I know it hard to guess hp but i was wondering if anyone could give me a guesstimate as to my hp. It is a 75 455 with pistons .15 in the hole. Heads are from a 71 with 71cc chambers cut .20 thou. Pistons are 33cc and a .27 cometic head gasket. TA 310 cam and TA full length headers. And heads are ported a little and everything is gasket matched. Also has Sp1intake and holley 850dp race carb
If your heads where home ported as you state" only a little" I will assume that they only flow more then stock at a valve lift mostly above that of the Cam you are running, which from my findings is the way those heads react to light porting work atleast on the Intake side! Staying with thinking along those lines a stock Intake flow level of 215 CFM@28" could make you up to 442 HP, but you would need to run .600" lift to average that CFM number so I would say you should have a minimum of 425 HP under your right foot here in the left hand drive states! By the way by using your numbers and a stock Bore and stroke 455 I find that you have a 9.5 to 1 comp. Also I am sure your head gasket is not .270" thick as you posted! If you want a General ball park number for HP from Intake airflow numbers at a 28" test pressure then it's as follows. I will use a number of 240 cfm. 240 X .598= 143.52 143.52 X .43= 61.7 61.7 is the potential HP of each cylinder at 100% VE. For a flat out full on race motor that's looking to make its peak HP well above 6000 rpm you want a minimum of 3.6 Intake cfm for every HP per cyl your looking to make, and maybe even more important at a port velocity of no more then 325 ftps.
That’s funny, I was going to estimate right at 420, I see most agree. Strap on an alternator, the clutch fan, and the power steering pump, and you’ll probably have 400 hp going into the torque converter, then with a 15% loss, be looking at around 340 to the wheels.
Hopefully you ported where it counts. Under the valve seats where the ports neck down. Lot of power hiding there. You should have a lot of fun in a nice 12 flat car.
Unfortunately Intake valve/ port wise , 95% of all modern Buick heads but for the nail heads have the main point of restriction not in the area of the valve bowl where most novist porters tend to grind as you elude to in your comment 70 GMuscle!
Everything will depend on the heads. "Heads are ported a little" means absolutely nothing to anyone trying to guess HP. The 310 cam is a single pattern cam, so no help on the exhaust side. Again, head flow? Nobody knows. Figure low 400's for HP, maybe more. Good converter and exhaust system, 13 second car. Where in the 13's? How heavy is the car? I get 9.27 SCR and 7.22 DCR. More static compression would help.
13s? Man I’d be very disappointed unless I was racing in Denver in hot summer, lol. I have less and gone 12.30@109. buicks are built to go you know, lol.
I disagree, you are way too optimistic, head flow is everything. He isn't going 12's in a full weight Buick without better head flow. We don't know how good his heads are, we just don't. I say 13's. Lets see what he runs.
Well my bowl ported 73 headed 73 blocked full weight, 4080 w me in it goes 12.40s. Best of 12.30. Performer w 750 qjet. 342 geared. 28” tall tires. At etown and cecil. So it can be done. Don’t know why others can’t. And to me it’s slow. And is to this board too. Some real quick full streeters here. my 12.30@109 was with a Holley 850. Part 9380.
I know it can be done, those are way better than stock heads. Combination and head flow is the key. With what the OP posted, I stand by my prediction.
As far as the HP goes no matter how much it makes somebody is always putting out "more". ET/MPH is what tells more to me and I would say a 12 second ET 455 with no head work is fully possible. Romel's seems like it has the engine to do it. No mention of gears or trans/converter so that point is moot. Of course it needs to be tuned well(and not everybody is an accomplished tuner) and have other aspects to back it, such as good traction and good launch(gears/converter/tires) to help it out. Race weight is a big factor. I'm sure there are plenty of "400" HP 455's out running "500" HP 455's. That is why I never really worry too much about what HP my engine allegedly puts out. I will say I'm confused by the 33cc pistons only .015" down the hole. Normally they would be closer to .030". Was the block decked? Are those factory '75 pistons? I believe the '75-76 blocks came with the odd 28cc piston dish that were .050" down effectively giving it the same compression as the '71-74 .030" down 33cc pistons. If aftermarket pistons why the "low compression" 33cc dish? 71cc head chamber after the .020" cut? "Porting?" Gasket match useless unless mucho head work was done prior. I'm waiting to hear what is the most restrictive area in the Buick head if not the under valve bowl area.
Ok. A little more info. When i say lightly ported, i opened up the bowl area a little and then tear dropped all the valve guides and cleaned up the short turn radius. The tranny is a built 350 with a shift kit and rearend is 3:55 posi running 20 inch rims. The deck was cut to get the pistons to that height. And i know there's no way of knowing hp for sure without knowing head flow. Just figured to get a rough estimate. Thanks. My name is actually Tom, i dont know why it says Romel
You have decent gearing, what torque converter do you have? Eh, that won't matter that much with those 20" rims because with those you'll never get good enough traction off the line to go any faster than the 13s but will go over 100 mph in the QM. I'm going to guess between 400 to 450 HP.
Coan 3000 stall. I have drag radials for the track. But i get very good traction with the tires i have on it surprising
Install bigger valves in those heads allow you to get a rally nice 3 angle seat in place which you can not do with the stock valve size as there close to being a hang job! The 3 angle job picks up a nice Chunk of air flow in the lift range where most non full race only Cams spend there most open time. If your going to do serious porting work then the bigger valves are a win win situation since you can get the 3 angle valve job in place and increase the valve size to valve bowl Throat ratio. If your looking for big Ass power gains ( over 525 hp) with under a 10 to 1 comp and you do not have a valve to Throat percentage that is atleast 85 percent then your done right then and there.
As far as gear, 20" rims don't really matter, it's the overall tire/rim height unless you are running on the rims in which case your 3.55's will be more like 4.72's In any case, if you get good traction with any kind of regular street radial, I'd say something is off. I still say the head flow is going to be the determining factor, that and the car weight. You have the pieces there for 12's. I say get it down the track to get a baseline. Then you will know.
