Alright folks, I've got a good one for you. I am rebuilding my High School car, 1987 Pontiac Trans Am with a 305 bored .40 over. Forged pistons and new cam already installed as well as a 3.75 crank totaling 335 c.i. I am currently porting and polishing the heads, 081 casting, and I need information on valve sizes. My research has found the optimum setup would be 1.94 intake and 1.60 exaust. I need to verify that before I go on. Max streetable HP with stock 305 is the goal. I know, I know, save the money and get the 350. Can't do it. I had this car in school before I joined the Navy. It sat idle for over a decade while I was gone, now she's coming back. I want the stock "looking" car and motor with a suprise fire breather underneath.

 

I'd agree that's about as big as you would want to go with the valves on a 305. DON'T just chuck in larger valves and seats- make sure you do the bowl work necessary to work with them or you might actually make the situation worse.

 

Thanks for the heads up. Where can I go to get some specific guidance on the how to's of good bowl work?

 

what the heck is a super stroker? Similar to a super soaker? for about 50 bucks more and the same amount of work I think I'd take a 383 and still have the "stock" look.. but than again that just makes too much sense..

 

Now that we have that out of the way, do you have any advice for what I am actually doing?

 

Ill only say it once, i promise. There is absolutely no difference externally in appearance between a 350 or 305. The only way someone could tell you installed a 350 is to run the numbers. Im not saying you should lie and tell people a 350 is a 305 either. Aside from all of that, I would recommend that you not go to radical on the camshaft. Due to the smaller ci, you are going to be pushing yourself farther up the RPM ladder. Stock crank and rods could mean trouble. At the minimum, use good rod bolts and upgraded fasteners through the bottom end.

 

I upgraded the rods when I stroked the engine and had arp bolts installed.
Here is the cam data.
DURATION @ .050 INTAKE 224 ROCKER ARM RATIO
VALVE ADJ INTAKE .000 DURATION @ .050 EXHAUST 231 INTAKE 1.50
VALVE ADJ EXHAUST .000 LOBE LIFT INTAKE .3180 EXHAUST 1.50
VALVE LIFT INTAKE .477 LOBE LIFT EXHAUST .3200
VALVE LIFT EXHAUST .480 LOBE SEPARATION 108.0
DURATION .006 INTAKE C/L 106.0
TAPPET LIFT INTAKE 267 ADVANCE 2
TAPPET LIFT EXHAUST 280 HYDRAULIC Y
VALVE TIMING .050 OVERHEAD CAM N
VALVE OPEN INTAKE 6 JOURNAL DIAMETER STD 1.868
VALVE OPEN EXHAUST 45 RECOMMEND VALVE SPRINGS
VALVE CLOSED INTAKE 38 DEPARTMENT P
VALVE CLOSED EXHAUST 5
Also I used ARP studs to mount the crankshaft. What do you think?

 

Ok, why don't you just say Comp xe268H? It's one of the most common SBC cams used...
That'd work just fine. I thought you'd have a roller block though? If so, use a roller cam.

 

Bowl work = professional porting. Or at least semi-pro! If you've never used a die grinder and ported a set of cylinder heads DON'T try this on your good heads- you're guaranteed to screw them up the first time.

 

OK. Pro work it is. Any more ideas on how to make a mean streetable 305?

 

i got a few...(looks in sig...)

 

I've got a couple 305 cars running also.
There's nothing in the world wrong with them.
I get great mileage, sound, and as said above, "They look the same".
I'm building a third 305 with LT4 cam, 1.6 rr, SR Torquer heads, Eldebrock TPI intake, SLP runners, and a few other things.
It'll run good enogh for me.

 

Kudos Firetag. 305's are a great engine. Let the crowds complain, it keeps our shortblocks cheap.

I too am fixing up my high school ride, with a TPI 305. It's in a 79 Malibu, but they bolt up just the same.

I used new Vortec heads, modified with beehive springs from Comp, and a Comp 262H cam. I have yet to really test it (T5 swap in the process), but when I did run it with a questionable automatic transmission it felt pretty stout. Vortecs I believe have 1.94/1.50 for valves.

I read a while ago that TFS came out with some 305 heads. That may be worth looking into. Especially since modifying Vortecs or any stock heads quickly approaches the price and simplicity of new castings. Or is the idea to keep the entire long block?

Is this a TPI, TBI or carb engine?

You could always add a turbo by the differential for a real treat!

