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Topic Review (Newest First)
06-20-2013 09:22 PM
vinniekq2
cam?

Quote:
Originally Posted by SPEED MASTERS CC View Post
The heads under consideration are the Enginequest 220cc with 50cc chambers. I have a pair of 1.75 dia. sprint car headers that I will tryout at the track also.
The 220 heads flow better than what I have now plus the compression gets raised a bit. The local speed shop thinks the gain will be more like 40-50 horse... The current headers are for looks. I know they are far from optimum.
the sprint headers might work better? the cam/heads/intake and headers need to match.
06-20-2013 09:02 PM
SPEED MASTERS CC The car weighs 2600 lbs with driver. The hot rod headers have a 1.625 primary pipe diameter. The converter is a 9 inch, 3800-4000 stall. The gear is 4.56 with 30 inch dia. slicks. Turbo 400 trans, foot braking. A small nitrous system might find its way into the program.
06-20-2013 08:56 PM
SPEED MASTERS CC The heads under consideration are the Enginequest 220cc with 50cc chambers. I have a pair of 1.75 dia. sprint car headers that I will tryout at the track also.
The 220 heads flow better than what I have now plus the compression gets raised a bit. The local speed shop thinks the gain will be more like 40-50 horse... The current headers are for looks. I know they are far from optimum.
06-20-2013 05:49 PM
vinniekq2 everything I posted is what you need first.as you can see techinspector reiterated the cylinder head issue.The pipe length on the primaries and tube diameter do not look like they are for high performance engines?
Run it as it is,probably sneek into the 11s if the car weighs 3000 pounds.Get some MPH runs and weigh the car,maybe Im wrong and that engine makes more power than I think it makes,,,
06-20-2013 03:43 PM
techinspector1
Quote:
Originally Posted by SPEED MASTERS CC View Post
I am considering changing cylinder heads from the current 64cc chambered 200 cc Sportsman 2's to 50cc chambered 220 cc heads from engine quest.

The engine is a 408 sbc, 11.7-1 compression, 250 duration at .05/.575 lift on a 106 lsa. The intake is a edelbrock dual quad. The fuel is E-85.

Would there be a worth while gain in output for the above combo?
I would be far more concerned with the flow of the heads than I would be with increasing the static compression ratio. If you found the right heads, you could make more power while lowering the static compression ratio.
06-20-2013 03:14 PM
ap72 MAYBE 5%, so on a 425hp engine MAYBE 25hp.

Easier ways to get that power, but to each their own.
06-20-2013 02:44 PM
SPEED MASTERS CC As far as the baffled headers go, they will be un-baffled for racing. The dual quad air gap is staying on for now. The cam is staying also, it rocks. No supercharger in this engines future. I just wanted to know what the gain would be going from 11.7-1 to 13.5/14-1 compression if any...
06-20-2013 10:22 AM
ap72
Quote:
Originally Posted by oldbogie View Post
The thing that counts is the Dynamic Compression Ratio (DCR) to get at this requires a timing card with the intake closing point in crankshaft degrees. To make the calculation the rod length and stroke are also needed because the math turns the rotational degrees of the crank into a trig function to compute the amount of stroke used up at the point where the intake valve closes.

A caution in that many timing cards give the event timing starting from .050 inch lift which is not yet the point where the valve is closed on its seat. Many models have you add 15 degrees for this situation but this rather models modern fast ramp cams, older design and muscle car era cams and many required by rule limitations of racing associations specify cams that tend to have long ramps which may hold the valve off its seat for 25 to 30 or more degrees. While admittedly this is much not of a gap between the valve and the seat one needs to keep in mind that reverse pumping is occurring with the compressive force of the rising piston behind it. You can calculate the total ramp if you have the total duration and the .050 duration, then subtracting the latter from the former, dividing by 2 will give the ramp degrees between .050 and totally closed. This assumes the ramp is symmetrical on both sides of the lobe.

As far as gains go, this depends upon the cam and the DCR. If the DCR is optimized ((keep in mind that the DCR is always less than the Static Compression Ratio (SCR)) then there is little gain to be had 2-3% maybe. If the DCR is sub-optimized then the gain can be substantially larger. Generally the DCR needs to be at least 8 to 1. I have a range I try to hit that goes to 9 but there are qualifiers to ratios above 8 and maybe a couple decimal points more. A street engine or any engine that's working with a lot of vehicle weight and high gear ratios needs to be lower where lighter weight and stiffer gearing will work with more. Lower octane pump fuel needs to stay around the 8:1 figure, high octane can tolerate more. Iron heads need to stay around 8, aluminum can push .5 to 1 full point more depending on octane, vehicle weight and gearing. Small chamber modern fast burn heads can tolerate more; way more than old smog era open chambers and some more than the old pre smog small chambers, basically this is where the spark plug is located in these older heads. Piston shape is important flat tops and D-dish pistons will favor higher ratios, round dishes and stepped pistons the latter looks a lot like a D dish but doesn't contain the dish in a bowl on the spark plug side, these will not tolerate as much compression ratio as a F/T or D dish but do better than a round dish. Domes are sometimes a necessary evil if large chamber heads are used they're not efficient but they are effective.

