Sorry for the poor photo angles. I do not have a degree dial but may get one. Car has run fine since I assembled it 6 years ago but just seems like I am missing power and haven't been able to track down the issue..

The engine is a 30 over 355 with flat top 4 relief pistons and older dart iron eagle 180 heads and sidepipes with vettpacks.. it has an ram intake and holley 670 carb. cam is a voodoo 262 flat tapped cam with 1.6 roller rockers. Acoocording to dyno 2000 it should be making 404hp and well over 400lbs of torque which means realistically more like 350-375 hp from what I've read. I do have an hei distributor and have installed performance weights and springs and have played with different size springs.
After reading a thread on this in another hot rodding forum I had to take another look at the timing /cam while doing some tidying up in the engine bay.. I am also considering a fst 650 rt plus carb to replace the working but rough looking street avenger 670 It took a while to get tuned . I have not yet done a compression check. Almost forgot, block is not decked but has steel shim head gaskets. And 64cc chambers. -12cc pistons which I believe put me around 9.8: if I remember right.

 

No, you are not off a tooth. If you have removed the distributor, make sure you rotate the crank a full turn to put both dots pointing straight up to put the #1 cylinder on the compression stroke for distributor installation...

Lars

 

There is less than 6000 miles on this engine since I built it. any advice would be helpful. It was my first engine build with very sbc knowledge prior to my research in the 2 years it took to price together the engine.

 

1. compression test
2. verify ignition timing
be warned the cheaper timing lights have directional pickups. Which means you can get the wrong timing value when the clamp is backwards. So I always recommend using two timing lights, and reverse the pickups, to help figure out which is the correct timing value on the crank.

Speaking of 2's
3. Use a different compression tester (always use 2x compression testers) because one is always bad. also never RENT a compression tester, its prob bad.

Engine only needs 3 things. Compression, spark, fuel. With comp and spark out of the way, you just need to make sure the a/f ratio is 12:1 range for naturally aspirated engines.
Put the car on a dynometer or install a wideband and tune the carb to yield 12.0 to 12.2:1 air fuel ratios (low 12's) with enough timing for the head era (LS is 22-25* range, Older SBC is more like 30-36 ranges) depends on compression ratio

 

pic of plugs just loaded. Couple things with plugs,
1. they should all be oil free. I see some oily residue on the threads, that is fine, as long as it doesn't get into the chamber or on the business end of the plug. Check the cylinders for oil (if you can look inside somehow I guess).
2. They should all look about the same. Any one plug or one side that shows a difference in color is showing you an issue, fuel distribution or something like that.
3. The color is a bit white for a carb. Modern EFI can show white plugs because they can run hot and lean (especially the way I tune mine) but a carb'd engine usually shows a tan plug because it isn't as fuel efficient as a modern EFI system. This leads back to my above post #4 use a wideband sensor to tune the engine to 12:1 a/f ratio at Wide Open Throttle.
for part throttle and cruise the a/f should be near 14.5 to 14.8:1 or even 15:1 is fine. Just no lower than say 14.4:1 for idle/cruise.

 

No problem with those plugs. It is nearly impossible to "read" plugs being used with 10% ethanol pump gas. If you have a concern with overall engine health, do cylinder leakdown testing - compression tests are useless except to identify gross problems.

If your only issue is a perceived lack of power, I would look to ignition timing. What kind of numbers are you set up with on timing? Air/fuel ratios can be off significantly, with only small impacts on power. The SA 670 carb runs extremely lean out of the box, so some slight gains can be made by setting it up correctly, if you haven't already done so.

I would be shocked if a 262 flat tappet cam got you 400 horsepower out of a 350... that might be expecting a little much.

Lars

 

Thanks Lars I was really hoping it was off to be honest. Still don't know why I seem to be missing the power I would expect. I did remove the intake to double check the ports lining up and make sure I had the right gasket (which I didnt) turns out I needed the smaller 1204 size and I used a 1205 when I assembled for some reason. I also purchased a cam button kit ill be installing. I also had a small antifreeze leak from one of the water pump bolts and I slight oil leak I'm going to correct..

 

There is no reason to install a cam button kit on a flat tappet cam with a double row roller chain... The lobe angle makes the lifters put a rearward force on the cam when the engine is running - there is no force that would cause the cam to move forward against a thrust button. Cam buttons are used with roller cams, which have the lobes ground flat for full roller contact to the lobe. Without the rearward force like a flat tappet cam, a roller cam can "rattle around" forward and aft, with only the tightness of the timing chain restraining its forward movement. This is not the case on a flat tappet cam.

 

Cam buttons are only used with roller cams. Flat tappet cams do not try to walk forward.

If something has changed recently, it might not be the carb setup. Probably lean but not what caused the recent loss in power.

Checking the timing curve is good advice. If you have the right tools, you can set the timing at the top of the curve and see if the initial changes. If the centrifugal advance mechanisim is binding, your initial will end up higher. That would tell you if you need to work on freeing up the mechanisim.

Edit: sorry, Lars types faster than me.

 

Got it.. guess ill skip the cam button.. For some reason when I put everything into the dyno software the voodoo 262/268 cam performed better than the next larger voodoo cam with the head flow numbers and engine components I inputted. Again I do believe 400hp is high and very optimistic but I wanted the best cam for my stock 2000rp. Stall and 3.08 gears. Strangely I remember the jets in this (used when I bought it) 670 SA carb being too fat requiring me to go smaller but I think I needed more from the power valve if I remember right. I Do have whats needed to do a leakdown test as well and I'll give that a shot. I have played with the timing quite a bit.. had it at 36 all in by 3000rpm with vacuum disconnected. Ive varied that a bit as well because I wasnt trusting my tdc mark on my balancer but I varified its was correct today.

