I am posting this in Performance as well as Engine.

With alot of your help, the sb to bb swap is complete. I took it out for a drive to see how it performs. It is mechanically good, great oil pressure, no bad noises.. etc.. But, I am not impressed with the perfomance. I am thinking i chose a bad cam. Taking off from idle is a real dog, the motors seems to want to die. Good power only starts happening at about 1500-2000 RPM. So the problem is getting it rolling. And also, it is kinda loud at the header/collector area. Maybe there are leaks there because all i used was some U-clamps to connect header-pipes? Would that cause loud 'cracking' noise on acceleration? Becasue when i let off the gas while cruising it becomes alot quieter.
Perhaps my carb/intake choice is not right for daily driver? I have an edelbrock torker intake, and holley 670 carb. The cam im running is the Crane 286 powermax (hyd).
It is a 402 BB with 9.5:1 CR, 4 speed, 3.08 rearend, and large rear tires.

Does anyone see any problems with my setup? What can i do to be satisfied? I wopuld really appreciate any comments/advice

Bubba

change the rear end gear to 3.73 ish and the intake to performer rpm would get my vote...
also, run 87 octane... heh! or raise the compression to like 10 ish

im running 10.3:1 compression with a cam that has 278ADV

torker intakes i just found out thru back to back intake swaps with track times. was kinda gutless down low (compared to a rpm). i picked up 2 tenths in e.t. going to a rpm intake and the bottom end for around town driving was crisper with no loss of top end power to 6500 rpm shift points.

timing needs to be dialed in .....give your combo around 18 degrees intial and 36 total. this will bring the bottom end alive. then add a 10 degree vacuum canister to the hei and put it on full port vacuum.

what are the cam specs?

raise the compression by installing steel shim gaskets this will get you around .5 increase in compression . thats if this isnt allready done.

you say the motor wants to die, sounds like carb problem. need some tunning. is this vacuum secondary carb or double pumper? get the timing squared away and move onto the carb. increase the fuel squiter to cover the bogs.


if this was my engine i would go buy a used 750 carb double pumper start the jets off at 73 front and 80 rear. no power valve in the rear.

sounds like you have exhaust leaks find them and fix them.

Do you have an M-21? That would explain a lot. I agree about the manifold. With 3.08s I would only use a dual plane of some flavor.

I have a saginaw 4 speed. Sounds like i have to get my timing tweeked. So, 16 BTDC? Also, I think a new intake is in line... RPM intake?Any dual plane intake?
Also, will exhaust leaks cause bad performance?

BUbba

performer rpm is a dual plane
i heard it is pretty much the old GM #163 intake, so either should work fine

do you think the big block and saginaw will ever be friends? :D

definately get the dual plane intake. My Gramps has a M-22 rock crusher he said will be mine soon.

if you are going to get a M-22, definately swap the rear gears around 3.73, or 3.9 that your cam and tranny wants...............

Originally posted by bubba68ss:
Also, will exhaust leaks cause bad performance?YES!!! Exhaust leaks will cause back fires and popping/crackling. Get that squared away and I can guarantee you will feel a difference right away!!! And even more of a difference once you straighten out your combo! graemlins/thumbsup.gif

Well, I hope someone mentioned early on that that cam is going to be dreadfully soft down low in a small, low compression motor. 270 duration would have felt much, much better. E.G., I use a 276 seat duration solid with 10.5:1 compression and 4.33s. The loud pedal does not dissapoint.
Fix the exhaust leaks. Give it PLENTY of timing 18 inital 38-42 total. Don't run premium fuel. You need a dual plane intake with such shallow gears and a manual tranny.

I also agree on the cam being to large, a smaller cam and even a regular performer intake would probably wake this engine up.

One question that nobody has asked is whether you have a vacuum advance distributor, and if you do . what vacuum source is it hooked up to ? It has been my experience in the last 30 years or so that the majority of street driven engines will run a heck of a lot better with a vacuum advance hooked up to straight manifold vacuum. There are probably some exceptions, but I have not seen them. You just cannot get enough advance at low & midrange rpm with a straight mechanical distibutor without having way too much total.
Just my opinion,

yeah, I agree by going to to straight manifold vacume it will bring his idle and part throttle timing up lots and still have a small initial setting for easy cranking and starting but attention must be paid to the mechanical curve to make sure it comes in at the right time and quick enough to add to and take over when the vacume advance falls off. There's definately a lot of power left on the table if the timing curve is wrong. Maybe some tuning will make it livable. I wonder what the cranking compression is on this combo.

I appreciate all the advice. The cam and intake seem to be the problem. I will fix the exhaust leaks tomorrow.

After spending two weeks on this swap, and then to be disapointed, really ruined my day. But i knew where to come to get cheered up.

