[Cwaustin]

Hi all,

I am building my first engine but i am having trouble finding a good combination of parts to use. ( I dont want to hear the crap about 400's, no i dont want a 350)

I have: -----> 1985 Camaro
an 817 400 small block .30 over
a scat all forged rotating assembly
64cc flat top pistons
6-inch "H" rods
3.75 inch stroke

I want to use:
Holley 750 carb or demon 750 carb
Victor jr intake
Want to run on pump gas as a fun street car
I had someone suggest Dart SHP Aluminum heads
and a mild cam

I am new to this so any help is appreciated and links

 

[johnsongrass1]

I beams are lighter than H beams.

A Hyd Roller cam in the [email protected] range and you'll be where you want to be.

The Holley HP is a good one.

What's your plans for pistons?

Have a budget in mind for all this?

 

[Cwaustin]

I got the Whole rotating assembly as a set and i figured "H" rods were better for torque

As for the pistons thats what I am confused about, I was told they would put the compression ratio to high for pump gas so i would need 'Bigger" heads

I didn't really have a budget, just buy the parts as I can (also because its for street I didn't think I would need anything to expensive?)

 

[ericnova72]

Skip the Dart SHP heads, flow numbers for them are not that great, especially considering the price.

You are correct, flat top pistons in a 400 with the common size of 64cc combustion chamber headss puts you too high for pump gas unless you use a rather large duration cam and you have a very good handle on tuning and maintaining an engine that is built to run right on the ragged edge of pump gas combinations....it's not a "set it and forget it" situation. It ends up well over 11:1 compression, possibly as high as 11.7:1 depending on final piston to deck clearance(quench) and your head gasket thickness.

You'll want to be looking at a cylinder head with a chamber volume in the 70-76cc range, if you want Dart that is the Pro 1 line-up.

ProFiler, and ProMaxx are a couple others to look at. AFR is another.

195cc intake runner is as small as you are going to want to look at, if you want real good street/strip power then look at 210cc-225cc intake runners.

 

[4 Jaw Chuck]

Moved to the basics forum since there needs to be some knowledge gained regarding engine construction before parts can be selected.

 

[BogiesAnnex1]

Hi all,

I am building my first engine but i am having trouble finding a good combination of parts to use. ( I dont want to hear the crap about 400's, no i dont want a 350)

I have: -----> 1985 Camaro
an 817 400 small block .30 over
a scat all forged rotating assembly
64cc flat top pistons
6-inch "H" rods
3.75 inch stroke

I want to use:
Holley 750 carb or demon 750 carb
Victor jr intake
Want to run on pump gas as a fun street car
I had someone suggest Dart SHP Aluminum heads
and a mild cam

I am new to this so any help is appreciated and links

Since this is your first build, I'm asking a simple but important question about the rod length and pistons. Are the pistons proper pin to crown height for a 6 inch rod? Six inch rods require the pin be moved up to lower the piston so it isn't pushed higher than the deck. So I'd like to know the source and part number of the pieces of the rotating assembly. This also can help with balance as some combinations can result in an internally balanced 400 which is better than the more conventional external balance.

Assuming the parts are correct, then the flat top pistons will push a 76ish cc chamber. For aftermarket heads this is still an advanced Ricardo style Vortec chamber not to be confused with the factory's use of open SMOG chambers. Heads run from less expensive imports to outrageously expensive domestics so your budget and abilities come to play. Pro comps on the low cost scale while affordable require some hand work in the ports to get them to breath well. Their idea of an NC port is not sufficient, the trick here is to start with their 190 cc port and gently massage and blend the rough places. On the higher end of the scale, AFRs out perform nearly everything just out of the box, since they are so good the earlier 190 port if you can find them used, or the new 195 will feed a 406 to its peak potential. Anybody else's head will take 205 to 210 cc port to equal the AFR 195 and that includes the larger port AFR for an engine of this size.

Bogie

 

[Cwaustin]

believe it was this rotating assembly: ( it is internally balanced) https://www.summitracing.com/parts/sca-1-41410bi/overview/

As for the Proper height for the pistons I assume they would wouldn't go higher than the deck, the block was untouched before I got it. also the engine shop has not brought it to my attention.

Thanks in advance for you patience as well

 

[BogiesAnnex1]

believe it was this rotating assembly: ( it is internally balanced) https://www.summitracing.com/parts/sca-1-41410bi/overview/

As for the Proper height for the pistons I assume they would wouldn't go higher than the deck, the block was untouched before I got it. also the engine shop has not brought it to my attention.

