How much timing?
 

Hello everyone, I have been reading some post on here and this place seems like a great place for info. I have recently built a 427 sbc with a lil m block, Brodix 11x heads ported by RFD, .630/.630 lift 4/7 swap comp cam with I believe 276/284 duration @50. It has a Proform 950 carburetor with the power valve blocked off and the main jets set at 88 square.

I took my S-10 out this weekend for test and tune and it performed very sluggish and only ran an ET of 6.84. My old 406 would run 6.40's allday long. After a plug check it was evident the motor was running lean, so we jetted the carb up to 94 square, the plugs looked alot better but the ET slowed to 7.00, you could imagine my disappointment! We decided to bump the timing up to 40 degrees and made another pass. The truck left alot harder and ran an ET of 6.63 at 104mph best pass of the day. I plan on sticking a 1050 Dominator on it this week to test, but could this thing actually want that 40 degrees or possibly 42 degrees of total timing? HELP!!

Have similar set up only a 429 sbc and a dominator 1150 and mine likes the 40 degree number,just what seems to work for my situation, running c14 also.I find sometimes its what ever works . :D :D

Get rid of the proform carb and 36-40 degrees

have you checked the top dead center mark on your balancer???sometimes they are not right , ..I had a $350. balancer and the mark was 1/4 inch off...just something you might check , it can make a big difference,,,,Paul

Thanks for your replies. I forgot, it also has custom made Wiseco pistons that are gas ported and puts the compression to 15 to 1. I am running Sunoco 116 octane. I plan on throwing the dominator on this weekend and play with the timing some more. Thanks for your point of views and I appreciate any opinions you guys have. I need to get this thing running to it's potential.

Like Maniac says double check the balancer for TDC, that engine should run good at 34/36 degrees, also you don't need 116 octane, 112 is plenty good. The lift is a little short in my opinion for that many inches, maybe go to 1.6 rockers, on that light of a vehicle.

JMO

Zip.

What they said PLUS....

In this heat it would be my guess that you went up too many jet sizes since it didnt repsond, no matter what the plugs look like.
I'd go back down 2 maybe 3 jet sizes from the current 94's and give it another go with the 40 degrees timing and see if it hauls the mail, I'd do that before I went out and bought another carb, but thats..... JMO>Cp

I think 94 jets sound rather big for a 950.

My 1050 dominator had 88 jets stock. I bought a 950HP brand new back when they first came out. It was jetted 78 square... but it also had two power valves.

I'm sorry guys, I went up to 92 squared not 94, that was a typo. The motor did respond by going up it went from having 88's and 36 degrees total timing with an ET of 6.84. I retarded the timing to 34 degrees and it went 7.0. The plugs were extremely lean, so I put the 92's in it and put the timing back to 36 degrees and it went 6.73. I then went to 40 dgrees timing with the 92's and it went 6.63. So it's going in the right direction, I was just wondering if 40 degrees seems high? The motor seems to like it better than 34-36 degrees. When the carb was on my 406 it had 84's in it and would go up to 86's when the air was good. The air was very good the day I took this new motor out. Only 80 degrees and no humidity.

Oh yeah! The dominator isn't costing me anything, my buddy has a spare laying around he's gonna let me try.

Personally, I'd be more focused on the trap speed than the et. MPH is a better indicator of proper tune than et because of fewer variables like traction etc. I'd tune it for the best mph then tweak the chassis and tire pressure for better et.....jmo,

Johnny

Well if the dominator is handy, slap that sum bitch on there and see what she'll do.

I think your pretty close to where you wanna be on the timing @ (40) most SBC's race motors I've ever tuned/ran like around 38-40.
34-36 sounds slow, every combo is different though, yours may be the exception, I run 41 in my BBC.

Cp

i just put on a quick fuel 850 on my 388 sbc 13.1 solid roller in a 3100lb car and went from running 7.05 to 6.80 running 36 total timing and 82 sq.jets. i was running a 750 holley.i would play with jetting and timing on your combo.