The 307 is an over looked 5-liter engine. In the 80's emissions were a big concern, not performance. A lot of people say they can't rev very high. I think they are looking at the low "yellow" lines on their early rally pacs. In 1987 Olds put a 5500 Red line tach in the 87 442, must have been a reason, although its still lower then most Chevy red lines. Also it is the stock shift points in all Hurst Olds and 442s in the 80's The 307 has the same basic block design as the 77 and up 350s and 403s. All 77-up Olds v8 had windowed main webs, beside the 350D, 350 DX and the 260D. The 307 has less rotating weight than the big slug 350 pistons and huge 403 pistons (which are larger than the 455). This means that the 307 puts less stress on the mains than the larger cubic inch motors do. With simple changes to the late 307-roller motor I plan to make near 300hp and 350-lbs/ft of torque. This will be from realizing the gains of the older style heads, a new, modern camshaft, and roller rockers to get the most of this motor. I am doing this on a stock bottom end, and the compression will be around 8.8:1 and run 87-octane fuel. The following parts I will be using to gain this amount of power.
Intake took a long time to figure out what to use. I keep the stock look I am going with an A4 intake that flows as well as Edlebrock performer. It is a little known olds fact but it is true from a test from a flow test conducted by Joe Elias. Plus it has all the sensors provisions.
Heads on the roller 307 Olds messed up the; there Idea was higher port velocity, which gives better throttle response and idle quality. The Olds engineers cut down the ports on both sides to do this, and changing to the roller cam they lost 10hp where on the other hand Chevy gained ten and didn't change their head design. Putting on a set of 5a old heads is the easiest way to gain flow. The 5A heads (307 heads) for this build up is port matched with the short side radius cut down, and the AIR tubes removed out of the exhaust ports. The valves in the head are going to be stock size 1.75 int and 1.5 exht but under cut stainless for helping keep it cooler and help low lift flow Problems with the 350 olds heads are you have to do a lot of milling to get the head combustion chamber down to the diameter of the 307 bore, it can be done but it is costly.
Rockers, didn't want to do the head work and keep the stock rockers so Crain Cams roller rockers will come into play to help free up Hp. It helps do to less friction plus they are 1.65 rockers so you get a little more lift to help with the Hp number. Real gains using this have been up to 27hp and 17-lbs/ft or torque. The only problem I cam across was hardened push rods the correct length. The 7.7 olds lengths are hard to find hardened but looking in a comp cams catalog ford uses the same length for the 351W with retro-fit hydraulic roller.7812-16
Stock vin9 cam is still a weak cam. Lunati camshaft 51804 that is on the safe side of the computer limits but it is 213/218 @. 05. A12 second Monte guy said the ecm gets stressed out at any thing wilder then 112 lob sep 218 duration and .5 lift @ 05. It might be able to step up to the 51809 218/226. The 809 cam will give you 310-320+ hp This 307 build up was doing it playing it safe with the 804 later it might get the 809 cam to test the waters.
Exhaust will be needed now. The stock manifolds would cap all the gain made. Flow tech coated headers with 1 3/4 primaries and three-inch collectors will do their job to help scavenge the exhaust a lot better also with an H pipe and flowmasters.
E-mail me at Gbody442@hotmail.com for more info