is there any gain in cleaning up the bowl area in 915 heads with a nice valve job already. if so where is the gain if not revving much over 5000 rpms. thanks for your opinions.
the bowl area
- Thread starter gtxrt
- Start date
Oh ya. Gasket matching and bowl blending are a great modifications.
.Back cutting the valves also adds a bit of flow.
.Back cutting the valves also adds a bit of flow.
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440Coronet500
Well-Known Member
IMO, cleaning up the bowls and roofs of the ports should give good gains. I only backface the intake valves and leave the exhaust valves as is. 440'
#41
Well-Known Member
I'd also like to see some data on this. There is not a single set of heads that I have been able to resist blending / cleaning up at the bowl despite seeing any measurable data. Still, I don't think I am wasting my time.
lewtot184
Well-Known Member
basically this would be a pocket port. i think there's 20-25hp in it (this may depend on other factors too). anyhow i do it with no downside.
R413
Well-Known Member
I did this once, I think it depends on the cam, and then if it has headers, big carb, gears, etc.
My story. I had a stock 1967 440 350 horse C-body engine that ran good. I put in a stock magnum cam, magnum exhaust manifolds, 440 HP AVS, 3.32 SG. In a 67 Belvedere. Car ran 14.20. Raced it many times and different days.
The heads were 516. So I swapped on a pair of 915 heads and cleaned up the bowl area like you describe. No other work or gasket matching. Both sets of heads with stock steel shim head gaskets. The car ran just the same after doing this. You couldn’t tell anything on the time slip or by seat of the pants.
My story. I had a stock 1967 440 350 horse C-body engine that ran good. I put in a stock magnum cam, magnum exhaust manifolds, 440 HP AVS, 3.32 SG. In a 67 Belvedere. Car ran 14.20. Raced it many times and different days.
The heads were 516. So I swapped on a pair of 915 heads and cleaned up the bowl area like you describe. No other work or gasket matching. Both sets of heads with stock steel shim head gaskets. The car ran just the same after doing this. You couldn’t tell anything on the time slip or by seat of the pants.
Years ago Mopar sold templates to use in pocket porting BB heads. I still have a set!
Mike
Mike
dvw
Well-Known Member
Depends on the valve job. One might very well been better. As well if material was removed from the short side making them worse. Properly done the 915 with proper work would've been quicker.
Doug
BSB67
Well-Known Member
Kinda hard to answer without knowing much anything else about what you have going on.
If the heads are the bottleneck, bowl blending will help “more”, if they are not the bottleneck, it will help “less”. More would be 20 hp, less would be 5 hp.
I did a head swap on my 400 hp-ish street car. 440, 3.23, stock converter, 0.455” lift cam, exhaust manifolds. I swapped from really good set of competition valve grind 915 heads (no porting) to a professionally ported 915s. Both sets of heads were done by the same guy. The ported 915 flowed 260-ish @ 0.500. I would guess the unported heads flowed 220-ish. The car picked up 2.5 mph, or about 25 hp. Of course the non-ported heads probably had 20,000 miles on them. If they would have been “fresh”, the difference would have been less I’m sure.
If your heads flow 220 now, i’d guess they will flow maybe 235 after bowl blending. This means you gain would be less than mine.
Better head flow will help everywhere in the rpm range.
Finally, on a stockish motor, I’d take a really good competition valve grind over bowl blended marginal valve grind heads.
If the heads are the bottleneck, bowl blending will help “more”, if they are not the bottleneck, it will help “less”. More would be 20 hp, less would be 5 hp.
I did a head swap on my 400 hp-ish street car. 440, 3.23, stock converter, 0.455” lift cam, exhaust manifolds. I swapped from really good set of competition valve grind 915 heads (no porting) to a professionally ported 915s. Both sets of heads were done by the same guy. The ported 915 flowed 260-ish @ 0.500. I would guess the unported heads flowed 220-ish. The car picked up 2.5 mph, or about 25 hp. Of course the non-ported heads probably had 20,000 miles on them. If they would have been “fresh”, the difference would have been less I’m sure.
If your heads flow 220 now, i’d guess they will flow maybe 235 after bowl blending. This means you gain would be less than mine.
Better head flow will help everywhere in the rpm range.
Finally, on a stockish motor, I’d take a really good competition valve grind over bowl blended marginal valve grind heads.
it has a very good valve job runs great now. i would have to pull the heads back off. for 20 hp i think i will do it. if i knew the engine was going to run this good i would of done it when i did the rebuilt lol
BSB67
Well-Known Member
I don’t know what your meaning of “good”is. Do you have the specifics on the valve grind? Any track data?
Don’t know if you’ll see 20 with a bowl blend.
You will not feel 20 hp in the seat of the pants
Don’t know if you’ll see 20 with a bowl blend.
You will not feel 20 hp in the seat of the pants
i know it was a performance valve job with back cut. when i do a compression test the needle swings up high on the first crank. i have a g-tech meter it shows if i recall 14.18 at 97 mph with 2.94 sure grip. he spent a lot of time getting valve and spring height even because am not running adjustable rocker arms
Orig69
Well-Known Member
The valve bowl area is the choke point where the biggest gain will be made if you know how to do it.
it's in a 1967 newport 4400 lbs with me in it no headers. small cam
RemCharger
Well-Known Member
Very impressive with those gears. Are you hitting 3rd before the traps?
lewtot184
Well-Known Member
some years back i was dissatisfied with the performance on one of my cars. suspected a head gasket problem but thinking back i may have had a different issue. anyhow, i yanked the engine took the heads off to replace the gaskets and did a pocket port, (i had done this before a few times but that was 20-25yrs previous and back then everything was hit and miss), on them and a friend did a "garage" valve job (no backcuts. we didn't know what that was back then,...lol). another friend gave me a hughs/engle 23/30 cam and i slapped it all back together. previous to all this i'd done a chassis dyno test and had a number. took the car back to the same dyno and dyno operator and the car picked up 38hp at the tire. that figured somewhere between 45-50hp at the crank. no other changes to the car; same gear, exhaust, wheel/tire combo. i'm sure the cam helped some but i still had the cast manifolds on and the previous cam was the mopar 272/.455 with a true 1.6 rocker. peak power was at the same rpm so i didn't get anything there. how much of the gain was cam or heads may be open for discussion but me messing with cams in near stock engines has me believing that there aren't big gains between them all (tried 4 different cams). i believe head work was at least half the gain. i know everybody has different combo's and the old "results very" thing is relevant but there's no-way in my opinion there's a downside.
yes hits 3rd at 90 mph
Orig69
Well-Known Member
I can remember (Car Craft magazine) in the 1980s a 68 440 engine rebuild that was done by Bill Bagshaw of Pro Parts they reused the original crank & rods and chose to use .030 over 440 six pack replacement pistons (I believe the part# was L2355F compression was 9.6 to 1) a DC 509 hydraulic camshaft. They installed larger valves (2.14 and 1.81) the valve bowl area in the original 906 cylinder heads were reworked using porting templates from Direct Connection. Other parts like hydraulic rocker arms, valve springs, large size valves, roller timing chain and the DC valve covers are also from Direct Connection. The intake manifold was a box stock Holley street dominator with a 750 cfm double pumper carburetor. This is a very basic motor using almost all Mopar parts. (The pistons I believe are from TRW) On the dyno this engine made 511 horsepower at 5500 rpm and 522 lbs./ft. at 4500 rpm
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