So, for the third time, I will buy another cam and hopefully it wont be "too big" also! What is a good cam to get? This is a daily driver and am not trying to set track records. Id just like to get into the throttle on the country roads around here and have a little fun sometimes. Nothing extreme. This is where i really need your guys' help. I will pick up a dual plane intake to help the lowend performance.

I agree you've got a big cam for 9.5:1. But before you get tunnel vision and convince yourself you need a swap, cover all the basics.

"75% of carburetor problems are ignition." Or something like that... Do you have an underhood tach (or a friend) and a timing light? With GM distributors, you can adjust the timing at idle, total timing with full advance, and also the rate at which the advance comes in. You can also get vacuum canisters that give different amounts of advance; and there are adjustable ones (rate and amount) available too -- surprisingly affordable.

Disconnect and plug the vacuum advance. Now check your timing at idle, 1500, 2000, 2500, 3000, 3500, and 4000 rpm. This will show you what the mechanical advance curve looks like. (This is also what the motor sees at WOT, when vacuum is low.) Reconnect the vacuum advance, and repeat the timing checks. (This simulates what the motor sees at cruise.) Post the results for TC members to look at. I'll defer to the others on what a big block timing curve should look like, but it has to be right or the motor will be fighting itself.

Is the carb new out of the box? Or was it tuned to your small block? Either way, it sounds like it needs to be optimized. Wants to die when you get on it heavy from idle? I'm not familiar with Holleys, but if it were an Edelbrock, I would recommend adjusting the amount of accelerator pump squirt. Try that, if you have the option. How is it jetted now?

And I agree -- fix those exhaust leaks.

And have fun with the "test 'n tune". You are having fun, right?

Cheers,
mark.

Most cam companies list suggested power ranges for the cams, your 402 will spin higher with a smaller cam than a 427 or 454 built with equal parts. Something in the 265-270 ish advertised duration range would probably be what your looking for. Comp's extreme energy 4X4 line may be good for your combo as well with a little wider lobe seperation and good lift values they are responsive at lower rpms but still spin up high real nice. What heads are on this engine? Small chamber oval ports?

Its fun in a crazy stressful way, and i am learning alot. Also, its an HEI system. I dont know whats going on with the timing curve. I almost need someone to tune it up for me. Also, the carb worked great for the ole' 283 but im sure its not near dialed in for the 402.

Yeah Baddbobb, they are closed chamber oval ports. The '70 402 is bored 40 over. Stock pistons with the (3/16" domes??). Perhaps i need to get an accurate compression ratio for my engine. How can i figure that out without totally dismanteling. oes it have to be completely accurate?

Bubba,

The advertised seat durations on the Crane are a little longer than other manufacturers. That cam only has 226 @ .050 intake. I run the same cam in my 408 with a dualplane, auto trans, but w/ 3.73 gears and 3000 converter. Even so, I need drag radials to keep from frying the tires. You have plenty of compression and plenty of motor. What you need is either a more suitable rear end gear or soemthing like a wide ratio T-10 with the deeper 1st & 2nd gears if you want to keep the 3.08's and "large" tires. If you are trying to start your car out at an idle with the gears and final drive ratio that the car has, you probably will be disappointed. Other things need to be checked. Make sure you are running plenty of initial advance - I run 20 initial with my HEI and full manifold vacuum for the vacuum advance. The other issue is the Torker, any single plane - low or high rise will be a slug below 1500. The carb just doesn't see enough flow from a single plane to work correctly at low RPM's. I run a Performer on mine, although I could get away with an RPM, I wouldn't even consider it on your setup. A divided plenum dual plane will help the low end considerably. Do some tuning and easier mods before getting too disgruntled.

I went back and read your other posts. When you first talked about this, you indicated you had a 3.55 12 bolt to install. Even without it, it still shouldn't be as bas as you are describing. What size tires are you running?

Joe hit the nail on the head..
If anything,change the intake and go for a gear swap.
For now,dial in your timing and run a shorter tire,like a 235/60

Ya, don't swap out that cam yet. I don't prefer long seat duration cams, having run both long and short. Long seat still means lack of low end cylinder pressure. Therefore, regardless of the short 226@.050, the motor is seeing much more duration in the sub 2500 rpm range.

Which is why long seat cams only work decently in low compression motors with plenty of gear. The gear helps the engine get up in R's, and the cam starts to look smaller. Torque is produced. Otherwise, compression makes it torque down low.

Anyway, that cam will want to make its best power in that motor from 3500-6000. Let it get there. IT will not make low speed torque.

As Joe indicated, steeper tranny gears are HIGHLY recommended. Especially for a stick car, especially for a smallish cammed motor.

I'd do:

1.) timing/ timing curve setting. Give it lots of advance and see how it responds.

2.) get a dual plane intake on there. And then get into the carb.

3.) Gear it somehow, PREFERABLY in the tranny especially if its drvien on the highway for any time.

