My neighbor has a 65 Mustang fastback with a 393 stroker with Edelbrock performer rpm heads . .550 lift flat tappet cam . 1 5/8 primary headers . Single 850 carb. Weighs 3200 lbs and has a 5 speed with a 4.56 gear and 28 tall tires. He runs low 11's at 119 mph in the 1/4 and turns his 6800. We talked about your combo yesterday. He knows that there is another 75 to 100 horse left in his combo with a head change and a roller cam, but he only runs his car about twice a year at Fun Ford shows. Otherwise it sets in his garage under a car cover. your et and mph tells me that your car is down on power. How old are your valve springs ? Your car can run perfect ,just not rev on big end with weak valve springs. Are they Pro Comp springs ? I have run many a big block Chevy on a 3/8 in fuel line. You need to know your fuel pressure in high gear. What is your cranking compression ? Did you advance or retard the cam when the motor was built ?
New comp springs. I used procomp bare castings and put good stuff in. 4 degrees advanced on the cam. 8.97 cranking pressure. Valve overlap is hurting things some I know
There is an article in the December 2017 Hot Rod magazine on header primary size in relation to cubic inch and rpm's. It clearly shows your primary tubes are too small . Could you post your cam card ? Something is holding your combo back . Can you borrow a larger carb to try ? Are you saying 8.97 is your compression ratio ? I asked if you had done a compression test to see if the rings are leaking compression. Do you have access to a leak down tester ? How much total timing are you running ?
My friend, you are only showing about 280 HP. Wasn't sure if you were adding driver weight, so a gave you 200 extra. (Not meant to be an insult..LOL) If it's 2800 w/driver, it looks even worse. Just to put that into perspective, my friend has a 302 / 2 bbl NHRA Stocker engine that makes 250 hp. You need that fuel pressure gauge, either on the cowl , or use an isolater . Start there, I guess, but something is bad wrong. Header and carb size are not going to get you there. Need to start all over. Leak test, degree cam , re-check TDC. Borrow a known carburetor ,timing light, etc. 4000 is a good starting point, but keep going until you can leave a at least 6000, without blowing the tires off it.
The 8.97 would be the dynamic compression. Which is borderline for a pump gas motor. I would first mount a fuel pressure gauge to start with, then test. Dont do a bunch of things at once, then it's easy to start losing track of what worked and what didn't.
He said it's a race engine so he should be running race gas. So that should not be an issue unless he has retarded the timing to where it is just lazy.
That would be what your lowest RPM will be during a run......So if you launch at 4000 RPM and the car drops to 2200 RPM then that would be your lowest WOT RPM.
BTW, I was talking to the folks at AFR about my 383 with a 5500 convertor. While I had them on the phone, I asked if an 850 would work on the car. They said an 850 would probably work, but a bigger carb would be better.
That holley chart might work for street cars, but in real world racing situations I have proven it wrong too many times. Ran a .060 over 350 in my old blue gasser. With a 5.86 gear and a 5800 stall it ran 6.60's in the 1/8th with a 750 race Holley. Dropped on a 950 right out of the box and it went 6.40's. Tried a 1050 Dominator with no help signal not strong enough and was lazy to 60 foot. Installed a tunnel ram and 2 660 double pumpers and went 6.10. Should have been way too much carb according to Holley,but it worked. I have many more examples to back that up.
The chart says a 350 with a 4000 stall can use more than than 1050 (stall and cfm stop at 4000 and 1050). I don't see where that's way off. I'm setting up a Brodix single plane/1050 and an Edelbrock tunnel ram/750s for my 383 right now.
Sorry it took so long. Been very busy. Don't have access to another carb. 8.97 is dynamic compression. Have not done a compression test or leak down. Shop crammed full of other people's stuff. No room to get car in now. Have to wait. Am looking into building 1 3/4" headers. Any benefit to collector over individual primaries like " boom tubes"?
I've seen some gassers with boom tubes and liked the look and sound. Not sure if that's something that works better on a blown application as opposed to na.
Yea, on a NA engine the collector helps pull the exhaust out of the cylinder. Helps keep the engine from getting spent exhaust gas from being pulled back into the cylinder. When you have pressure on the intake side, you don't have to worry about it as much. The boost takes care of the reversion problem. Or maybe not.
I ran a set of zoomies on a stack injected big block Nova and saw no difference in performance versus a set of hooker collector headers. It got the alcohol fumes out from under the car and out of my eyes. Looked cool with flames when I sprayed my 300 hp nitrous fogger. your motor will benefit from collectors. When you get them built you can tune the length with a grease pencil. 1-3/4 primaries and minimum 3 inch collector. Are you building chassis or fenderwell headers ?
They do blow a lot of dirt around. Just go take your leaf blower and point it straight at the ground and see how much dirt gets stirred up. Speedway sells an 80 degree extension that works good for making a turn out.
Just go on the internet and type in header flanges for 351 Windsor and hit search and you will see what's available.
Ok I'm shopping for header components to build a set. 1 3/4" with 3" collector or 1 7/8" with 3 1/2" collector??? Which is the best for my procomp headed Windsor???
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