Victor Jrs on 306 Need some advice please!

[ImportEater98]

Hey folks. Putting together my 306 right now and I'm sort of in a pickle. After this season a 408 goes into the works. I don't want to have to buy heads twice, so I'd rather just buy the heads that will work best with the 408, but can squeek by with the 306. I have decided on victor jrs. I know they are a bit big for a 306 and that you have to flycut STOCK pistons. My shortblock is fresh, though it has a stock crank, rods, and KB Silvo-lite Hyperutectics (9.5:1). You can see why i don't want to waste my time building a releltively weak shortblock. My question is....what will i have to do to make these heads work? Whats max lift on the cam without flycutting? I could buy AFR185's, but they would be too small for the 408. Also i want to convert to a non roller cam...any suggestions? I will be using a Victor Jr intake and Holley 650 carb. Any REAL AND ACCURATE advice would be greatly appreciated. Thanks - John

 

[90mustangGT]

Those heads will be huge for a 306. You would probally make more power with some stock heads. I don't know, maby not. If I were you, I would look to either buy some new or used aftermarket heads, because they have good resale, when you build the 408, you can sell them for about what you paid for them so no loss, only power to gain. Why are you wasting money building up a 306 when that money could be towards a 408? I have a fresh 306 shortblock sittin in my garage, but I am building a 427+ so I'm not going to waste my time/money on it.

 

[ImportEater98]

Im not "wasting" my money on a 306. Its what i got, and whats in my budget for the season. I built my car from nothing spending thousands this winter so far. I can wait and not race till spring of 07 while i build a 408, or i can race this year on what i got..What would you do?

 

[304billet]

I would run the box stock Victor jr's w/ 11:1 comp, .600 lift solid roller, with a port matched intake.

Then when u do the 408, have those Jr.' s Stage 3 ported.

U could do the same thing with AFR 185' or TFS Track Heat cnc'd 185 from Summit. U could have either head ported to flow as well as or better than a 205.

 

[vikingpower]

If the valve angles are the same on the Jr.'s as the stock heads, then you'd be ok as long as your cam doesnt have too much duration. Call Comp or another cam company and ask them to help you choose a cam. Or call Edelbrock, they could probly tell you exactly what you can get away with. Also, if you can get the heads angle milled to around 15 degrees you should gain some clearance. That's how TW heads can still use a 2.02 intake valve with the stock pistons and maintain clearance up to about 224 @ .050 or something. I'd guess that you'd be able to run about 220 @ .050 with the 2.08 intake valves they come with (after angle milling). Just be sure to check the actual valve to piston clearance with clay and all that when you're assembling the engine.

 

[vikingpower]

I would run the box stock Victor jr's w/ 11:1 comp, .600 lift solid roller, with a port matched intake.

Then when u do the 408, have those Jr.' s Stage 3 ported.

U could do the same thing with AFR 185' or TFS Track Heat cnc'd 185 from Summit. U could have either head ported to flow as well as or better than a 205.

How much power does your 304 make? How do you like the Victor manifold? I'm considering buying one of those instead getting my RPM ported.

 

[M.A.V.]

I was in the SAME situation as you ,I`m going to build a 408 later but I have a 308 now.After I built the 308 I found out that one of my ported `65 289 heads(54 cc) with 1.94/1.60`valves was cracked. I had`nt had the block zero decked because I figured the 289 heads would yeild a little over 10 to 1 compression anyway.My pistons are .015 in the hole at TDC. I bought a set of Victor jr.s (60cc chambers)and with my Speed-pro Hypereutectic pistons my compression would have been around 8.7 to1 with a a felpro head gasket .042 compressed thickness. (If I remember right).

So I ordered a pair of Cometic MLS gaskets with .025 thickness and bolted the Victor jr.s on. this calculated to 9.2 to 1 compression.
The Speed-pro pistons have really big valve reliefs in them so piston to valve clearance is not a problem for me.

I have an X-303 cam ,Offy tunnel ram intake with 2 holley 450 carbs,a 3,800 converter ,with a reverse manual c-4 and a 4.11 rear with spool.

The car (`72 Maverick) weighs 3140 with me in it and on Pep Boys Futura tires It has run a best of 12.45 @ 106.6 (best mph was 107.4) with a 60` of 1.87 with me feathering the throttle on the launch to try and keep it from spinning so bad , Then when I shifted to second it broke the tires completely loose and I lifted almost all the way out of it ,and then jumped back on the gas. With my new slicks ,a good 60` and a little luck I think my car may run a 12 flat or maybe even an 11.9 and that ain`t to bad for a "mismatched" 9.2 to 1 compression 308 with an alphabet cam!


The engine LOVES to rev Due to the big heads Its like the higher you rev it the happier it is. But I havent turn it past 6,300 due to the Hyper pistons and stock rods. On the pass listed above I shifted at 6,200
I think you can get away with using the Victor jr.s But I would have the block zero decked and use a thin gasket to try for around 10.2 to 1 compression or better. And the car will need some gears and either a 5 speed or an auto with a pretty loose converter to get the revs up quickly.

I dont think you would have alot of low end torque compared to smaller heads.