BBC builders
 

I am looking for educated advice from BBC builders. This is on a 427 BBC. I rebuilt this engine earlier this year with the hopes of making big gaines in ET and have seen no improvement. The only things that were changed in the rebuild was the bore increased .010 to 4.320 and new CP 47cc domed pistons installed. The engine was 9.3-1 prior to the rebuild and is now 12.2-1. That is almost a 3 point increase in compression with no change in ET. Is my combination way off or could it be that my domes are severely limiting flame travel?

454 block bored to 4.320
3.76 stroke
6.135 H beam floating pins
CP custom 427 47cc pistons
assembly balanced
Solid roller cam, lifters and rockers, stud girdle
677/712 lift
252/262 duration @ 50
108 lobe center
102 installed centerline
stock Merlin Iron 320cc runner, 119 chamber rectangle heads with 2.3/1.88 valves
stock Team G 2" plenum intake
Pro-Systems 1000HP carb
Hooker 2" OD 1 7/8 ID headers w/ 18 extensions

Thanks in advance.

Was there any difference in the weight of the pistons? you should have gained some low end power with the higher compression... good luck..

hey travis, i like your specs on your motor, since you moved up
on your compression i think your cam will work well, the only thing
i can think of is the strok or the breathing, your cc went from 119 to
36 after the 47cc domes, you might benefit better with 350 runners
with that size of valves 2.3, thats big, and i have seen better results
with the vic jr intake for better breathing, and with that comp. are
you running a vacum pump? and i guess all your running now is
racing fuel, also you did not mention ignition or what distrib you
are using, good luck bud :wink:

good advice from signs on the intake,

X2 on ditching Team G, it's definelty holding you back.

I run a dart single plane on my BBC 496 with good results but a Vic jr is a good choice too.

Did you change the jetting on the carb?

More compression should warrant more fuel, I'd go up at least 2 jet sizes for starters.
What is your total timing?
Mine likes 40 with 110/112 leaded race gas any lower than that and it's a pig.
Your heads sound plenty big, your cam could be holding you back some too.
Another thing is your convertor could be too loose fro your new combo, just food for thought.

Goodluck, Cp

x 3 on ditching team G,

x 2 on heads plenty big,

what fuel are you using, before and now...

need lots more info on car, trans, convertor, gears, tire, weight, et, mph.. :?:

additional information
 

Additional specs. The car is a 69 Camaro weighing in at 2950 wet.

msd pro billet distributor
38 degrees locked out timing
digital 6 plus ignition
running vp 110 same that I was running when it was a 9-1 motor
4 link backhalved with 29.5 x10.5 tires no problems launching
powerglide w/brake
8" 4500 converter
9" with 4.56 gear
shifting at 6700
trapping at 7000

ET 10.10 at 133 with the 800 holley I had on it before I installed the pro systems carb, I did play with jetting and timing for the past 4 months trying to improve my times before the carb swap. The carb change has gained 2/10's but I was expecting to see this motor run 9.80's after the engine build. I suspect the problem is somewhere in my engine combo but I am not sure what to change at this point.

I did install an evac kit running to the headers to help with the pressure in the engine as well.

how does the car 60'? before and after the carb change?

the carb change helped 2 tenths, what about mph?

what altitude you running at? DA?

what gearset in the powerglide? 1.76?

Back to the carb swap, you say you played with the 800 then swapped to the 1000cfm when you rebuilt the motor, have you done any tuning on this carb since the rebuild?

If not I'd jet it up till the mph slows and give the motor some more timing, 40 to 41 TT.
JMO>Cp

My thoughts and past experience comparing your combo to what I put together back in the mid 80's. You have a Good combo of engine parts. I Personally do not think the Big dome or intake is hurting you at all. What I do know is you got to gear a 427 like a small block. Especially when using a PG. I also think you need more stall/flash from your converter. Something around 5700 to 6200 stall/flash. I would have a minimum of a 5:14 rear gear. I my self would have a 5:38 or a 5:57 in the rear. Then make the 4 link work for your cars 60 footer. I would be shifting that Bad Dude more closer to 7600 to 7800 r.p.m.s. I think your car is capable of mid to low 9's with a gear & converter change. Another thought, when is the last time you had your converter checked ??

The combo I put together back in the mid 80's had a old Edelbrock V Jr. The one that had the twisted/angled carb & a modified 850 on it. A Crower solid lifter cam (not a roller), 188 iron ported heads w/ 2.250 intake valves, 13.1 compression, 6.135 7/16's rods, GM 427 crank. A Good Basic 427 build. The car is a SG style ladder bar a-arm car, weight was 2500 l.b.s. race ready. This chassis by no means was up to par. The first night out with the car, it ran 10:00's @ 137 m.p.h. I couldn't run any faster because I did not have the SG licenses. Later in the year with another guy driving the car, it ran some 9:80's with no other changes. The next year we maid a head & cam change. The car picked up a bunch ever where. The e.t was down in the low 9:00's and m.p.h went up to 143. The guy that owned the car was a Bull head. The chassis & springs were set up for a Military truck. I felt with the correct changes, that car was capable of running 8:50's easy.

