Why did chevy use 2 different spring retainers on the stock 5.0 heads? exhaust has one style and the intake has another. Can I use just one type of these on there since the aftermarket ones are all the same?

Are the valves from the 87+ 5.0 TPI heads and the 5.0 TBI heads the same dimensions?

 

The exhaust valves use rotators and they are much thicker then the intake valve retainers. The exhaust spring pockets are deeper as well to accommodate for the thicker retainer so it has the same installed height on the spring.

You can get rid of them but you will have to shim up the difference when you install the new hardware. I can't find my notes from the 305 heads I was measuring to build but I think the rotators are .060 to .100 thick.

 

Im mostly thinking that I will use whichever retainer is lighter in weight. What about the valves..... are they the same size?

 

Intake and exhaust valves are very different diameters.

 

I think he means between the two heads? (the TPI and TBI heads)

If that's the case then yes they are same. Unless someone installed bigger valves at some point in one of the heads. They should be 1.84 intake and 1.5 exhaust.

Given the option I would ditch the heavy rotators. They weigh a lot by comparison. You can tell that just by holding it in your hand.

 

Yes i did mean between the different heads. I am putting the 081s on my TBI motor and dropped the heads off at the machine shop and they asked that i bring the other valves too since i may have damaged the originals when cleaning them.

So if i use the ligher retainers I will have to shim the intake valves or shim the exhaust valves?

 

My TBI 350 had rotators on both the intake and exhaust.

 

You will have to measure to find out. That is the only way to know for sure.

 

ok I will get them back in a couple weeks and see from there. Thanks

 

The exhasut ports springs will need a shim. .187" i believe if i measured correctly.

Seems Summit doesnt have much to except to combine a bunch of different sizes. Would a hardned washer from the hardware store be alright. I had to use one before and didnt have any problems.

 

If you switch from stock rotator/retainers to stock non-rotator/retainers (i.e. identical to the intake side) you will need to shim about 1/16" to make up the difference and bring the installed height back down to stock spec (1.70"). A .060" shim in each exhaust spring pocket will get you close.

 

thanks. I was a bit confused there on the shim size. part ordered.

 

I found out it really depends on the retainer you use. The Elgin retainers I switched to increased installed height quiet a lot over the stock retainer and rotators, they were designed to do so. It was puzzling me so I did some research and found a good Crane Cams tech article explaining the different types of retainers; ones that install stock height and + and - install height. They also increased retainer to seal clearance quiet a lot too, sorry I don't have the notes handy for exact reference.

My intakes needed .100 shim to get 1.7 install height and if I'm not mistaken the exhaust were .160 to get there.

 

Im only trying the match the same height as the intakes valves on the stock 081 heads. The exhasut valve seats are cut further into the head and the valves are the same lenght. I measured something really different but I dunno if i did it right. I did order .06 shims based on the above suggestion. They werent much but i think i will need maybe double or triple that height. Anyone know for sure?

 

What are you measuring with and what retainers are you using?

 

Im using a scientific calipher with inch and mm readings. The exhaust ports use was i heard are called rotator retainers. They spin the valve i guess. The intakes valves have a flat retainer just like u would find on summits website under retainers. Im only gonna be using the flat ones since they weigh less but there is that height difference that i need to take up on the exhaust spring seats. I can take a picture later when i get home.

 

Yep re-read post #2 on rotators. If you take the rotators and the oil shield off you will probably have to shim at least .100 to make up the difference. The oil shield is .030, so it need considered as well.

If you are measuring from the bottom of the retainer (the outer "ledge") to the spring pocket bottom and getting 1.86 you may have off-set or even the wrong retainers. A part number for them would help more then a picture if you got it.

Your machine shop shouldn't charge you anything to double check your measurements. Just take in one of your heads and the hardware and ask them to check your measurements because they sound off. You could have the wrong retainers, using 10' when it should be 7'. They could be offset to increase spring height.

I was just last night measuring a set of 305 heads (416 casting) for shims. Using aftermarket retainers and no oil shields the exhaust was 1.81-1.83 and intakes were 1.73-1.75 but I have aftermarket valves and valve job so yours will be a bit different.

 

everything is stock from the original heads and i have a set of 081s and the TBI swirl port heads and both are the same. same retainers, same locks, same springs sizes. I will be using the oil shield just to keep things consistant.

in the last pic u can really see the difference in the heights