Obviously something's wrong if I'm using a. 045 would that raise compression to where I couldn't run 87 octane?Īctually, what is the limit in terms of compression where I can't run 87 anymore? I realize tighter squish will increase compression but how much? 047 cause compression to be around 120 psi? when it should be 150 What squish clearance do these motors typically come out of the factory with? I believe this untouched motor originally had a 5 hole gasket in it 073.Īre these WSM pistons that far out of spec with the OEM pistons? So, my final squish is going to be around. 061 I am disappointed at the thickness of the clearance but the test worked great! I removed the head and WOW, it worked better than I thought! All lead was between. I then bolted the head on and turned the motor over hard by hand until it hit tdc and then rotated past.
125 lead to both sides of the piston against the cylinder wall and directly over the wrist pin. I am attempting a lead test to get a clear measurement. I pulled the cylinders and pistons, removed the rings, looked every thing over, then I bolted the cylinders w/pistons back on with no base gasket.
It's a very important measurement and I know the benefits of a proper or tight squish from my land toy motors I've built. I want to ask some questions about squish. That said this post isn't about the previous rebuild and what I may have done wrong or the present re-ring which I will be doing everything wright.
It's bone stock but I went with WSM 1st over pistons. So I tore it back down to see if I could determine what the problem was and re-ring it. After break in I was only able to attain 120 psi comp. Pushrods length need not be changed nor would you necessarily need to fit slightly higher rocker arm ratios but they do perform better with the roller rockers because of the tip contact is kept flatter if the tips can roll across the top of the valves rather than the limited contact angles of the stock stamped rocker.I have an spx and I rebuilt the motor. I used the Rhoads sets, stock new springs, 68 grind cams and titanium lash caps. It is also reasonable to expect that changing the valves to stainless is one thing but so is machining knurled valve guides and hardening the valve seats if you go for the pre-73 cylinder heads so that they will run on unleaded gas.ĭon is right about the steep bump sticks too.you will need to choose one which will give you the power you desire but temper your choice with driveability on the street.įor my money, I would go with the number 68 grind cams as they went into many of Pontiacs high performance motors, they have a slight lope and give a good smooth performance right through the power curves and good engine vacuum for your brakes, and you won't need to change converter stall either, which is sometimes thrown into the equation with some cam set-ups.Ī new set of lifters are new stock lifters or Rhoads sets. It is sometimes a good idea to sit and think a while and get yourself a plan and budget together, thinking what you want to use the car for and how much power you can reasonably expect. But you can see how one thing leads to another, and can quickly blow your budget.Ĭheck out Wallace Racing's site, that will tell you which heads cc head chamber sizes and the compression ratios obtained. Some roller tip rockers, like the PRW's will help prevent wear on the valve tips. All this extra comp will help to "add a bit more power".Īlso be sure to use polylocks, and adjust the rockers to no more than 1/4 to 1/2 turn below 0 lash. 027 thick Cometics, with a 4.160 bore and increase the comp a bit more. While they're doing the heads, it's good insurance to buy new stainless steel valves to replace the almost 40 year old ones.Īnd if you do this, since you'll need new head gaskets, you can buy the. I don't know what your budget is for this project, but one thing leads to another. 050 off the intake port side so that the intake manifold will still line up correctly. 050 off the surface, also have them take. While the motor is out, it would be a good idea to have some taken off the heads to increase compression. The biggest thing I would consider is a RA4 duplicate, such as the Melling SPC-8, and then only with Rhoads RL-9518 lifters to smooth out the low end a bit. Now, if the car is a 4-speed sick, the Summit 2802 will work (with the appropriate springs). With stock springs, a duplicate of the 068 Pontiac cam is about the biggest thing you can get by with. But if you use this cam, you'll have to use new springs, cause it has more lift than a stock cam. If it's an auto tranny car, the cheapest decent cam would be the Summit 2801. You didn't mention what the motor is going into. Click to expand.Everybody seems to have different opinions when it come to cams.
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