[PontiacJim1959]

Steve, that's some great work. I recall in my youth back in the late 70's early 80's that the big question amongst the Ford guys was, "Do you have the Cleveland heads or Windsors?" If you wanted to impress, it had better been the Cleveland heads. LOL I was generally a Pontiac guy and the only Ford product I can recall I owned was a 1973 Mercury Capri, 2600CC V-6 4-speed with headers/duals. I believe the engine had been worked over as it sounded like a Ferrari and it ran like a scalded dog - until I over revved it and spun a bearing.

I recall that the Boss 302 heads were actually too big for the street and did not perform well - which may have been the initial design? Then changes were made that improved them. I never saw a Boss 302 in my neck of the woods as they were rare to begin with. We did have a '67 Shelby KR500, and another guy had one of those white 1966/67 427/4-speed Fairlane 500 with that unique fiberglass center hood scoop hoods. I knew what the Shelby was by its reputation, but had no clue what the Fairlane was back then - it was just some old Ford. LOL

Now you may laugh at this and think me crazy, but what if you took one of the KRE or Edelbrock heads with the larger 2.19" intakes, had it hogged out to flow 330-340 CFM's, and then played around with adding the clay to shape and contour the intake passages to increase the velocity and maintain a maximum amount of flow as you did with the Boss heads, BUT, aim the heads for use on a 400CI, 461CI, and 455CI street engine. This would mean cutting the CFM's down, but with the hogged out heads you would begin with, you could then shape those intake runners to drop them down so they flow let's say 240-250CFM's, but the velocity would be kept high and give the engine that kick in the pants when you nailed the gas, but would not run out of steam at the top end - let's say an RPM range of 2,000 - 5,800, basically a stock RPM range, and limiting the valve lift near .500" - .520".

Could the exhaust ports be recontoured like the big block Chevies with the D-port that takes advantage of the anti-revision properties? Possibly create a "round port" for the intake runners by adding the clay to the hogged out runners?

I realize that this can all be done with just improving a stock iron head through porting/bowl work and contouring it, but, could having the liberty of experimenting with shaping the large intake runners/bowl of a 320-330 CFM head into different configurations produce a better velocity within the intake runners and a higher flow rate over a much broader and useable RPM range than simply porting a stock set of 2.11" heads?

Just food for thought.

[steve25]

Stan and Jim ,I have to apologize to you both as I can not get the flowtest done I promised you both since one of the motors in my flowbench has crapped out on me yesterday, but I have a new one coming in tomorrow and will install it and get back on track by maybe even Friday morning.

Jim what you describe is part of the porting game that is done with heads used in the Super stock classes all the time, as if you do not, then chances are very good that you don't win!

It's called redundant port area and folks in the know work like mad to keep the port velocity to the level they want while filling in redundant port area is 1) it hurts power and 2) since your limited to a certain amount of port CCs you want to have those CCs to work with and enlarge the port(s) where you pick up the most flow gain of course.


Jim here are the flow test results from the stock Ford 4 Bbl Boss head ( only 1 port tested) and the ported 2 BBL M head.
Please note that the minimum port area in the 4 BBL head 3.56 sq inches, the ported 2 BBL head is 3.24 sq inches, or some 10% less!

Once again the valve size difference is 2.19 for the 4 BBL head, and 2.10" for the 2 BBL head.

Both heads have a 45 degree seat and the 2.10" valve in the 2 BBL head has a 32 degree back cut.

The stock 2BBL head peaked in flow at 205 cfm @ .600" .

Flowtest results, first the stock Boss 4 BBL closed chamber head.

.100"....200"....300".....400"....450"....500".... 550"....600"....650"....700"
49.3---131.6--197-----243-----258----265.9--270.5---279.6--285.7----288.6

Ported 2 BBL head.
71.9---154----226----271.3----278.5---286.6---290
Flow gain seen over the stock head with its 2.05" valve.
3.4----11.8---37-----72--------79-------87------90

This is a classic example of how superior port shape can make for a killer head with no down side if the motor is geared and Camed right!

As most of us know Pontiac made the dam same mistake as Ford did by trying to run the RAV heads on a 366 cid motor no less with the 303 cid motor!

The only thing back then that kinda saved the 366 motor was the swap over to ported RA4 heads, and even then it was too late!

I very much wish someone would interview a Pontiac engineer who is still around and was involved or close to being involved in the RAV development program and ask them what they where thinking back then when they seemed to have known better then to go off the cliff as they did !

