What can you guys offer in the way of constructive criticism on this combo?

396 (.060 over)
1966 block decked .010
Speed Pro forged pistons (37.1cc domes)
Comp Magnum 292 cam (.550lift,244 duration)
forged crank, cut .010
Eagle rods
Comp roller tip rockers, manley SS valves
old GM rectangular port/cc heads, were 2.19/1.72(now 1.88), with some port cleanup and bowl work. Heads milled .010. Originally 104.9cc, now are ???
Compression should be 10.5:1 (or so my machine shop tells me)..I am worried it may be higher.

I am looking for a streetable 450hp, with no problems with pump gas. Any words of wisdom would be helpful before I start assembling this. Will be going into a 70 Chevelle with 4.11 rear/4 speed m-21.

With 4.11s you might get away with it but most street 396s don't like Big Port heads. The 215 style Oval port should work better.

My friends 67 375hp velle ran 12:70 @108. with same combo except using the stock 143 chevy cam and exhaust manifolds thru flowmasters.
I would look for a small solid cam imho about mid 240° duration .550 lift on 110° lobe sep.
using M&H racemaster tires and drivin it like he stole it. :D

Be sure the cam is grooved in the rear journal.

Oval port heads would be a plus.

Decking the block .010 "probably" means the pistons are .010-.015 down in the hole. Add a .040 head gasket, and you're on the verge of having too much piston to head clearance. High compression and poor quench is a bad combination. I'd "zero deck" the block, and touch up the combustion chambers to smooth them, and gain a little more combustion chamber volume.

compression is going to be around the 11.5 mark with your combo....which is still ok to run pump gas........you will have to pay attention to the timing and get it under control......

if your concerned about the compression get into the head chambers and clean them up and open them up some.......run head gasket around the .050" mark...most really cheap gaskets measure around this thickness......open the relief cuts on the block as well.........this will help lower compression some.

the cam will big enough to run on 91 octane.....

just be ready for a 7000 rpm shift point......thats where the power is going to be upstairs.......low speed torque is going to blow under 3000 rpms..the engine will feel soggy down low.......... your building an engine that will shine from 4000 to 7000 rpms.......

its a sloppy way of building 450 hp......

an easier street friendly way would be something like i built.

makes about 470 hp at the flexplate puts down 373 hp to the rear wheels...107+ mph in the 1/4 in a 3900 lb car.

using rpm intake, 3310 carb, 233/239 @ .050 cam, 10.5 to 1 comp. and runs on 87 octane fuel.

granted your combo will be fun but it will be a handful getting everything tuned in to work like you want on the street.....i have built them this way before......

If this helps my 402 030 over 408CID L2240nf 060 pistons 215 heads 102cc 2.19 in 1.75 exh.Comp cam 270H magnum manley valves 911-6 springs.Ede perf 2-0 intake heddman 1 3/4 headers pulled 426 on dyno Using Q-Jet by Sean Murphy. Good luck with combo

Thanks for the feedback so far. I agree the ovals would probably have been better, but the heads I have are what came with my motor, so it was easy to use them..
I should also add that I have a Weiand Xcelerator single plane intake. Carb has not been purchased, but shop tells me to run a Holley 850. They are trying to talk me out of a dual plane intake with a 750..

Yes, the rear cam journal has been grooved.

Tonite I installed pistons. They came up .010" below the deck surface. Maybe .011" max. I am going to try to cc the heads and see what they really are..they "were" 104.9cc original based on the casting info I have, but were milled .010" (guessing that it may have removed 2cc??)..

But also the heads have 1.88 exhaust valves, and originally were supposed to have 1.72's..so I figure I may have picked up some volume when this mod was done (by others)??

Playing around with #'s, I am figuring between 11.3 and 11.6:1 based on what I know right now, but that does not factor in that the head volume may be off.

Any tips on cc'ing a head? I am also concerned about quench. Hope I dont have a detonation problem when this is together, and really dont want to have to run octane booster, etc.

Also, one other question to Ddennis..with regard to your comments on the shift point..do you think this cam will be good up to 7000 rpm in this combo? I was thinking that was more into the territory of solid cams, where the Comp 292 that I am running is a hydraulic.

thanks,

even being a hydraulic cam it still will zing up there. this is an older grind that has slower ramps it is somewhat easy on the springs. even my current smaller 233/239 @ .050 hyd. cam runs 6500 rpms and makes best power there...but it will keep going as long as i keep my foot in it.....i have had it to 7000 rpms a few times but there is nothing there that makes the car any faster.....other hyd. i have ran have ran past 7000 rpms with no ill effect.

with your heads and cam.....this will want the rpms to make best power and trap speeds.....and just based on other bbc 396 motors i have built i would say you will see about 7000 rpms for best overall performance.....

