, move the shift points. None of this is expensive, just time consuming.

Appraiser

http://www.wallaceracing.com/cr_test2.php
This is a pontiac website compression calculator. The 400 pontiac and 400 sbc have much in common, including bore size and stroke. I am working on a stock sbc 400, and the stock dished pistons are .30 down the bore along the edge where it's closest to the deck.. I roughed in your info and came up with about 10.5 with 64cc heads. Those heads are, however, good mixers that don't require a lot of advance. use a fat gasket and a little shroud relief. you can dial it in on the wallace racing calculator. good luck

Supervisor42

err, you mean .030" right? .30 is more than ¼" ...

Appraiser

dang me. yes I mean .030 or 30 thou.

sofakingdom

iTrader: (1)

Measure the actual deck height. DO NOT "assume" anything!!!

If the pistons are at stock (.025") deck height, then with a 1014 (.039") head gasket, 6cc valve reliefs, and 64cc chambers, the CR will be 10.8:1. With a 1044 head gasket (.049"), it will be about 10.5:1. If the deck height is .045" as would be the case if the pistons are TRWs or the like, the CR will be 10.3:1 with the 1014 gasket or 10.1 with the 1044.

This is why you need to measure: it can vary quite widely.

Drilling the steam holes is a total piece of cake. There is no reason to be afraid of that. It's so easy, even a moron like me can do it. Just center-punch a mark on the heads using a head gasket as a template, and drill them with a 3/16" bit; angle the ones nearer the intake surface over towarrd the exhaust flange. Nothing about how they are done is "critical", except that they BE there. Total no-brainer.

Appraiser

your right, soda, measure everthing. and thanks for the drill info, I need to do it and have been wondering how to set up 30 degree angle. Maybe its not so critical. my drill press has a tilt table, but only has about 6 inches of depth, so I cannot get anywhere near the center of the head.

sofakingdom

iTrader: (1)

I don't even bother with a press, just give it a hand job.... drill it straight 1/16 or 2 deep, then tilt the drill and go all the way. Like I said, it's not the least bit critical. The only reason for drilling it at an agle in the first place, is that the steam hole is right at the edge of the "tubular" structure inside the casting that the one group of head bolts passes through.

Blkmaroman

I ran outside and put a feeler guage on top of the piton when it was as high as it would go, and with about a .020 it felt like the guage may have been just a bit above the deck surface. But that was with my fingernail, i was just wanting to get a general idea. Im calling the machine shop tommorow to see how much they will charge to cc the heads, im getting them pressure tested to make sure they are good to go anyways. And this is a frequent driver, maybe not an every time out driver, but pretty frequent. ANd the cam is a crane 236I,244E @.050 with a lift of about 488 i think. And i think i will drill the steam holes because last time i called the machine shops they wanted like 40 a head to drill em. Im hoping 200 will get my heads done, or somewhere in the neighborhood.

Appraiser

A while back I had to buy a dial indicator, it has a magnetic base and rods sticking out which can be adjusted infinitely. I have used it for lots of things and it was only maybe 20 to 25 bucks from Summit. Not a great deal for a very usefull tool. I zero'd it out on the deck of the block, then shift to the top of the piston at top dead center, and el presto, I know exactly. Today I was using it to measure valve spring retainer to valve seal distance. Much easier than my caliper and micrometer.
By the way, nice buy. Have you thought about adding more compression and running E85?

Blkmaroman

I just ran outside and put a straightedge over the deck, i couldnt get it over the middle of the pistons because it wasnt long enough but with it over about a quarter of the piston, I could slide a .020 guage under with little resistance, and a .022 with a fair amount of resistance, and a .024 would even try to go. Im not to familiar with the E85 thing, ive heard it has high octane but not as much potential energy so it acutally hurts power. But im not to familiar with it, im kinda stuck and stubburn to try new things like that. Im gonna see about my heads tommorow, we will see how that goes, hopefully good so i can bolt this thing together but i dont want to rush it.

Blkmaroman

Well, i called the machine shops and they thought i was crazy. They said they didnt enlarge the cc's and didnt know anybody that did it. This sucks, i was really hoping i could get bigger combustion chambers and be good to go, now i guess im gonna have to run a thicker heads gasket but i though that would kill my power and cause more detonation. Im beginning to revert back to just putting it together with stock gaskets and seeing how it does and probably mixing in some race gas.

KrisW

iTrader: (5)

Well, it proves that your machine shop is not performance oriented, that's for sure. It doesn't mean that they don't do good work, but they probably would rather fix parts for auto repair shops than hot rodders. Oh, well...