One last thing, the 427's do not get the respect it deserves. People refuse to believe they just got beat by a small engine. :oops:


Ron 92Camaro

Maxpower and cp, everything listed has been after the rebuild. The car was running 1.45-1.47 60 ft times with the old carb. I went up/down/sideways on the jetting trying to get it to improve and that was the best it would do. I changed fuel pressure and float level and played with timing from 34 to 41. The old motor liked 41 but the new motor likes 38. I have only made 5 passes with the new carb and jetting was set to 84/92 by Patrick at PS. It ran a tenth faster at same mph than the 800 with that. The a/f gauges were reading rich so I went to 82/90 last time after consulting with Patrick and it picked up another tenth and 2 mph. It is still just a little rich so next time out it will have 80/90 jets. I have not played with timing since the new carb but that is on my list next. The glide is 1.76 as far as I know. It was in the car when I bought it last year.

Ron, I know that 427's are supposed to like high rpm but with the old motor it ran the fastest shifting at 6700. Which is about what the chassis dyno showed because it was dropping off quickly after 6700. By 7000 it showed a loss of 50hp. The torque curve from 4900 to 6200 was with 10 ft lbs. Now I don't know how much changed on the torque curve from the old motor and the new since the cam is the same and the car runs the same times that it ran previously. I am sure there is a couple more tenths in the car with tuning with the new carb but what doesn't make since to me is that everything being equal before the carb change. Why didn't the 3 pts of compression seem to make any difference in my et's. The car hooks good and doesn't blow off the tires. It lifts the left wheel about a foot and the right wheel about 6 inches on launch.

Thanks for all the information guys. I know there is something wrong with the combo somewhere I am just trying to narrow it down before I spend another 5 grand swapping out parts if you know what I mean.

I'm thinking that a change of the manifold, as mentioned in 2 above post, maybe a 454R and put a 1" spacer under the carb. That should give it a little more wind. Not many people i know runs the team G except on the street.

JMO

Zip.

good advice and info everyone 8)

doesn't the data and the dyno show the mismatch between heads and camshaft and gearing... :?:

whenever the heads are too big or the cam too small and the RPM to operate in proper range is not present, most likely you will be dissappointed :cry: ... some things you can bandaid, but when talking cylinder heads and camshaft, gearing, not really possible.. .02cents

I agree with Ronmiller, I think you need more converter more than anything, but it will probably like a bigger cam to go with it......especially in the duration. I like everything else on the cam where it is. With a BBC with square ports and small inches it really needs a minimum of 5500 stall. The victor jr is what I prefer to. If you do put in a bigger stall speed converter a dominator will probably add a tenth or two as well.

I will try a new billet roller cam and possibly a new intake over the winter shutdown. Who should I talk to to get the best cam profile for my combo. I just checked the converter since I hadn't done that since the rebuild. Before the rebuild last year it was hitting 4500 stall and now it is only hitting 3900. I have made probably 50 passes since I checked the stall previsously. Now I have 2 questions. One, did the stall of the converter change because of the added compression of the engine or is it just from use. Secondly, even though I didn't change the cam would the added compression move the torque and horsepower curve of the motor and if so, would it move the curve up or down?

update on combo
 

So far the best run on the car was 9.87 at 136 in cold air. But consistanly running 10.0's in 70-80 degree air. I decided to replace the cam and I emailed several cam builders with my combo and based on several recommendations ended up going with a Lunati grind with 110 Lobe seperation, 272/280 duration and .722/.722 lift. Installed cam at 107. Ran it for first time today and at 35 degrees ignition advance it was breaking up badly above 6000. Removed 3 degrees and it improved. Removed another 2 degrees for a total of 30 degrees to clear it up. The best run was 10.11. Checked the torque converter and verified it is stalling at 4000 and I will be replacing it after tuning in the new cam and putting it on the dyno to get its new torque curve to build the new converter. I am a little confused as to why 20 degrees more duration would require 8 degrees less advance. Anyone have any thoughts on what might be the issue?

427
 

I ran a 427 .03 over 12.5 comp canfield 310 heads cam 671/690 248/254 dur 106.5 cl victor 454r 4500 intake i had a 850 on it and went to a 1050 it picked up 3 tenths car weighed 2600lbs with a 4.56 gear 32 tall tire it ran 9.70s went to a 4.88 it went 9.50s it really liked the steeper gears this was also with a turbo 350 and 5000 stall. Just thought this might help.

Re: update on combo
 

I know your starting to dig a money pit here changing parts in all, but I'm gonna say your combo definetly warrants a 1050 dominator, converter change ( 8 incher, 5000 min, preferably 5500 stall) plus a intake change AND to further compliment the combo, more gearing(513)

Clueless as to why you'd need less timing with that cam though.
That dont make any sense to me? 30 TT :shock: I've never seen a BBC run with that low a timing, not worth a shiznit anyway.
Our combos are very similar, save for the smaller CI and the carb.