this maybe solid cam territory but there is just no cut off point to where hyd. cams stop....with a good set of springs it will go ......personally if it was my set up i would have gone to solid cam....just because i know the engine will want the rpms with the rect. heads.....the 396 itself likes to rpm(stroke and bore) and its hard to get away with a low rpm 396 that makes great power numbers....

you have the foundation for a really high rpm engine that can make a lot of power....my choices would be a victor jr intake, 850 holley and a solid cam 250/260 range with 4.56 gears

with this it would put your into the mid 11's on the motor at around the 115 - 117 mph mark. with the solid cam intake and carb......as mentioned above.....and it would run on 91 octane fuel and you would have a cranking compression of about 160-170 psi......it would pull very very hard from 4200 rpms to 7200 rpms......

I don't drag or race anymore but you've got a high rpm motor there. I don't think you're going to notice if it's 450 or 500 hp in the seat of your pants. Your top end will. Your top speed at rpm/gearing should help you figure out your HP without a dyno. But your torque curve is going to be pushed over pretty good.

It's going to pull like a dog racing from hell at 3-3500 all the way to 7-7500 though IMO.

I would run better than 91 octane in that monster just to be on the safe side.

With the manual you could run a dual plane but I suspect that intake may choke down on you around 6500. You might want to run a single plane with an 800 or 850.

BTW, your car will pull to the right at most gas stations.

Is this thing going to be too racy for the street? I wonder if its a bit overboard..I really was looking for more of a 80/20 or 90/10 street/strip setup.

I have been back and forth with the intake/carb thing..comp cams says single plane and 850, but my gut was telling me dual plane/750..I guess I am gonna find out!

What is the casting number on the heads you're running and what mods have been done?

Rectangular heads will push the torque curve to the right and oval down lower.

A single plane will make you bog some low but this is really more of an issue in SBCs. I don't think it will be an issue with your tranny, torque and RE.

If you are looking for speed, don't care as much for reliability and paying for the pricey stuff, then go for speed.

If all you want is street occasional strip take the rect heads off, sell them to a racer and put some nice ovals with big valves on. Stay at or below 6500 and it will live longer. You'll still pull tree stumps.

I don't think you'll have any low end or vacuum problems running a 4.11 with a muncie with any of the intakes/combos you've mentioned. Either way you're gonna have fun. It's just your current setup has your torque curve 3000-7500. To breathe at 7500 well you need a big carb and a single plane IMO.

I'm cheap so I spend only as much as I have to. I've got ovals closed chamber and a 750. And flat cast pistons. All BBC get lousy gas mileage anyway.

The heads are 3919840, but they have 2.19 intake and were modified in the past to have 1.88 exhaust. My shop also did some further port work, but i don't know the final cc (yet). I hope you are right about the vacuum, as I want to run power brakes.

with the 244 cam your idle vacuum will be around 10" of hg at 900-1000 rpms.......

OVR,

I'm certanly no engine builder but I can tell you that the solid lifter Lunati cam in my 60 over 396, which has less duration than the Comp grind you mentioned above, only gets me about 15" of vacuum at a 750/800 RPM idle. My power brakes work but I'm guessing your 408 is going to pull between 12/13" with that cam - right on the edge (perhaps past it) for power brakes.

Copied and pasted from Comp's site"

"292H Magnum™ is for the serious “Street/Strip” type car. An aftermarket torque converter should be used as well as headers, intake and increased compression. The 292H has a radical rough idle."

While the 292H may compliment your 840's and the single plan I'm kinda thinkin that the whole shabang will miss your stated goal of 90/10, 80/20 use. It's gonna idle between 800/1000, I think PB's will be iffy, and it's gonna be lazy in the RPM band where it'll probably spend most of it's time on the street (although the 4.11's help).

Too late to reshuffle the deck?

Dan

Did you say that you have not bought the intake yet?

If not, and money or using those heads is a concern, why not get an oval port intake for the square port heads? Yes it is a little bit old school(old NMCA tricks), but you will increase intake velocity as well as VE which both will help your streetability.

Then when you decide to go to some good oval heads, you'll have the correct intake ready to match.

With those heads I think you'll be happier with a larger carb. It's much easier to de-tune a larger carb for the street than it is to make to small of a carb to flow.

My .02 for what it's worth.( I actually like your combo as is, I just would have like to seen a solid cam as well)

Rob

Don't use the single plane manifold with your heads and small BB. The 850 sort of works on 454 street cars that are heavy but a vac. carb usually is better and your 396 has absolutely no need of that big a carb.

cc your heads and domes.
my 840's were at 110cc when I checked them.