I have a 402 BBC with oval port heads, the guy i bought it from said that for mild street application oval port heads are easier/better to make good power. Is 500 HP a reasonable expectaton with porting and the right cam and so on. Planning on running a tunnel ram. Any thoughts or comments would be appreciated

what casting number on the heads

500 hp with a 402 is not that difficult. I have that + with my .040 over 402. If you want to build a tunnel ram car, I would build a 454. The larger CI's will like it better. Oval ports are great on 402's. Mine are 063 castings with a little work. Good luck.

Regards,

NOOOOOOO,,not a tunnel ram graemlins/sad.gif RPM air gap and a hydraulic or solid flat tappet cam with 1.75/3" headers,,,will get you the torque not horsepower that you need :D oh no...another 4 speed guy graemlins/clonk.gif

The tunnel ram isnt a definate but i found a great deal on it with carbs, plus ive always had a thing for a tunnel ram or blower stickin out of the hood. Starting playing around on Desktop Dyno and built a 402. With about .620 lift and 260 duration at .050, it said about 575 horse, with 485 torque. Dont spose anyone could tell me the stock size of the 402 heads with out the casting #'s ill try to get them later when i work on my car. could anyone tell the me pros and cons of a tunnel ram besides keeping the holleys in tune?

If it's an oval port boat tunnel ram it actually will work very well if the weather doesn't get too cold. Just use small carbs. On a 402 the origonal oval ports will work just fine.

575hp out of a 402 doesn't sound very realistic IMO unless it's got a ton of compression and is a pretty radical piece that won't have very decent street manors.

well its gonna have a big cam and a pretty big port job. 10.5 compression dont know how accurate the desktop dyno is but thats what it said. plus its got a 4 speed beind it so the low end isnt as important

What flow numbers did you enter when using DD2000? What cam specs did you use as well? As with any prediction software, junk in, junk out...the accuracy of the output is only as good as the data you use to model with.

My own 414 ci bbc (based on a destroked 427) has 10.5 to 1 compression and makes in the neighborhood of 525 to 540 hp using a Comp street roller cam.

You 402 has a smaller bore which will limit head flow which limits power...valves will be shrouded which doesn't help either. My 4.280" bore will breath better than the smaller 402 bore...don't do a ton of porting as it really won't be worth it IMO. Basic bowl blending & cleanup as well as a good 3 angle valve job is all you really need.

Are you shooting for a specific ET or simply bragging rights with a certain power figure?

Low end isn't important? :confused:

Not really shooting for anything, dont plan on really racing much, maybe a open drag sometimes but nothing real competitive. And im not looking to say "oh yeah well my car has 575 horse" i just pluged in numbers as to what i thought id be putting in. What kind of power are you pulling? Im not looking to getinto a pissing contest, just looking for some advice.

heres what i plugged into DTD200

260 duration 629 lift @50 solid
oval port heads ported
10.5/1 comp
900CFM
Large tube headers, mufflers
Tunnel ram manifold
put in 2.190 1.9 valves
Did i mess something up there? im not the most proficient engine expert, so if i messed up please point it out to me so i can adjust it

that setup will net you a "thunder slug". you really should consider a larger displacement motor .

with a tunnel ram? something like 632" is in order.

i was right with ya years ago anthony i was wanting to put a tunnel ram on my .030 over 396 but i never got around to doing it(the cool factor was in mind not performance)

but to get 500 hp i dont see it hard to get it with oval port heads.......on all the big blocks that i have ran and built all had the oval port heads on them....

one combo i ran a few years back wasnt all that bad for street driving and i pulled down 11 mpg on the highway ...lol(4.56 gears)....

combo as follows

-396 bored .060 over
-trw 11 to 1 (375 hp replacement pistons) with a true compression ratio of 11.7 to 1
- closed chamber oval port heads that had a factory rating of 96.4 cc but was 101 cc when they was done cleaned up and unshrouded
-heads was ported with 2.19/1.88 valves
-single plane victor jr intake
-850 double pumper holley
-clevite cam 262/273@.050 with .561/.600 lift solid cam
-roller rockers from crane
-summit headers(79 bucks)
-4.56 gears
-th350 3500 tci convertor
this engine ran in a camaro that was 3600 lbs even with driver and ran 11.70's at 116 mph traction sucked but it pulled way hard to 7000 rpms it want more rpms but i didnt let it so it was bouncing of the 7000 grand chip at the end of the 1/4 mile i was running some real short tires (street radials) that just wouldnt hook very well.


