I put up a threat before about making a 350 fuel injected engine for my firebird but i have decided not to do that and just make it a carbed engine. the block has been bored .040 over Plans: Forged Flat top pistons by Federal Mogul Stock rods Vortec Heads casthing #062 Stock crankshaft Needs suggestions on: Camshaft (not a rollerbock so no roller cam) Intake Carb The goal is to make atleast 400hp or more and trying not to spend more then 300 bucks on one perticular item.

If you want a decent carb, you're going to either have to spend more than $300, or buy used. Or, use what you don't spend on the other things to get a better carb.

Cam - Comp XE274 flat tappet hydraulic. Want a little more power up top, XE284.

Intake - Performer RPM (standard or air gap, your choice - I don't think it really matters).

Did you have upgraded rod bolts like ARP installed? Cheap insurance when using stock rods.

No i didnt, im still on the edge about getting forged rods or not wether it would be worth it.

And 274 intake duration right

The Vortec heads and the Comp XE274 (as per five7kid) should be able to make 400hp provided you've got the static compression needed to be build adequate cylinder pressure.
With a budget in mind, stock rods are capable of supporting 400 hp ( for drag racing or street engines anyway) as long as you upgrade to ARP rod bolts (again as per five7kid).

what kind of compression do you have in mind? there flat top pistons not dished so or domed and have 4 valve reliefs so i dont think the compression should drop

350 bored 40, with Speed-Pro flattops, and vortec heads, even with fairly thick gaskets and unmilled heads, you'll be over 9.7:1. Ideally, you want 0.040" piston-to-head, so assemble the short-block, measure how far the pistons are down from the deck, and choose your head gaskets accordingly.

Not sure of your piston dish/valve relief volume. My Speed Pros (H345NCP) have 4 valve reliefs /-6cc volume. Using that as a spec, a .026" gasket ( Victor Reinz 5746) will get you about 10:1 static compression. That's with a standard deck height of .025" in the hole and the 64cc Vortec heads..
The XE274H installed straight up should work really well that CR.

Well this is what the pistons look like

I couldn't find the dish/valve relief volume for that piston in the Federal catalog. However based on the info that is available I calculate it has slightly less valve relief volume than mine which are listed in the Federal catalog as -5cc.
Using -4cc and the rest of the specs you're over 10.2:1 SCR. Keep in mind that's with the .026 gasket and .025" in the hole piston deck. The thinner gasket ( as opposed to a traditional .039" ) helps to close up the quench a little but it may come at the cost of too high a CR.
It depends on the cam you choose.
Here are a couple of builds you may have seen that meet your 400hp objective.

http://www.carcraft.com/techarticles...ine/index.html

http://www.popularhotrodding.com/eng...ock/index.html

So wouldnt i need a lil bit thicker gasket to lower the SCR and the goal is to get a 10.1 SCR

What year block are you working with? What is the casting number on the block? How is the core shift? All of these must be considered if you're going to build 400hp or better. A stock Nodular iron crank with 2 bolt mains and ARP studs will be good for 400 or more hp. If you insist on using stock rods, find some powdered metal rods, or some GM "X" rods that have been shot peened and polished. We need to know trans and gear ratio to help you pick out the best cam. As said above, the RPM Air Gap would be a good choice.

Its 3970010 is the casting number and its a Four bolt main

The goal is have a Dynamic Compression Ratio between 7.5 and 8.5:1. The DCR is a product of SCR and cam timing.

Thank you for sending hat carcraft link it will help out alot with parts numbers

And i bought the pistons off of ebay this is the item descripiton if it helps any

NEW IN THE BOX 8 FORGED FLAT TOP +040 PISTONS BY FEDERAL MOGUL (THE OLD TRW/SPEEDPRO/SEALED POWER FORGINGS.MADE IN USA) FOR SMALL BLOCK CHEVROLET 350 (STANDARD 4.00 BORE SIZE + 040 OVERSIZE. FOR STOCK 5.7 INCH RODS.STANDARD 4 VALVE RELIEF DESIGN.WITH PRESSED PIN AND TAKES A 5/64-5/64-3/16 STOCK TYPE RING SET

The XE274 cam and the .026 head gasket results in a DCR of 8.3:1 and an SCR of 10.26. Both of those numbers are on the high limit for a conventional street engine particualarly with iron heads. If you swap in a .039" gasket you get DCR at 8.05 and SCR at 9.94.
My Vortec combo has 9.98:1 SCR with a 8.02 DCR and I have no trouble on 94 octane fuel.