 

if you wanna know how to do a really quick "street" 305, look in my vBGarage.

 

What sort of work did you have done to your heads?

 

mild bowl blending and backcut stock valves, everything else is just supporting mods for the camshaft and stuff, comp 981 springs, screw-in studs and guide plates, etc...

 

There are three head castings that I would use for a 305, I am going to list them in rank of power generated

1.) L30 305 Vortec head 059 casting (1.84/1.50 valve, 56cc chamber)

2.) 113 Aluminum Vette ZZ4 casting (1.94/1.50 valve, 58cc chamber)

3.) 14022601 HO Truck/Van 305 head (1.84/1.50 valve, 53cc chamber)

People have also used the 906/062 L31 Vortec head castings after milling them down.

I am still running TBI swirlies on my very mild 305 TPI.

 

Just port and polish. I am considering having someone do some bowl work to them because of some of the replys that have been posted.
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Nice Ride mw66nova. I think I am going to copy some of your stuff. What size intake and exhaust valves are in your heads?

 

stock 1.84/1.5 valves with a backcut.

 

What do you think of putting 1.94 intakes and 1.60 exhaust in 081 casting?

 

That seems awfully big for a 3.76-3.8 bore. Won't that give you around 0.25" to divide between the cylinder wall and valves. I'd almost think that would hurt more than help.

Just a thought.

 

I have read that you can go as high as 2.02 but that is counter-productive. Articles from hot-rod mag online say ideal is 1.94 and 1.60. Anybody done this before? Does the math make since?

 

NHRA stock eliminator guys are limited to stock 1.84/1.5 valves and are running high 10's. i simply don't think that the valve size is the issue here. i have run a 1.94/1.5 combo before in a set of 113 heads and the best ET i got was a 12.31@108mph in perfect conditions. they do help, but unless you're running something crazy, i don't think they're worth the time. if you can get a set of 113's, i would go with them over the 416's or 081's.

 

If I was going to put larger valves in a 305 head to be used on a 305 motor
I would go with a 1.94x 1.56" valve set max. 1.94x 1.50" are fine.

If using a modified 305 head on a 350ci motor the 1.94"x 1.60" valve set combo is best. 2.02's add no flow advantage over the 1.94 valve on these heads when thye are ported and weaken the casting between the valves too much to be worth it.

 

I think two excellent size combinations for a very strong 305, without risking overkill or problems, are 1.90/1.55 and 1.94/1.50.

The way I see it, simply because of your cam's longer durations and the new stroke, the need(and risk) of extreme increases in valve sizes should be offset.

I think 1.90/1.55 will be the best fit, not tight and risky like 1.94/1.60, and there would be strong improvements in flow in both directions over the stock 1.84/1.50. And with your "stock lift" cam's longer durations, not to mention the stroke, the entire package would "act" like it's a lot larger, giving you a strong punch in hp, with an even stronger punch in torque. And that's what the 305 needs more of: torque.

On the otherhand, since you'll be gaining an increase in torque anyway(simply because of the new stroke), there might be no need to increase the exhaust valve size at all, staying at 1.50. So if you think your newfound stroked-torque will be sufficient, and you simply want to add power, then only increase the intake size to 1.94.

I suppose if it's possible to get the best of both, without risking fit or overkill, then 1.94/1.55 might give it to you. But like 1.94/1.60, I think that might make for a tight, risky combination.

So personally, I think the 1.90/1.55 combination, along with that increased stroke, giving you a stronger increase both ways, would be the best. But that's just my

I like your project. Please post some videos when you get the engine up and running. I'm curious to hear it. And keep us posted.

 

I saw an exhaust thread where you're in search of your exhaust system. And in this thread you're covering the engine. But what plans do you have for your intake? And unless I missed it, I don't recall you mentioning what kind of intake your TA has, carb or TPI.

I see it's a 1987, and you want it "stock looking," which I'd guess means it's TPI. If so, and you do nothing else to the stock set-up, you should, at least, change the stock air box. The 1985-1987 air box was the absolute worst! If you don't do something custom, then, at the very least, you'd benefit by swapping it for a 1988+ set-up(if you can find one).

And I'm sure you've already thought about all this, but I'll mention it anyway... then there's the MAF, throttle body, plenum, runners and intake manifold to deal with. You could prolly get away with keeping the stock set-up, but even a 305 will benefit by improving all that. Afterall, since your worked heads and motor will be capable of handling more airflow, you might as well plan to, eventually, have an intake that can deliver it.

