I was wondering what to do to my engine? Just had it rebuilt and not to impressed with the results. Modifications include 9:5 to 1 speed pro speed hypereutectic pistons ta performance 284-88h cam heads redone with new valve springs edelbrock intake and edelbrock 750 carb and double roller timing chain and shorty header from ta performance. I was expecting tires smoking from the start and i can barely get a chirp. Runs really good mid range to top end. What can i do to get some morepower out of the hole? Nitrous? The speed shop that tuned it said that the timing is advanced so far that they eliminated the vacuum advance because my distributor is putting out way too much timing. Suggested an msd which im not opposed too but is there anything else i should try before i spend more money and vet no results. It is in a heavy 72 riviera with 2.93 gears which i know hurts but any input would really be appreciated thanks!
That is not what you call a big cam but it is not a mild cam by any means and the heavier the car the milder cam you need when you are trying to keep the torque up off the line especially with a stock driveline. Somebody who told you what cam to buy forgot to mention that you need to install a better than stock torque converter to get the rpm up into a range where the cam can make some decent torque. Even a mild cam moves the torque peak up the rpm range so you have to get the rpm up to that spot off the line. Probably a decent name brand 25-28oo stall converter will do the job. That 13" block of steel they call a converter in your car now probably is 1600 if it is lucky. The stock converter "OK" that TA lists is pretty much the bare minimum so the car won't stall when you place it in gear and certainly not for optimum off the line performance. If all you want off the line is a tire fryer add a few hundred rpm more than I suggested but remember if the car is spinning the tires your ET is suffering. I can't say I'm too excited about the Edelbrock carb but if the car is pulling ok in the mid and top end and not bogging off the line it is doing ok. A quick fix to help the low end is to throw a 1" 4-hole spacer under the carb to help out the low end torque. Every little bit helps. Hopefully they blocked off most of the exhaust crossover to the intake from the heads to keep some of the excessive heat out of the intake/carb. Good exhaust after the headers? I don't know how the shop set up the dist. but they should have limited the dist. centrifugal advance total so that you can have a decent initial. Read Larry's timing thread. 34* or so total is about right. Vacuum advance is good for cruising around. If they feel you have enough timing in the dist. already for cruising without vacuum advance then you probably have too much. 9.5:1 should be fine with 34* and some vacuum advance on premium gas. Hopefully the shop degreed your cam in for optimum performance. What kind of double roller timing set did you use because if it is the billet roller set degreeing it in is an absolute.
You need less Cam and some head work, or at least less Cam and between 3.23 to 3.55 rear gear! Your increase in compression and its added cylinder pressure is going right out the tail pipe with the overlap of that Cam!
Two easy fixes: 1. Please reconnect the vacuum advance. The engine NEEDS the extra advance at part throttle. Otherwise it will run like the ignition is retarded in any situation but full WOT. A car will feel very sluggish without it. No vacuum advance is only for race cars. If it pings with vacuum go back on the initial timing because i suspect it to be too aggressive anyway. Should not be more than 32-34 degrees total mechanical timing. Maybe you can also run fuel with more octane? 2. Get a set of Rhoads lifters. After the oil is warmed up they will make your cam act like 10-15 degrees smaller at low rpm but will restore the full duration above 3000 rpm. I have tamed quite a few cams that were too big with this and lost no power at the top. Only downside is the slight ticking of the valve train due to the concept of those bled down lifters...
Check the distributor part number. It may not be original. The correct distributor for a 1972 455 is 1112110.
How deep in the hole are those "9.5:1" pistons? I bet you have nowhere near 9.5:1 compression. Was the camshaft degree-d when they installed it? What do you have for cranking compression pressure? Your "speed shop" screwed-up the ignition advance. Make them fix it. (This assumes they have the skill to do it.)
