Engine Big head 306...someone edjumicate.

[tannerc91gt]

Swapping the 398 for a fresh from the machine shop 306. Forged pistons are TRW cut for a 2.08/1.6 valve, crank and rods are ford parts.
Ive got a few parts I want to carry over from my W build, for cost and time saving purposes.
Timing cover and waterpump will make the jump. Timing cover has a plate for a mechanical pump drive but has been blocked. Waterpump is the wrong rotation if I remember right but its run off a Moroso drive so its a simple polarity swap.
ignition system minus the dizzy, carb and headers will carry over as well. With a swap to an 8.2 Vic Jr intake.
The only stumbling point is the AFR 205's. Ive seen a 306 with a set of 185s cut to 205 specs haul to a few 10.0x passes but it was on a healthy shot and had a custom cam. was far from a dog off the bottle but the nitrous really helped move things along.
I'm not beyond spraying, as ive done it before. And ive considered going forced induction in the semi-near future anyways. Don't want to go to a set of 185s if they will be my bottle neck eventually but on the otherhand without more cubes that may not be a concern.
In terms of a camshaft, ill have a NIB TFS2 but I don't think that's the ticket so ill be trying to spec one of those as well.

I understand there are more important specs than the intake port size, just wanting to hear from who's done it and how successful they were or weren't.

 

[clement]

if it were mine, and the vic jr was unported i would bolt it on and try it with the tfs stage 2 cam since you already have it. if you are going to open it up (probably even if you dont) it would likely work better with a custom grind. but since you have all the parts i would put it together and see what it runs. the biggest problem i have seen when you have an intake thats quite a bit smaller than the head is that you might get a stumble out of an out of the box holley (even an HP). but AED carbs seem to work fine where the holleys dont.

 

[CarMichael Angelo]

Here ya go. If there was ever a debate on whether it made sense to do what you're contemplating, this thread covers it all.
http://www.stangnet.com/mustang-forums/threads/nikwoacs-commitment-issues-engine-build.833852/

 

[tannerc91gt]

Here ya go. If there was ever a debate on whether it made sense to do what you're contemplating, this thread covers it all.
http://www.stangnet.com/mustang-forums/threads/nikwoacs-commitment-issues-engine-build.833852/

Was waiting for him to wander in here actually. Hadn't compared the TFS heads he used to my AFRs but I know its not completely undoable. Just thinking a custom cam may be required. And the Vic Jr may be a little small but id rather cut it out a bit. Don't think ill see enough rpm to see a super victor

 

[84Ttop]

buddy of mine had a 306 with ported tfs high ports and a xx trim vortech, went 8.90's all day long. not a slouch if you ask me. remember, good parts are only as good as your combination. afr 205's with the right cam, intake, carb, etc will make some steam, the wrong cam or carb etc. could really make it lack luster.

 

[tannerc91gt]

Will be a 306, thinking shorter duration (read 230-240) .600 lift ballpark cam, 112 lsa, Vic Jr and a 750 carb. With my suspension and good tires I think 11s aren't unreasonable and some spray should pick it up substantially.
Someone smarter than me is welcome to tell me if I'm off track.
Edit:I actually like the specs on the 286HR, but their nitrous cam has a little more action on the exhaust side, might help take advantage of the larger exhaust runner on the 205, along with the 1 3/4 longtubes. This seems more doable once you look at other small cube large head combos, even factory (IE: LSx, coyote, etc). Just going to have to really keep the air moving to utilize these heads. RPM would be a big help but for longevity I don't think higher than 6500 or so will keep the block together long.

 

[clement]

with a short stroke you can rpm it. your minimum cross section will now be in the intake instead of the heads. dont overthink it, just put it together, see where it is and make changes from there.

 

[NIKwoaC]

If you try to run a big cam on those heads and plan on keeping the RPMs under 6500 you may be disappointed.

TW 205s are "bigger" than AFR 205s, so if I can do it, I don't see why you couldn't. A sub 6500 RPM NA 302/306 is what it is and it's not going to light the world on fire without some form of motivation AKA boost or juice. Still, if done right it'll be fun to drive and won't be a slouch at the track.

My cam specs are as follows, and I shift between 6200-6400.

----------------Intake----Exhaust
Duration @ .006:----265*-----276*
Duration @ .050:----215*-----224*
Lobe lift:----------.355"-----.354"
Lift W/1.6 rocker:---.568"-----.566"

Lobe separation: 112*

EDIT: clement is right, you can't just look at the heads alone, intake is obviously also a key contributor.

 

[tannerc91gt]

Didn't want to run a big cam for the sake of a big cam, I guess my thinking was to flow as much air as I could to take advantage of the heads. The intake will need to be portmatched I just don't think it'll see enough rpm to run a super Vic. It'll be carbureted so I'm not dealing with the limitations of the ecu, but being a stock bottom end there's a limit to safe rpm.
Like you, I don't want to downgrade my top end because a 306 isn't the end all set up I want to run and it will very likely see more cubes and boost down the road , or more nitrous. The AFRs are a smaller head than the equivelant tfs,so I might be a little better off. There are just a lot more parts at play here than a big set of heads

 

[clement]

if you dont know how do calculate target cross section (which is air speed) for a given displacement why are you going do any port work to any part of it? my advise is to put the cam, heads and UNported intake you have on it and a good carb and see where it is. you might be surprised. if you port match that intake you will have enough cross section in the heads/intake to turn 8k rpm with a decent size cam 347. also, if you port match the intake on that small displacement it will need a smaller venturi carb than it would unported. its gonna flow what its gonna flow. an OOTB vic jr will flow fine.

