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I did some light clean-up on a pair of 799 heads going on my 98 vette. I was careful not to really change the port shape much. Just knocked down and blended the the ramps and tried to get a little more biased swirl on the intake side. I want to keep up velocity, as this is a street car with a small tr 230/224 cam. I tried to help the exhaust side just a bit more to help the reverse split cam. opinions?
They look fairly good but you can do a lot more and retain good velocity
On mine we cut the swirl ramp and rocker arm boss out, then I just used sanding rolls on the rest of the intake side
On the exhaust side, nothing but sanding rolls (to a finer grit than the intake side)
These heads and switching from a 230/224 cam to a 230/238 cam picked the car up .5 and 4 mph average (and .6 @ 5mph bests). The combo absolutely destroys the 230/224 stock head combo at every RPM and throttle point. Pulls harder from idle all the way to my 6700rpm shift points.
IMO if there is any possible wiggle room in your budget I would consider a similar cam swap. The initial throttle response and torque hit right off idle was mind blowing...the TR230 had it's place but Geoff (who designed it and spec'ced my current cam) will attest he gets better results consistently from a wide traditional split on mild port stock castings.
yea on a tight budget. That's why I used the cam (TR230/224) laying around. Also the same reason I didn't just send the heads off to AI for porting.
Your heads look good. I was concerned that taking out the rocker lump, and getting the ramps smaller would add volume, thus hurt the low end. I'm no pro by any means, just setting out to build what I can with the little I got. Also heard many horror stories of people taking to much out at the wrong places, and hurting performance. I did some research, but head porting seems to be the "black" art, and no one really wants to share their secrets.
You think I can go a little more on the ramps, and take out the bosses without doing harm on the performance?
Looking to try and get to the low 400's HP, but more importantly area under the torque curve.
I removed my rocker boss and swirl ramp as well. And then just blended them as you have to this point and this was on 241's. has been times in sig. Not sure it did much but seems to work well and drives well on the street.
I notice both of you left a lot of material supporting the exhaust guide boss. What are the reasons behind not thinning it out more
Again I'm no pro, but my theory is the intake track (LS6 manifold front (air induction system as a whole)) is going to be the restriction 265CFM ish max. Getting aggressive on the exhaust port would be a no no. The lower velocity would pig the speed and scavenging, especially with my reverse split, and valve timing events. I'm going to team this combo with a LG 1/78" pro header, out to a C5 Ti axle back.
I notice both of you left a lot of material supporting the exhaust guide boss. What are the reasons behind not thinning it out more
the guy who was cutting mine ran out of time and only had time to work the exhaust was the main reason
plus with a cam with 8* bias to the exhaust side I figured it wouldn't hurt as bad, figure if I get as much air as possible in it will force itself out
he now has an at home flow bench so these heads will be getting reworked here in a few weeks to a more professional level along with a new valve job
yea on a tight budget. That's why I used the cam (TR230/224) laying around. Also the same reason I didn't just send the heads off to AI for porting.
Your heads look good. I was concerned that taking out the rocker lump, and getting the ramps smaller would add volume, thus hurt the low end. I'm no pro by any means, just setting out to build what I can with the little I got. Also heard many horror stories of people taking to much out at the wrong places, and hurting performance. I did some research, but head porting seems to be the "black" art, and no one really wants to share their secrets.
You think I can go a little more on the ramps, and take out the bosses without doing harm on the performance?
Looking to try and get to the low 400's HP, but more importantly area under the torque curve.
There is enough info out there if you look for it. Everyone has a little different Idea of what works and what doesn't. Obviously the Pro's aren't gonna come in and spill their guts as that isn't good for business.
I tought that removing the swirl ramp would kill performance on a street car ?
by removing the roker arm boss dont you risk oïl seapage? solution ? lock tite or else ?
thanks
dan
My thought is it will cause the head to "back up". Low and mid would take some hit but up top with the air moving would see the benefit. I made the decision to keep the bump, and focus on velocity and bias swirl. Having said that my "pro" ported heads back in the day had the ramps removed, and they worked good on my street car.
Most pictures of the heads I see seem to be "over ported" for the application. I'm on a 3.90 bore with a small reverse slit cam so I didn't go HOG wild
I guess we'll see how it works out this Spring?
You should consider having a nice valve job done as well then carefully blend into the port throat.
There is power in the valve job.
I agree that 02WSsicks should. It should look like KCS valve job. I want to also but finding a shop that I can believe in is the tough part . Everyone I've contacted in my area acts like I'm just another Camry.
Is this why people choose cams with a fast ramp rate ? To make the valve hurry up and get past the crappy factory valve job ?
I agree that 02WSsicks should. It should look like KCS valve job. I want to also but finding a shop that I can believe in is the tough part . Everyone I've contacted in my area acts like I'm just another Camry.
Is this why people choose cams with a fast ramp rate ? To make the valve hurry up and get past the crappy factory valve job ?
It's about area. The cylinder is pulling on the port the hardest way before the valve is fully open, so the more area you can make available to the cylinder, the better. This is also why I want big valves. At any lift, there is more curtain area available, so a big valve with a slow steady lobe seems like a small valve with a fast aggressive lobe.
The valvejob is so important because as most cylinder head gurus will tell you, the valve job plays a vital role up until the valve has been lifted by 25% of its diameter. For a 2" valve, that's .500" lift...
It explains why a LS3 is so potent. It also explains why a Futral F13 is strong. 230/232 112+4 opens the intake 7 degrees before TDC. I don't know why the crew at YellowBullet gave you a hard time about it, the big valve/small port post.
We're getting off the subject though; what should 02WSsicks look for in a valve job ? Ron, tell us about your valve job.
With the Valve job I would think the initial cut from the combustion chamber has much room for improvement. I'd think just blending the cast grain to the 1st angle would help.
I was very careful not to score the angle, but smooth the transitions (not pictured in the original post).
12-11-2014, 06:29 AM
Light 799 head clean up opinions? 