 

LAFireboyd, the engine has the q-jet carb on it now but I want to put a holley or edelbrock on it. I have not yet decided on which one. I do want to upgrade the intake and the best review I have had for my set up is the rpm air gap by edelbrock. Do you have iny input on this? Eventually, I will be putting new heads on it as well. BTW, thanks for your post to my exhaust thread, that's the best input I have had so far. I will post some pics as the project comes along. Right now the entire car is in pieces. I mean the only thing on the body is the fuel tank and the front suspension. Not even a wireing harness is in it.

 

Stick with the q-jet. The Edelbrock would be an unqualified down-grade, and the Holley would require a bunch of changes to make it work, and in the end you wouldn't gain a lick of performance - while losing economy.

 

i had a feeling with the 108lsa he was not fuel injected

 

ms66nova, what do you think about the carb issue?
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Sorry, mw66nova. I get fat fingers alot.

 

depends on purpose. if you desire fuel economy, the q-jet is the way to go, but if you want all out power and easy adjustablilty, then a 650 double pumper would be my only choice. that's what i'm running on my 305.

 

Why was the Edelbrock going to be a downgrade?

 

it's a super easy carb to work on, but lacks in the performance department AND the economy department. it's the carb that people who don't work on carbs put on their cars.

 

So a Holly double pumper is the HP gain way to go?

 

yep. i wouldn't see you needing more than a 650 either.

 

What do I need to know about tuning one and how to set one up?

 

there are some good books out there about tuning carbs, holleys are pretty basic as far as design goes. The main things you need to learn how to do is set the idle fuel mixture, the idle, select and change jets (reading plugs comes in handy), and power valve selection..

 

I'd take a QuadraJet over any aftermarket carb for any purpose. Sure, they're a pain to setup, but once they are the dividends are huge in comparison.

Many hours of R&D have been thrown at them. GM has spent a few more dollars there than Holley or Edelbrock could ever dream of. With the QuadraJet, clearly it shows.

Besides, correct me if I'm wrong, but if you want it stock looking isn't the shiny piece on top the main one people will see before they decode block numbers?
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Wait...1987, is that a CCD carb?

 

scrap the crapajet..oh umm sorry, the quadrajet idea unless you're more concerned about mpg as Matt(mw66nova) said. Drop a 650dp on that 305, tune it and rock on

 

Always heard the 5.0 called the 5.slow back in 'the day', but I'm slowly overcoming that ignorance. Took awhile though =)

 

it still is lol!...f#rd's 5.0(302) was a way better motor than Gm's 5.0(305).

 

Yeah, but Chevy's original 5.0, came out in 1969, the Z/28 rocks both of them out of town.

I'd still go with the Q-Jet. I'm not disagreeing with mw66nova at all, if you are looking for nothing but power, then go with the Holley. But why lose the fuel mileage when the power you'd gain by going with the holly won't be enough to tell the difference in every day driving?

I may have missed if you said this was going to be other than a daily driver and if I did, I apologize, but in my opinion, in this day of $3.00 a gallon gas, is a few extra horses worth losing 3-5mpg? Personally, I'd take 280 horses and 23mpg over 300 and 18 any day because it hits me where it counts. Right in the wallet. But that's just me.

Holley = power
Qjet = best mileage of the three brands and second in hp, mostly because of tunability issues (It's a beeotch to work with and set up)

 

just so everyone knows:

i had a 600cfm vacuum secondary (4150 style though) on my first 305 combo back about 3 years ago. the car ran 13.70's and got ~14mpg in town and could click off 19ish on the highway.

i put on a 600 double pumper and immediately dropped to a 13.2 in the 1/4. i had a 650 main body laying around and i put that on the car and went 13.03 @ 103mph, my car still didn't run the bottom end of the track like it does now. with the 650 double pumper, i was getting 16mpg in the city and 22+mpg on the highway! this was with a 700r4 with a 4000 stall ATI lockup converter and 4.10 gears outback with a 28" tall tire.

the car now has a 4100 stall non-lockup style converter in front of a th350 manual reverse valve body and 4.56's with the same 28" tall tire. i'd be lucky to get 8mpg, lol! but the purpose of the car changed some.

 

OK so I think the best combo will be a Holley 650 Double Pumper. Whats the difference in a lock up and non lock up converter and the advantages of each?