Thanks in advance for you patience as well

A trip through Summit and then to SCAT for detail information serves as a reminder to me why I buy pieces instead of kits, their idea of information and my idea is a lot different. So I'm left to make some assumptions since all I know is the kit supplies CP pistons.

So I'm assuming a .025 piston crown to block deck with another having a zero deck block.

With the .025 deck and a .030 thick gasket:
A 64 cc chamber would push an SCR of 10.99 to 1
A 76 cc chamber would push an SCR of 9.73 to 1

With a zero deck block and a .045 thick gasket:
A 64 cc chamber would push an SCR of 11.69 to 1
A 76 cc chamber would push an scr of 10.27 to 1

For aluminum heads none of these Static Compression Ratios are out of line with unleaded pump gas. The key will be the Dynamic Compression Ratio (DCR) but that takes knowing the intake valve closing point in crnak degrees of the cam. So you need to pick some cams with their timing card data to calculate that we can do it here or you can use online sites to plug in your data to see what you get. For aluminum heads on pump gas you want to see a DCR around 8.5 to 1.

H beam to I beam rods as to which is better for performance is probably more in the eyes of the advertiser than anything. A general rule I look to is continuous operation over 6000 RPM I lean toward H beams as they generally tolerate the loading better than I beams. The power difference is zilch between configurations this if any that is measurable is length sensitive but truly isn't much. My experience shows that piston side loads against the cylinder wall show less wear with a longer rod and that longer rods tend to take a piston that is lighter because it is shorter and this makes getting to internal balance without Mallory metal a lot easier with SBCs running the 3.75 and longer strokes. I prefer internal balance as it takes some of the twisting moments off the crank which is additional structural load within the crank that is imparted to the bearings and onto the block structure. These loads also demand a better quality damper if you're going to run the motor hard.

You look to me to be on the right path to a solid build.

Bogie

 

[Cwaustin]

Buying pieces in stead of parts is duly noted for the future

And is seems to me I would want it decked at .25 and a 76 cc chamber so i get the 9.73 to 1

Based on the heads i think i would be looking at AFR 195cc eliminator heads If i choose these
Believe these https://www.summitracing.com/parts/afr-1094-716/overview/

But then what would i need to do for the rockers/ratio on the heads?

As far as the damper goes could I also use the stock with the 168 flexplate?

 

[ericnova72]

You could use the AFR Eliminator Street version rather than the Competition version if you feel you won't use the full potential of the race head, plus it will save you $400.

Competition version is better at high lifts, but if your cam choice doesn't get you into the .650" lift range it is mostly a waste of money.

You'll need a full roller rocker arm, AFR does not recommend stock or the stock type with just a roller tip.

You are also going to want to investigate whether the headers you plan to use for whatever vehicle you put this in will clear angle spark plugs, straight spark plugs, or both.

Angle plug fit headers tend to be more race oriented and thus more expensive, with fewer available brands.

Hope you got a better rear axle swap in the back of your mind, if you hook the 400 to the road well your stock puny 7.5" `0-bolt rear has a very limited lifespan ahead of it.

 

[rdobbs77]

Buying pieces in stead of parts is duly noted for the future

And is seems to me I would want it decked at .25 and a 76 cc chamber so i get the 9.73 to 1

Based on the heads i think i would be looking at AFR 195cc eliminator heads If i choose these
Believe these https://www.summitracing.com/parts/afr-1094-716/overview/

But then what would i need to do for the rockers/ratio on the heads?

As far as the damper goes could I also use the stock with the 168 flexplate?

you will either go with a 1.5 or 1.6 ratio. Were it me in wondering to decide, i'd take the max lift of the cam and compare it to the top max lift output (flow rate wise) from your head and make a decision. For example (very generic-throwing out number-not doing the math) if you have a 550 lift cam and your heads produce peak HP at 650 lift then you would want to increase your lift and opt for a larger rocker ratio from the 1.5 in order to give you more lift and take advantage of the heads. Likewise, if your cam is a 550 lift and the top flow rate on your head occurs at .500 lift, then upgrading to a 1.6 ratio is not going to achieve you anything. Increasing rocker ratio is basically increasing the lift of a cam without buying a new one, among other things. Keeping valves open longer or shorter also have pros/cons based on setup.

btw, nothing wrong with Dart heads.

 

[Cwaustin]

Yes a rear end swap is definitely in the future but that's another story one step at a time

Yes I do want to use the street version that should be fine for my application
so AFR 195 cc street heads
Full rockers with a 1.5 ratio?

Then for my cam i was told earlier i should use a hyd roller cam thats [email protected]
What about hyd flat tap cam?