If you're not gonna take a leap and do it yourself, then you don't have any options left, do you? You really shouldn't be scared to do a little work yourself with a dremel tool set and a die grinder. But, to each his own...

Blkmaroman

Well, good news. I called a few more machine shops, and one about 25 miles down the road said they could enlarge em to about 72CC for me, and he is the guy I brought my heads too originally before i put em on my 350. I just forgot all about him. So will 72CC put me in pump gas range?

Blkmaroman

I put my new numbers into the compression calculator and im gonna be at about 10to1 which i think will get me by on 93.

KrisW

iTrader: (5)

72cc is what I ran in my 400 and it was awesome. 10 to 1 is a good place to be in my opinion.

Get it done and on the road!

Blkmaroman

Believe me im ready. I appreciate the rosponses from everyone, i never would have thought of enlarging the cc's. ANd if i have any more problems, i know where to come. THanks again.

Appraiser

Blk, how bout a trade. I will take your vortec's and you can have my ported 493's. These are stock 71 400 heads with the steam holes already in. I ran the numbers, and these 76cc with flat top pistons with 5cc valve releif, and 22 thousands down the hole come out to about 9.75 which is a lot safer than 10+ on an iron head motor. My head shop says the 493's are the same as a 487 an they said I would find a 487 cast on the head somewhere. They were right. 487s ran on a high output 350. My 400 still has dished pistons, so I need 64 cc heads to make her zoom. Even with 64cc I will still be under 9.5 compression

KrisW

iTrader: (5)

Don't forget; vortec heads require a different intake manifold as well...

F-BIRD'88

4.125" bore 3.75' stroke -7cc piston volume
.022" piston deck clearance
4.20"x.041" gasket 64cc heads
10.65:1 cr.
try it as is, with conservative timing (30-32deg) and cool(er) plugs

Blkmaroman

Ive hauled a few sets of those stock 400 heads to the junk yard. The vortec heads are way better than any other stock head, that why im getting them modified, only 100 buck and im ready to rock. ANd i ran these heads on my 350 so ive already got the intake for em. Im alright with 10 to 1. But the 10.5 to 1 was alittle more than i wanted to deal with, just because of tuning. Heads go to the shop tommorow and motor goes in car soon.

Blkmaroman

Well i got ahold of the machine shop today and he said that he couldnt open up the cc any, he said he was going to take some material off by the spark plug hole but coolant flows near there and hes afraid it could crack easily. He said he milled 3 thausands off em and had to do a crack repair. So now i cant drill one of the steam holes because the crack repair was in the same spot one the steam holes goes. He told me he got me a couple .020 spacer shims that would do the same thing for me as the cc would. My question is will the spacer shim hurt anything and or how much power loss will i have with it because of my quench being larger. And will i be ok with not having one of the steam holes drilled, he told me ill be fine without one on the street, but i dont know. This is starting to become a damn headache. I talked to some local hot rod guys and they said id be fine with a 11to1 compression, they said theve run 11.5to1 on cast iron heads and been fine. IM just trying to figure things out, thanks.
----------
he also said he was gonna unshroud the valves while he was at it, but there wasnt enough material left to unshroud the valves

Blkmaroman

Ive been reading up on quench and with the spacer shim and my head gaskets along with my deck hight i would have a quench of like .080 IF i just put it together with no spacer shim i would have a quench of .060 which is alot but i think i would be better off with that and 10.9to1 instead of a quench of .080 and 10.2to1. What do you guys think, im running out of options, i think race gas might be in my future plans, damnit.

Apeiron

I'd go for the lower compression, preferably with a thicker head gasket though instead of a shim. .060" is still a bit too large to see any benefit from "squish" anyway. If you've got a cracked head, I'd replace that too.

skinny z

Do you have the specs from the timing card that came with the cam? Or the actual part number? You may be able to run you vortecs with over 10.5:1 static compression ratio.

Blkmaroman

He already repaired the crack and he assures me its good to go, ill have no problems. He already ordered the shims enen though i didnt ask him too, he said he uses them all the time and thats what he would use. I looked on summit heres the cam specs. I am gonna pick everything up either tommorow or early next week and i need to know if i need the shim or not, i would prefer to be as close to good quench as possible which means no shim, let me know how the cam looks as far as compression thanks.Brand: Crane Cams
Product Line: Crane PowerMax Camshafts
Part Type: Camshafts
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 3,000-6,500
Intake Duration at 050 inch Lift: 234
Exhaust Duration at 050 inch Lift: 242
Duration at 050 inch Lift: 234 int./242 exh.
Advertised Intake Duration: 296
Advertised Exhaust Duration: 304
Advertised Duration: 296 int./304 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.473 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Valve Lift with Factory Rocker Arm Ratio: 0.473 int./0.488 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Grind Number: H-296-2
Quantity: Sold individually.

