85_305

Yes, a lot of misconceptions indeed. Although I agree with the "No replacement for Displacement" saying, again as dahaus said I am not building a pro-stock/Jonh Force dragster here. I am building an 18-year olds first car

Oh and btw, what all was done to your stroker car if you dont mind my asking? Is all you did was stroke it or no

iansane

From what I understand the worst part about a 305 isn't the 45 less cubes, it's the shrouding of the valve. Especially if you want to run larger valves.

dahaus

First of all, yes there is some concern with valve shrouding, but bigger isn't always better. The biggest and in my opinion is a 1.94/1.5 setup for a 305. If the biggest valves made were the best then people would complain about not being able to put big block valves in a 350. And since we are on the subject of heads. The only aftermarket head worth a damn that I have seen is the World Products S/R Torquer 305 heads. They are cast iron and have 1.94/1.5 valves with a lot more flow than stock. I have modified 305 heads for bigger intake valves and port/polish the runners with success, but I do not particularly recomend this. The stock 305 heads are very weak.

I have heard that Top Line has a set of 305 heads out, but they are going through a ownership change so everything is on hold with them.

Something I want to try is using the Vortech 305 heads on a performance motor. I have see an article, in I believe Hot Rod, where they installed a set of 350 vortech heads on a 305 in a camaro, with great results. But, I know the 350 heads have a shrouding problem on the 305. I wonder, if a person took a set of 305 vortech heads and put bigger intake valves in with some mild porting and polishing, would it be better? Somebody needs to try it. Vortech 305 heads are plentiful and cheap at the salvage yard.

As for my stroker buildup, here is the specs:

.030 bore 305 block
Elgin 3.75" stroker crank
Stock 400 rods w/ ARP bolts
Cast 305 flat top pistons
Note: I recommend you use 305 length rods and the KeithBlack hyperuetec pistons (I can't spell today)
Stock 305 58cc heads with 1.94 intake valves and mild port and polish
268H Comp Cam (Hydraulic Flat Tappet)
1.5 rockers
Weiand Stealth intake
600 Holley carb

Use the recommended rods and pistons, better heads, more lift with 1.6 roller rockers, roller cam, and attention to detail, and you might be pretty close to your goal of 400hp.

You better hurry though. You got me thinking and I might try this combination.

85_305

Thanks for spilling Good stuff. I was interested in a 305 stroker for a while, but I didn't think it would give me enough performance for the price.
But would you take World Products S/R Torquer 305 heads over the Vortec heads?

dahaus

I don't know. I haven't seen any flow tests or examples with the 305 vortech heads. Now, if I were to compare the 350 vortech to the S/R Torquer on a 305, I would pick the S/R Torquer. They are specifically designed for use on the 305

iansane

I may be wrong on this but I thought even the stock 305 heads shrouded the valves? It's just because of the small bore?

dahaus

I don't know all the measurements, but we are talking about less than a quarter of an inch difference in bore size. Yes, you will always have valve shrouding. It is a well know fact that head designs have inadequecies. This is why it is such a big topic. People are always trying to find that extra flow from their heads.

All I can say is installing 1.94 intake valves on 305 heads, with the 1.72 or 1.84 valves, will make an improvement on the dyno. One thing that most machinests do is open up the chamber on the shrouded side of the valve. They will grind out to the edge of the bore. This is common even with 350 and 400 heads. Try grabbing the modifying cylinder heads book and you can read all about these problem areas.

iansane

A quarter of an inch if HUGE amount in heads. Of course it's going to be less than that.

Have you seen such improvments (going from 1.72s to 1.94s) without anything else done? (porting, cleaning, cam change, etc) I can't imagine someone would actually dyno such a small change. I was under the impression those larger valves barely fit within the bore of a 305. I remember seeing a picture of the whole problem awhile back on thirdgen.org tech section. I'll see if I can dig it up.

85_305

1.94's fit in 305's just fine. I believe that's what the aluminum L98's have and they fit fine on 305's

LagunaS3

I had an 80 El Camino with a factory 305 (biggest engine offered for that car in that year). I put a fairly small Comp XE cam in it, Vortec heads, RPM Air Gap, AFB 625 carb, MSD HEI Dist., headers, shift kit, and 3.42 gears. That combo ran 13's. I also know they make a stroker kit for these engines...it takes them to 331 CID. As for the displacement argument, let's remember that 67 Z28 Camaro's are 302's. It was a mixture of 327 and 283 components. So obviously with the right parts small cube motors can sure run...and many to higher RPM's than their larger counterparts. That being said I put a 468 BBC into the car the following year and went MUCH faster.

Zach

BTW. I used the XE cam from Comp instead of a Magnum because of the way the intake ramp works. It basically fools the motor into thinking it has more compression by waiting until the very last moment to throw the intake valves open. So, with low factory compression even with 62-64cc heads, the cam worked VERY well.

dahaus

I have a set of 305 heads, somewhere, that have been modified with 1.94 intakes. If I can find them, I will try to post a picture so you can see what I mean.

And to answer the question about dyno gains with just the valves, no I haven't tried that, and wouldn't suggest that. Here is why.

When you machine the seat for the bigger intake valves you will have a large lip, in the bowl, from the transition of the old size to the new. You must enlarge this area slightly to take advantage of the larger valve. And when I say slightly, I mean slightly. These castings are thin. That is why I suggested going aftermarket, if the budget fits. To add to this, you must also unshroud the intake valve on the cylinder wall side. If you just put 1.94 valves in and don't do anything else, it would probably run worse.

I recently built a flow bench and am wanting to do some comparison tests. Maybe this will better quantify the gains that can be made. We will see.

I do know that I am definately not the only who does this. I read about doing this modification many years ago in a Hot Rod article and many articles since.

dahaus

Iansane, I think I understand your concern now. 350 heads, with 1.94 valves, have a clearance problem on 305s. The valves on 350 heads are a little farther apart from each other. Thus, causing a shrouding problem at the cylinder wall.

SLOW84TA

I simply think making a 305 fast would be a waste before any part for a 305 would be the same for a 350 as they are mostly the same. So why not spend the same money and have the 45+ cubic inchs. Much more power poltentional. You can find short blocks so cheap. So do yourself that favor.

iansane

All SBC heads should theoretically have the same pattern of valves. They shouldn't be in different places. Otherwise stud girdles wouldn't work (or they'd have different models for 305 vs 350). So they problem you're refering to, is on all SBC heads.

dahaus

I never thought about it like that. You're right. I have never really measured the difference. It was just a comparison thing and what had been told to me. I guess you got me there. I am going to have to put my foot in my mouth.

But, did you read the link, earlier in this thread, that shows a 305 buildup producing 325hp. It was pretty interesting to see the difference in the heads. And amazingly the 350 vortech head did the best!!!