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Discussion Starter #1
hi guys can u give some opinion on this combo and how many hp and torque

1969 396ci block
9,5:1 compression or 10:1
xe 268H cam with matching valve springs
headers dual exhaust 2,5 inch flowmaster 40 serie
edelbrock intake
750 edelbrock carb
roller rockers
msd ignition Hei and 6al
balanced rods and pistons
stock m77 oil pump

and good ported peanut heads ,Manley underhead cut valves 2.06intake 1.725ex.
these heads flow stock like 220 230 cfm how much will the flow with the manley valves and bowl work and valve guide work etc.

I know other heads will flow much better but are very expensive over here
so this is what to use

th350 3.42 gears 3300 car with bbc

thanks
 

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Would like to share my combo.

First I can't find the cam you listed, except in a small block version. What brand and where did you find it? Not to question your intellegence, but, you do know that a 396 is a big block right? Please don't take me wrong, I'm just trying to help.

My truck has a 396 bored out to 408(.090 over) I have 11.89:1 compression, closed chamber heads with oval ports opened way out, .544/.544 lift 230 duration at .050. Holley 750 true mechanical double pumper with four corner idle and progressive linkage. Desktop dyno 2000 has given mine 525hp and 565 ft lbs of torque.

Jay
 

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Discussion Starter #3
hi jay i know its a big block
here are the cam specs




Part Number 11-242-3
Grind Number CB XE268H-10
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.515 0.52
Duration At 0.006 Tappet Lift 268 280
Valve Timing At 0.006
Open Close
Intake 28 60
Exhaust 74 26
Duration At 0.05 224 230
Lobe Lift 0.303 0.3063
Lobe Separation 110
 

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I had a 402in my old 72 C30.I ran real great off the low end.But seemed to not have much for the top.Of course it was stock.I ended up taking that engine out.Putting the crank and heads(LS-3big oval)in a 454 block.Making a 427.I like the 427 a lot more than a 396 or a 454 for a hot rod engine.
 

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I recently built a 396 for my 1970 truck. I use the engine as a spare for when the 454 needs to come out and also built it just for fun. I have the 396 in the truck now.

With about same compression and cam. The 454 made much better low speed torque (good tire spinner). The 396 spins the tires but just not as hard, especially with the AC on. But my 4000 pound truck makes it hard to spin tires with a 1500 stall towing converter , a LSD 3.08 gear, and 275/60-15's in the rear. The mild range power of the 396 is also less than the 454 but not as apparent. The 396 seems to make the same power above 4000 rpm as the 454. But since the truck has a 3.08 gear, the engine spends most of it's time under 3500 rpm, which is a problem for the smaller 396.

In the 396, I used the bigger 2.19/1.88 valves and did a home bowl smooth job. The heads are the 820's with 240cc intake ports and 110cc combustion chambers (stock 71 402 heads). I had the heads flowed at a local race shop and they flowed around 260in/200ex cfm at 0.500". I don't have the complete flow sheet in front of me since I'm at work right now.

The 396 engine has 9:1cr and I'm using a custom compcam which is made from a 252H high energy lobe on the intake and a 260H lobe on the exhaust. The engine will detonation with 87 octane and requires at least 89. The weight and gear of the truck make it detonate more. It makes usable power to about 5300 rpms and the 454 would quit making power about 300rpms less. The 396 is now 413 cid, I used pistions for a 0.070" over 402.

A 396 in a 3300lb car with a 3.42 gear will make a nice combo. You don't need that low end torque of a 454. My 396 is easier to drive fast on the street because I don't need to worry as much about the rear end of the truck trying to be where the front of the truck is. The 396 is much easier to modulate.

FYI, Flow Masters are worthless. Get a set of Hooker areo-chambers for a louder than stock exhaust system or a set of Dynomax Super Turbos for a quiet high flow system. Both of these mufflers out flow the Flow Masters.

Also, use diesel engine oil (Rotella T 15w-40) with your new cam setup if you what it to live more than a week.
 

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Discussion Starter #8
well got good news i was going for a 396ci here on a local sort off ebay
but i won a 454ci its going to cost me more but some parts are cheaper
and better to get (pistons)and i have to drive 400miles total to pick it up and get it home.
owner told me it was a good running block
but its going a part and get a rebuild
block number 361959
head number 346236 peanut heads

so every body thanks for replay
i think iam going to keep the same specs for the build
maybe a xe274 cam
and in the future better heads

well still got a few qeustions: stock compresion of that motor and piston style
dish flat top?

thanks all
 

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It may be pretty difficult to know what your compression might be with not knowing the piston volume, but you can get the heads cc'd once the motor gets tore down and then buy a piston to get the compression you want. The block was made form 1973 - 1990 and the heds were from 1975 - 1987. I found this info from the site below. As far as head flow, there is another site that has the stock flow numbers for a 236 head. I would probably stick with the xe268h cam. Those heads are not going to want to make power very high at all. I would capitalize on the low RPM power of the heads instead of trying to get them to make a little more up high. When you get a new set of heads, you will probably want a different cam either way anyway. Also on that site, there are flow numbers for a ported set of "360" peanut oval heads. You can probably get a pretty good idea what a set of ported 236 heads would flow from that. Personally, I would put the heads on without porting them. You will probably not be able to get much out of them when you buy new heads.