Calculation of the DCR is dependent upon calculation of the SCR, to get to the desired DCR you've got to play the two back and forth a few times.
he's running E85, not gas. Its DAMN HARD to get enough compression to detonate with E85. You still won't see much gain after about 14-15:1 compression though.


I'm not sure if this engine is rules restricted or not, but adding a supercharger would be almost the same cost and provide a lot more power, assuming the long block can handle that much power.
06-20-2013 09:41 AM
oldbogie
Quote:
Originally Posted by SPEED MASTERS CC View Post
I am considering changing cylinder heads from the current 64cc chambered 200 cc Sportsman 2's to 50cc chambered 220 cc heads from engine quest.

The engine is a 408 sbc, 11.7-1 compression, 250 duration at .05/.575 lift on a 106 lsa. The intake is a edelbrock dual quad. The fuel is E-85.

Would there be a worth while gain in output for the above combo?
The thing that counts is the Dynamic Compression Ratio (DCR) to get at this requires a timing card with the intake closing point in crankshaft degrees. To make the calculation the rod length and stroke are also needed because the math turns the rotational degrees of the crank into a trig function to compute the amount of stroke used up at the point where the intake valve closes.

A caution in that many timing cards give the event timing starting from .050 inch lift which is not yet the point where the valve is closed on its seat. Many models have you add 15 degrees for this situation but this rather models modern fast ramp cams, older design and muscle car era cams and many required by rule limitations of racing associations specify cams that tend to have long ramps which may hold the valve off its seat for 25 to 30 or more degrees. While admittedly this is much not of a gap between the valve and the seat one needs to keep in mind that reverse pumping is occurring with the compressive force of the rising piston behind it. You can calculate the total ramp if you have the total duration and the .050 duration, then subtracting the latter from the former, dividing by 2 will give the ramp degrees between .050 and totally closed. This assumes the ramp is symmetrical on both sides of the lobe.

As far as gains go, this depends upon the cam and the DCR. If the DCR is optimized ((keep in mind that the DCR is always less than the Static Compression Ratio (SCR)) then there is little gain to be had 2-3% maybe. If the DCR is sub-optimized then the gain can be substantially larger. Generally the DCR needs to be at least 8 to 1. I have a range I try to hit that goes to 9 but there are qualifiers to ratios above 8 and maybe a couple decimal points more. A street engine or any engine that's working with a lot of vehicle weight and high gear ratios needs to be lower where lighter weight and stiffer gearing will work with more. Lower octane pump fuel needs to stay around the 8:1 figure, high octane can tolerate more. Iron heads need to stay around 8, aluminum can push .5 to 1 full point more depending on octane, vehicle weight and gearing. Small chamber modern fast burn heads can tolerate more; way more than old smog era open chambers and some more than the old pre smog small chambers, basically this is where the spark plug is located in these older heads. Piston shape is important flat tops and D-dish pistons will favor higher ratios, round dishes and stepped pistons the latter looks a lot like a D dish but doesn't contain the dish in a bowl on the spark plug side, these will not tolerate as much compression ratio as a F/T or D dish but do better than a round dish. Domes are sometimes a necessary evil if large chamber heads are used they're not efficient but they are effective.

Calculation of the DCR is dependent upon calculation of the SCR, to get to the desired DCR you've got to play the two back and forth a few times.
06-20-2013 09:13 AM
vinniekq2 you could gain power with a bigger cam,better intake and carb and way better headers.Those baffled hot rod headers could be costing you 50 hp?
those sportsman II heads can flow 275 cfm with porting,or you can buy heads that flow 320 CFM out of the box
06-20-2013 07:45 AM
ap72 I believe those 50cc heads are on a 21 degree valve angle (they've been angle milled 2 degrees), if that is the case it may be a headache to get the intake and exhaust to work right.

To be honest a simpler way to see a power gain would be changing to a better intake, milling the heads you have and maybe getting them ported, and getting a different cam.

The total cost will be the same but it'll be an easier approach with less headache.

Adding a supercharger or a shot of nitrous would also work- if you're willing to consider that.
06-20-2013 07:32 AM
SPEED MASTERS CC
Sbc 408 small chamber heads for more compression

I am considering changing cylinder heads from the current 64cc chambered 200 cc Sportsman 2's to 50cc chambered 220 cc heads from engine quest.

The engine is a 408 sbc, 11.7-1 compression, 250 duration at .05/.575 lift on a 106 lsa. The intake is a edelbrock dual quad. The fuel is E-85.

Would there be a worth while gain in output for the above combo?

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