I run the same cam in my 496, (excellent choice by the way), I run TT @ 40 to 41, never misses a beat.
What plugs are you running? And what gap? I have merlin vr 345cc heads on my motor and use the NGK's racing plug in the #8 heat range gapped @ .032
I can get the offical part # if you like, just let me know.
Cp

Are you sure you are only running 30 deg of total adv? Did you locate TDC with a degree wheel? Is this a stock balancer that could have slipped? Hard to understand why it would want 30 deg of timing.

I am hoping the issue is a lean condition since I didn't change the jetting after swapping the cam. I have jetted the car up several jet sizes and moved the timing back to 36 and will see how she does this weekend at the track. The balancer is accurate and I did verify TDC when installing and degreeing cam. The spark plugs are autolite ar133's. Same plugs and gap as before. After I get this thing running properly with the new cam, then I will get a new converter that is built for the combo from FTI. I need to find out at what rpm the engine falls off before I decide on a gear change. I will let you guys know if the added fuel fixes the issue.

Racing this weekend huh?

Where do you live Florida?> :shock: :lol: :lol:

That's right, Gainesville, FL. Home of the Gators and the Gator Nationals. It is great when the track only closes for one month out of the year. Of course, the downside to that is the fact that you have to rush to do your rebuilds or updates so your not sitting around while other people are having fun.

We are supposed to get 8" of snow tomorrow...


P.S.
I hope you get a sunburn.

I am guessing the guy at the track last weekend running his snowmobile didn't hear about your snow. I guess he is just another snowbird trapped in Florida. If I see him this weekend, I will let him know. Better yet, I will borrow it and come visit. He was running 10.20's at 128 on that sled.

:shock: :shock: :shock: Now that's scary fast for a snowmobile!

The added fuel did not help and may have made it worse. I did verify it is not losing fuel pressure. It did cut the best 60 foot ever though of 1.397 but fell on its face at 100 feet. It feels like it is losing several cylinders. The last run I couldn't even get it to rev up to stahl on the brake at 4000 rpm before it started breaking up. I guess my next move is to change the plugs. I currently have ar133 plugs. I have to run the shortest plug possible because of a header clearance issue. What plugs do you guys use? The car does seem like it has an erratic idle since replacing the cam. I just figured that it was the added duration but now I am not so sure. I guess if the plugs don't fix the issue, I will have to test the msd and coil and see if there is a problem there.

I had bad luck with autolites....they are a great replacement for the street but performance wise...not so much....get some NGK's or AC's in might help you with the break up thing...as far as falling on its face @ 100feet...that sounds like a fuel restriction someplace....what is your fuel pressure when @ idle...or when going down the track glance at the fuel pressure gauge and see where it is at...I bet it is falling off about then....

It is not a fuel problem. Fuel pressure is 6.25 psi and constant. When I said falling on its face, I mean it starts breaking up to the point where it sounds like your going to lose some parts and is losing power like it is dropping cylinders. Since it is just under 12-1 compression and I am running 110 vp fuel, I know it is not detonation. The reason for using the autolite racing plugs is because they are short and do not have a projected tip. I have 2 plug wires that touch the headers even with these short plugs. I have those two wires wrapped with protective heat shields so they dont melt the boots. The other reason is that with the projected tip plugs, the pistons have a tendency to close the gap on them. I am going to try a hotter plug and new wires and coil to see if that fixes the problem.

That might be your problem. When you leave and the header heats up, the boot could be allowing the spark to jump. The more timing you add the hotter the cylinder is and could accelerate the problem also. I ran the sleeve over the wire on one engine and it caused the wire to burn badly for several inches. Removed wire, cut off damaged portion, and put it back on WITHOUT the sleeve and had no more problems. Just trying to help a neighbor as I'm located in Ocala.

Replaced the plugs with AR134 which is one heat range hotter than the old plug and did not regap from the stock .025. I contacted Autolite and they said not to regap them. Installed new Taylor wires. Checked for coil bind and have .080 clearance and reset the valve lash. The breakup is gone. Set timing at 32 and then 36 and it pulled hard all the way up through 7500 rpm. Checked that stall on the converter with the new cam and it appears to be stalling at 4500 which is 600 rpm higher than before with the old cam which stalled at 3900. I got the jetting perfect and ran a 9.87 at 137, 9.86 at 137 and a 9.79 at 139. This was in much better weather than the best run on the old cam which was a 9.87 at 137 in 66 degree weather with 80 percent humidity. Yesterday the temp was 50 with 40 percent humidity. So it doesn't look like the new cam made any performance in horsepower. I will test next time out with launch rpm and shift points to see if I find any gains there. Thanks for all the advice guys.

harleym, are you saying that you run the plug wire with no boot on the plugs that have an interference fit with the header?