BBC casting numbers
http://www.mortec.com/bbc.htm

236 peanut flow numbers (scroll to to bbc numbers)
http://users.erols.com/srweiss/tablehdc.htm#BBChevy

Adam
 

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346236.....75-87...oval...OPEN...454, 120cc chamber, 225/116cc ports

Those heads have very small intake ports (225cc), so don't except much high rpm power. You could run even a bigger cam with those heads to try getting some air into your engine. A 106 or 108 LSA would also help them make some power.

120cc chambers will require a good size dome to make compression. The domes on my 454 are about 1/8" tall and it only makes about 8.75:1 cr with 120cc 781 heads. If you are going for +10:1 cr then the domes will be pretty tall. Do the math before you buy anything.

I would look for some 049 or 781 heads and sell those 236's to someone with a motor home.
 

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xe268

I've got a xe268 cam in my 427 vette. So far so good---I love the cam around town, as it has a lot of bottom end. I also have 3:55 rear end which helps and a 2200-2400 Hughes stall converter in a turbo 4400 trans. Comp says that you don't need a stall converter with the 268, but it really seems to compliment the cam. I'm able to feather the gas and keep the tires right on the edge of breaking loose for faster starts. Of course burning rubber is not a problem & it's fun too. I agonized a long time over the xe274 because I already had the converter, but now I'm glad I got the xe268. It has a nice noticeable idle, great low end and I'm yet to really test it past 5,000 rpm or so. It keeps pulling and wants to wind higher, but it's not totally broken in either, so I'll wait to really romp on it. The rest of the combo is: 9:1 compression, large oval ports, gasket-matched performer, 750 Demon dp, Hooker headers, HEI dist, 21/2 Flowmaster 40s. It's a blast to drive!! Eventually I want to build a big block stroker and have a spare motor, but now I'm getting ahead of myself. Two thunbs up for the xe268!
 

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Can any one help me too?

Do you guys know how much my CR will drop if I go to open chamber heads?

I have .319 dome pistons in a 407.7(396-4.155 bore.) right now it's at 11.89:1 with closed chamber heads.

Just thinking about trying to get a little closer to running pump gas. Right now I have to be at least at 100.

Thanks,
Jay
 

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Here is a site that will tell you your compression
http://www.angelfire.com/fl/procrastination/motor.html

According to this site, the gm 290 head has a 105cc chamber, I would assume that is a closed chamber, I am not sure how much variation there is among closed chamber heads.
http://www.chevyhiperformance.com/techarticles/41598_cylinder_head_flow_bench_database/index8.html

Assuming a 3.76 stroke and a 4.155 bore, with a .05 quench, you would have to have around a 32cc dome to get 10.9:1 with a 105cc chamber. If you went with an open chamber head with a 118cc chamber, your compression would drop to around 9.5:1 assuming the 105cc's is the correct current chamber of your heads.

Adam
 

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Let me repeat my earlier stats.

I really appreiciate your efforts. But, I need to repeat some things.

My CR is 11.89:1 Now.
Factory heads are 105cc, yes(There is only one factory set of closed chamber)
My pistons are .319 dome.

I will go to the link you provided to get more but thank you.

Jay
 

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Discussion Starter #15
ok guys thanks for ur time and replay
11 November i will pick up the motor just called the man today.

question is now what cam to use xe268 xe274 (car is no daily driver)
i will go to better oval port heads in the future
don't want to swap cams again when i get better heads or pistons (close chamber open chamber dome)

saw some pistons from kb .133 dome9.1/11.1:comp for nice price
don't want to spend a fortune on parts
a friend off mine will mille the heads a littel more down to give me alittel more compresion with the open chambers
so would the xe274 be a dog with lets say 9.2:1 9.3:1 compresion

thanks for ur time
 

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Yeah that cam has a decent power range.3.42 gears.Might be a little light though.I would at least go to a 3.73.For the bigger cam.274H Is preety good overall.And most people that go thru a bigblock build.Are'nt going to get mileage anyway.So you might as well go with a big cam.The 274H is good for a street driven performance car.I had a bbc 427 10:1 with that cam.It was great.I could drive that car everyday.And it had a nice lump in its idle.Real strong mid-range.And the mileage was not that much worse than the stock 454 was.
.
 

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If you are not going to change the cam when you get new heads, I would recommend the Xe274H. Comp recommends 9.5:1 with the cam one step higher than the 274, so I would assume that 9.2 would work with this one. They also have a magnum flat tappet cam that is very similar in size 230 230 @.050 .520 .520 lift) that needs 9:1. I would not recommend that cam for your setup, but it is a good comparason for compression requirements.

Adam
 

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Discussion Starter #18
cant find the part were comp recommend 9.5 comp for that cam ist that
the xe286 cam http://www.compcams.com/catalog/092_093.html

I'm reading allot of articles now, on bbc most people say
bbc likes to eat cams by first start up,so cant i use the original valve springs
for initial start up and change them after the cam has run in.

don't know the max lift of bbc valve springs

thanks for ur help and time
 

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Yes, I was saying that they recommend 9.5:1 for the xe286h. There seems to be a pattern of 1/2:1 incriments between the cams as far as recommended compression goes. If that holds true here, it looks like the xe274h would be ok with around 9:1. Your motor is on the small end of big blocks; I dont know what effect that has on all this, but it may be somethign to look into. I dont know about the valve spring thing. I would call comp and see what they recommend. They are usually pretty helpful.

Adam
 

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Discussion Starter #20
thanks Adam
what do u mean by:
Your motor is on the small end of big blocks; I dont know what effect that has on all this, but it may be something to look into

i will buy the valve springs that match the cam but going to look for
break in springs or if i can use the original for break in
thanks
 
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