 

[tannerc91gt]

if you dont know how do calculate target cross section (which is air speed) for a given displacement why are you going do any port work to any part of it? my advise is to put the cam, heads and UNported intake you have on it and a good carb and see where it is. you might be surprised. if you port match that intake you will have enough cross section in the heads/intake to turn 8k rpm with a decent size cam 347. also, if you port match the intake on that small displacement it will need a smaller venturi carb than it would unported. its gonna flow what its gonna flow. an OOTB vic jr will flow fine.

Would just end up being gasket matched, and probably not by me. Not trying to make the combo out to be more than it is. It'll still be mismatched on some level regardless of my efforts. Supposed to pick the shortblock up next weekend, and it will go together with what I have. I hope to be surprised but I'm not expecting to blow anyones doors off

 

[NIKwoaC]

Didn't want to run a big cam for the sake of a big cam, I guess my thinking was to flow as much air as I could to take advantage of the heads. The intake will need to be portmatched I just don't think it'll see enough rpm to run a super Vic. It'll be carbureted so I'm not dealing with the limitations of the ecu, but being a stock bottom end there's a limit to safe rpm.
Like you, I don't want to downgrade my top end because a 306 isn't the end all set up I want to run and it will very likely see more cubes and boost down the road , or more nitrous. The AFRs are a smaller head than the equivelant tfs,so I might be a little better off. There are just a lot more parts at play here than a big set of heads

The heads are going to flow more than enough for what you're trying to do with a 306. In simplified terms, "big" cams are used as a band-aid to get "small" heads to move enough air to feed a given engine at a given RPM. You don't have "small" heads, you have "big" heads. As such, you'll need "less" cam to make power in the rpm range that you want.

If you're thinking about possibly picking up a cam for this motor, going custom would be a really good choice.

 

[clement]

The heads are going to flow more than enough for what you're trying to do with a 306. In simplified terms, "big" cams are used as a band-aid to get "small" heads to move enough air to feed a given engine at a given RPM. You don't have "small" heads, you have "big" heads. As such, you'll need "less" cam to make power in the rpm range that you want.

If you're thinking about possibly picking up a cam for this motor, going custom would be a really good choice.

exactly.

Would just end up being gasket matched, and probably not by me.

and its gonna increase the cross section which will make you have to rev it even higher. but whatever, learn the hard way.

 

[tannerc91gt]

and its gonna increase the cross section which will make you have to rev it even higher. but whatever, learn the hard way.

Wasn't intended to be an argument. There are obviously things that I don't know, or I wouldn't have made the thread. I appreciate yours, and everyone else's input and will take it into consideration.

 

[clement]

i was just trying to make a point. do some reading on cross section vs. fluid speed. i know you already bought a 306, im not sure why you wouldnt have just put a rebuilt stock windsor shortblock in it with your topend. ive gotten carb'd HC 358s into the high 10s on motor on pump gas.

 

[tannerc91gt]

do some reading on cross section vs. fluid speed. i know you already bought a 306, im not sure why you wouldnt have just put a rebuilt stock windsor in it. ive gotten those into the high 10s on motor on pump gas.

The 398 I have is high compression cast internals flat tappet. My initial goal was to just sell it but the 306 was offered in trade. Seemed easier than starting from scratch. I'm not 100% sold on the idea which was the reason for the thread. No trade has been made.ill gladly do some reading on the subject before a trade is made.

 

[clement]

just change pistons in the windsor. thats easy as long as the bore is in good shape. just make sure to have the rotating assembly rebalanced. if its a scat 9000 you would be surprised what they will take. run the right oil and the flat tappet cam wont be a problem. a carb with 1 and 3/8" -ish venturis and itll run.

 

[tannerc91gt]

I was wanting to convert it to roller, not that the cam in it now is bad. But the AFRs are sprung for a much higher seat pressure so Imo the cam would be on borrowed time. Otherwise dished pistons would be an easy fix. I know the cast rotating assembly would take a beating but to have it rebalanced, converted to roller, and buying the required parts was looking like a good chunk of change to invest into a shortblock I have nothing vested in. Hence the purpose of this thread, wanted to kind of see how a 302 based motor may perform with my parts before I made any moves.I don't know that id be disappointed stepping down the displacement but I know (now more so after discussing) that id be leaving a lot more on the table.

 

[ratio411]

I would go "small" (relatively speaking of course) on the intake and cam, since the heads are going to be in no way a bottleneck on a 306.

The guys are correct about the short stroke in these engines LOVING to rev.
You can spin the hell out of a 302 based engine (289 even more so), and not have an issue.
I think more than the rpm you are worried about, you need to worry more about splitting the block.
302 roller blocks are known for falling apart around 400-500 hp, while stock Windsor blocks have endured 700-800 hp before splitting.

In short, don't worry about going over 6500 rpm in a 302, that's nothing for a short stroke.... be worried about the block not holding up to your future power adder IMO.

 

[clement]

so whats the problem with changing valvesprings? they are cheap. the PSI springs ive got that are 570lbs at 1.300" that i run with my little street roller and crower hippos were $30 on ebay. so you should be able to find some used flat tappet ARCA springs on ebay pretty cheap. if you have to buy everything new and have someone else do all the work than yeah, its probably going to cost you some $. but if you do it yourself and find a machinist that isnt going to rape you it probably wont cost you $200 (including valvesprings) plus the cost of pistons. you gotta pay to play.