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  #16 (permalink)  
Old 06-13-2012, 09:39 PM
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Quote:
Originally Posted by ap72
If you can gasket match its not that much harder to work the bowl area- that is where the real gains will be made. Work the bowls and get a proper cam and you'll come close to seeing that 50hp. The majority of your flow increase is a half inch either side of the valve seat. Not by the intake manifold.

As for the carb, if you're happpy with it keep it but a well tuned 800cfm or larger carb that is properly built will show gains from idle to redline, but its not cheap.
Not sure if I'm ready to tackle porting without an experienced dude looking over my shoulder. I've been wrenching for over 40 years but I have claimed to be a machinist. I have good steady hands for an old fart but I really don't know what to remove from where.

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  #17 (permalink)  
Old 06-14-2012, 08:36 AM
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Quote:
Originally Posted by Greg T
Not sure if I'm ready to tackle porting without an experienced dude looking over my shoulder. I've been wrenching for over 40 years but I have claimed to be a machinist. I have good steady hands for an old fart but I really don't know what to remove from where.
that's what the internet is for. there are plenty of experienced guys willing to share. there are a lot of posts on this site alone. its hard to do a great job but a fairly good job can be done by anyone with enough diligence.
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  #18 (permalink)  
Old 06-14-2012, 09:48 AM
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Quote:
Originally Posted by Greg T
Not sure if I'm ready to tackle porting without an experienced dude looking over my shoulder. I've been wrenching for over 40 years but I have claimed to be a machinist. I have good steady hands for an old fart but I really don't know what to remove from where.
Greg,
You know as well as most people on here that without a flow bench, porting can hurt more than help. While there is a lot of good info on here and the internet to be found on porting, it still requires some experience and the right equipment. If you don't feel comfortable and don't have the equipment, I would leave it alone. It sounds like you have built a good motor and only a few horses short of your goal.
Do you know what your compression ratio is? If you are going to be removing the heads anyway, you might consider a thinner head gasket the next time around if it won't raise your compression past pump gas and you have adequate P/V clearance to do it. This will only gain you a few ponies too and may not be what you are looking for. Just a thought.
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Old 06-14-2012, 01:13 PM
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Quote:
Originally Posted by S10 Racer
Greg,
You know as well as most people on here that without a flow bench, porting can hurt more than help. While there is a lot of good info on here and the internet to be found on porting, it still requires some experience and the right equipment. If you don't feel comfortable and don't have the equipment, I would leave it alone. It sounds like you have built a good motor and only a few horses short of your goal.
Do you know what your compression ratio is? If you are going to be removing the heads anyway, you might consider a thinner head gasket the next time around if it won't raise your compression past pump gas and you have adequate P/V clearance to do it. This will only gain you a few ponies too and may not be what you are looking for. Just a thought.
Static CR is 10.6:1 so I dare not go much further. She runs well at 35* total advance and 92 octane pump fuel.
The reason I'm only going to gasket match the ports is because it won't hurt and I'll already have it apart. But I have seen people destroy some very expensive heads around here so I'm just not willing to take the risk.
We've got some excellent engine builders in town but they only do their own stuff. So, I think I will most likely just freshen things up, gasket match and reassemble.
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  #20 (permalink)  
Old 06-14-2012, 06:32 PM
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Be careful doing a gasket match. You do not want to end up w/a bulge where the head and intake meet! A bulge will momentarily cause the air flow to slow, causing it to stack up and less flow will be the result. Instead of matching the ports to a gasket, you should (if you do anything) match the head ports to the intake ports, then if necessary open the gasket up to prevent it from intruding into the port opening. I like to always have the edge of the gasket back from the openings at least 0.050" all the way around.

To do a good port match isn't as easy as using a gasket as a template. The surfaces of both the head and intake need to be plotted and compared to see where there is material that needs removing. The head-to-intake position has to be carefully maintained as it will be on the assembled engine. This isn't as easy as it sounds because the bolt holes in the intake are larger than the bolts, so the intake can move fore and aft if not held in position.

The following section of a Circle Track article under Line Up and Measure Down tells how to plot the datum points you need.

One last thing to consider: If the intake runner is a little smaller, that is not a problem but the other way around IS a problem. You can do a search for how to port match head to intake or similar terms (just not gasket match ) for more.
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Old 06-14-2012, 11:20 PM
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Quote:
Originally Posted by cobalt327
Be careful doing a gasket match. You do not want to end up w/a bulge where the head and intake meet! A bulge will momentarily cause the air flow to slow, causing it to stack up and less flow will be the result. Instead of matching the ports to a gasket, you should (if you do anything) match the head ports to the intake ports, then if necessary open the gasket up to prevent it from intruding into the port opening. I like to always have the edge of the gasket back from the openings at least 0.050" all the way around.

To do a good port match isn't as easy as using a gasket as a template. The surfaces of both the head and intake need to be plotted and compared to see where there is material that needs removing. The head-to-intake position has to be carefully maintained as it will be on the assembled engine. This isn't as easy as it sounds because the bolt holes in the intake are larger than the bolts, so the intake can move fore and aft if not held in position.

The following section of a Circle Track article under Line Up and Measure Down tells how to plot the datum points you need.

One last thing to consider: If the intake runner is a little smaller, that is not a problem but the other way around IS a problem. You can do a search for how to port match head to intake or similar terms (just not gasket match ) for more.
What I had in mind was to open the ports to match the gaskets but to slowly taper and blend them in so that there is no step or defined line where the material has been removed. I was going to make it as smooth as possible so as to make it appear to be factory rather than cut.
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Old 06-15-2012, 06:03 PM
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Greg- having a lot of overlap allows a cylinder head to better fill a given volume at higher engine speeds. It helps to "jumpstart" the intake event. Typically if you are running a large engine but have cylinder heads on the small side, then a tight LSA would be of great benefit. You seem very eager to learn and have a good base of knowledge. I would suspect you'd have a good time on this website right here:

http://www.yellowbullet.com/forum

Tons of guys in there that have forgotten more than we will ever know about engines. Just have some thick skin in some of the sections because it can get rough, lol. The technical section has a lot of guys with 7,8, and 9 second cars:

http://www.yellowbullet.com/forum/forumdisplay.php?f=4

This site right here has a few smart guys in it, but it has a lot of old school guys that have their heads stuck in the sand since '73. You will get a lot of mixed advice in here. Just read everything with an open mind.
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  #23 (permalink)  
Old 06-15-2012, 06:57 PM
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Checked out the bullet site link. Its all good, but if you are going to beat that drum do it somewhere else, old school savvy, class and respect is the way we like it as compared to in your face testosterone charged bragging.

It is not all about ET's here, head in the sand my arse
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  #24 (permalink)  
Old 06-15-2012, 07:08 PM
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Thanx, folks. I'll check those out. I'd love to have the full machine shop in my back yard but around here it's just not possible.
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