 

[johnsongrass1]

I said [email protected] range. Not Exact. I don't make specifics on cams. I'd rather just pay someone in current technology and get the right one the first time.

Yes FT would do you well if you wanna save a few bucks and simplify things some. Rollers have big advantages over FT's but come at a cost. If you decide on the FT than I would for sure go custom designed and ask for the better cam cores and EDM lifters to give you your best shot at surviving the 1st 1000 miles.

 

[vinniekq2]

Johns above post I think needs clarifying or maybe Ill learn something here?
EDM lifters as far as I know are solid flat tappets only?
Nothing wrong with a solid flat tappet cam for performance.
If you plan on keeping the redline to 6k (ish) then a hydraulic roller works well for most people. A solid flat or solid roller will rev higher with less expense than a hydraulic counter part.
Personally I would use AFR 210s and an 850 cfm Holley for anything north of 500 hp.

 

[BuzzLOL]

I am building my first engine but i am having trouble finding a good combination of parts to use.

I have: -----> 1985 Camaro
an 817 400 small block .30 over
a scat all forged rotating assembly
64cc flat top pistons
6-inch "H" rods
3.75 inch stroke

Didn't see any mention of the HP you're looking for to be happy with this street engine...

The stock 76cc '400' iron heads would work and flow up to about 385 HP... need porting, bigger valves, different heads etc. if more power is wanted... The stock heads with flat top pistons and a mild performance cam (about 204/204 - 224/234 durations at .050" lift) basically gives you a 1960's good MPG, daily driver muscle car type engine... A SBC 400 can produce up to about 550 HP with modern heads and cams (and more money) and still be comfortably street Daily Drivable ("DD")... Aluminum heads can tolerate higher compression ratio on pump gas than iron heads because aluminum bleeds off heat (and some power) faster... of course, aluminum heads also saves about 50 lbs... and aluminum intake manifold and water pump saves even more weight...

When the term .025" deck is used, that is referring to a stock, uncut cylinder block... because that is typical of 350's... but 400's often have pistons found further down in the block because of the crappy smog era piston design... and some aftermarket cheap 'rebuilder pistons' may even produce a ridiculous .060 - .090' 'deck' (distance from main piston top surface to block deck)... so that's what we are often fighting with 400's... You'll have to determine what 'deck height' your rotating kit provides... This involves adding crank stroke to rod length to piston 'compression height'... and verifying the piston compression height is actually the height claimed... Summit had been selling pistons with inaccurate heights...

Also, usually don't want to use a thicker head gasket to lower compression ratio as this can screw up the "engine quench" effects just as badly as excessive deck:

http://www.crankshaftcoalition.com/wiki/Quench

A search will produce many more easy to read articles and theories on engine quench... if want to understand it further...

You can use 1.5, 1.6, 1.65, or 1.7 ratio rockers depending on other parts used... usually stick with 1.5 ratio for the cutting edge state-of-the-art design 'extreme' cams as they can get noisy with higher ratio rockers... and they tend to have shorter street life...

Have you seen this video on 400's?

.

 

[BuzzLOL]

Your internally balanced rotating assembly can't use the original stock '400' UNbalanced front dampener and flexplate/flywheel... need balanced parts... you want a better quality dampener and flexplate, anyways... some SFI 'approved' ones... 350 front dampeners are all balanced... 350 flexplates/flywheels came balanced 1967 on, then mostly unbalanced after 1985... rear of crankshaft bolt pattern also changed...

 

[Cwaustin]

I was looking to make closer to the 500hp mark and I did not see the video thank you for sharing. I cant seem to find must information on modifying 400's

As for the heads I really like the 190cc AFR heads so i think I am going to go with those on the downside the price haha

 

[vinniekq2]

190 cc heads are a little small but adequate for 500 hp.
The GM block is marginal at 500 hp.
500 horse power is a good time to add a bigger pan
A hydraulic roller cam is about minimum for that power setting,,,

 

[BogiesAnnex1]

I was looking to make closer to the 500hp mark and I did not see the video thank you for sharing. I cant seem to find must information on modifying 400's

As for the heads I really like the 190cc AFR heads so i think I am going to go with those on the downside the price haha

About 460 is the cut line for anything street able from a 406. Going beyond that is the arena of race configurations. The problem is the bigger an engine gets the harder it is to move the power to displacement ratio. That results in moving to much more radical components to force higher RPMs because that's where the power is. Basically the problem becomes the block, the stock 400 block just isn't up to the next step. I know the power increase doesn't seem like much, but to get and keep 500 and above especially naturally aspirated takes a huge step in component selection.

Bogie