Tailgate porting..

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Re: Tailgate porting..

Post by Old as Dirt » Sun May 10, 2015 12:53 pm

rfoll wrote:Yes it was also pretty nice here yesterday. I think the cam says you should have a bigger carb. A 3310 750 or 780 vacuum carb would work very well. Common carb and cheap to acquire. Just add lighter springs to the vacuum pot to quicken the secondary opening as needed.
Found the 4777 on Craigslist for 60.00.. had it gone through/new gaskets and made sure it wasn't modified.. guy I bought it from had flooding problems(crap in the NS) and was tired of messing with it.. guy that did the work runs a 400SB with a Team G intake/830CFM Holley and a 236*@ .050 Cam.. I trust he did it right.. may try a 750 DP down the road if we change the intake to a Single Plane setup.. according to "PipeMax" the required CFM is 648 @ 5400rpm.. so yep, I could see it as being a bit restricted up top..
Last edited by Old as Dirt on Sun May 10, 2015 1:24 pm, edited 1 time in total.

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Re: Tailgate porting..

Post by F-BIRD'88 » Sun May 10, 2015 1:23 pm

A750 hp carb body kit will hotrod that 650 carb.

high cr... use cooler non projected tip plugs luke champion Rv8c in those heads.

Cam may want to even be further advanced on install to max torque.

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Re: Tailgate porting..

Post by Old as Dirt » Sun May 10, 2015 1:47 pm

F-BIRD'88 wrote:A750 hp carb body kit will hotrod that 650 carb.

high cr... use cooler non projected tip plugs luke champion Rv8c in those heads.

Cam may want to even be further advanced on install to max torque.
I'll check into the plug you mentioned.. these heads require a short reach gasketed plug.. have a set of AC R43's on hand to try(little colder than the R44's), and can advance the cam some as the PTV is good, even with the thin head gasket.. like 3.7mm(.145) intake and 3.2mm(.126) Exhaust.. used checking springs to see what it was while degreeing the cam.. didn't have a cam card with the shortblock and the owner didn't have a clue as to the specs.. so I went about it blind.. according to my readings(only had a metric dial with 2" travel) after converting from MM to Decimals the open/close @ .006(.16mm) at the lifter(off the top edge) and .050(1.28mm) numbers all pointed to the cam being a Comp XE294H.. installed on a 106 Intake CL.. came out on the money.. just had to do a lot of playing around with the degree wheel.. Run the drill motor to lube the engine.. check, take readings.. check, write everything down.. check, LOL.. I think I seated the rings already.. :mrgreen:
degree the cam.jpg
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Re: Tailgate porting..

Post by user-612937456 » Sun May 10, 2015 2:10 pm

A mellings Gm L78 (360-327) cam copy for $60.00 at auto zone would be a huge improvement if you are under a tight buget

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Re: Tailgate porting..

Post by Old as Dirt » Sun May 10, 2015 2:41 pm

gvx wrote:A mellings Gm L78 (360-327) cam copy for $60.00 at auto zone would be a huge improvement if you are under a tight buget
I thought the "L78" was a 396/375HP BB?
You thinking L79?

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Re: Tailgate porting..

Post by MadBill » Sun May 10, 2015 3:09 pm

Here's different 'element' to consider (probably too late now, but...), living as you do in the "North Wet" Iron dust is highly corrosive to paint when it gets damp. My '70 1/2 Z28 still shows the etchings from pocket porting the heads in my driveway when it was less than a year old.. #-o
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Re: Tailgate porting..

Post by Old as Dirt » Sun May 10, 2015 3:22 pm

MadBill wrote:Here's different 'element' to consider (probably too late now, but...), living as you do in the "North Wet" Iron dust is highly corrosive to paint when it gets damp. My '70 1/2 Z28 still shows the etchings from pocket porting the heads in my driveway when it was less than a year old.. #-o
Oh Crap.. the wife would kill me if the paint on her new Camaro went south.. hope I did enough cleanup with the shop vac.. yikes!

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Re: Tailgate porting..