one thing i have found out, of the 10 years of running bbc 396 motors they dont respond with "big tube headers" i have tried a set of 2" primary tubes off and on thru out the years but have never dropped e.t. with them......my worst case was when i was running low 12.20@110 and i change the headers and i was running 13.teens@102 with no other changes........the following weekend i put the old headers back on and i was right back to running 12.20's and got my mph back.......

i use to run a small block 305ci(8.2 to 1 comp.) with a tunnel ram and two 600 vs carbs with a 305 comp cam and 4.56 gears with 4500 stall in a station wagon 81 malibu and it was turning 13.60 at the track and i drove it on the street.......timming was locked out and the carbs was adjusted well...it was soggy down low but it was a fun ride i figured if i could get that thing to run ....i dont see why a tunnel ram would be any different on a 402....

i thought about putting a tunnel ram on my 396 becaused i missed the look of the 305ci but never did it.

IMO, I wouldn't be worrying if the combo made x amount of horsepower. Tell us how you'll drive the car. Is it your only ride or a weekend cruiser ? Is this the first motor you've put together ? Are you looking to run it on pump gas ? State how you plan on using the car and be realistic with your expectaions and you'll get a lot of good advice. IMHO if you really want a tunnel ram, be honest about your capabilities. Sometimes it seems a 4 barrel is tough to get properly tuned. 2x4's would be even harder. Not trying to rain on your parade, but not every good running BB makes 500hp and people still enjoy them. Remember this hobby is supposed to be fun.

not looking for X amount of horse power. The car will be a occasional driver, sometimes to work, definatly cruising on the weekends. Not planning on really racing the car. More or less the tunnel ram is more for the look. I love the look of them, plus i struck a good deal on one. I will not be building the motor, i have a very good engine builder that is doing the work. He told me to figure out what i want, and he would make suggestions from there. This being the reason why im on this websight looking for advice. What i am really looking for is good power, not neccesaraly 500 + horse but i want a rough idol, not really concerned with low end power for in town driving. The numbers i have posted came from Desktop dyno from the numbers ive punched in. ANY advice is truely appreciated. Seems like one guy likes them and the next doesnt. so there are my intentions. More advice would be great.

I responded in your other topic on the tunnel ram, so let me answer a bit of your question about DD. I plugged in way more specific data (actual cylinder head flow numbers etc) and it predicted in the low 700's hp for my 496. My actual dyno pulls topped out at 640. In no way do I feel bad about the disparity - I do feel that DD is best for seeing the general trend lines of change in power when comparing different parts, rather than the actual specific power that an engine will make. Chances are good that if you built an engine the same way DD makes assumptions, then the power would probably be close.

Will the distributor you are using have vacumn advance? One of the ways that I have found to give a street engine more idle lope is to use a ported vacumn source, rather than manifold vacumn.

Thomas

havent decided on distibutors, which would you suggest. and im not sure on the vaccume. Havent gotten that far. Like i said before any advice is appreciated and taken into consideration

i would say..........stick with small dia. headers....like the ones from summit for 79 bucks these headers have carried me well into the 11's and high 10's.....

if your heads are closed chambered heads stick with the 2.06/1.72 valves to help keep up air flow speed...plus they wont be shrouded as bad like the bigger valves.

at least run a good compression ratio somewhere around 10.5 would be just fine...plus it would help with the tunnel ram..

you want a rough idle....really anything over the 230 @ .050 gives a very nice lobey idle

i really think you would be happy with the idle my 396 has now its pretty lobey and i get comments almost everytime i go fill up.....

delta cams ground it for me for 49 bucks
233/239@.050 with .548/.551 lift with 111 lobe center this cam has great pulling power from 2500 to 6000 rpms (maybe even more once i pull the chip and put in a 6600)

im running a true 10.2 compression with this cam and i can run pump 87 gas with out ping.....

Anthony, I wasnt gonna respond, but now twice you mentioned that low end power was not too important to you. You also said twice that you would not race the car, (much) and that it is primarily for the street. Let me tell you, from someone who has been there, that you should be trying to get all you power at low to midrange RPMS, and forget about the tunnel ram. I had an engine that was built more for race than street, and I had it in front of a 4 speed at one time...it was a real disappointment on the street, I was very unhappy with it at low speeds, and I think you probably will be too. I would hate to see you put all that money and time into it, then not be satisfied with it..I personally would go with a good CR, but still within pump gas range...then stick with oval port heads and a more reasonable intake...dual plane, or even a Team G single plane, I think they look really great too...I had a friend who ran a tunnel ram and 2-4's on a small block, and he sold them at a swap meet...not happy either. But remember, every situation is different, you just might be OK with it. Im trying to give you a different perspective, and make you think a little. Hope this helps, and doesnt confuse you more :eek: . John