about 2 months ago i started a thread asking what you buick nuts thought my combo would run.69 lark, 75 455,(heads as well)cam 469/495 290 dur.350 turbo 2000 stall 3.08 gears.poston s divider intake 800 cfm qjet,average exhaust(no headers).........some said mid 14's some said high 13's.well my buddy has a 84 monte ss with a stock 350(dumped the 305)rv type cam stock tranny stock 3.42 non posi rear a set of mc crearys on the back and it will run 14.5 all day long.based on that he thinks my buick will run low 13's. do any of you guys think this is possible?
If you're running stock manifolds through stock exhaust, THAT will be the biggest thing slowing you down. I put a healthy 455 .030 over with stage1 heads into my GS with the stock exhaust - and then switched to headers and dual 2.5" mandrel bent exhaust and picked up 9/10ths in the quarter !!! going from a 14.5 to a 13.6. Switching from the stock 2.93 rear to a 3.42 posi got it down to 13.15 My car is heavy thoug, a convertible @ almost 4100 with my 165# in the seat.
from my experinence over the years with many 455 cars, if it hooks up good i would be happy if it runs around 14 flat. but i would guess high 14, due to low torque and h/p of the 75 moter.
If it is a 75 motor, it has open chamber heads, which have a 7.9:1` compression ratio. Assuming you have a cam compatible with that low compression, I would expect you to be able to run in the high 14's to low 15's. E.T. is all in the leave, and 60'. If you can get it to leave without spinning (Easier said than done), you will get your best times. In any case, just get it down the track. You'll be able to tell by your trap speed what kind of horsepower you are making.
well if it runs high 14's i guess i should put a small block chevy in it.i figure my lark weighs around what the before mentioned monte ss does and its stock less a crane econopower cam.if he can run 14.5s all day and im lucky to run with him i guess all them extra cubic inches and torque aint helpin me much........thanks for the opinions though i got what i asked for.
SBC, why bother! It's a BUICK. All you need to do is put earlier heads on it and maybe a different cam. Then you could probably run high 13's or better. The problem is the open chamber heads.
larry you are right a set of good heads would wake it up i agree.i just figured a torque monster 455 would beat my friends 350 monte.i wonder if someone had lets say a 400 horse 455 and a c.r. of 11.1 then cut his ratio down to 9.5:1 how much hp he would lose?
That's the point though. The 75 and 76 motors had such low compression that the torque, and more importantly the horsepower, wasn't what it should be. Put the wrong cam in that type of motor, and it could be worse. You don't want a cam with any overlap, because it will bleed off cylinder pressure and make things worse. You really haven't told us much about the cam. Do you have the duration at .050 figures and the LDA. The 75 and 76 cylinder blocks are beefier than the earlier blocks, and a great basis for a buildup. How does the car feel? Does it pull good? It would be alot easier to work with the 455 if it isn't giving you the performance you are loking for. No one on this BB wants to see you put a small block chevvy into it. Give us as much info on the engine as possible and we will try to help.
we put the short block together yesterday.the cam card is at my buddies garage.ill get back with the specs when i can.have you ever heard of tricking an engine into thinking it has more compression?we are at the point of degreeing the cam.this was all supposed to be a budget type build up.i got the car for 300 bucks engine 200 less intake and carb,ebay cam(crane blue racer)69 bucks, rollmaster timing set 80,all rings bearings oil pump kit etc. with a friends discount(dirt cheap)friend did the heads for 175.local machine shop tanked the block and did the cam bearings/freeze plugs and checked the bores.i think that was 130.00......but dont worry no chevys going in there.
the biggest power drop is the 75-76 pistons, about 20 cc more dish then the 70 pistons (10 cc = about 1. in compression), the heads are only 10 cc more then the 70, so the biggest bang for the buck on a 75-76 block is to go with some flat tops, but those are forged pistons and that would cost at least $600 when all said and done. that would get the compression up to about 10 to 1. just putting 70 heads on a 75 bock raises commpression 1. that helps but you still have a moter with only about 8.5 to 1. the 75-76 455 are not the torque monsters, you need commpression to build torque. but they are good blocks to build from. cams ussualy are to get more top end h/p, in turn you need to build your set up to take advantage of higher rpm h/p. the bigger the cam the lower the low end torque, meaning the torque peak moves up in rpm, thats why bigger cam need more commpression, lower gears, and higher stall. just my 2 cents. kelly
My Skylark has a stock low comp '73 455, a 2700 converter, and a 3.73 posi. It went 14.46 @ 93 with slicks, and elevation at 4500ft. Kevin
Yes, that's what I am talking about. The combination of static compression ratio, and cam timing gives the dynamic compression ratio. (DCR) That's why you don't want any overlap in the cam. You can't afford to bleed off any cylinder pressure. You need a small cam with a wider LDA. I'm not an expert with this, but maybe someone could recommend something to maximize performance in your motor. Like Kelly said, your best bet is to change the pistons and use earlier heads. Then use a compatible cam. You'll blow that chevvy into the weeds, especially in a street encounter. If you have the motor apart, spend some money on pistons. Once you feel 500 ft lbs of torque, you won't regret it. Good luck.
larry we are on the same page now.i dont want to get into the dcr discussion right now but there are ways to make an 8.1 engine think it has more compression than it does.lets just say thats the reason i bought a rollmaster 9 keyway timing set.i have a friend with an 11 second 454 chevelle that has 8.5:1 compression although he is runnin a big stall and 4.10 gears.im not sayin everything that will work on a chevy will on a buick but some things do work on all engines.
I think what you're getting at lark is the phasing of the cam. You will want to advance the cam, over what the cam maker says, to get your parts to work their best. It's actually the intake closing event (IC) that determines cylinder pressure, not overlap. If you can get the intake valve to close sooner, trapping as much compression as you can, U will maximixe power. Most cams nowadays are advanced 4 degress from the manufacturer, you may want to advance yours an additional 2-4 degrees. Keep in mind that as you advance, you will give up top end power.
even the 73 has closed chamber heads, i think they have about 9 to 1 comp. lark69, get it running good, and take it to the track and have fun, then go from there.
thats the plan, have fun with it.even if it runs 14's as long as its consistent is what wins at the track........