Assuming zero deck height?

I found another problem though the vortec heads in stock form cant handle the lift of that cam. there only capable of.450 according to that car craft article and the machine shops around here arenot so cheap about head work

And if five7kid is right this is assuming the deck heigh is 0 and i come to find out that the deck heigh is below zero i should use a thinner gasket and if the deck height is above 0 i should used a thicker gasket?

Right, anything above .450" lift, you need to verify each valve travel. Or, have the top of the guides cut for positive-type valve stem seals, and you'll kill two birds with one stone - better valve stem seals, and more valve travel capability. Regardless, the valve springs should be replaced. You can also have the spring seats cut at the same time for bigger diameter, better valve springs - that would be 3 birds with one machining operation.

The deck height plus the compressed head gasket thickness should equal .040". This gives you the proper quench height which is critical for controlling detonation. You should never try to vary CR with head gasket thickness. Set the quench height, use piston and chamber volume to control CR (plus cam to control DCR).

ok sounds good with the heads

but what do you mean with using the piston and chamber volume? and how would i be able to calculate the CR

DCR and SCR calculations were done using an assumed .025" piston below deck.
I solved the valve spring/max lift issue by going to Comp Beehive springs. No machining or valve seal mods required.

Here's a link to an article about the upgrade.

http://www.carcraft.com/techarticles...ade/index.html

You should be setting compressions ratios by changing the combustion chamber volume, piston dish or dome volume and if you're at the machining stage by decking the block the appropriate amount. Any of those will impact your SCR.

So What cituations am i looking at? am i going to need to deck the block?
or will i befine with a .039 or a .025 gasket and if so which one? im getting a little confused now...

Here's what we do when we put together an inexpensive engine.
First determine the objectives for the engine. 400 hp and on a budget as you stated.
Has the block been to the machine shop yet? If it hasn't, it should be checked out for all the possible out of tolerances. If the block is relatively square and true (remember your objectives with respect to hp and budget ) then you can forgo the decking and work with the piston deck that you have.
Calculate your compression ratio with that deck height. Try a couple of different head gaskets to try and arrive at the best SCR for the cam you want to run. ( I believe what five7kid was saying was that if building an engine from the ground up, the best way to establish a given compression ratio is by machine work and component selection not just swapping out head gaskets.) If it's not possible to get a decent SCR you may want to mill the heads for a little added compression. Keep in mind that the machining costs money. The performance gains from an added point of compression and the ideal quench might not be worth the added cost for the machine work.
If your objectives were a little different, maybe 500+hp and 7500 rpm then it's another story.

Here's a link to a thread with a build that's similar to yours.
http://www.thirdgen.org/techboard/te...-searched.html (Compression ratio? (I searched).)

Alright two things more and thank you guys for al your help what is the best way ti find the deck height and what is the best way to find the valve relief volume?


http://www.jegs.com/i/Sealed+Power/8...5NP40/10002/-1
i almost found this on jegs which might also help you guys out in helping me

The compression ratio that is stated on jegs is that going to be my compression ratio?

Probably not.

The "nominal" deck height of a standard SBC is 9.025 inches. The compression distance of those pistons is 1.560" (found on summitracing.com, not jegs.com). Block deck height minus the sum of rod length plus 1/2 of the stroke plus compression distance = "deck clearance" or how far in the hole your pistons will be. Factory machining varied a little bit, but assuming it is close to 9.025", those pistons would give you 0.025" in the hole. If so, use a 0.015" compressed height gaskets for the proper .040" quench height.

The typical 4-valve-relief flat top SBC piston volume is 5cc.

