|06-24-2010 04:38 PM|
The porting articles cam from reliable sources and its not intended to be a "max effort" port job. Just a simple clean up to make it flow better for a mild cam. Did you ever flow test those cylinder heads in your old posts? I would be interested in how it worked out. The cam that I listed is on a 112LSA. Not a 110. More than a few people from thirdgen.org recommended it because they said it worked great for them. It really doesnt matter either way as I am going to an XE as said in my earlier post, which should be a better cam. I would love to use long tubes! The problem is no one makes long tube header Y pipes and I would not be willing to let a muffler shop press bend some kinked y-pipe. The SLP's are a 1 3/4" header in to a 2 1/2" Y pipe to a 3" collector. This should support a 305 with 300hp just fine.... If the LSX cars can make it work out with more bore size and flow...
Old bogie -
If I could find a 350 vortec for about the same price as this is going to cost me I would. I also do not support ditching the 700R4. I have owned 5 liter mustangs with T5's and both an lt1/lsx car with T56 and being auto has grown on me the past 2 years. I almost want to ask if you have ever had a fast automatic? (Respectfully)......I like not having to shift constantly and having a free hand. Also TPI likes lower RPMs so having an auto actually works out. The shift points can be easily changed via governor. Give it a trans cooler, a shift kit from TransGo and a decent converter with lock-up and its actually a blast to drive. A lot of what your saying about porting goes with my original post and what i've read. I DO have access to a flow bench, FWIW. Everyone keeps saying the 305 will fall short of my expectations, well my expectations are really low. This ISNT supposed to be a 500HP monster. Just a nice driver with a little more power, and what's wrong with using a 305 for that? You can trust me when I say I have had fast cars, and it seems drivability always suffers. The BEST fast and drive able car I had was a 1985 Mustang GT with worked gt40's and a 670 Holley S/A with a weiand stealth intake and a lunati 112 224 .510 cam. It ran mid-high 12's on drag radials and didnt overheat while in traffic with the A/C on. This is pretty similar in what I am expecting ultimately... just a little slower at mid 13's.
wow, this is getting really long...
So my porting answer is answered and contradicted... I guess I will have to make my own decision. I really dont want to do a motor swap... the 305 can accomplish the task.. I want this car to remain mostly numbers matching as it is an all stock, all original 105,000 mile car that has been taken care of REALLY well! I dont want to tear it up, it just needs a little help to be more fun to drive. Understand that I sold a fast car to get something I can cruise/show and hit the track every once in a while that drives really good, has A/C etc.... Thanks guys! I appreciate the feedback!! Keep it coming!
|06-24-2010 02:22 PM|
|cool rockin daddy||The last two posts should be enough to sway you from not doing anything more but opening exhaust system up on your 305 and saving your pennies for a 350. What I don't understand is you can get a vortec engine complete for $500 or less. One piece rear main seal, roller cam, best production heads from GM. What's not to like about that?|
|06-24-2010 02:14 PM|
Simple porting is a no brainer with the Chevy. The ports of the small block really are very good as production engines of that era go, among the best of the best. The basic shapes are correct, unlike many other engines where chassis packaging compromises significantly reduced performance potential and the solutions in porting are so subtle as require a flow bench and a ton of knowledge to make any improvement. For the SBC, if you just clean up what's there, streamline the guide boss with emphasis space for flow on the cylinder wall side of the guides both intake and exhaust you've done plenty. The cuts, unless you're building a competition race motor need to be conservative. You will notice a line in the castings, this is referred to as the paste line and is where upper and lower mold pattens are joined in the cope and drag of the casting box. Grinding no further than what it takes to eliminate this line is sufficient for a street engine. Going further than this gains very little power, and that way up around 6 to 8,000 RPM, but seriously weakens the casting to where long term street reliability and durability is compromised to where the head becomes more crack prone than it already is. BUT, as I said earlier; any carving of the ports, especially the intake, moves the power peaks up the RPM band. Without a cam that can rev there and gears that allow the engine to run there, street/cruise performance will be reduced. This is because bigger ports always reduce mixture velocity. Mixture velocity provides a ram effect that allows the cylinder to continue to fill after the piston has hit bottom and is coming up on the compression stroke. Since the larger port reduces this velocity which results in lower flow inertia, the incoming flow cannot overcome the reverse pumping from the rising piston resulting in the mixture being blown back into the intake at low thru moderate RPMs. Now to get enough inertia back into the mixture to overcome the rising piston's compression forces when the intake is still open, the engine has to rev higher in the RPM band. This is what and why bigger ports and or a bigger cam allways cause the power band to move to higher RPMs. This is also why the car manufacturers tend to look at a bigger displacement when more power is needed, as the typical person doesn't want to listen to smaller engine turning higher revs as this becomes a cabin noise and engine longevity issue as the revs go up. So you'd be way ahead to save your pennies and dimes for the time when you can afford a 350 or 383 swap rather than peeing your financial resources away on the 305 which without being mated to a T5 or T56 ahead of some stiffer rear gears will always fall short of your expectations.
|06-24-2010 11:50 AM|
Everything you posted about porting the 305 heads (and other stock SBC heads in general) is incorrect.
