I do have a "road runner" convertor that is basically new. I know that sounds so sketchy, but it was another basically new convertor that he threw in. I don't know much about it, that is what he called it. I will look it over and try and ID it.

I know you guys are more knowledgeable than I am, but I can't imagine the PTC being a bad deal in a light car driven correctly. Got some other pieces today so things are looking up.

I wouldn't have an issue with the PTC. Use it. If it's a bit loose they can tighten it up a bit.

I'll say the number 1 and 2 issues I see are guys not running near enough converter and not enough gear.

+1

Having seen the last set of heads in person my vote is gasket match and do not touch the runners or chambers without more practice. There are plenty off bb heads laying around Chiloquin to practice on. Karls Machine shop has a sf300 that was up and running about 5 years ago. Perfect field trip. Good project, stay warm!

I am pretty sure I could do it a little better now LOL. The original intent of the question is to see what some simple work can do. Kind of a time vs. benefit thing. The big picture always been to run aluminum heads. As many have said, and the calculator does not lie, fully rebuilding iron heads gets into aluminum head costs pretty quick.

Still researching the convertor thing. With the amount of cars that I have, and my wife and I commuting together (she is not a fan of old, smelly cars) I am not real concerned with drivability, etc. It will be an occasional weekend warrior car.

The gears are going to stay for now.

As a school project porting the heads will be good. If you can get to say 240>250cfm with them it could improve things 20>30hp as an approximate gain with the low CR. It may only be worth a 1/10th or so. However keeping that small 3310 will do you no favors at all. An 850DP will be the order of the day (even without the porting) in my opinion as I have said before, that alone could be worth 2/10ths over the VS, and even more so to get the full benefit of the time taken in doing the heads, 440's like air and lots of it, you'll be launching on 2 pump shots and 4bbls not 2 and 1 shot. The cam is small but should work to around 5800rpm and with your 3.73's and a weight of approx 3300lbs all in?....the car could go well in the 11's with a good hook and trap@around 5600 with converter slip.

So you can say doing the heads will benefit some but not much with your current 750VS as I see it,....coming off the line with that 3310 and an 850DP will be Night & Day and the 60fts/ET will show it as well as the mph.

When I get home this evening I will see what actual carb it is that I have. It is a Holley 750 and a close relative of the 3310. I also have a couple of 3310’s.

What I'm trying to get across to you is the difference between a VS and a DP carb and how much harder the latter will hit, size matters also, you open up the heads to breath better you need more carb than a 750. I ran an 850DP on my 340!!!. Run the car with what you have and then borrow an 800>850>950DP if you can and you will see/feel the difference with that PTC verter.

I am not doubting that more cam, compression and carb would really make things work. From what I gather these things love CFM. I know with my first 440 every size I went up in CFM netted me solid seat of the pants performance improvements.

However, it is a budget thing for the time being and the carb is basically brand new sitting in a box and this is the project so I need to use it right now.

It is the 80508SA Holley which I understand is a close relative of the 3310 with an electric choke. Please correct me if I am wrong.

It's a 4160 750 CFM carb that doesn't have a rear metering block, doesn't have 4 corner idle and has a choke, all of which I don't care for. And that's just a cursory glance at it.

I realize that budget is a big deal, but I'd use the PTC converter you have and get a different carb long before I used that carb and spent money on a converter.

Toyota I understand that its a budget deal, just trying to get you to understand the BIG difference between a VS and a DP with the motor spec you will have, even if it was a 750DP it would be much better, I'm not on about more cam/comp etc., thats a known fact, you don't have to have all that before you use a DP carb....I tried several VS type carbs on my 340 as an experiment, they were all flat out of the hole and lost me ET. As I said, run what you have, get some slips and then put a DP on and see the difference....all the best.

As a counterpoint to the “you neeeeeed a DP carb”, there sure are a lot of really fast stock eliminator cars running factory type Holley VS carbs.

When my buddies GTO was a bracket car, he preferred a modded 3310 I did for him over a DP carb.
The DP felt a lot stronger, but it didn’t ET much different at all(a few hun).

That was on a 13:1 motor making over 500hp running low 11’s in a 3650lb car.

Yes and I understand at that level those motors/carbs are well sorted and yes they will run as good as but that takes a lot of knowledge/work and setting up, were talking about a general build where a VS will run ok for sure but will not have the performance of a DP and the op is talking about performance not a daily driven street car. Many have tried working with VS carbs for racing, some succeeded to a point but where do you see any performance oriented build using a VS carb other than when rules dictate.

I see them on cars at the drag strip all the time.

Years ago I bought an old 780VS all apart in a box for $3.
Cut the choke off, put a kit in it, and a quick change spring kit.
Ran it for a few years on my re-ringed 68 440 short block with some Napa store rebuilt 346’s on it, 1-3/4” headers, std performer, and Crower 271hdp cam.
Ran 12.40’s day in and day out. I won a few $1000 bracket races with that combo.

IMO, the OP absolutely doesn’t “need” a DP carb.

As they say, “ymmv”

ok you da man I won't argue with you, all I can do is relay what my short time in Drag Racing taught me and my experiences on track and not what I have read.

I’m not arguing with anyone, as I said......”imo” the OP’s proposed build isn’t in need of a DP carb.

Everyone has their own set of priorities, and will build/buy as they see fit.
I’m sure if/when he decides a DP carb will be a worthwhile upgrade, he’ll get one.

If I were in his shoes, with a basically new 750vs in my possession, I wouldn’t be looking for another carb for the planned combo.

I tried a couple different 850dp on my past/similar combo, I even had a 650dp on it for a little while which was a fun street carb, and had a couple 3310s. On mine the 850dp annular ran slightly harder than the others. The difference was about .1 and 1mph as best I could tell.

Test everything you can get your hands on that seems to make sense, but keep budget in mind (or only take a chance on something with good resale value that is a great deal, that you know you can get $ back out of later if you let it go). Used and borrowed carbs are a winner for that....

I don't think most people understand why a double pumper could perform better than a velocity control carb when throttle bore and venturii are the same. if a double pumper and a velocity control (same cfm/venturii/throttle bore) are wide open at max power then there won't be any power difference. a double pumper MAY produce more mid-range but that's just an indicator of the engine wanting more air quicker and the carb isn't big enough to begin with. this is why I like multi-carb. have your cake and eat it too. get's you out of the single 4bbl cfm b.s.

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Ok we are discussing, I would like to hear your opinion on whether once he has a some runs with that 750VS and a good tune, do you think he would go any quicker with say an 850DP with the given set up and that PTC verter, bearing in mind the goal here is Performance as I understand things which is why he originally asked about porting the heads etc. and is why I suggested what I did as an upgrade.