rb20 cam pulleys

[squbafreak15]

alright heres the situation i bought the engine. it came with another one the older rb (red top) for parts is wut i was gona use it for. got it in my s13 droped it off to get it wired and its not getting compression so he cant get it running. so what comes to mind is bent valve or bad rings. but the guy wiring was wondering if both of the timing pulleys on the cams are suposed to be the same size.

so not really thinking about the pulleys being the wrong size ive gone ahead and had the head of the other rb i have presure tested and it was good. so i went ahead and had it hot tanked. well we are about to pull the engine out put it on the stand check the rings and swap the heads. and well if i need to order new pulleys id like to do it asap to get this thing running and outa my buddys shop.

[mott6904]

Wow if the guy wiring the car doesnt now if the cam gears are the same size then i wouldnt let him wire it. The cam gears are the same size, the crank gear is half the size of the cam gears, because the crank makes two rotations when the cam makes one. Anyways back to your problem. If you have no compression at all then i would say it is timed wrong or it has bent valves. If it has low compression then i could be rings. It is low comression then throw some marvel magic oil in the cyclinders and let it sit overnight then test again. If the compression reading goes up then you have a ring problem. I didnt think the older redtop head is the same as the silver top engines, i could be wrong.

[squbafreak15]

well the gears are the same size. and it is timed right we thot the same thing then went and check his timing and its dead on and theres no compression so i guess well do that oil thing that you mentioned after we change the head

[mott6904]

If you have the head off you will be able to tell if you have bent valves. Are you sure that the older head will fit on the newer block.

[squbafreak15]

ya it should. the intake mani is diffrent is the only diffrence ive noticed but ill just use the newer intake mani so it will have eccs

[Bluefire]

Why don't you do a leakdown to see where its leaking from. FYI i've a had a few SR swaps show zero to low compression. I found out that if the motor has been sitting around for awhile, the valves and valve seats can develop a bit of surface rust, preventing a good seal.

The fix: I use the leakdown tester to pressurize the cylinder (piston at top, all valves closed). Then Ill take some kind of extension and a hammer. I then give each of the lifters a decent tap. This usually knocks off carbon buildup and some rust and helps the valve seal back up. You can actually see pressure start to increase on the leakdown tester as the valves start to seal back up.

[SullivanRacing06]

if its been sitting for a while then it prob has a few stuck rings, use atf or marvelk mystery oil spin the motor over for a bit and recheck the compression, some of these motors have been sitting around and the rings stick

[squbafreak15]

how much of that marvel oil should i put in?

[mott6904]

I would say about two cap fulls

[Carl H]

cant bolt the silvertop intake manifold to the redtop head...redtops had butterflies in the intake mani and thus are 'dual port' so 12 ports instead of 6.super lame.might be able to use the valves out of it...iirc the intake cam on the redtop has a bit more duration as well.

[squbafreak15]

damn so i just wasted the money on getting that head cleaned up. i guess ill try the mavel trick if that doesnt work ill do the valve job. and im not sure which cams go into the red one. i have 5 cams 3 cams outa engines and then 2 that are in the silver top. he broke one of the cams at one point. when we were loading everythign in the truck.. is there any thing on the cams that would show that its from the older engine or that its more agressive

[squbafreak15]

well if i put the old head with the old intake mani on there will i be able to run it? all the plugs and sensors seem to be the same just in diffrent spots