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Love some help in choosing the right intake set-up..

Question

Hi all..I'm finally gonna try to get my ol' ragtop back on the road again... Many years ago I converted my 350ci.(freshly rebuilt) from 2bbl. to a 4bbl. intake set-up. I drove the car for about 10k miles then put the car away...30 or so years ago. The engine, I feel never really ran as well as it should.



i will explain what i know:


Engine bored .30 over, (just over 10k now)


Ram Air IV cam (no info)


high perf. valve springs with threaded studs and lockers.


later model 4bbl. stocker intake ('70-'73)


Big quadrajet service replacement. Pt.# 7041263, ('71 400 manual tranny.) with a divorced choke setup.


Auto tranny turbo 400.


Future projects; factory cast iron exhaust manafolds and a differential with 3:08 gears.


Ultra Dyne cam. thats best suited for this engine ( I was told ) I have all the specs with this cam.



I just recently put a gasket kit in the carb over the winter but I dont know if I should use it. I did not look at the jets and rods numbers.


I remember this engine as loping rough idle. and not alot of low end..but the mid and high were quite fast.


Any thoughts on this to make any improvements? I want everyday driveability but some fun under the pedal.


Please help me get this girl back on the road!


Thanks for any and all input.


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With what you describe it sounds like your motor likes to rev a bit. I would go with something like the Edelbrock RPM intake. This will be good from 1500 to 6500 and just wake up the motor a bit. For a carb I would not go any bigger than about 700 cfm.



http://www.summitracing.com/int/parts/edl-7156/overview/make/pontiac


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You have a choice to make on your intake. The factory intake is very good for street use over the Edelbrock RPM, but the Edelbrock is better in the higher RPM range, which is probably where the car won't spend a lot of time. My opinion is to stick with the stock intake manifold and save the money. notallthere is spot on about keeping the carb to 700 cfm.



I think the real issue lies in your valve train, mainly the camshaft profile and its matching components. The RA IV cam was designed for the performance wars. The advertised intake and exhaust durations are 308 and 320 degrees, respectively. At .050 inch lift, the durations are 231 and 240 respectively. The lift is .47 inches using a 1.5 ratio rocker. So the cam profile moves the power/torque band into the middle and high end rpm ranges.



You said you have an Ultradyne cam, Here are some of their cam specs. So I would check your cam specs against this table to see if you have a good street cam. Also are your springs, lifters, rockers and push rods matched to this cam?



AID AED ID050 ED050 IL1.5 EL1.5 Application Notes


254 262 199 207 0.40 0.43 Mild street cam for 350. Better than stock power & economy.


262 272 207 217 0.43 0.45 Good street performance cam for 350-455. OK with stock parts.


276 286 221 230 0.45 0.45 Excellent 455 performance. Biggest cam for stock valve train.


280 288 223 231 0.46 0.49 Great street performance


288 296 231 239 0.49 0.51 Hot street/bracket


296 301 239 247 0.51 0.53 Hot street/bracket


304 312 247 255 0.53 0.55 Bracket car


272 272 217 217 0.45 0.45 Most popular cam. 350-455. Works with stock parts.





AID Advertised Intake Duration IL1.5 Intake Lift, 1.5 ratio rocker arms

AED Advertised Exhaust Duration EL1.5 Exhaust Lift, 1.5 ratio rocker arms

ID050 Intake Duration @ .050" lift ED050 Exhaust Duration @ .050" lift

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Sounds like a neat project. Good luck


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Thanks for the helpful replies here so far...


My Ultradyne cam specs are attached, it appears to be close to the one listed at the bottom of the list.


So far the concensus is to get rid of the 800cfm carb. One thing I noticed with the carb is a St.steel (thin sheet) shim between the base gasket to intake. I'm not sure of its purpose but I think its some sort of heat sheild/sink but it was not sealing well as its got signs of blowby leakage which of course caused the rough running issues. Hell, I dont know why I need it?


So now Ive got some thoughts to ponder.


Get a smaller carb? I would need to find one with a divorced type of choke I believe.


Install a Edelbrock dual plane that I bought years ago? (P4B). Its been mentioned here that its not the best for low end.


I didn't mention that my heads are a casting number #47..Any issues with these?


And finally, would it be wise to install my set of factory cast R.A. style exhaust manafolds?