Do not deshoud out to the cylinder wall. The air does not flow in that direction.
It flows toward the spark plug. Flow a garden hose thru the intake port and watch the water flow pattern thru the port into the chamber.
If you only "pocket port" these heads you will get minimum results.
The meat and potatoes (air flow gain) is deep in the port. The whole port.
On a 305 cid motor you can keep the stock 1.84x 1.50 valves or cut down some old usable/regrindable 1.94 x 1.60 valves to a 1.90" x 1.55" custom valve size on a lathe and regrind the valve seat. Or use a 1.94x 1.50 valve pair. Irreduardless only minumum deshrouding is nessessary. The area between the valve edge and cylinder wall zone is not a critical area.
If the new larger valve is .050" bigger radius you only need to clearance deshoud by .050" (or less) around the valve.
You need high speed carbide porting cutting burrs, 1 with a 6" shaft to get deep in the intake port around the guide boss. The sanding rolls are for finishing. (mostly eye wash)
Do the whole port including the valves guide boss area.
Use a felpro 1205 gasket as a guide. Raise the port roof don't lower the floor but recontour the short side radius.
The 110LSA xe cams are not compatable with the stock TPI computer.
Buy a EFI computer friendly XE cam on 113 or 114LSA.
raise the cr 10:1 if you want a larger than stock cam. (shave the heads, thin head gasket)
You will need high 4.10 rear gears and a high stall 3000-3500-4000 converter to get a 305 going. (especially with a big cam.)
Use long tune headers, 2.5" Y 'ed into 1 big 3" exhaust. Use two small case 2.5" cats.
Search my old posts for pics of the desired finished 305 head port and bowl contour. Pocket porting is not going to cut it.
|06-22-2010 10:29 PM|
|ThirdDegree||I dont intend on abusing the car, just need the power for driving. I cannot pull out in 50mph traffic without a 20 car head start! I am talking to Kelly @ Blow Hard Racing, he is spec-ing me out some cylinder head $numbers$. He wants to go 1.84 to keep valve shrouding minimal... I think its a good idea. The exhaust is not including the $400 bucks, anything I can swap over (which is every bolt on almost) isn't included in that price. I am trying to find SLP's 1 3/4 headers and 3 1/2" y pipe....then were making an x-over, then 2 1/2 side by side, 2 mufflers, voila - true duals. Everything mandrel bent. Cam was swapped for an XE.|
|06-22-2010 09:55 PM|
|cool rockin daddy||
Trust me on the headers and exhaust. You will be amazed at the difference. You might be satisfied with that. Actually, you better be....headers and exhaust will cost you $400 easy.
The deal on the Camaro of that year is heavy and down on power. But what it can do way better than a Mustang is CORNER. Autocross your Camaro until you can do a motor the right way. You don't need the power as much for that.
|06-22-2010 04:32 PM|
I am ordering this cam kit tonight which would be perfect for a bolt on 305 TPI
I am also ordering some Hedman headers and y-pipe and I already have an air foil and a 3" flowmaster cat back.
Im looking for mid-low 14's.
|06-22-2010 04:20 PM|
|cool rockin daddy||Get some junk heads and practice. Even then, you will not be able to do much in terms of HP without a flow bench. Give a shout out to F-bird88 on this forum. He is a big believer in 305 heads but it takes hours and experience to get them right. Save the money and get a 350. Lay out your engine plan and build it piece by piece or wait til you have the dough to do it all at once. In my experience with a 305 (1978 Nova Ralleye) the biggest thing you can do is open up the exhaust with headers and good pipes.|
|06-22-2010 03:03 PM|
Help with cylinder head ID and porting
I have an 85 Z28, with TPI. I have a good knowledge of these cars it just when they switched to TPI that seems to keep everybody guessing. Anyway, being that it has a flat tappet cam I would think that it has the L69 416's and not the roller 081's. After going back and fourth between 350 or LT1 or 305 my wife sealed my fate with a limit on car money to do some stuff to the house. So unfortunately I am going to have to use what I got. I have never ported a set of heads and I am very weary about doing this. It seems to me I would be better of paying someone else to do it or get some practice parts before doing so.
From the articles I have read on porting, you should do these things.
-Remove the ridge from the intake and exhaust ports
-Only remove material from 1/2 of the valve seat (into the throat)
-Scribe a line where the bore would be with a head gasket as a guide and unshroud the valves a little then smooth out the combustion chamber without removing more that 2cc's of material.
-Pocket Porting ONLY - this includes a gasket match intake and exhaust with some deep pocket action in the 1/2" before the guides.
-Last get coarse emery rolls to sand out the casting flash on the ports.
Now here's where information get a little conflicting! This article says to cut the guides down to a cone shape
This article says to leave a minimum of 0.125" of material around the guide bosses.
So which method is correct? Who has done porting? Is there anything I am missing besides a good valve job? I posted this question on thridgen.og, but it seems to me every post on that board has an argument, so.... yeah. Thanks.