Biggest Valves in factory heads?

[newtownhood]

I'm finally doing a full rebuild on my '86 GN. I'm getting a set of Diamond Pistons, .030 over, cam upgrade( I forget which one off-hand...highly recommended on this site 3yrs ago, it's written down somewhere), Eagle Crank and Rods, I have a set of new GM LT-1 valvsprings I was going to use, but my questionis how big of valves can I install in the factory heads with the enlarged bore? With the necessary machining,and replacement manley stainless valves, is it cheaper to replace the heads? And if so, what are some suggestions? The car will be a semi-daily driver and ran on pump gas(91-93) I think I have a TA-49 Turbo, redtop injectors, and a 93 Chip...and a 2800 stall Pat's convertor. Is boring one of these engines .030-over bad for longevity? Do Diamond Pistons come with rings, if not, what rings should I use? Also, is anyone interested in helping me put my car back together in Bucks County? It's been apart for a few years, so I might need help figuring out where things go...I can help you out with future car audio and electronics needs. Pizza and beer? :smile:

 

[corymc]

i dont know if these are the biggest but i have 1.775 intake 1.50 exhaust
Diamond Pistons dont come with rings, mine uses hastings rings

 

[turboclam]

With all the money you're spending I would do a roller cam. It's piece of mind. And if you do a roller, those LT1 springs won't work. You need 130# springs. You can go through a Buick vender like Full Throttle or you can call Jeg's or Summit for a cam kit. At this point I would just buy the whole kit with the double roller chain and all. Hope this helps.

 

[newtownhood]

I was going to use a speed-pro cam kit, with the double roller timing chain. I wasn't actually originally planning to go too balls-out, but I guess the former owner had an issue changing the oil, so the cylinders and mains had wear. So when I bought the Eagle crank, they told me to buy the rods too. I got both for $1k and no tax. Good deal? Anyone else have input about valve size or brand to use? I've used Manleys in the past in other stuff which is why I was considering using them again.

 

[Cheeseburger]

The biggest valves i have used on a stock iron head are 1.81 int and 1.50 exhaust.
You will need to offset the int valve guide for that size valve to work.

 

[Cheeseburger]

The biggest valves i have used on a stock iron head are 1.81 int and 1.50 exhaust.
You will need to offset the int valve guide for that size valve to work.

 

[Big Turbo Scott]

With all the money you're spending I would do a roller cam. It's piece of mind. And if you do a roller, those LT1 springs won't work. You need 130# springs. You can go through a Buick vender like Full Throttle or you can call Jeg's or Summit for a cam kit. At this point I would just buy the whole kit with the double roller chain and all. Hope this helps.

And,according to "harry" the turbo clam,make sure you have LOTS &LOTS of zip ties and an old used lite green trash can to make an intercooler duct!


Shoemakervankiserbacher who at hendrick what?????????

 

[Turbo1dr]

Use Total Seal Gapless rings.

 

[newtownhood]

I was thinking they might be a good ring set. Will the 1.81 and 1.50 valves be ok for street use, about 5k miles a year?

 

[turboclam]

I would still do a roller cam.

 

[johnnyttype]

I was thinking they might be a good ring set. Will the 1.81 and 1.50 valves be ok for street use, about 5k miles a year?

i use 1.77 intakes and 1.5 exh. FWIW i do not think that the 1.81's are necessary. i doubt it will make much of a difference if any, some good port work in the bowls will give you more. i actually believe someone said they prefered 1.71 intakes because the larger valves had shrouding issues. anyone else hear this before?

 

[NCTURBOS]

1.775" intake valve & 1.50" exhaust valve is as big as you want to go without having to move the guides, seats, etc. around. Ferrea valves seem to be the valve of choice for most, and is what we use in our heads. This combination of parts and port work has been in the 9-sec. 1/4mi. times, which is plenty for most. IMHO, at this known performance level it isn't cost effective to go any more drastic with the 8-bolt iron head, as clamping force is more of an issue.

...If class racing where the 8-bolt iron head is required...We're working on something more drastic there... We just have to weigh out the performance vs. the cost vs. the reliability/longevity of the head...


K.