Thanks again for the replies as its giving the bug to get her on the road again.




post-2401-0-64194100-1427383472_thumb.jp

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Based on your cam profile, it would appear your cam is the third from the top - the excellent 455 performance cam. All Pontiac 326-455 except the 265/301s are externally the same dimensionally and only vary by the bore and stroke combination. So this cam will work with your 350 motor.



The #47 is the base head for the 350 V8 in '69. It has 1.96" intake valves and 1.66" exhaust valves and the motor has a compression ratio of 8.6:1 putting out around 265HP with a 2 bbl carb. The 350 V8 with the 4 bbl and #48 head was rated at 325HP, featured a more desirable 2.11" intake, 1.77" exhaust and a 10.4:1 compression ratio. So most stock Pontiac heads with a 2.11/1.77 would be more desirable over what you currently have, from a performance perspective that is. That said, I assume this is the original, numbers matching engine and heads? So keeping them together maybe more important to you. I can respect that.



Talk to an engine builder, and ask him if your stock heads can be machined to 2.11/1.77? If so, do it. Get a mutli-angle valve job and spend some money on a quality porting job and gasket matching work. All will do wonders for performance and economy of your motor. Do you know if you or someone else has installed harden valve guides to make up for the lack of lead in the gas? Also do you have harden valves for the same reason?



The RA manifolds are the best stock Pontiac exhaust manifolds they made, so if the manifolds match the shape of your exhaust ports, by all means use them. They are more efficient than the stock log style exhaust manifold to be sure. Ram Air Restoration makes accurate reproductions too, if you need them.


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Thanks...the heads are the original 2 bbl.heads and were rebuilt prior to the use of unleaded gas. So for now I will have to stick with them.( only 10k after the rebuild as I stated earlier) But I will eventually get some machine work done on them. Im looking for some "instant gratification" so I'm going to put the fresh gasketed 800cfm back on and see how it runs with no vacuum leaks. I've also been worried by some folks saying that Pontiacs tend to leak oil at the rear main seal area after they've been sitting for a period of time. I guess we'll see the outcome after the start-up. It just may be that I'll be ripping into this mill more than I want too but that's life.


So, all in all, I'm thanking you Frosty and others for taking the time to follow up on my questions here....I will return

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The stock Pontiac rope seal breaks down somewhat when it sits for long periods of time without running. It can be annoying drips under the car to a major leak. There is a new aftermarket seal - BOP's Viton rear mail seal that is suppose to not leak. So evaluate what is going on with your engine before you determine you have to replace the rear main.



If you do tear into the rear main, also inspect the front main timing chain over while you are at it. Mine was leaking. They don't always, but check it while you are doing.


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Thanks Frosty, I will look it over(under)...You also mentioned "Also are your springs, lifters, rockers and push rods matched to this cam?"


Can you please explain that as well?


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Often times, camshaft manufacturers will build a cam with a certain valve train geometry in mind. This means their cam shaft design incorporates the specs of their cam along with the characteristics of a specific spring pressure and height of the springs, the length of the push rods, the type of lifters (hydraulic, solid, or roller) and the height/shape/ratio of the rockers (1.5:1, 1.6:1 are typical ratios). So everything is designed to work in concert with each other to delivery the optimal performance for the RPM range it is expected to work in. This is especially important in a hi-performance/race application.



So from companies like Comp Cams, Melling, or Crane, you can buy the entire valve train: cam, lifters, push rods, and springs as a complete kit. It costs more, but you know that all these parts are designed to work together in your engine.



From what you've said, I suspect you are running the stock Pontiac push rods and springs, which is okay, so long as your cam/lifter combination will work or is designed with that in mind (and the springs and push roads are not worn out or bent). Ultradyne has several cam combinations that clearly do work with the stock valve train.



As I often say in this forum to guys, do your homework. If you want to run a certain part or parts, what else does it impact and what else might you need to change to allow it to work optimally? Engine mods are especially touchy subject since something like the cam will dramatically impact how the engine performs.


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Thanks for the advice on that issue...I will have many more questions in the future regarding this project. Still going thru my checklist of preparing engine for initial startup. 30 years of water in the block sure can get rusty! I'm preparing for the big "flush" of the block.


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Glad to help. Be sure to flush the radiator and heater core.


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