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04-03-2019, 07:23 PM | #21 |
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Re: 40 V8 compression change all cylinders same time
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04-03-2019, 08:06 PM | #22 | |
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Re: 40 V8 compression change all cylinders same time
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__________________ If it Makes Spark, we do it !!!! www.bubbasignition.com [email protected] Can you give me some more details of how to determine TDC with the head on and what is the valve position when TDC is achieved? Can I put a long thin rod in the number one spark plug hole and determine when the piston is at top dead center? Should the dot on the cam gear and the dot on the gear on the crank line up on top dead center? If the dots do not line up at top dead center on number one piston then I know the cam gear has slipped? I have never rebuilt a flathead engine or set the timing marks before. |
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04-03-2019, 08:11 PM | #23 |
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Re: 40 V8 compression change all cylinders same time
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04-03-2019, 08:26 PM | #24 |
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Re: 40 V8 compression change all cylinders same time
"L78CHEVELLE"- Don't take this wrong, but you do understand the concept of a "press-on" cam gear, don't you? From your "handle", I think you might be familiar with only "bolt-on" cam gears. Early Ford V8's are different.
Last edited by tubman; 04-04-2019 at 07:41 AM. |
04-04-2019, 05:47 AM | #25 |
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Re: 40 V8 compression change all cylinders same time
I personally have never installed the press on gear in the early flatheads (done plenty Cummins diesels with press on gears) but reading I see in one article that the cam and the gear have a mark to index the cam gear to cam and of course the 2 dots for the cam to crank gear. Since it ran good to begin with the dots must have been right but the possibility of the cam gear slipping on the cam could have happened. I wish I could say but I don't know on these era flatheads how to find TDC without a head off.
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04-04-2019, 06:31 AM | #26 |
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Re: 40 V8 compression change all cylinders same time
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You have the intake off. Number one cylinder is right hand side, at the front. Use the cable tie method to locate top dead centre on the No1 piston. Observe the valves on either no.1 or No.6 cylinder. They should both be open by the same (small) amount. This would be an indication that the cam and crank are in the correct relationship. Link to thread describing tdc finding: https://fordbarn.com/forum/showthread.php?t=110405 Mart. |
04-04-2019, 09:52 AM | #27 |
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Re: 40 V8 compression change all cylinders same time
Thanks to everyone that has responded to my request for help. I have printed off the responses and will study them and try to come up with a solution to my problem. I first need to find out what the problem is and then see what my ability is to correct the problem and go from there. I will up date the post as I catch up to the suggestions I have been given.
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04-11-2019, 03:44 PM | #28 |
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Re: 40 V8 compression change all cylinders same time
Took the front of the engine off today. My 40 has the late production engine with the bolt on camshaft gear. The mark on the camshaft does line up with the mark on the crankshaft gear. Now I am even more confused. Has the camshaft worn down in 2,000 miles? I did use the diesel oil with Zinc in it since the rebuild. I did pump one squirt of oil in a cylinder and turned it over. Still got the 65 compression reading. Amy one got any ideas?
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04-11-2019, 09:24 PM | #29 | |
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Re: 40 V8 compression change all cylinders same time
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" When I was a boy of fourteen, my father was so ignorant I could hardly stand to have the old man around. But when I got to be twenty-one, I was astonished at how much he had learned " Mark Twain. |
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04-11-2019, 09:38 PM | #30 |
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Re: 40 V8 compression change all cylinders same time
If it's a new rebuild I'd suggest running it. Breaking it in on the bench is less effect then underload. If you trust your builder.
Think there was a post earlier on finding tdc with the head in. No marker on a stock 40s motor. You can make one. Find the compression stroke on #1 (thumb over hole), then the Basic idea is a stop (like a zip tie end) that you put in the plug hole of the head/cylinder and then rotate it till it stops (mark it on the cam pully), then rotate it the opposite direction till it stops again and mark it. The distance between the two is a rough tdc. A couple times is best. Or even better is with the head off and a dead stop. There are better methods here, if I look. One idea was a spark plug that was hollowed out and a bent rod was welded in that would impede the piston from completing a cycle. Either of these methods must be done by hand cranking. Never with the starter motor. If your cam is off, it'll be apparent with the crank indexed to timing. Valves lashing correct... Here is a barn version of a index. I use a timing bolt that has a welded point. Post #8 https://www.fordbarn.com/forum/showt...8503&showall=1 Just for fun.... Stock cam? or a regrind? . Last edited by Tinker; 04-12-2019 at 12:15 AM. |
04-12-2019, 10:19 AM | #31 |
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Re: 40 V8 compression change all cylinders same time
Stock cam that is new. Everything in the engine is new except the crank which was like new. Engine ran as designed for about 2,000 miles after the rebuild. Compression change and poor performance started about 300 miles ago and now the engine is down to 65 on each cylinder and very hard to start when it warms up to operating temperature. Valve clearance is 11 intake and 14 exhaust. Can some one tell me from experience a similar situation and cure from back in the day? The car is useless the way it is. Do not want to put a modern drive train in an original low mileage car. This problem is something odd for sure.
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04-12-2019, 10:28 AM | #32 | |
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Re: 40 V8 compression change all cylinders same time
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04-12-2019, 01:10 PM | #33 |
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Re: 40 V8 compression change all cylinders same time
Forgive me for asking, but you say the valve lash is .011" intake and .014" exhaust. What procedure did you use to position the cam for the lash adjustment? Did you make a valve lash adjustment before this problem arose?
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04-12-2019, 06:15 PM | #34 |
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Re: 40 V8 compression change all cylinders same time
I have the problem with the low engine compression and checked the valve lash as a possible cause thinking with a new engine the adjustments could have changed during the break in. The new rebuild has the adjustable lifters. I checked the lash on each valve by opening the intake valve on each cylinder all the way open and checking the exhaust while the intake valve is at its peak opening. Then turn the exhaust valve on each cylinder to it's peak opening and checking the lash on the intake valve of that same cylinder. I think that would be a fool proof method. Is my thinking wrong on this method? The compression was 100 or more on each cylinder about a year ago when I checked it for peace of mind. Gradually the engine has run worse and worse. I am thinking maybe the new camshaft has been soft causing it to wear down and the valves are not opening enough. I thought the Shell Rotella oil would have prevented that. Got the camshaft from a well know supplier in southern Ohio.
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04-12-2019, 06:19 PM | #35 |
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Re: 40 V8 compression change all cylinders same time
If the cam was that worn down the valve clearances would have opened up.
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04-12-2019, 07:09 PM | #36 | |
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Re: 40 V8 compression change all cylinders same time
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04-12-2019, 07:49 PM | #37 |
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Re: 40 V8 compression change all cylinders same time
Re-torqued the heads? Any chance of posting pictures of front gears and engine? Mike
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04-12-2019, 08:23 PM | #38 | |
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Re: 40 V8 compression change all cylinders same time
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04-12-2019, 08:55 PM | #39 |
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Re: 40 V8 compression change all cylinders same time
What is the cam? maybe I missed it, sorry
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04-13-2019, 07:21 AM | #40 |
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Re: 40 V8 compression change all cylinders same time
And valve springs, are they higher than original spring pressure?
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