Then do the normal calculations: http://www.kb-silvolite.com/calc.php?action=comp

Thats with cylinder head volume of 64cc
Gasket thickness of .015
gasket bore of 4
cylinder bore of 4.040
Piston deck of .025
and a 3.48 stroke

Isnt that SCR a little high ?


Cylinder Head Volume (cc)Cylinder Head Vol
(cubic in.)03.904Piston Head Volume (cc)Piston Head Vol
(cubic in.)-0.305Gasket Thickness (in.)Swept Volume
(cubic in.)43.731Gasket Bore (in.)T.D.C. Volume
(cubic in.)04.105Cylinder Bore Diameter (in.)Gasket Volume
(cubic in.)00.192Deck Clearance (in.)
Note: Neg. nubmer above deck, Pos. number below deckDeck Volume
(cubic in.)00.314Stroke (in.)STATIC COMPRESSION RATIO11.653

I am not sure about the compression on this engine, but I do know it is unwise to lower compression by either not decking the block or using thicker head gaskets. If you do either of those things to lower compression you might go from 10 to 9.5, but the reducing the quench will make it even more likely to detonate, so you may seem to have helped the problem, but you actually just lost horsepower from compression and resistance to knock from losing your
quench, sounds like a bad deal to me.

If that is a 6 cc piston, then you CR should be 10.3 with a zero deck height and a .040 head gasket, but I can not fathom that a flat top piston with four valve reliefs will only be 6 cc, My pistons have 2 valve reliefs and are 5cc!
10.3 may be a little high for pump gas, but with a tight quench and a good combustion chamber, I think you will be ok, just be careful with your timing.



I doubt it will actually be that high anyway, every chamber I have measured always seems to be a couple cc high, and I think if you measured those pistons you would find an additional cc or two.

This compression calculator calls a 3.9cc piston a dome, and it subtracts from the chamber volume, you needed to use a negative number for a flat top piston.

the 3.9 is the head volume of 64cc and the -.305 is the piston volumem which is -5

Ok sowhat would be the best way to mesaure the piston volume then and if it came out to 8 cc i would have a 10.1 SCR

BUt im also having trouble findign the DCR i have the rod lenth 5.7in but i cant get the angle the lobe seperatino is 110 and the advertised duration is 274 on intake but i cant find the groudn in advance

Typical 350 head gasket bore size is 4.1".

Incorrect. A positive number in the piston volume is a "dish" and adds to the total chamber volume; negative number is a dome.

This compression calculator uses a dome as a positive number, and dish as negative.http://www.race-cars.net/calculators...alculator.html

While this calculator has a dome as a negative number, and dish as positive.http://kb-silvolite.com/calc.php?action=comp

so am I right? I realize that a valve relief adds to chamber volume, but the calculator can use a negative or positive number, so I figured that was what he got wrong

You need to get that from the cam card http://static.summitracing.com/globa...a-12-246-3.pdf . They don't list 0.0050" but do list .006" - should be close.

I come up with 10.4 static and 8.4 dynamic with the XE274.

I would be careful which DCR calculators you use, I have tried three, and come up with three different numbers.Maybe someone her can give you a heads up on a very accurate calculator.

I would also like to see you use accurate cam timing in you dcr calculations.
this is how KB has you use your cam timing to figure dcr-Intake Closing Point (degrees)
ABDC @ 0.050 lift plus 15 degrees , as you can tell that is already a very inacurate practice, due to the extreme differnces in ramp profiles from cam to cam.

Is that dynamic too close to call? should i probly go with a different cam?

You can accurately determine your deck height using simple feeler gauges. The tricky part is to precisely find top dead centre. I use a piston stop and a degreed balancer. If you have a dial indicator, that is also effective. Once you've found TDC, use the feeler gauges and a true straight edge laid across the cylinder. Measure between the straight edge and the piston and there's your piston deck height. As five78kid states, .025" below deck is about the OEM spec for a SBC.
Valve relief volume is generally listed in the parts catalouge. I use Speed Pro H345NCP Hypereutectic flat top pistons with 4 valve reliefs and the catalouge specs the valve relief volume to be 5cc.

how would i deterime and accurate one? i have not done this before

I would accuratley measure the volume of your pistons and cylinder heads before assuming anything, I would also choose your cam based off of rpm range, going with a bigger cam so you can run on pump gas is not a good practice!

