Max effort stage II with carb

[unboostedV6]

The mixture distribution became more even among all cylinders when the secondaries opened. The rear cylinders fattened up as the fronts probably leaned out a little. You took 4 jet #'s out of the primaries...take the same 4#'s out of the secondaries, too. That cam is good for a power peak around 73-7400 rpm and a torque peak around 55-5700rpm on a 13.5:1 engine. I think it'll have to rev higher before you see the peaks w/ 10.8:1. I shift my 266-266, .640" cammed engine at 8000 and currently make around 380 rear wheel hp. Pull some timing out...try 32 deg total. 36 seems a bit much for pump gas.
Don, his link from the first page works.
Greg

 

[Alky V6]

I agree with Greg. You shouldn't be dropping the primaries that much and not do anything with the secondaries.

I don't understand why you were leaning the primaries when the readings showed that you were leaning out. Or was the single pass readout the first pass?

 

[buickstage II]

I agree with Greg. You shouldn't be dropping the primaries that much and not do anything with the secondaries.

I don't understand why you were leaning the primaries when the readings showed that you were leaning out. Or was the single pass readout the first pass?

the single pass was the final run, i thought the lower the number the richer the mixture?
i spoke to my machine shop who did a great job for me, they run 2 top alcohol car so they have a bit of knowledge and experience.
i told him that i think its valve floating andhe asked if the top of the valve stems had any star patterns on the top, and i confirmed that, in which he said it's a pretty sure thing then.
he also stressed to me before i started it to check the cylinder pressure, if it was under 200psi im definately not going to be anywhere near 1.8 hp per cu.i
when i did test it, it was 135-140psi, which definatey show the C.R being way to low for the cam, another confirmation is the amount of unburnt fuel on the plugs at low rev's.
he also said to just lock up the distributor at 32 degrees to try and hepl this

seriously hanging to get it on the dyno soon when i get some parts, to get this tune even close!

cheers Simon

 

[BlownV6]

Simon, I was going to suggest that you lock your distributor also. Lower compression will want more timing to burn the fuel at low RPM and that will help with the fouling out plugs issue. It will also sound quite a bit better and more of a thump to the exhaust. Im still thinking you should be able to see 350HP on the chassy dyno when you figure it out!! Remember one thing your engine man probably hasnt messed with a buick v6 stage2 headed motor , I think hes going to be suprissed at the HP level it makes in the end. Mike

 

[buickstage II]

Simon, I was going to suggest that you lock your distributor also. Lower compression will want more timing to burn the fuel at low RPM and that will help with the fouling out plugs issue. It will also sound quite a bit better and more of a thump to the exhaust. Im still thinking you should be able to see 350HP on the chassy dyno when you figure it out!! Remember one thing your engine man probably hasnt messed with a buick v6 stage2 headed motor , I think hes going to be suprissed at the HP level it makes in the end. Mike

Hi Mike,
you better believe he will be suprised! although he did say straight up that the cam would like to see high 12:1 CR
more thump would be nice!

mike don't have a set of higher comp pistons at all?

im liking the idea of N/A here, anyone ever run like 6 enderle throttle body's with injection and gas? hmmm

 

[BlownV6]

There is no doubt that more compression will make more power, but then your stuck with high octain racing gas that is very expensive. I guess if its now going to switch to just a race car that wont matter. If its a street car then stay where you are on compression. You can advance the cam or loosen up the lash and get more cranking compression but I wouldnt try that yet. I think your on the right track , just refine what you have there right now. IT will make the power!! Mike

 

[Alky V6]

Simon. On a holley carb, the smaller the jet number, the smaller the orifice. Less fuel will pass through a smaller orifice. The jet number has a direct correlation to the size of the orifice. Very strange how the mixture went richer with the leaner jet size. Were you experiencing missing on the top end with the first runs?

That cam needs CRs in the low to mid 13s.

 

[unboostedV6]

Simon, what fuel pump, regulator, pressure and line sizes do you have? Inadequate fuel to the float bowls will do exactly that - get leaner with bigger jets and richer with smaller jets. I suspect, though, as Mike and Don do, that valve control is the main problem. The float is probably causing odd air/fuel readings. A carburetor requires controlled valve events to do its job properly.
Greg

 

[BlownV6]

Greg , Were you in the booze again last night???? LOL Kidding!! Mike

 

[unboostedV6]

Demon Methanol ! Ask me what happens when a big name, well trusted alky carb builder underestimates needle & seat size. Go 'head, Go'head!!

