flat head spark knock

R

roadstar

Member
I have about 300 miles so far on my pick up with the stock 21 stud engine. It has ford aluminum heads but otherwise stock.

This week end I identified the rattel noise I was hearing as spark knock.

Sounds very similar to my old corvette with high compression engine when it didn't have enough octane.

I have only put reg 87 octain gas in the truck and hope thats the problem.

but I know the flathead doesn't have anything close to high compression.

Anyone else have this problem.
 
road,
I mentioned this another post but I think it bears repeating here....
The aluminum intake on my '35 had blown a hole somewhere between the heat
riser passage into the runners. It ran like dream except for the detonation issue.
In desperation I changed the intake which took care of the detonation issue.
I then poked and proded until I discovered the hole in the heat riser by running
water into the intake and observed it coming out of the heat riser passages.
I've heard this 'rattle' on many similar equipped cars....to a greater or lesser degree.
Charlie ny
 
Walt Dupont--Me. said:
You have to screw down the vacuum brake to keep it from pinging. Walt
Click to expand...


Before you do this, undo the big cover-nut, pull the vacuum plunger and spring out, and see if the leather on the end of the plunger is still in good condition.

I developed a detonation problem because the leather was missing off the tip of the plunger.
 
Thanks for the advise. I see from my responces and from the other thread about detonation it seems to almost be a common problem.
 
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