Who can talk about bigger valves?

sizemoremk

Registered User
What do bigger valves mean to cam selection and/or porting?

What are the things to know when looking for bigger valves?

thanks!
 
sizemoremk said:
What do bigger valves mean to cam selection and/or porting?

What are the things to know when looking for bigger valves?

thanks!
The way i see from porting my own heads is that you dont get more than a 30 to 40 rwhp gain on a stock valve port job with a cam. I only lost 1 pound of boost from porting my stock valve head and it looks real good and smooth.

If you can afford it, get bigger valves put in after you port your heads to notice much of a difference. Each valve will be about $15 as will the valve seats.

If you want to know the exact cam to get that matches your head with bigger valves then you would have to flow it. You really dont need to flow it, you could just go with the average 210/220 duration cam with around .520 lift.
 
Rgr

I have been talking with RGR about getting bigger valves. It would be worth your time to ask him about hooking you up. I have yet to order them, but will be doing so as soon as the moneys there. Hes been a big help so far. Mike
 
littleboylan said:
I have been talking with RGR about getting bigger valves. It would be worth your time to ask him about hooking you up. I have yet to order them, but will be doing so as soon as the moneys there. Hes been a big help so far. Mike
What size valve and how much are you getting them for. Can you buy valve seats from him also?
 
CMac89 said:
What size valve and how much are you getting them for. Can you buy valve seats from him also?

Larger seats are not the answer. I've got them in my heads and it didn't do squat for the flow numbers.
 
If you go with valves that will fit in the stock seats, you can save some bucks. You can't fit 1.60" exhaust valves in the stock seats. Depending on how talented the person is who sets up your valve depths and stuff, you can make gains or see loss in changing valve seats. I think you can fit 1.54" exhaust valves in the stocks seats. I'm not sure but maybe you can fit 1.84" intake valves in the stock seats too. One of the most important things in going with larger valves is to unshroud them in the chambers. Bigger valves will be shrouded more and perform worse than smaller ones if you don't unshroud them. If you go too big, you will be shrouded by the cylinder wall. Remember, we have a tiny bore compared to most cars that run 1.9" and larger intake valves.

If you do any welding on the exhaust ports, your seats will most likely become unseated from the expanding and contracting, if that is the case, you will need to put in new seats.

When home porting, don't forsake velocity and swirl while trying to just make a larger port. If you enlarge the exhaust port at the exit and don't have a giant bowl and throat of the port, you just scrapped your heads. Try to keep the bowl, throat and exit as close to the same cross section as possible.
When porting intakes, you can gasket match the inlet side smooth out the port and keep the swirl of the air the same as stock or even enhance it a little. Try not to mess up the transition area of where the fuel injector squirts in.
 
So if you don;t go too big to fit in the stock seat, all that would be required is a valve job then correct?

Don't the SBC valves have different retainers? What else would be required? I know new springs would be in order, I've seen it recommended that srpring weigh be 120 closed and 280 opened. I looked through ye ole' summit catalog, and didn't see a set that matched those criteria...

Would we need sbc springs and retainers if we went to sbc valves?

Kinda wanting to see what the cost of home porting and bigger valves, vs steg stageII is. I'm not sure I can afford the stegs, the wife was not happy with my last purchase of MAF and 42# injectors, so I guess the budget will depend heavily on what I can get out of my parts car....

Thanks guys!
 
The SBC valves use the same retainers, they are just a different height. I think they are a smidge longer. I had to shim up my roller rockers when I did my valves. I think you would only need new springs if your cam requires them. The stock springs could be shimmed up to the correct pressure to match the bigger valves.
 
Hummmm

So, would bigger valves and same spring with a .500 lift cam work OK???

I've seen it said that .500 is the limit for stock springs.... Is that a hairy limit, or would new aftermarket springs and .520 lift cam be better????

One more thing, to make sure I am gettig the facts straight.

The big valves would help out at lower lifts, correct? Does it means that cam lift doesn't need to be as tall???

Thanks!
 
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XR7 Dave said:
Larger seats are not the answer. I've got them in my heads and it didn't do squat for the flow numbers.
I wasn't saying that seats would increase flow numbers. You cant just put a valve thats bigger than the seats and expect the valve to seat.

I also dont know the biggest valve you can go on stock seats, but I would atleast go the size of the Stiegemeyer valves. Thats 1.84 intake and 1.60 exhaust, but 230cfm is all you are going to get out of the intake side. You wont get over 190cfm (if even that) on the exhaust side unless you weld and reshape the ports.

Somehow we need to get a 2.02" intake valve in there to get around 250 cfm then cars would really wake up.
 
I've been told that a 2.02" valve would be too close to the cylinder wall when it's open causing it to be shrouded and you would get worse flow. Remember, we are working with a 3.810" bore compared to the 4" bore on the small block ford and small block chevy.
 
Heads

Slysc said:
I've been told that a 2.02" valve would be too close to the cylinder wall when it's open causing it to be shrouded and you would get worse flow. Remember, we are working with a 3.810" bore compared to the 4" bore on the small block ford and small block chevy.
I just had my new heads done and picked them up today. I did all the porting. The heads are stock valve seat. 1.84 intake and 1.6 exhaust and yes the seats are ok with that size valves. With the 5 angle and valve seats cut and heads milled and cost of valves was $580.00
 
catwithboost said:
I just had my new heads done and picked them up today. I did all the porting. The heads are stock valve seat. 1.84 intake and 1.6 exhaust and yes the seats are ok with that size valves. With the 5 angle and valve seats cut and heads milled and cost of valves was $580.00
Looks like I am going to buy some intake valves and rip my heads back off, put them in, and then buy a 279/270 duration (at .050), .850/.750 lift (at .050), on a 104lsa. :eek: :eek: :eek: .

My machinist for our race cars includes a 3-angle valve job on a complete head/valve job. He charged me $267 for new guides, stem seals, all new seats, facing the valves, two new valve because an intake and exhaust valve was bad, surfacing, hot tank, and pressure check.

He's a high class race motor builder, head porter, machinist. Not some guy that does cheap *** head work.
 
catwithboost said:
I just had my new heads done and picked them up today. I did all the porting. The heads are stock valve seat. 1.84 intake and 1.6 exhaust and yes the seats are ok with that size valves. With the 5 angle and valve seats cut and heads milled and cost of valves was $580.00

What springs are you using, and can you get a part number for the valves
they used? I assume these are SBC valves???

Did they have to shim the springs or anything???

Thanks!
 
sizemoremk said:
What springs are you using, and can you get a part number for the valves
they used? I assume these are SBC valves???

Did they have to shim the springs or anything???

Thanks!
If you ever need some valvetrain parts go straight through "catwithboost." He straight hooks a brotha up. :)
 
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