Let me just say this, I have never ran a UD or the new Lunati UD cams so I can't comment on them. I have pretty much stuck to Crane and had good luck with longevity. Crane rates their cams at a slightly lower lobe lift [ .004 I think ], so advertised seat timing is a little longer, but I can honestly say, I have never wiped a lobe on a Crane. IMO, the result of a slightly less agressive ramp. I tend to stay a little more conservative though, that is just my nature. I know guys run the real aggressive cams on the street, but from personal experience, the more agressive you get, you better have paid attention to all the details in detail.

Originally posted by bubba68ss:
After spending two weeks on this swap, and then to be disapointed, really ruined my day. But i knew where to come to get cheered up.
Hey, man, don't worry about the soft performance right after the rebuild. It takes most of us quite a while to get our combos sorted out. I'm sure just a few little things here and there will make a big difference for you.

For instance, you mentioned your exhaust was just kind of rigged up for the time being. I have one thought to offer on that, because you also mentioned the engine is really soft down low.
You always hear people talk about putting in crossover pipes on their duals. Some do, some don't. One time, out of curiosity, I had a shop install some duals on my Nova without the crossover. I drove it down the street and it had a really soft response to the pedal. I took it back (immediately!) and had them put in a crossover pipe. I immediately gained the low end crispness that is so nice to have in a daily driven street car.
I would think that your exhaust, added to your single plane intake is probably causing some of that softness in the low end. I'd get the exhaust sorted out and get yourself a good dual plane intake and I think you'll be much happier for starters. The other tune up stuff will take a little longer, but you'll get there.

We all have to go through this stuff. Just keep your cool and approach things one at a time. Oh, and having quieter exhaust will also help you diagnose other engine issues better. graemlins/thumbsup.gif

My 396 responded extremely well to a 2 1/2" X-pipe system - like night and day. With 3.08's and 26" tires I have no traction in first gear. I went through this exact disappointment, but it gets better.

Joe, trust me I was worried about switching from the gentle Crane 304-2 to the UD "race" cam. I also like Crane products. I almost went with their F256 profile as an L88 substitute.

The engine had 30,000+ miles on that F304-2 when it was redone. Cam was mint btw. 7000 everytime it was taken out for a spin.

Well hopefully Bubba can get his car sorted out.

Hey Bubba, if I was closer, I'd be glad to help you sort this out! Hang in there, before you know it you'll have that baby purring like baby Tiger.

Mine's already half apart till next spring. Green's going to get a new paint job (only, I am not sure it's going to stay green ) and a different motor while apart.

Having one of these cars is just about as exciting as having a wife/girlfriend that is into dyeing their hair. You can literally drive a new version every year without ever really having to go through the agg of trying out the headlights or poking the quarter panels!

If I read correctly you have a stock HEI. You must do something with the advance curve it is extremely slow. That one change should help your low speed a bunch.

Well i located a performer dual plane intake, and today i am going to fix up the exhaust leaks. Ill also plug vaccum advance into intake vaccuum to see what happens.
Keep the advice coming. I cant wait to straighten this out, I know i will be happy with it soon

Yes, tune her up good...

What about a set of Rhoades(Sp?) lifters???

And next, a dual plane..

And I'd leave the 3.08's alone for now b/c of fuel costs..

pdq67

He could do the Rhoads lifters deal while it is apart, but I use the same cam and pull around 12 - 13" vacuum. I have a boatload of off idle power with the automatic. Half/most of the low end power problem is the single plane intake. By his own notes, he states the motor is gutless below 1500, which is just what E-brock says about the single planes themselves.

now i'm just going to have to open my mouth on the "cam to big" for this motor.

frankly you guys its not. i looked up in my crane cam book just to verify my memory. but that cam only has 226/236 @ .050 (i assumed this was the split duration cam ) even with a 9.5 to 1 motor you are just fine.

the deal with this combo is its just not tuned yet at all.

before you go riping thru the engine at least get this thing dialed in.

i posted early to get the timing dialed in. the 396 really response to the timing and it will make it feel so much stronger.

get your 18 degrees initial and 36 total set all in around 2500 rpms and put a 10 degree vacuum can on the hei and plug it into full vacuum port. once you do this the engine will talk to ya.

at the track this timming set up gives you room to fine tune it if you need alittle more total.

as posted before run 87 octane fuel.

going with an eddy dual plan rpm intake would really make the bottom end even responsive.

there is plenty in the carb as well.

your engine now is just roughed in. need to take the time to dial it in now. at most you should just change the intake cause that is a given.


try the simple things first im sure you wont regret it.

I would have chose a different cam for this engine but yes I bet it will be livable at lower rpms when the intake is swapped and the tune is dialed in. Keep us posted with the changes and results.

Thanks to all oncce again. I will keep posted. Im going to ebay to see if there any; good dual planes up for bid.