Also Jim of interest to you might be that the stock Pontiac D port end Exh ports in a high comp head and there 1.77" valve can be ported to a 240 cfm flow level, and with header who's flange is 1/8" bigger the the Exh port exit have little reversion issues, in fact a head inlet like this will pick up the Exh flow another 4 % above .400" lift!

[PontiacJim1959]

Steve, no rush on anything. Once you are up and running, just keep posting and I'll keep reading and commenting/questioning.

Quite a difference out of those ported 302 M heads over stock and the Boss 302 4Bbl heads. Is there an advantage over the 45 degree valves versus 30 degree? I assume the valve curtain area might be different where the 45 curtain might be directed/concentrated "more" downward while the 30 degree might be directed wider/broader in its valve curtain area? If so, then in my mind the narrower, but more concentrated 45 degree valve curtain area could be better applied to a smaller cylinder diameter, ie a 302 bore vs 460 bore? Kinda like what has been mentioned where a chamfer is needed in the cylinder bore of the 350 to benefit the larger 2.11" intake valve. That said, would a 45 degree cut on the 2.11" intake have benefit in the smaller bore 350 whereas the 30 degree is a better choice on the 400/455 bores due to a wider curtain area that can be utilized by the larger bore? Am I making sense?

In porting those M heads, are the walls ported to within a hair away from busting through any water jackets? I see that some guys will port that much, even bust through, then fill/seal the break, but they are for racing and I assume would not last in a street engine where heating and cooling could easily crack them.

I imagine the thinking on the RAV heads on the 303 was for the track racing circuit where you want to take advantage of higher RPM's. I think Pontiac learned like Ford did with too big of a head on the smaller engine. Would have been interesting if the same kind of treatment was given them as the Shelby team with the Boss 302 head in the Hot Rod article. May have been a completely different animal.

I know that you can also damage port flow if you are not familiar with head porting or grind in the wrong areas. I basically followed Jim Hand's book (Pete McCarthy's video) with some of it and opened up the throats using the valves cut down as templates. Nothing fancy. I did not do any contour shaping in the intake ports other than open them up at the gaskets for RA IV size and blend them in about 1/2" or so and cut a little on the pushrod bulge.. Used a snap gage to get them all the same sizes. I won't know if it'll improve performance in a big way, or if I hung myself. I have not had them flowed, so just winging it with fingers crossed. My machinist liked them and said they should flow real well as they do port work but no flow bench on site to test their work. I may at some point get one of the ports flowed just for curiosity sake to see where the flow/lift number stops.

My goal is to fabricate an old school looking tunnel ram like the Nash. I gotta have a tunnel ram for my project build - its a late 70's - early 80's look thing. The Gutsram tunnel ram is not what I want as it is too boxy and looks more like a 1990's Pro-Stock intake and not the Weiand look I am after. But, I won't get to that point until my car is closer to completion and the engine is assembled and near ready to be installed. It is a work in progress - just like me a 61. LOL

[steve25]

Hi Jim!

wallace racing has a nice calculator for figuring out and seing changes in valve curtain area, have you used it?

Seat angle wise in my opinion you always want to run what gives you the best average flow numbers in the lift range you will be popping the valves open in.

A 30 degree seat will always provide better low to upper mid lift flow ( about .350" lift) then a 45 degree seat, but in terms of ultimate high lift flow a 30 degree seat will limit the ultimate size of the throat you can use as compared to a 45 degrees seat , so the flow needs have to weighted out.

A good starting point for a tunnel ram on Pontiac is a Weiand one made for a Mopar 383/ 440 motor if you can turn one up.

I got my new flowbench motor yesterday so on the weekend I will get back to getting the flowtest done and posted up.

[steve25]

Jim, here's mostly the flowtest results you where asking for.

Unfortunately I thought I had a 2.11" 45 degree seat valve with no 30 degree back cut on it to test, but I do not, as such the 2 flowtest here show a 2.11" 45 degree seat in a ported 1970 #13 D port head with no cut down stem, and then the second test with a cut down stem.

Test 1, no stem reduction.
.050...100"...200"...300".....400"...450"...500".. ..550"....600"...650"...700"
33.2---66.3--136.9--200.7..251.6---=----=-------=------=------=

Test 2' with undercut stem.
33.4...67.8--138.2--202.7--252.4--266.3--269---272---276---279

Now I have to set back up and get the flow test done that Stan wanted to see.

[PontiacJim1959]

Steve,

That works. It does show a flow improvement by a small amount in just using the undercut stem. That said, the undercut stems seemed to be favored over straight stems when reading magazine articles, but with the small amount of improvement, I am not sure it is worth paying extra money to upgrade to undercut stems for a street engine unless it is possibly in saving some weight off the valve making them a little lighter for higher RPM applications.