Post by lada ok » Sun May 10, 2015 4:44 pm

Re: How much difference?
Postby lada ok » Fri May 08, 2015 11:53 am

If you spent 3-4 hrs with a variable speed grinder ( wood router ) ... put a 1/4 " radius, ( that's 1/2 " on the diam ) using 1 " +/- flapper wheels of different grit, on what is the top side of the runner, use a 1"+ .. spacer block that matches the carb base and the mani and air corrector bells on the top of the carb, throw away the choke butterflies and spindles, and there we are, let us know how it goes ( and plug and smooth the spindle holes )
lada ok

Keep in touch and let esp HP / TQ / track times etc us all know how the project goes ,

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Re: Tailgate porting..

Post by user-612937456 » Sun May 10, 2015 5:22 pm

Old as Dirt wrote:
gvx wrote:A mellings Gm L78 (360-327) cam copy for $60.00 at auto zone would be a huge improvement if you are under a tight buget
I thought the "L78" was a 396/375HP BB?
You thinking L79?
Yes it was a mis-type L 79 GM part #3863151 almost the same grind as a later model SBC L82 camshaft with a little more intake lift GM Part #3896962, or get a better induction to take advantage of the cam and porting job you are doing

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Re: Tailgate porting..

Post by Old as Dirt » Mon May 11, 2015 12:58 am

Thoughts on changes.. would you work in this direction with a wider floor with smaller radiused corners like the right side?

What about the guide? Make it less of an angle and eliminate more of the bottom, but still leave enough for support?
441 porting changes.jpg
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Re: Tailgate porting..

Post by Biteme » Mon May 11, 2015 6:49 am

I'd take it from the roof, as long as you leave enough meat for the studs.
I'd square up the left side but leave a bigger radius than on the right.
And I'd take at least 40 thou off the dividing wall, right through to the bowl.
And I'd take a lot more off the guide boss.
How thick is the wall against the pushrod? Take it down to 60 thou.
Then I'd look at the short side, which is where the fun begins :-)

Make up a tester by hooking up the wife's vacuum cleaner to something 4" round. Then suck air through the port (with the valve in). Then hang ribbons into the port while it's flowing air at various lifts. This'll give you an idea of where the air wants to go. DONT try to make the air move into an area it doesn't want to go, just give it more room to move where it does want to go.
Hope this helps. I'm no pro but this is what I've done a couple of times and both motors went well. :D

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Re: Tailgate porting..

Post by Truckedup » Mon May 11, 2015 7:40 am

I say since you're already into the job then just continue on..If it makes an improvement you will know the truth..If the porting makes less power than you can say nothing and no one will know but you... :D
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Re: Tailgate porting..

Post by rfoll » Mon May 11, 2015 9:54 am

The L79 cam is stone age technology, and about as fast as a stone rolling down the driveway. Oregon cam grinders in Vancouver WA, ( http://www.oregoncamshaft.com), will regrind your existing cam to nearly anything you want for $70. Click the red button on the bottom of the home page to go to the list of patterns he has available.
So much to do, so little time...

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Re: Tailgate porting..

Post by BigBro74 » Mon May 11, 2015 10:23 am

we have all been there trying to make stuff work- you have enough stall and gear it wont be too bad if I read correctly (4.88- 3600rpm) keep the octane up somehow and use cool plugs. keep the engine temp down.

the one thing (if it were me) that you could do really easy is find 1.5 rockers and run them on both sides. the cam is too big already and the 1.6's will make it "act" bigger. could maybe even find some "variable duration" type hydraulic lifters to Band-Aid the situation like crane hi-intensity or (gasp) rhoads (sp?). they are not ideal but would be good in your situation. the cranes actually work pretty good but you may have to call- not sure if they still catalog but when last I called they still had them. a friend used them in a similar situation and they work pretty much as advertised....

you could also use an ignition advance curve to your advantage in this application.

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Re: Tailgate porting..

Post by F-BIRD'88 » Mon May 11, 2015 11:07 am

You don't need a different cam or noisy- leaky fubar lifters.
The cam is fine. It just may (or may not) respond a bit by optimizing the installed C/L.
A BIT....requires measured testing to see if any real perf gain loss. "fine tuning"

It will go fast. The more you improve the heads the better.

I assumed those heads had the "peanut plug" . Yup if it has the older spark plug type
then choose accordingly A bit cooler than stock like a NGK 7 number, non projected.
Any brand will do. Autolite has a good plug cross reference online tool.

I like NGK AC delco and Champion.

Like said keep it cool and be sure to feed it the coldest possible air to the carb.

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