Critique my Sbf combination

[91stangracer]

Hi all, I'm in the stages of planning my next build for my bracket car. Don't do alot of posting here, but definitely alot of reading. Alot of smart folks in here.

This engine I'm planning is not built for any specific classes or set of rules. It's for my bracket car, and kind of a dream engine if you will.

The car is a fox body mustang. Glass hood, doors and hatch, gutted, caged all the usual stuff. I'm guessing between 2500-2700 lbs race weight.

Trans is a 1.76 powerglide, with transbrake. 8" converter.

The combo I am planning and collecting parts for. 8.2 deck 306" Cleveland head deal.

T Meyer track boss intake
TFS 225 Cleveland heads
Custom solid roller.
Flat top Pistons, should be around 11:1
Lightweight I beams
8000 RPM shift point.

Couple questions I do have. What size header primary tube and collector? I am thinking 1 7/8 primary with 3" collector would be sufficient?

Carburetor, this is also methanol application. (I admit, I don't know why and it sounds dumb, I have a small fascination with wanting to make a dominator work on it) (if) a dominator would work on this combination, would it be better to have the 4150 pad milled off and 4500 pad welded and blended? Or 2" spacer/adapter. Ita kind of against the grain for a bracket race engine. But it's kinda of a dream engine. And to see how fast I can me the 306 go, and do things that some say you (shouldn't) do, too big of headed, too big of carburetor, too much RPM etc....

This 1/8 mile only, currently car has a 4:30 gear in it with a really mild 302.

650 alky carb
Chinese Vic jr intake
TFS twisted wedge 170's
9.27:1
Frpp E 303 hyd roller cam
Stock refreshed bottom end. Runs 7.0's in the 1/8 @ 96 currently. At heavier weight. I just went through and added the fiberglass parts, tube k member, strange race brakes and took all the weight out. See we will see what this runs next season.

Thanks for all your help and replies in helping critique this combination.

Travis

[n2omike]

95% of the time on these types of posts... the writer's mind is already made up... and he is just looking for that ONE person to agree with everything he is doing, in order to find 'validation'. All the good advice goes out the window. If this is the case, good luck. lol

Captain Obvious would say it's a tricky combination. Small cubic inch + oversized heads + powerglide + peaky engine = a very difficult combination to get to work correctly. It will take a very expensive high quality, very high stall speed converter to make an attempt at getting out of the hole, and it will need a LOT more gear. Plus, the engine will need a good shortblock and valvetrain in order to reliably spin that high throughout a season of bracket racing.

If you want to make the build more affordable, faster and less problematic... add cubic inches. You existing combo expanded out to 363 cubic inches in a big bore aftermarket block will make a LOT more power, will be FAR less picky with converter/gear, and will last a lot longer, as you won't be splitting the factory block every year or two trying to spin it 8000 rpm every time you go to the track.

If your heart is set on this combination, you can try and source a 750 Dominator, and maybe pick a cam who's lobes aren't insanely aggressive, in order to not need shaft rockers, etc. With alcohol, you'll also want to make a huge increase in compression... as much as you can get with that small of a engine displacement. The compression will pump up the midrange and help it launch better. Just don't go to such a huge dome that it kills flame travel. Get a loose converter, a ton of gear... and let-er-rip. An aftermarket block and good internals will greatly help with expected service life.

As you know, cubic inches are the key to going fast on a budget. A stock (351W) block 6500 rpm 408 is your best bang for the buck. Will go faster and last longer than what you are proposing.

Good Luck with whatever you do.

[91stangracer]

Thanks for the reply Mike. I don't disagree with you. I have my heart set on the "combo" I do understand that there is no replacement for displacement. I am and I'm not trying to get validation. I wasn't trying to make it that kind of a post.

I do a bunch of reading on here, and pick up alot of things and try to wrap my head around some. Things like anytime you can spread the throttle blades closer to the valves (dominator) you'll pick up power, and while I feel like understand the reasoning behind that, but how do you make a big carb work on an engine like that? Or is it too big? When I read some of the carburetor posts on here. I've read anything between when you reach 500 (ish) hp typically a dominator will gain hp over a 4150. But I've also read different hp ratings etc when you need to switch to a 4500. I've also read that the 750 dominators the way they have skirted boosters are not ideal. But not ideal as in what? Are they junk? Are they not good for a drag racing application? I'm not really sure. That's why I'm just hoping all you smart people chime in and I can be a sponge.

Thanks again for the reply Mike and happy holidays to you, and thanks for anyone else chiming in on this post.

[englertracing]

Have you considered CHI cylinder heads?