Camshaft, Hydraulic Flat Tappet, Advertised Duration 296/304, Lift .473/.488, Chevy

Supervisor42

I hope this ain't for the street. It ain't gonna idle too swell. With that much duration you're going to need atleast 10.5:1, 11:1 would be better.
We thought you were building a mild street engine.
Someone run the DCR numbers.
I bet it's going to be less than 8.5:1 ...

Apeiron

The cam doesn't look that bad, the extra cubes will tame it down a little. It's still big though.

Supervisor42

"Streetable" is a relative term after all. Hell, I keep thinking in 108º LSA terms anyway(must be a sign of age). It's gonna be a powerful sucker. I hope it's got good rods.
BUILD IT!!

Blkmaroman

So you think ill be fine with 11to1 with that cam, will that cam take the compression down enough for me to run pump gas. I figured the 400 would eat that cam up, and i wanted a cam that would make up for the lack of exhaust flow on vortec heads and this cam seemed like it would do it. And my version of streetable is very wide, ive never even had power steering on the car, i just dont hook it up, so i can handle a car thats not very streetable just fine. The rearend on my s10 is welded up and i love it, most people wouldnt do that for the street.

Apeiron

You might be ok with 11:1 with a fast burning Vortec head and a cam that'll bleed off some cylinder pressure. Some of the other guys would know better than I would. Polishing the combustion chambers and piston faces might help avoid detonation.

No, most people are much smarter than that.

Blkmaroman

ANd ive got a 2800 stall which is not as big as id like but i have to run it for now. And ive got 3.42 gears which also arent as big as id like but i have to run them as well. And the tranny is a th350.

Blkmaroman

My mom always said i was pretty bright, thats why she called me son. lol

Supervisor42

In your case it'll be streetable.
Ape says run 10.2:1 with that cam and heads.
Super says 11:1 with stiff ignition advance springs to bring timing in later.
It depends on a lot of other variables too, like how hot it's going to run, 93 octane gas or 92 gasohol, timing curve etc.
We could both be right and we could both be wrong depending on the other variables...
BUILD IT!
(and shoot video)

Blkmaroman

It wont run hot without one of the steam holes will it? Because i cant drill one of em due to a crack repair.

Supervisor42

Is it exhaust side or intake side? One of the middle 2 or between outside pair?

Blkmaroman

I havent picked them up yet, and i cant remember exactly but it was right in between the combustion chambers where the steam hole near the intake side goes and i believe it was before the last combustion chamber on the head.

Supervisor42

It's the exhaust side ones that are the critical ones. They keep a pocket of steam from forming and being trapped on the bottom side of the cylinders. The top sides are better because of the slant of the cylinders.
If you could put the missing hole between #2 and #4 cylinders it should be fine. They run cooler than the rest.

skinny z

That grind number dosen't match any small block Chevy in the Crane catalouge. At least not on line.
However, if you use those specs for the cam and the info you've supplied then you shouldn't have too much trouble running that combo with premium fuel.
Standard 400 bore and stroke/5.7" rods/64cc heads/.023 piston below deck/5cc piston dish/.039x4.150 gasket/296I 304E adv duration/110LSA straight up(ICL 110degrees)/ gets a dynamic compression of about 7.8:1 with a static compression of 10.9:1.
That big cam bleeds off a lot a cylinder pressure so it makes usable with such a high static ratio even with the iron vortecs.
I run a dynamic ratio closer to 8.5:1, use 94 octane on a 350 vortec and 268 adv cam. 34 degress total ignition lead.

Blkmaroman

http://store.summitracing.com/partde...1&autoview=sku

skinny z

Their on line catalouge didn't show that application but I checked out the link.
You should be good to go with the vortecs (at 64cc) and .039 gasket.
10.9 :1 may seem high for a static compression ratio but it's the cam the makes the difference.
Like I said I'm running a higher dynamic compression ratio than what you'll have with your current combo and aside from needing 94 octane, there are no problems. A plus on your side is that the vortecs don't need a lot of timing to make their best power so that helps too.