I think you will end up with roughly 10:1, which is ok with good combustion chambers, good quench, and a decent cam. there is about a million hot rods with flat tops, a similar cam, and 64 cc heads running on pump gas, you will just have to be careful with your timing.

The speed pro catalog volume is not accurate enough, when building a motor to run on the ragged edge of pump gas operation, you want to be real sure of all the variables.

Here's a link to the XE274H cam.
http://www.compcams.com/Cam_Specs/Ca...x?csid=87&sb=0
Using the following specs.
XE274 274/286 adv duration. 110 LCA. 106 ICL.
64cc chamber
4.04 cylinder bore x 3.48 stroke
.026" x 4.100" gasket (.051" quench )
.025" piston below deck
5cc piston valve relief volume
10.15:1 SCR
8.21:1 DCR
with .039" x 4.10 gasket (.064" quench)
9.84:1 SCR
7.97:1 DCR

werent you guys just telling me that, that quench is too big?

I did those calculations to show what you could expect without the expense of decking the block.
As it is you would be running over 10:1 with the iron heads.
If you want to hit the .040" quench mark ( and keep in mind piston rock with the added clearence for the forgings ) you might deck the block at .000" and use a .040" gasket.
Now you have 10.4:1 SCR and 8.43:1 DCR.
That's really pushing it.
If you want to run the ragged edge with that kind of compression, take barts advice and measure all the components to ensure accuracey in your math.

So what would be the best way out of this situation? Cause i dont feel like pushing it on the edge and have a good chance of something going wrong. should i end up getting different pistons?

And to get to the bottom of the line will i be able to assemble the block and have it run off of pump gas withOUT decking the block and be safe. Or should i go a different rout to come to a safer SCR and DCR cause im not an expert when it comes to calculating this and i dont feel like having a couple hundered dollar mistake

Would these be a better choice for a piston for the fact they have +10cc which will bring my compression down to 10.1:1

http://store.summitracing.com/partde...0&autoview=sku

I would consider keeping the pistons and switching heads, you could run an aluminum headed motor with this compression and not have to worry about it.

I do not know if you bought your heads yet, but if not, sometimes vortecs can be as expensive as an aftermarket head, I have never had any luck finding good used cores, always cracked, and even if you do find good used ones, by the time you rebuild them(guides, valve job,etc.)you may indeed have been able to buy new ones, so keeping your pistons and buying alum. heads may be the best bang for the buck.The extra flow and weight savings is an added bonus as well!

Ofcourse, all of this is irrelevent if you already have good vortecs, if so, I would sell your pistons and buy a KB or speed pro hyper with a small dish, I have always found it silly to use a forged piston with a stock rod, I have seen a lot of motors throw stock rods, but very few tear up a piston. TRWs are not a real good forging anyway, they are terribly heavy, made from an inferior material compared to most forgings,require more piston to bore clearance, and are not a whole lot stronger than a high quality hyper.

With that being said, I do not mean to scare you from these pistons, they are a good piston and more durable than a hyper, I just believe they are not worth the additional cost, and by the time you need a forged piston you probably better have some better rods anyway.

The piston in the link is what I would reccomend, I think it fits your application perfectly.

Well i dont have the heads but i do have the pistons and i paid 200bucks for them. But if you could be so kinds like you have been in helping me and and teaching me new things to just point me in a directions of some other good heads then thank you.

Well i redid the calculator with 10cc volume reliefts which is what the pistons int he links are and i came up with 9.8:1 SCR and 7.9 DCR and thats with a .015 gasket and a .025 deck height

If you do not have heads yet, I would say go AFR if you have plenty to spend, but if you are like me and on a budget, I had good luck with the patriot performance heads, they flowed well and the quality seemed good, but most any aftermarket head will be of high quality, and if you asked 100 people which was best, you would get 100 answers.(well, probably at least 50 people would say AFR).Some good names are Canfield, RHS, Dart,Brodix, and many others, the only one I would NOT reccomend is edelbrock, just let them stick to making intake manifolds.