Stuck valve?--340 V8---Compression check RESULTS

[RedFish]

Question... On the day it suddenly started crossfiring, was it raining ? or had you washed the engine ?
Reason I asked is if a little water gets in the distributer it may not cause a problem until heat causes it to condensate up to the top of the cap. Then fire jumps all around.

 

[blano86]

The block is stamped ' HM 340 R '. I think it is a 1972 340. It was not raining when it started to act up. I looked at the timing chain today and it is what I think is a dual roller chain? It has metal gears. It looked fine. Since I tore it down that far I am going to have it rebuilt.

I think the 340 is totally stock, and I want to add some more horses with out changing too much with the rebuild. Does a little more radical cam cause me to get new rockers etc.? Remember I am a newb!

Another issue is how much for a rebuild? I called a local machine shop that has some good reviews and they said they could do a long block rebuild for about $2,000. Also they said a valve job would be $548 for both heads. Is that too much or a good price? Should I just let them do a short block? I have a friend who is a lot more mechanically wise, so he could help me with the short block.

Does any one have any tips for a rebuild for a 340 that is stock? Any ideas for extra horse power without replacing too many parts (radical cam = new rockers/lifter/springs)?

Another issue is ethics. Do I need to take any precautions before I hand over my 340? Like take vin Numbers and numbers on parts such as heads? Should I be worried about this? How will I know that my crank went back in the engine? Any pointers will help.

Sorry for all of these questions, but this is what I have been thinking about. I have never had an engine rebuilt.

Thanks to all that have responded with their thoughts.

 

[fishy68]

the block is stamped ' hm 340 r '. I think it is a 1972 340. It was not raining when it started to act up. I looked at the timing chain today and it is what i think is a dual roller chain? It has metal gears. It looked fine. Since i tore it down that far i am going to have it rebuilt.

I think the 340 is totally stock, and i want to add some more horses with out changing too much with the rebuild. Does a little more radical cam cause me to get new rockers etc.? Remember i am a newb!

you can put a somewhat bigger cam in it without changing the rockers but there are limits to what the stock rockers will take plus there's the known issue of them not being very accurate on their ratio. A good set of aftermarket rockers (no cheap chinese junk) is a good upgrade. also remember the valve springs will have to be changed if the cam is.

another issue is how much for a rebuild?

that can't be answered very accurately by us since we can't see the engine and the shape it's in (what's worn in what areas). Plus machine shop prices vary accross the country so it may be $2000 here in il but in ca it may be $3000.

i called a local machine shop that has some good reviews and they said they could do a long block rebuild for about $2,000. Also they said a valve job would be $548 for both heads. Is that too much or a good price? Should i just let them do a short block? I have a friend who is a lot more mechanically wise, so he could help me with the short block.

depends on exactly what they consider a "total rebuild" but generally $2000 for a long block and $548 for a total rebuild of the heads is a decent price. ask them what all that entails and post back what they say and we can say more.

does any one have any tips for a rebuild for a 340 that is stock? Any ideas for extra horse power without replacing too many parts (radical cam = new rockers/lifter/springs)?

buy yourself this book, read it cover to cover and you'll learn a lot.

http://www.amazon.com/dp/0895864797/?tag=joeychgo-20

another issue is ethics. Do i need to take any precautions before i hand over my 340? Like take vin numbers and numbers on parts such as heads? Should i be worried about this? How will i know that my crank went back in the engine? Any pointers will help.

i guess it wouldn't hurt to record the numbers considering all the crooks out there but if you have real issues with trusting them maybe you should find someone else.

sorry for all of these questions, but this is what i have been thinking about. I have never had an engine rebuilt.

Thanks to all that have responded with their thoughts.

...8)...

 

[Dusterdude72]

You jumped into a rebuild pretty fast.

it would have been worth it to check into a few things first liek had been mentioned.

such as a wet test (you already had a compression gauge....just needed to put a little fluid in the cylinders) and a leak down test.

to me it sounds like either an ignition problem or gummed up valve or bad rings but not a jumped tooth.

I actually just had a 98 jeep cherokee with a 4.0 l that had 200,000 miles on it and it felt like it had a lumpy cam in it because it had a miss to it and when you punched the gas from a stop it would pop and back fire and was very sluggish off the go.

I ran a compression check and a wet test and so on and on all the cylinders it was around 120psi - 135psi give or take and then I found one cylinder that was only reading 30 psi and didnt get any better when I sprayed oil in the cylinder.

anyhow, long story short, I pulled the head and lapped all the valves,put new gaskets on,valve guide seals ,bolted it back together,put fresh fluids in it and it ran like brand new again.

it just had nasty carbon build up on the valves and wasnt allowing the valves to fully seat.

it pays to investigate a bit, you could save yourself alot of cash.

unless of course you have the money to have your engine rebuilt how you want and this is just the excuse to have it done LOL

 

[green1]

72, probably low comp. $500 for valve job? Run like hell. Need more #' s off the block, down low on the side.