Thanks for good toughts! Our 98 gas is same than yours 93-94, based on wikipedia. I dont have pistons yet, just planning.
As far as valve guide seals, yes some can wipe too much oil from the stem, esp. exhaust. On the viton types an 11/32 reamer passed through the seal can do the trick. Stab it through the guide by hand leaving 6 very light grooves (flutes on reamer). I've never done that on a Buick though. Not sure what other tricks people use.
Well then if you're just in the planning stage you should consider these pistons; http://www.buyracingparts.com/pisto...totec-forged-350-buick-dished-piston-kit.html The price includes rings as well. You would be able to dial in your compression ratio because the compression distance is customizable to minimize machining of the deck. that combined with various head gasket thicknesses available you could dial in your compression ratio where you want it to be. Here is what the ad says about them; "AutoTec is a High Quality, Precision Manufactured piston option. That comes at a very respectable price. Our Design Specific Forging allows us to manufacture our parts with less machining time, thus allowing us to keep production cost down. Then pass that savings on to you, the customer. Made out of 4032 High Silicone Aluminum Alloy, it has great wear resistance, a low expansion rate, is very durable, and is very low in friction. These pistons accommodate multiple uses including. Your local auto shop, muscle car restorations, performance street rods, as well as many spec racing classes. They can also withstand mild nitrous kits and small turbo or super chargers. Just about everyone can benefit from the excellent value the AutoTec line carries. Keeping in mind these pistons were originally designed for about 600 Horsepower. In Small Block applications, we have customers that frequently fine tune engines that yield 850+ Horsepower with a bit of Super Charger boost. Bore, Ring Pack, and Compression Distance changes can be made to any shelf part at no extra charge. Meaning that if you do not see your application listed in the guide, we can make what you need without charging a custom price. Every part is made with same high quality machines and tools as our RaceTec line including diamond turned ring grooves, and skirts. Not to mention our parts are 100% made in the USA." You should consider upgrading to a roller cam as well customized to your combo, no cam break-in means very little risk that the cam will be wiped out from break-in, only from the slim chance that a roller lifter is defective which very rarely happens. Derek
Yes I would love to have Autotecs, but my budget is little short now as usual. Thats why roller cam is also out of the plan. We have to pay +24% tax for every goods come from outside of EU, so with shipping costs Autotecs will be around ~1000$. Also car is my daily driver at summers, and Im not planning to race or rev it over 5k so I think Im good with cast pistons.
You can sand them or you can leave the edges alone. No the chamber doesn't match bore it more matches piston dish.
Taking the sharp edge off around the combustion chamber the mill left behind reduces the chances of auto-igniting the compressed mix, and for such little time spent should be considered mandatory.
I agree, there is a ring around the head that should be smoothed out in my opinion. Drop a set of heads on with the pistons out of the block and you can see this.
X2. Good practice to radius all those sharp edges on head, edges on valves, & any sharp areas around spark plug threads.:TU: Very easy to do.....
Does anyone know IVC point for TA 284-88H camshaft? If I'll end little over 10:1 comp I have to choose bit rougher cam than crower lvl3. Any suggestions? I want good low and mid end torque, and Im not going to spin over 5k. I have about 2000rpm converter and 3.08 rear.
If the TA 284 cam is set 4 degrees advanced with the intake lobe center at 106, the IVC point will be 68 ABDC compared to 66 ABDC for the Crower Level 3. However the TA 284 cam has 11.5 degrees more overlap, rougher idle, less off idle torque and less gas mileage. The difference could be made up by only advancing the Crower cam 2 degree so it is not worth going to the TA 284. Since you have a 2000 rpm converter I would consider the TA C110 cam. The IVC is still at 66 ABDC but it will have a stronger mid range than the Crower Level 3. Try to keep the compression ratio close to 10:1
With crower's 66 ABDC I'll have 8:1 DCR, is ok or too much? I have 3-way timing set so I can adjust +/- 4 dergees.
If your gas octane is higher than ours then you might be ok. Since you have a 2000 rpm converter you can afford to move the power band up by installing the cam closer to zero advance and giving yourself a better margin. How did you like the power band of the Comp 260 cam?
Our 98E5 (5% ethanol) gas is same octane than yours 93-94, based on wikipedia. Comp was ok I think, two black lines from stoplights anyday and pulled strong to 5k, never even tried to spin more. Car was fastest I've owned but I dont have much to compare because I only had fullsize nailheads before :grin:
The Crower level3 cam will be similar in performance to the Comp 260 and will offer a little more power at 5000 rpm. As you already know, the longer advertised duration of the Crower cam will allow a higher compression ratio than the Comp 260. Eliminating sharp edges in the combustion chamber will help prevent detonation. I would bolt the heads to the bare block and scribe the bore circle on to the head and grind the chamber walls out to the scribe lines. I would also remove the reference boss near the spark plug hole. This would drop the compression ratio a little. https://dl.dropboxusercontent.com/u/39382077/350 head.gif
What is your suggestion for cam choice if I want to keep little over 10:1 static compression but want to bring DCR bit down?
Depending on what rear gears you want to run and torque converter . Ta 310/ta. 413 both really need at least 3.42 gears and 2500 converter . Or level 4 crower. Might be a choice Or custom grind from Scott brown
If your not spinning more than 5000 then anything more than level 3 would be a waste. The level 3 will provide way more torque than a 260. Real world, NOT theory.
In my opinion the best you can do to lower the DCR is use the Crower level 3 and install it with the intake lobe center between 110-112 degrees ATDC. The reason is, the Crower level 3 lobe profile has a big difference between the .050" duration and the Advertised duration, 66 degrees. This is what allows a short .050" durations for good low end torque along with a later closing intake valve to keep the DCR low. Even if you go with a custom cam it is hard to find a lobe profile with more than a 66 degree minor intensity. If you go with a cam that has more duration and a later closing intake valve you will lose low end power. As Steve pointed out, if you lose low end and limit the upper end to 5000 rpm the power band is short. I still recommend doing the combustion chamber modifications I suggested, have slightly less than 10:1 and install the Level 3 cam with the intake lobe center at 108 ATDC.
How about 9.4:1 for crower 3? If I choose different pistons that is what I'll get. e. What is optimum CR to aim for crower 3?
