Chevy Nova Forum banner
21 - 40 of 41 Posts

·
Premium Member
Joined
·
1,372 Posts
Yeah, If it were me, I'd just go with what was in there. It's not a terribly radical cam and it's got good streetable profile specs. You have an auto or manual trans and if auto, do you have a higher than stock stall speed? Like 22-2400 rpm?
 

·
Registered
Joined
·
126 Posts
Discussion Starter · #22 ·
How can I find out what torque converter I have ? It doesn’t say anything on the converter … sorry Iam on Europe / portugal .. very very few people understand here much about classic muscle cars and the big block .. have to all learn it for myself … I rather have a reliable cam.. but would love a fast throttle response if anything
 

·
Premium Member
Joined
·
1,372 Posts
No worries and glad you're keeping it real across the pond!! The converter may or may not be stock. Pictures of it would be some help and taking a measurement of the diameter would be beneficial as well. Still, no way to know without either some stampings on the shell (front or back) or trying it out once the car is built by which that time, you've already put the cam in and... well... that's that.

I would just go on the safe side and replace the cam, like for like. Easy cam to find and that should be a simple installation. Just really need to make sure you use a high ZDDP oil the entire life of the engine, not just upon break-in. Before you break it in, ask us here and you'll get the expert advice you'll need to have that cam live a long and happy life in the heart of that big block.

IF you can find out (send pics) any info on the heads, we can try to help. Casting and stamping numbers between the springs are a good start.
 

·
Premium Member
Joined
·
1,372 Posts
Well, you heads are as follows:
3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber (Large or small hex spark plugs used)

Appears they have triple springs and some good hardened retainers with studs and guide plates so likely some aftermarket parts there, probably from a cam package, although with out taking them off and testing them, no clue. I would just stick with the cam make and grind you had. I however would venture towards a machine shop if possible to ask them if they could check the open and closed seat pressures of your springs to make sure you don't ruin another cam. If there aren't any around, you can do it yourself by buying a spring pressure tester like this, coupled with a large vice (I've even known people to use a large C-clamp with a good piece of 1/8" plate to back the spring. Lots of youtube vids on this procedure.

 

·
Premium Member
Joined
·
1,372 Posts
If you want the locations of many info site, there are the ones I regularly use for engine and head ID. Lots of great info here:






Keep in mind these are only some of the great sites. Many more out there and lots of people here too!! I am a small block guy myself so I have only general knowledge on the BBC engines but many here are wizards on the BBC.
 

·
Registered
Joined
·
126 Posts
Discussion Starter · #29 ·
Well, you heads are as follows:
3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber (Large or small hex spark plugs used)

Appears they have triple springs and some good hardened retainers with studs and guide plates so likely some aftermarket parts there, probably from a cam package, although with out taking them off and testing them, no clue. I would just stick with the cam make and grind you had. I however would venture towards a machine shop if possible to ask them if they could check the open and closed seat pressures of your springs to make sure you don't ruin another cam. If there aren't any around, you can do it yourself by buying a spring pressure tester like this, coupled with a large vice (I've even known people to use a large C-clamp with a good piece of 1/8" plate to back the spring. Lots of youtube vids on this procedure.

how do i know how much pressure i should have on each spring?
 

·
Premium Member
Joined
·
1,372 Posts
all based on the cam selection so, if using the same cam you had in there (verified), then the specifications of that cam will tell you what open and closed spring pressures you will need and the total pushrod lengths will be calculated by that. Just something more to verify before initial fire on the rebuild.

Rectangle Font Line Parallel Slope



Here's a good article about determining the correct spring pressures but I'm sure someone else here can help too:

 

·
Registered
Joined
·
764 Posts
Need to check the numbers on the head but it’s small chamber / flat heads pistons .. soo I guess high compression?
Guess again, not even close.
454 with .060" overbore, 100cc closed chamber head, flat top piston with 5cc valve relief, undecked block so piston is .020" down @ TDC, .041" thick x 4.370" bore head gasket(common Fel-Pro)....just 8.98:1 compression, lets call it "9:1"

And it could be worse, depending on the brand/type of pistons....most of the available cast replscement pistons are "rebuilder height" and are .010 to.022" shorter than stock.....if you have a set of those, then compression ratio is only 8.7:1.