[russxr67]

If you are insistent on keeping the capacity at 306 inches then the 225 head is too big unless you’re aiming at revving it into the stratosphere. A smaller head would be ideal. I’d be looking at starting with a set of 185 CHI heads and matching intake and go from there.
Not really sure why you want to limit yourself with those small cubes though. It’s pretty well known that cubes are king.

[turbo camino]

The 750 Dominators aren't 'junk', they just don't do anything that a 750 CFM 4150 can't do except cost more money. Nothing wrong with wanting a Dominator just because it's cool, because they are, but a 750 Dominator is just a fashion statement. The gains from the spread throttle bore locations are tiny.

A 1050 will run well on a surprisingly mild engine - on gasoline. For methanol, add another 100 inches, or another 3-4 points of compression, or both. Or, easier, just leave it as is and switch to gas. Back in my misspent youth I ran a 9375 on a 11:1 383 Chevy, with a Comp 280 hydraulic FT(!), and it worked great. No changes to the carb except screwing in power valves F&R and dropping the jet size.

[91stangracer]

Englertracing I haven't actually. Online flow charts like pretty comparable to the TFS heads, unless there is something I'm missing. Better design, etc..?

Russ thanks for the reply, really just to do it. There are a couple 306 inch engines out there with big heads (220) that run pretty good.

Turbo Camino. Thanks for the reply as well. They are cool, and believe me I know it sounds like a dumb way to go about it. I guess the way I think about it. Is all these little things add up to making power. Honestly I was thinking differently when it came to methanol. Because you burn more than gasoline, so you want volume, larger heads, intake etc... To a point. Obviously not like 240 cnc head on a 306. I read a quote I cant remember where. Said more liquid methanol you can get to the valve, the more power you will make. I figured if you have a good induction system, with a descent sized head, and a adequate sized header, and a custom cam to help control it all, it would work pretty well. My current engine was a hurry up and get something together to get this going within my budget. I was told not to run alcohol because I don't have the compression for it, and cylinder head isn't large enough for it, and with using one of the alphabet cams from Ford that is ancient technology that shouldn't work with alcohol either. That's what I was told and some of the things I had read on forums and such trying to research and learn. After running alcohol, my current 306 has ran phenomenal, and with awesome throttle response. (This is just my take on it) alcohol is 49% oxygenated, so if you are running a fuel that carries oxygen and you burn more of it, is that not making more power? You are filling the cylinder with that much more fuel and oxygen, and I would think that anytime you burn more fuel and oxygen you are making more power? Sorry kind of got off track. Maybe my thinking is bass ackwards? I'm not sure lol and the winter months are too long...

[englertracing]

Look at the chi 3v 208 it flows almost as well ....

[englertracing]

Also why 11-1 on methanol?
How about 16-1

[n2omike]

Also why 11-1 on methanol?
How about 16-1

There's not very much swept volume to work with in order to build very much compression. Will be lucky to get a solid 12 to 1 with a decent chamber dome/shape. NEEDS more displacement. 363 in an aftermarket block will look just like a 306... and run circles around it.

[rustbucket79]

Let me throw a couple of darts at your proposed combination.

You said flat top pistons, should be 11:1
Calculator shows 9.6:1 at zero deck and a 4 cc valve relief.

Grafting A dominator flange on a 4150 intake without addressing the plenum is doomed to fail. We dyno’d a large BBC that had a World single plane that was clearly a 4150 manifold the manufacturer had just half assed a dominator flange to it just to get one in the market place. The back two cylinders were so lean we had to drill secondary jets just to make a few pulls. Ultimately that engine received a Super Victor and the car ran 8.80’s. Don’t make the same mistake.

The combo is considered doomed to fail because it’s the truth. Your dream engine is something you would see in competition eliminator, turning 11,000 RPM.

8000 is low, power glide will murder this combo, 1 7/8 headers will kill any chance at making torque below 7000.

Now if you add 15# boost.....

[1972ho]

I have been running a ford SVO v-6 engine for over 15 years in a 1984 ford tbird at 2600 lbs. and the engine was 270 cid and it ran 10.08 at 132.00 mph with a 850 holley,so it should be possible depending on how quick you want to go with the 306.Next year I’m going to run it bigger at 285 cid and a larger roller cam at 15.0-1 compression should be a high 9 second car.Have fun with your project engine you need to turn up the rpm on it.

[englertracing]

Yeah playing with a calculator a 4"x3", 60cc head, 0.030 pth, and a 0.010 oversized gasket and 4cc valve relief piston gets 9.7..
Pretty bad
You could always order pistons with blank tops and take some bondo molds and let eric at rebco machine work some tight fitting dome magic....
But what if you built it 4.125x3.250?