Engine Gurus, In a few threads regarding cylinder heads some of us have brought up the subject of unshrouding the valves. I have seen substantial gains on the flow bench buy unshrouding the valves in the combustion chambers. This leads me to my question below. The bore on my engine is 4.350. I open up the combustion chamber to be exactly the same size as the bore. Has anyone ever tried taking the block and putting a nice chamfer on the block by the intake valve and then opening up the bore on the head to meet that chamfer??? Does anyone think this is a good idea? Or would it not be worth the time and energy? What do you guys (or gals) think. Take Care
I'm no engine guru, but that is exactly want I'm doing to my 494. As it was explained to me by Bob G. Take the bore and the chamber around the valve area out to the head gasket. Insuring not to go down in the bore any further than just above the the top piston ring at TDC. I know a lot of people have writen off Bob G. of Performance Concepts or he has lost the trust of many people. But he is alive and well kicking out BBB and other stuff. He did the machine and block work on Rick Crawford's engine. Set up his heads for Jezels and provided tons of NOS info. Rick's engine to date has 50+ pass on a 225 shot and 20+ pass with 350 shot. I've been using Bob since the early 90's. I got his number from Dave Johnson (70 stage2) when he owned Northwest Buick Performance out of Washington state. I was talking to Dave about running NOS on a buick and he said I needed to call this guy Bob G. If I was to say one thing that is cool about old Bobby is that for Rick and I, he took trade in on my buick stuff. I credited over $1500 by cleaning out garage. I could of posted my stuff and sold it, but I saved tons of time and work with one stop shopping :eek2: This is not meant to be a promote Bob post but just tossing out some info for you guys. Bob like many people fell on hard times, but he is alive and kicking.
Hi Cory, glad to hear you had good results with Bob G. not too many people can say the same!! The machine work was excellent but he sends that out to McIntosh Performane and not done in house as I was led to believe. Bob did keep my new Stage 3 heads and installed his used ones on my motor with the wrong valve springs which wiped the cam and bearings out within 20 minutes in my sons car after it was supposedly broken in on his dyno which I later found out was broken for over a year. Scotty from PG Performance saved me big time and to date my son has over 220 runs with no problems except when the trans let go and the engine over reved alittle and bent the exhaust valves. The Skyhawk runs in the 8:60's @ 160mph on race gas with no nitrous while keeping the rpm's below 7000 for longevity sake. Scotty from PG is working out of Pat Musi in Jersey now and his knowledge can only expand further in that facility. Bob G. used to call Scotty all the time because Scotty has done it all way back in the day before we ever thought about nitrous on a Buick. Sorry to drag this out but the name Bob G. hits a nerve and I still cannot get my money back from his negligance.
John - That may not be such a crazy idea!:grin: Both Chevy and Pontiac thought it was worth doing!:Smarty: Sure seems like there could be some benefit.
Skyhawk, like I said he lost the trust of the the masses. I fully understand everybodies displeasure with being treated like that. Rick and I both farmed out to him for machine work and block prep, understanding that he would work through a machine shop. I in know way was trying to push Bob, just stating that I haven't had any problems. I may someday regret working with him, but have no complaints to date. In fact, I need to call Scotty about grinding a new roller cam for Rick. Again I'm not a spokesman for Bob, just passing out info.
Hey John This is exactly what we ol timers did back in the day with our 400-430 motors before the 455's came out.We'd put bigger intakes in the 400 head and chamfer the cylinder to unshroud the valve a bit.Did it help? Who knows,we did'nt have the fancy technology that there is today,but it seemed to and a lot of the good running buicks used this tecnique. gary
I have used Bob G. in the past with no complaint. If you are running nitrous he is your man with a Buick. He designed my cam and ported my intake for my nitrous motor. I used a Buick shop that has a pretty good reputation with lots of problems, if I put the name on this board my post would be removed, figure that one out it should be easy. Bob helped me straighten out the problems and made sick power out of a pump gas street motor. Try 814 HP and 826 ft. lbs. before 6000 RPM with only 225 HP nitrous pills. I used the engine for 5 years and 100's of passes before I sold it and it just had a freshen up this year which would be 8 years of use. Sorry John not really an answer for your question, just sticking up for someone that treated me right not trying to defend his rep for what he did to anyone else.
I've seen a photo of a block with that done to it on this site. I just can't remember who did it. :spank:
John, other than a slight loss in compression, your idea is basically fine. Other engines have done this same thing for years. Getting more air into the cylinder is the way to make power, period. Jim Burek
John, Have you tried this, or any of you. Seems to be a great idea. I guess the first place to try it is the flow bench.
Jeff, No I have not tried this modification but it sure makes sense to me. We are lucky with our 455s that we are working with a 4.313 to 4.350 bore. Its less of an issue for us. Later