Those are some good flow numbers from an iron head looking at the where the .500"/.550" numbers are which is what I consider more in the range of a "street/strip" cam lift - my opinion.

I looked at the Wallace Valve Curtain Calculator and played around with it.

I'll be following along on Stan's question.

[steve25]

Jim I which I could have shown it, but a 30 degree back cut on the valve provides a much greater flow gain then does the necked down stem .

[PontiacJim1959]

Originally Posted by steve25

Jim I which I could have shown it, but a 30 degree back cut on the valve provides a much greater flow gain then does the necked down stem .

OK, I can see where that would allow additional flow. So the under cut would not be a "big deal" for additional flow, but when combined with the 30 degree back cut, then we see improvements. Hmmm. I could see the combo being used in a magazine article to promote the undercut stem when in fact the 30 degree back cut was doing all the improvements. Magazines promoting a specific brand of valve wouldn't mislead us with such trickery, would they? LOL

[Skippy597]

Wow, there is so much good info in this thread, I'm saving it for reference.

I just built a 350 with big valve 16 heads and a small summit 2801 cam so was curious about the combo, looks like I'll be fine but I am running 1.65 rockers but still should be fine.

So to revive an old thread what's the thought on notching bores for more power on pretty much anything? Seems like a 400 with big valve heads would still benefit greatly from the notches but I don't remember reading this anywhere else and don't know of anyone doing it.

[rkraczek]

I just built a .030 over '68 350 with unported #16 big valve heads with a summit 2800 cam. Runs great with good street manners with that small cam. Going to take it to the dyno for a baseline run once I get the q-jet dialed. Compression calculators put me around 9.7-9.8:1 static and 7.8:1 or so dynamic for anyone that cares. Block is zero decked and the heads were milled slightly for cleanup. New valves and positive seals, stock valvetrain. 1 5/8 headers with Pypes x-pipe 2.5 inch exhaust. Running Felpro 8518 head gaskets.

[Jack Gifford]

An engine I ran early in my mini-pulling was a '58 bored 1/16" over (381 c.i.) with unported #16 heads and alky through a 4-port Hilborn on top of a tunnel ram. It worked well for me up to 7,200 RPM with a mild flat tappet cam. Heads were milled to give 10:1 c.r.

[srmmmm]

My build was based on a 1970 350 block with chamfered cylinders bored .060 over with an Eagle 4.25" crank. I have 1977 6X-4 heads from a W72 option 400. Calculated CR is 9.13:1 with Ross flat top at even deck height. Edelbrock Torker I with the stepped plenum floor and a Q-Jet for a 1971 Buick GS455 Stage-I (my roommates at General Motors Institute worked at Rochester Products and got me a spare carb for his GS at factory cost, $52 in 1975!) with Stage-II modifications. Comp Cams XR276HR with Johnson rollers and 1.5 ratio Comp roller rockers (.502 / .510 lift). The Johnsons worked with the factory valley pan.

Built by Len Williams in Tulsa - he had no problems with valve clearances at all but did have significant machining to get all the valve spring seats at an even height. The two problems encountered dealt with the original cam kit from Comp - some of the Comp roller lifter plungers were seized in the body and the push rods weren't the correct length.

Headers were 1-3/4" X 30" Hookers. 34 degrees advance at 3200 RPM.

Power goal was 1 HP per cubic inch. Three problems showed up on the dyno - secondary air valve spring was binding causing the air valve to suddenly snap open, secondaries were running way to rich (bsfc of .544), and the tach signal coming off the MSD distributor was not clean enough for a steady read. After eight runs, the tech finally plugged in what the actual rpm was along the curve resulting in corrected numbers of 442 Lb Ft @ 4600 rpm and 453 HP @ 5600 rpm. Even though the 350 has a small bore, the larger valves really let the engine take advantage of that 4.25" stroke. Restoration on the car is supposed to be done by the end of March - fingers crossed.

[gtospieg]

Interesting thread...I'm running a 350HO ish engine in my 67.... '69 block from a '69 Lemans and '69 48 heads. The block code is XS. I get some interesting questions about that when someone KNOWS what an XS block really is.

[PunchT37]

A 265 hp 350?
http://wallaceracing.com/engine.htm

[SD455DJ]

Originally Posted by PunchT37

A 265 hp 350?
http://wallaceracing.com/engine.htm

As in '66 RA 389 engine.

Dennis

[gtospieg]

PunchT37.... yes it started life as a lowly 2bbl 350.
SD455DJ yes...it appears to be a 66/67 RA HO 4 speed....mine does have RA
Best is 14.38 @98.11...3860lbs with me in it