It's not like a small block....flat top pistons in a big block are not a good thing if you are looking for naturally aspirated power since it is near impossible to find a head with a small enough chamber to even get you to 9.5:1.
 

·
Registered
Joined
·
126 Posts
Discussion Starter · #32 ·
Guess again, not even close.
454 with .060" overbore, 100cc closed chamber head, flat top piston with 5cc valve relief, undecked block so piston is .020" down @ TDC, .041" thick x 4.370" bore head gasket(common Fel-Pro)....just 8.98:1 compression, lets call it "9:1"

And it could be worse, depending on the brand/type of pistons....most of the available cast replscement pistons are "rebuilder height" and are .010 to.022" shorter than stock.....if you have a set of those, then compression ratio is only 8.7:1.

It's not like a small block....flat top pistons in a big block are not a good thing if you are looking for naturally aspirated power since it is near impossible to find a head with a small enough chamber to even get you to 9.5:1.
Hummm deck was also skimmed..with air gap 2.0 intake and a Holley 870 what was the engine good for ? Wonder what the last owner had in mind whe. Building this engine .. or did he not know at all what he was doing ?? Can you guess how many horsepower this engine would produce with this setup ?
 

·
Registered
Joined
·
1,279 Posts
The 290 head is a semi open chamber head. Common 1970 ish 396 head. I had 2 sets of them. Not a bad oval port head. I would guess your chamber volume is closer to 105 or so. Its not the true closed chamber head like a 702 casting head. But based on what Eric said up there, not helping your compression with a bigger chamber.
 

·
Registered
Joined
·
126 Posts
Discussion Starter · #35 ·
Does heads are original from the 396 chevelle 1970.. which made 390 hp.. what was different to my engine apart that I have actually a 468 and air gap manifold .. should it not be more powerful? Sorry my questions .. trying to learn obviously
 

·
Premium Member
Joined
·
1,372 Posts
Just put a centrifugal blower (and get your carb built for blow-through) on it and you're all good! 6psi boost and you'll make crazy easy power with a reliable engine too! MAy cost some money up front but way cheaper than new BB heads and bulding that thing for more compression. New heads & pistons will set you back right there and the machine work... Probably less for a blower... Just a thought and you already have the compression set for a safe 5-6 psi boost.
 

·
Registered
Joined
·
1,279 Posts
Does heads are original from the 396 chevelle 1970.. which made 390 hp.. what was different to my engine apart that I have actually a 468 and air gap manifold .. should it not be more powerful? Sorry my questions .. trying to learn obviously
1970 was rated at 350 hp on the 396. But it was also 10.5:1 compression. If yours is a flat top piston engine, it may have been 8:1 as a 454 with 118 cc heads. So closing up the chamber from 118 to 106 would have raised compression up some.
 

·
Registered
Joined
·
764 Posts
how do you come to this calculation? How do I up the compression ?
Use a compression ratio calculator, I use the one at Wallace Racing.

Wallace Racing - Automotive Calculators
Compression Ratio Calculator - Wallace Racing

Math don't lie, unlike the factory....forget you ever heard what the factory gave for compression ratio. Its always lower than what the factory spec is.

The 396 had a pretty big dome, 30-ish cc or a little more. Even the lowest 325 hp engine had domes in it. I believe even the lowly and rather rare 396" 265HP 2 barrel carb Caprice/Impala/Station Wagon 1969 engine had a small dome in it.

106cc head puts a stock deck block, flat top piston 454 at 8.6:1 compression. If block got a .010" skim cut on the deck, it would come up to 8.75:1.

You see this problem alot with guys who are familiar with "flat tops gets 9.5:1 compression on a small block" and apply that thinking it will be the same for the Big Block....not so because the combustion chamber is sooo much bigger.
 

·
Registered
Joined
·
26 Posts
Might have missed it in previous replies, but please explain from your original post “…never really ran right”.as others stated, yes you wiped out your cam lifters etc, def replace them. My point being don’t rebuild engine the same if it never ran right, I’ve starved monster motors for oil and they still ran good…until the exploded. You obviously need to better match engine components better than origina builder to ensure you get better bang for buck next time around. Good luck!
 
21 - 40 of 41 Posts
Top