Earlier today i got the timing light out and set it to 16. It responds so much nicer already. Im working on the exhaust leaks tomorrow (putting x-pipe on). Then the right intake goes on, and 3.55's to top it off. I think by then i should be good.

You mentioned about full vacuum port and vac. canister? Can you tell me where to get the canister and where to hook up that vac line?
Bubba

Should i run 87 octane because i have lo CR motor? is that the reasoning? Just curious.

bubba

Bubba,

All this talk about the cam timing is inaccurate. If this exact same cam profile was marketed by Isky, it would only have an advertised seat duration of about 278 - 280 beacuase of the way they rate them. In a Comp, the comparable rating would be about 282 because they typically rate the cams at .006 lift as opposed to Crane at .004. So don't'get too hung up on the seat timing. Heck, if GM made this, the cam would be listed as 320 degrees or more.

If you haven't done so, run a search on setting timing. You want to set your motor for total timing. Most HEI units only have around 18* mechanical advance built in. I run 20 initial with my 9.5/1 408 motor and 38 total with the same cam. I usually run 92 octane. With the price of fuel today, it is only about .20 more per gallon.

You'll want to mark your balancer for total timing that you want (do a search on how to do it). Set it for total timing desired, will need to be set at about 2500 RPM. Then check your initial timing. THe closed chamber heads like ignition advance. If/when you go do a manifold swap you could get the HEI recurved by a local shop for not that much and really know what you have.

Hang in there, once you get it dialed in, you will be impressed.

Would this intake be a good choice? intake (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7927736092&category=36474) (it'll clean up!, but its affordable for me!) Will the holley carb fit with it? Ive never been sure with that kind of opening on the intake (looks like rochester carb??)

Bubba

Bubba,the BBC Performer is a great intake..I ran on my 454 and there isn't much noticeable difference in timeslips between an RPM intake.
The Performer is a dual flange bolt pattern,so you can run a qjet or a squarebore Holley.

Bubba,

Portland swap meet at the expo center this weekend. Probably can find an intake there for a deal. Also email David Shultze (Oregon Club member) at : rspanther@qcsn.com . He will be there and can probably help you out some. He lives in Troutdale and is a good friend of mine.

Oct 16-17, NW Collector Show/Swap, Portland Expo, Portland, OR

I'd go, but I am in the middle of a move graemlins/clonk.gif graemlins/angry.gif

I found the X pipe on my ride picked up the bottom end which was quite soft. That'll help too.

That's the same intake I run on my 408 motor. All you need is the Holley carb plate for use on this intake. Costs about $15.00 or so. Includes a flat steel plate and 2 gaskets. Sandwich the plate between the gaskets and install the Holley on top it, bolt down as normal. The plate provides an increased are for carb base sealing.

I had ported my intake a little to match the heads that I have which were also ported a little, but it probably is not worth the effort.

That intake or one similiar will make a huge difference in your off idle performance. Any of the intakes rated from idle to 5500 are perfect for your application.

Taking off from idle is a real dog, the motors seems to want to die.

This right there tells me the combo is not the problem, something is wrong. You need to have your basics checked b4 you can proceed. I'd bet money on not enough timing/advance hooked-up to ported. Maybe accelerator pump not shooting enough or too much.

That thing should fry the tires even if its not running 100%.

What do you mean not hooked up to ported? I just installed a edelbrock performer RPM intake and the bottom end has much more power. Now Ill move on to timing, 16 initial and 36 at 3000 RPM?

bubba

At least 16/36. You will have to make sure how much timing you really have. I run 18/36 and have ran it as high as 20/38 (my HEI only has 18 mechanical advance). On the vac advance, they are telling you to run it on full manifold vacuum.

Ill try hooking up to manifold vacuum. Its just hooked up to the carb right now (wonder how much that actually advances).
Getting alignment tomorrow (front end dropped about an inch with the big block), getting X-pipe installed, and mess with the timing. Its running pretty good right now, but amn still a little nervous to get into the throttle alot because it only has about 50 miles on it. The roads were wet today and I was having a little fun around corners, but nothing to heavy. I definately gotta put those 3.55's in (what can I expect going from 3.08's to 3.55's?)

Bubba

I'd say, expect a much better throttle response and take off.....but nothing "neck breaking" tongue.gif

Please let us know the before and after once you get your exhaust up. I love this part!!! tongue.gif :D

I have a 70 402 big block with a comp cam 268xe, a 750 q-jet and 10.5 comp engine, It runs real strong out of the hole and hits 2nd pretty hard with a turbo 400 tranny. 3.31 gears, runs real nice for street, and pretty fast too. I believe the cam is the problem also, thats what they told me down at the engine shop

With 50 miles on it, keep it easy for a bit imho. Yes, I'm wondering if you get the same low speed pickup I felt with a new X pipe....