 

[BlownV6]

OK I get it now!! When the float bowls run out of fuel( which will happen faster with bigger jets) Then it gets leaner because not enough fuel is available in the bowl. YOU DIDNT EXPLAIN THAT LAST NIGHT!!! Mike

 

[unboostedV6]

Thank you for your patience, understanding, and ability to translate my thoughts.
Hey Mike - do you have any of those pop-up S2 pistons in a smaller bore? Like 4.010-4.020"?

Greg

 

[BlownV6]

Thank you for your patience, understanding, and ability to translate my thoughts.
Hey Mike - do you have any of those pop-up S2 pistons in a smaller bore? Like 4.010-4.020"?

Greg

PM sent Mike

 

[buickstage II]

Greg, i have a Magnafuel quickstart 275 (rated 750hp on gas @ 18psi) and mp 9633 reg, dash 8 stainless from pump to reg, 2 dash 4 from reg to carb.
ive got 6 psi at the carb.

any reason why the carb doesn't have the same jet size in primary and main?
is that because of v/s and double pumper?
but do not know why it went richer with a smaller primary jet???

the reason 10.8 was the magic number, and alot of people are still telling me so, is BECAUSE THEY BUILD V8 MOTORS!
the only person who said to me that the static comp needs to be more! is the guy who did all the machine work, off the top of his head he said what it should have and what the cranking cylinder pressure should be (which is only 135-140psi), guess thats what experience is all about as he races Top Alcohol and build top end drag cars

greg your cam sounds very similair to mine, shifting at 8000! thats cool! what gearbox do you have, poerglide? what are your spring pressures too? what spark plugs do you run also?

do you think the power curve look right on the dyno?

i took a punt on these pistons too!
eBay Motors: je pistons for buick (item 110337772223 end time Jan-20-09 19:14:12 PST)

cheers Simon

 

[unboostedV6]

Simon, the jets are different front to rear in most carbs because the primary side has a "power valve". This valve is closed at high vacuum and opens at the vacuum rating stamped on the valve. When open, it allows fuel to flow through the power valve channel restriction or "PVCR" which are holes drilled in the primary metering block. The area of the PVCR's is equal to the difference in the area's of the primary and secondary main jets. Thus, when the engine is under load, the primaries and secondaries flow an equal amount of fuel - in theory, anyway.
Greg

 

[cstavro]

i'm curious to see how much power you'll make. although 'as much as possible' isn't much guidance. that cam is very excessive for 450 bhp.

what size valves are you running? how much porting have you done? what do the heads flow?

i've had the ruggles power book since 1998. his biggest point was that you can't build it like a v8...and they're VERY sensitive to cam. and they turn 9000 rpm with the carillo rods, no prob. you just need titanium valves. ruggles also found that big ports, with smaller cam, makes plenty of hp tyvm, with better fuel economy.

if it were valve float, the redline will drop with each subsequent dyno test. so i don't think it's your valves. it might be pushrods deflecting under spring pressure. i take it you have solid roller lifters (nothing to collapse).

 

[laz]

Hey let me tell you theres nothing wrong with a v/s carb back in the early 90s we ran a pro 5.0 mustang 357 cubic inch windsor with c3 heads a 750 v/s 3310 carb ran 8.60s later on the pro series holleys came out we put a 1000 cfm dp carb guess what it ran no faster on nitrous and ran 3 tenths slower on motor only . I cant see the way the linkage opens limiting power and since the motor is small vacum is a good choice in my opinoin and a 750 is plenty of carb for that cubic inch .

 

[buickstage II]

Well its been sometime since i have had it running and i had the car on the rollers this week with good or at least better results! i ended up using some Comp springs 947 without the inner because of the stem diameter, which left me with 270# and 650# i adjusted the total timing on the distributor but it seems 36 degrees works best. so without looking back i was averaging high 26# HP and seeing very smooth lines on the dyno graph too, AFR's were about 13.0 when the secondaries open and high 12's all the way to 6000rpm which was were it was peaking.
so would anyone dare to say 270HP is max for this combo with 10.8 :1 ???
of course the choice of converter, gearbox and diff would help. And fuel too! as its only 98 octane


thanks for all your help guys,
Cheers Simon

 

[BlownV6]

What total timing did you try and what were the results at each setting. How many RPM did you pull it to , any idea how loose that converter is?? I now have a little cheat sheet that gives an idea of what compression does to HP numbers. Goes as follows from 7 to 8 = +4.40% , 8 to 9 = +3.54% , 9 to 10 = 2.96% , 10 to 11 = 2.43% , 11 to 12 = 2.19% , 12 to 13 = 1.80% Im too tired to figure this out right now , and I dont know what kind of comp your thinking of trying , but you can get an idea what the compression might do to those numbers. Mike

 

[Alky V6]

Have you tried an a/f in the mid 12s?