25th92rs

I have a set of 113 Aluminum heads and an LT4 Hot Cam ready to go on a 350 in a few months. I'm curious as to if I'll have max lift issues with the .494" lift of the hot cam with 1.5 rockers. I've heard mixed opinions on how much lift the stock 113's allow before guide to retainer clearance is compromised. Some have said beware and others are running the Hot Cam and seem to be fine, i just want to make sure.

rodj

http://forums.corvetteforum.com/c4-t...113-heads.html

I think the age of your old tired valve springs would be a more important factor ;buy some LT4/ZZ4 drop in replacements
http://paceperformance.com/i-6255251...-diameter.html

and the matching retainers

25th92rs

yeah, i've got the spring and retainer kit as well, just curious on if anyone knows the answer about the max lift for the heads. They're packed away in a box right now so I thought I'd get a quick answer here.

leesvet

The max lift should be documented. Contact GM performance techs for a straight answer on that.

I agree with rodj...I'd be more concerned with the springs. At extreme lift there could be binding issues. Just to be safe a new set with the known compressed height will tell you real quick & easy if there is a problem ahead.

tequilaboy

The answer will depend upon the intake or exhaust valve and also type of retainer and seal (if any) is used.

I just pulled one of my old 113 heads with LT4 springs out of a box and popped a couple of valve springs off to check.

On my 1988 113 heads, the exhaust guides are taller than the intake guides, so there is less clearance between the exhaust retainer to guide or retainer to seal if one used as compared to the intake.

It is possible that the guide height has changed over the years with the 113 heads. I have not seen many other references to this issue.

Using one cylinder as an example.

Intake valve with seal:

With the LT4 retainer and typical intake valve seal installed, I have ~9/16" retainer to seal clearance or approx. 0.56". This is not a precision measuement but should be close enough to give you an idea.

Exhaust valve without seal:

With the LT4 retainer and no seal installed, I have approx. 19/32 retainer to guide clearance or approx. 0.59".

If using the LT4 retainers, the intake should be fine with seal, for the exhaust you will want to check if you have enough clearance to use a seal.

I ran a slightly bigger Comp 503 cam with 1.5 rockers with 0.503 intake, 0.510 exhaust lift and chose to run without a seal on the exhaust guide to ensure adequate retainer to seal clearance.

Note: My car did not have seals on the exhaust side to begin with, although it is common today to use seals on both intake and exhaust.

leesvet

Good points...

IIRC then heads did change in 88, so the alum 86-87 were of one ex port shape & possibly guide type, then the 88+ were another. I never heard about 2 different size guides on the same yr oem...interesting. Makes me wonder IF the longer guide could be used both sides to increase the lift range and spring height? Longer valve stem of course...There are plenty of aftermarket guides available...perhaps something there could be found to satisfy the needs of high lift, long spring w/seal?
This is one of the situations that the math teacher warned us about..!

25th92rs

Thank you, taquilaboy. Finally a good answer. My heads a tucked away in a box pretty deep in my garage so this was still easier than measuring them myself. I'm running stock ratio 1.5 rockers with the Hot Cam so my lift will be around .494. Sounds like I should be good to go, I'm not sure what year car my 113's came off of but they do have the "D" shaped exhaust ports so it's at least 1988, but i'm thinking they were from a '90 vette.

25th92rs

yeah, no kidding. Normally I'm a measure 5 times cut once kind of guy, but i've been piecing this motor together over a long period of time so my normal system is all messed up. I guess i just gotta go dig those heads out again, get the calipers out and start measuring! I've seen plenty of 113 headed motors running the lt4 hot cam and bigger but what is never known is if that person had to put a crap ton of work into just getting everything clearanced. I guess it's time i jump into it!

cv67

If it were me Id take the heads in and have them cut anyway just to be safe plus you decide you want more later on you know you got the room. God fobid you run into valve float it "its close" you may drop a valve real easy.
Cheap to have done.

rodj

128 heads had rotators on the exh valves that the later 113 head didn't have
The exh spring need shimming to makeup for removal of the rotators

http://temp.corvetteforum.net/c4/vader86/113heads.html

Street89vette

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ghoastrider1

anyone thought about screw in studs with the high valve spring pressures?