 

I actually believe I read that before and it makes total sense to me which is likely why I didn't have one and why I saw no contact with the timing chain cover. I was unaware they were only for roller cams though.

 

Oh yeah forgot to mention I run ethonal free gas whenever possible which is about 95% of the time.. I had an issue with a new edelbrock aluminum carb reacting with the ethonal and being full of a clear jelly like substance after sitting in my garage over the winter.. it was not fun to clean up So I avoid it whenever possible due to that as well as other factors.

 

On the cam, keep in mind that the 262/268 (advertised) duration cam runs around 218/224 at .050". The stock L46 and L82 cams were 222 at .050". Chances are good that your cam is going to run about as well as the stock Chevy cam. Your only advantage is that your heads are much better than the stock Vette heads, so you'll pick up a slight advantage there, but you're probably not over 350hp net (the L46 was 350 gross with a similar cam).

Your timing looks good. Have you had a wideband on the exhaust to see what A/F numbers you're running? I've never seen an SA carb run rich out of the box - they are grossly lean to meet California C.A.R.B. certification requirements. Here at over 5,000 ft elevation, I richen them up significantly to get them to run right.

Lars

 

Do you suggest I swap to a larger cam? Originally I had the 268 in mind. It I were to go to a roller cam besides the retro style lifters is there anything else I need to address? I thought I remember something about the fuel pump rod and distributor gear possibly being a concern?
As far as the carb... It was purchased used on ebay and looks to have had things swapped in the past. I had to swap the rear metering block since the original was crumbling.. I am looking hard at the FST rt plus 650cfm carb as it seems to be a decent value for the money and a step up from the SA design
Keep in mind this is a street car that rarely sees even 5000rpm. My original engine was an l48 and I pulled it right after I got the car as it appeared to have some flat lobes on the cam. I noticed a few rockers were super loose. it was rough (as was the whole car for $2700) The block I swapped in is a 4 bolt block from a 76 c10 pickup that was freshly machined. I did install the pistons and crank and now im wishing I went with a scat 383 crank instead of the 350 version. I believe I was concerned about the compression being too high for pump gas at the time. I am looking at purchasing a wideband but as of yet the only tuning Ive done was based on my plugs which were loading up before and gas smell its very possible im too lean now but Ive experienced no popping. I believe I have the lightest spring in the vacuum can and I have the orange cam in the power valve arm

 

With my most recent experience, if you are noticing you are down on power from where it normally is, then I would take off your valve covers and check your lash. If its hydraulic or mechanical and you have extra lash you may be rounding your lobes. Have you been using a high zddp oil?
I lost a wheel on a roller lifter which is abrupt and a lot more lash but the idea is the same.....a gradual wear will speed up and then you notice it

 

Im not down from what I normally have but rather I have always felt the engine has not put out what it should. granted I dont have a lot to compare it too. My uncles 76 for example has a 355 with an unknown cam in it but GM heads with headers and a holley 750 carb/rpm combo and the far seems to just have much more getup and go... granted its a 4 speed.

The issue I remembered when building the engine was I could not get the dots to really line up when I installed the timing chain. It seemed the cam sprocket dot either was slightly to the left or right in relation to the crank dot. Tts hard to see from this photo but the crank is ever so slightly retarded from TDC in the photo which gives the illusion they are lines up better.
And yes I used all the correct break in lubes and procedures and use zddp additive.

 

The dots mark the gear teeth that need to be pointed together - it's not the dots themselves that are the indicator. Obviously, the marked teeth on your assembly can be aligned to point straight at each other - your cam is not off a tooth.

As noted in my previous post, the cam is installed on the #1 cylinder compression stroke (firing position) when both dots are straight up (12:00 position; not 12:00 and 6:00). I install my cams with the dots straight up so I don't screw up my distributor installation. In the firing position, the cam and crank dots look like this:


As you can see, with the cam dot pointing straight up, there is a cam gear tooth at the 6:00 position that ends up being aligned directly to a crank gear tooth (with the dot). If you rotate the assembly to align the next cam gear tooth to the crank tooth ("one tooth off"), the top gear dot will be visually WAY out of whack. You are correctly assembled - no doubt about it.

What rear end gears do you have with that automatic? 3.08 or 3.23..?

Lars

 

3.08

 

Hate to tell you this, but a 350 (with a 3.48 stroke and less than 400 ft/lbs of resulting torque), hooked up to a 3.08 rear through an automatic will never feel snappy no matter what cam you put in it. I'm betting you're putting out exactly what you can expect from the engine (probably in the 350hp net/380 ft/lbs torque range), but you are handicapped with the rest of the driveline not being well matched to take advantage of that power in the range that you are wanting. A change from 3.08 to 3.73 rear end gears would gain you roughly 20% more torque at the rear wheels, which is what it sounds like you are wanting... This would allow that engine to give you the "feel" I think you're looking for. But it's not cheap doing rear end gear swap if you need to hire someone to do it.
Lars

 

Im also looking for opinions one whether I should consider this 750 carb or the 650 below it? I do not see jetting numbers but I did find a thread stating the 750 comes with the jetting normally found on 650 carbs which suggests they are also jetted lean. My guess is though due to the rpms I normally see is that the 650 will work best?

or